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					Nokia Siemens Networks
GSM/EDGE BSS, rel.
RG10(BSS), operating
documentation, issue 06, Doc
change delivery 2


BSC/TCSM description


Product description of Flexi BSC
DN70577137

Issue 1-3
Approval Date 2010-10-29
                                                                     Product description of Flexi BSC




    The information in this document is subject to change without notice and describes only the
    product defined in the introduction of this documentation. This documentation is intended for the
    use of Nokia Siemens Networks customers only for the purposes of the agreement under which
    the document is submitted, and no part of it may be used, reproduced, modified or transmitted
    in any form or means without the prior written permission of Nokia Siemens Networks. The
    documentation has been prepared to be used by professional and properly trained personnel,
    and the customer assumes full responsibility when using it. Nokia Siemens Networks welcomes
    customer comments as part of the process of continuous development and improvement of the
    documentation.
    The information or statements given in this documentation concerning the suitability, capacity,
    or performance of the mentioned hardware or software products are given "as is" and all liability
    arising in connection with such hardware or software products shall be defined conclusively and
    finally in a separate agreement between Nokia Siemens Networks and the customer. However,
    Nokia Siemens Networks has made all reasonable efforts to ensure that the instructions
    contained in the document are adequate and free of material errors and omissions. Nokia
    Siemens Networks will, if deemed necessary by Nokia Siemens Networks, explain issues which
    may not be covered by the document.
    Nokia Siemens Networks will correct errors in this documentation as soon as possible. IN NO
    EVENT WILL Nokia Siemens Networks BE LIABLE FOR ERRORS IN THIS DOCUMENTA-
    TION OR FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO SPECIAL, DIRECT, INDI-
    RECT, INCIDENTAL OR CONSEQUENTIAL OR ANY LOSSES, SUCH AS BUT NOT LIMITED
    TO LOSS OF PROFIT, REVENUE, BUSINESS INTERRUPTION, BUSINESS OPPORTUNITY
    OR DATA,THAT MAY ARISE FROM THE USE OF THIS DOCUMENT OR THE INFORMATION
    IN IT.
    This documentation and the product it describes are considered protected by copyrights and
    other intellectual property rights according to the applicable laws.
    The wave logo is a trademark of Nokia Siemens Networks Oy. Nokia is a registered trademark
    of Nokia Corporation. Siemens is a registered trademark of Siemens AG.
    Other product names mentioned in this document may be trademarks of their respective
    owners, and they are mentioned for identification purposes only.
    Copyright © Nokia Siemens Networks 2010. All rights reserved


    f      Important Notice on Product Safety
           Elevated voltages are inevitably present at specific points in this electrical equipment.
           Some of the parts may also have elevated operating temperatures.
           Non-observance of these conditions and the safety instructions can result in personal
           injury or in property damage.
           Therefore, only trained and qualified personnel may install and maintain the system.
           The system complies with the standard EN 60950 / IEC 60950. All equipment connected
           has to comply with the applicable safety standards.


           The same text in German:
           Wichtiger Hinweis zur Produktsicherheit
           In elektrischen Anlagen stehen zwangsläufig bestimmte Teile der Geräte unter Span-
           nung. Einige Teile können auch eine hohe Betriebstemperatur aufweisen.
           Eine Nichtbeachtung dieser Situation und der Warnungshinweise kann zu Körperverlet-
           zungen und Sachschäden führen.
           Deshalb wird vorausgesetzt, dass nur geschultes und qualifiziertes Personal die
           Anlagen installiert und wartet.
           Das System entspricht den Anforderungen der EN 60950 / IEC 60950. Angeschlossene
           Geräte müssen die zutreffenden Sicherheitsbestimmungen erfüllen.




2                   Id:0900d8058080e116                                                      DN70577137
                                                                                                Issue 1-3
Product description of Flexi BSC




                         Table of Contents
                         This document has 55 pages.

                         1          Summary of changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

                         2          Overview of Flexi BSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

                         3          Functionality of the Flexi BSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .              11
                         3.1        General functionalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .         11
                         3.2        Data and messaging services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .                 13
                         3.3        Operability, capacity, quality and value added services . . . . . . . . . . . .                             16

                         4          Architecture of the Flexi BSC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .              21
                         4.1        Bit Group Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .        22
                         4.2        Call control computers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .          22
                         4.2.1      Marker and Cellular Management Unit (MCMU) . . . . . . . . . . . . . . . . . .                              23
                         4.2.2      BSC Signalling Unit (BCSU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .                24
                         4.3        Operation and Maintenance Unit (OMU) . . . . . . . . . . . . . . . . . . . . . . . .                        25
                         4.4        Ethernet-based Message Bus (EMB) . . . . . . . . . . . . . . . . . . . . . . . . . .                        27
                         4.5        Ethernet Exchange Terminal (EET) . . . . . . . . . . . . . . . . . . . . . . . . . . . .                    27
                         4.6        Exchange Terminal (ET) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .              27
                         4.7        SDH/Sonet Exchange Terminal (SET). . . . . . . . . . . . . . . . . . . . . . . . . .                        28
                         4.8        LAN Switch Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .        28
                         4.9        Clock and Synchronisation Unit (CLS). . . . . . . . . . . . . . . . . . . . . . . . . .                     29
                         4.10       Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     30

                         5          Interfaces relating to the Flexi BSC . . . . . . . . . . . . . . . . . . . . . . . . . . . .                32
                         5.1        A interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   32
                         5.2        Ater interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    33
                         5.3        Abis interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    33
                         5.4        Gb interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    34
                         5.5        Lb interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    35
                         5.6        O&M interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       35
                         5.7        CBC interface (BSC-CBC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .               36

                         6          The Flexi BSC software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

                         7          Configurations, capacity and performance of the Flexi BSC . . . . . . . . .                                 40
                         7.1        Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      40
                         7.2        Traffic handling capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .           40
                         7.3        Connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    41
                         7.4        Signalling capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       41
                         7.5        Packet handling capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .            42

                         8          Mechanical design and power supply of the Flexi BSC . . . . . . . . . . . . . 44

                         9          Reliability of the Flexi BSC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

                         10         The Flexi BSC operating environment . . . . . . . . . . . . . . . . . . . . . . . . . . 53




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                                                                            Product description of Flexi BSC




    List of Figures
    Figure 1    Flexi BSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
    Figure 2    Architecture of Flexi BSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
    Figure 3    Structure of the MCMU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
    Figure 4    Structure of the BCSU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
    Figure 5    Structure of the OMU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
    Figure 6    LAN topology of Flexi BSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
    Figure 7    The protocol stack on the Gb interface . . . . . . . . . . . . . . . . . . . . . . . . . . 35
    Figure 8    The Flexi BSC conceptual model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
    Figure 9    CC3C-B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
    Figure 10   BC1C-B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
    Figure 11   SGC1C-A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
    Figure 12   DC3C-B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
    Figure 13   CC3C-A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
    Figure 14   Flexi BSC cabinet with optional cabling cabinet . . . . . . . . . . . . . . . . . . . 48
    Figure 15   Climatogram of the Flexi BSC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
    Figure 16   Crossed-out wheeled bin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55




4                Id:0900d8058080e116                                                                     DN70577137
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Product description of Flexi BSC




                         List of Tables
                         Table 1   GSM/EDGE BSC products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
                         Table 2   Flexi BSC maximum capacity steps in S14 hardware environment . . . 40
                         Table 3   Circuit switched processing capacity of the Flexi BSC with nominal call mix
                                   41
                         Table 4   Signalling capacity of the Flexi BSC . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
                         Table 5   Breakdown of the typical power consumption (in Watts) for Flexi BSC 49
                         Table 6   Flexi BSC system hardware availability . . . . . . . . . . . . . . . . . . . . . . . . 52




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                          Product description of Flexi BSC




6   Id:0900d8058080e116                     DN70577137
                                               Issue 1-3
Product description of Flexi BSC                                                         Summary of changes




                   1 Summary of changes
                         Changes between document issues are cumulative. Therefore, the latest document
                         issue contains all changes made to previous issues.

                         Changes made between 1-3 and 1-2
                         The number of TRXs for 1024 kbit/s and 2 Mbit/s have been updated in Table 4, section
                         Signalling capacity.

                         Changes made between 1-2 and 1-1
                         In chapter 8, under Power Consumption, the power consumption value is changed.

                         Changes made between 1-1 and 1-0
                         The feature name has been changed from BSS20984 Flexi EDGE Dual 2G TRX Auto-
                         matic Power Down to BSS20984 2G TRX Automatic Power Down.
                         In chapter 8, under Power Consumption, Table 5 Breakdown of the typical power con-
                         sumption (in Watts) for Flexi BSC has been modified.




DN70577137                                       Id:0900d8058080efe2                                         7
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Overview of Flexi BSC                                                          Product description of Flexi BSC




                  2 Overview of Flexi BSC
                        The Flexi BSC is the latest step in the evolution of Nokia Siemens Networks Base
                        Station Controller. It is a modern fault-tolerant system for GSM 800, GSM 900, GSM
                        1800, and GSM 1900 networks.
                        The Flexi BSC is based on modular software and hardware architecture. The distributed
                        architecture is implemented with a high-capacity and redundant multiprocessor system
                        - the DX 200 computing platform. The system enables the distribution of processing
                        capacity to several computer units with dedicated tasks.
                        The DX 200 product family covers a wide application area in GSM/EDGE mobile
                        networks and fixed telephone networks. It contains products for digital mobile applica-
                        tions, such as Base Station Controller (BSC), Transcoder Submultiplexer (TCSM),
                        Mobile Switching Centre (MSC), MSC Server (MSS), DX HLR (HLR), and Serving
                        GPRS Support Node (SGSN).
                        The main function of the Flexi BSC is to control and manage the Base Station Subsys-
                        tem (BSS) and the radio channels. Based on long experience in cellular networks, the
                        Flexi BSC is designed for efficient use of radio resources and is easy to operate and
                        maintain. The Flexi BSC is a stable, mature and highly reliable product with field-proven
                        multivendor functionality.
                        Together with the functionally distributed modular architecture of the DX 200 computing
                        platform and the latest commercially available industry standard hardware components,
                        the Flexi BSC is easily expandable and cost-efficient and has high capacity.




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                                                                                                      Issue 1-3
Product description of Flexi BSC                                                            Overview of Flexi BSC




                         Figure 1     Flexi BSC
                         For more information on other versions of the BSC, refer to Product Description of
                         BSC3i High Capacity Base Station Controller and Product Description of BSC2i and
                         BSCi High Capacity Base Station Controller.

                          General     Product name          Explanation
                          name
                          BSC                               Base Station Controller, a general term for all
                                                            BSC versions
                          BSCi/2i     BSCi                  High Capacity (upgraded) version of the first
                                                            generation DX 200 BSC (BSCE)
                                      BSC2i                 High Capacity version of the second genera-
                                                            tion DX 200 BSC2
                          Flexi BSC   BSC3i 660             660-TRX one-cabinet configuration, upgrade-
                          product                           able to Flexi BSC
                          family
                                      BSC3i 1000/2000       1000-TRX one-cabinet or 2000-TRX two-
                                                            cabinet configuration, upgradeable to Flexi
                                                            BSC
                                      Flexi BSC             3000-TRX one-cabinet configuration

                         Table 1      GSM/EDGE BSC products



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Overview of Flexi BSC                                                       Product description of Flexi BSC



                        Related topics in Flexi BSC Product Description
                        •   Functionality of the Flexi BSC
                        •   Architecture of the Flexi BSC
                        •   Interfaces relating to the Flexi BSC
                        •   The Flexi BSC software
                        •   Configurations, capacity and performance of the Flexi BSC
                        •   Mechanical design and power supply of the Flexi BSC
                        •   Reliability of the Flexi BSC
                        •   The Flexi BSC operating environment

                        Other related topics
                        Descriptions
                        •   TCSM Support in BSC
                        •   Transmission Management in BSS
                        •   Radio Network Configuration Management
                        •   Engineering for Flexi BSC
                        Instructions
                        •   Installation Site Requirements for Flexi BSC and TCSM
                        •   Installing Flexi BSC and TCSM3i
                        •   Jumper Settings of the Plug-in units in Flexi BSC
                        •   Jumper Settings of the Cartridges in Flexi BSC and TCSM3i
                        •   Cabling Instructions for Flexi BSC
                        •   Connector Panels and External Cables in Flexi BSC and TCSM3i
                        •   Commissioning BSC3i and Flexi BSC
                        •   BSS Integration
                        •   BSS (BSC) Traffic Handling Capacity, Network Planning and Overload Protection
                        •   Creating and Managing BSC Hardware




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                                                                                                 Issue 1-3
Product description of Flexi BSC                                                   Functionality of the Flexi BSC




                   3 Functionality of the Flexi BSC
                         The Flexi BSC manages a variety of tasks ranging from channel administration to short
                         messaging service. The most important basic and optional functionalities are explained
                         briefly below. For more details, see BSS software descriptions.
                         Interfaces to other network elements are described in Interfaces relating to the Flexi
                         BSC.


                 3.1     General functionalities
                         Call control
                         Basic Call provides speech and data services to the mobile subscriber by offering the
                         means for establishing speech or data calls with half or full rate.

                         Management of terrestrial channels
                         •   allocation of traffic channels between the BSC and the BTSs
                         •   pool support for A interface circuits
                         •   flexible channel assignments, for example, half rate and high speed circuit switched
                             data
                         •   multiplexing and handling of Ater channels

                         Management of radio channels
                         •   Management of common signalling of traffic channel configurations.
                         •   Management of traffic channels (TCH) and stand-alone dedicated control channels
                             (SDCCH):
                              • resource management
                              • channel allocation
                              • link supervision
                              • channel release
                              • power control
                         •   Management of broadcast control channels (BCCH) and common control channels
                             (CCCH):
                              • random access
                              • access grant
                              • paging
                              • system information broadcast
                         •   Management of frequency hopping which enables effective use of radio resources
                             and enhanced voice quality for a GSM subscriber.
                         •   Handovers
                             Existing handover types are:
                              • intra-BSC, intra-cell (both intra-TRX and inter-TRX), which means that the
                                 handover takes place within the area controlled by the BSC and the mobile stays
                                 in the same cell
                              • intra-BSC, inter-cell, which means that the mobile stays in the area of the BSC
                                 but moves from one cell to another




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Functionality of the Flexi BSC                                                   Product description of Flexi BSC




                                 • inter-BSC, both outgoing and incoming, which means that the mobile moves into
                                   the area of another BSC
                              The handover threshold comparison includes the evaluation of uplink/downlink
                              level, quality and interference, MS-BTS distance evaluation, the evaluation of a
                              rapid field drop, the detection of a fast/slow-moving MS, the detection of a turn-
                              around-corner MS, power budget evaluation, and umbrella handover evaluation.
                              If two or more criteria for a handover are present simultaneously, the handover is
                              done according to the priority order.

                         Management of signalling channels between the BSC and the BTSs
                         The BSC supervises all 16, 32, or 64 kbit/s permanent point-to-point LAPD signalling
                         connections, consisting of one connection per transceiver unit (TRX) and BTS operation
                         and maintenance unit (OMU).

                         GPRS/EDGE packet data handling
                          •   connection establishment and management
                          •   resource allocation
                          •   scheduling
                          •   data transfer
                          •   MS uplink power control
                          •   Gb load sharing (uplink)
                          •   flow control (downlink)

                         Maintenance
                         The BSC offers the possibility for the following maintenance procedures:
                          •   fault localisation for the BSC
                          •   reconfiguration of the BSC
                          •   reconfiguration support to the BTS
                          •   updating of the software in the BSC, TCSM and BTS

                         Operation
                         During normal operation, the BSC offers various possibilities for the operator:
                          •   modification of the parameters of the BSC and the BTS
                          •   modification of the radio network parameters
                          •   configuration of the BSC hardware
                          •   administration of the BSC equipment

                         User interface
                         The BSC has a user-friendly interface with plain-text messages and commands, which
                         are easy to learn and use. This user interface complies with the recommendations of the
                         International Telecommunication Union (ITU-T).
                         You can find more information on the user interface and commands in the MML
                         commands section of the BSC documentation set.

                         Measurements and observations
                         To run the network effectively, that is, to minimise costs and maximise service quality to
                         the subscriber, you need information on the performance and service level of the BSC
                         and the radio network. Useful information is, for example, how much traffic different cells
                         carry, whether there is congestion on the SDCCH or TCH channels, and how many han-



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Product description of Flexi BSC                                                   Functionality of the Flexi BSC



                         dovers are successful and how many fail. Traffic measurements provide this informa-
                         tion.
                         When you analyse the information, you can, for example, find out whether the load is
                         distributed evenly or whether there are both heavily and lightly loaded parts in the
                         network. If the load distribution is not even, you can make changes to the dimensioning
                         of the network to balance it and improve performance. When you observe certain traffic
                         characteristics over a period of time, you are able to forecast the time when new
                         resources or extensions must be introduced into the network.
                         The BSC measures traffic, observes signalling events, and traces a specific call. It then
                         forwards these results to NetAct for further processing. The measurements are grouped
                         together to enable better functionality and handling. This gives you an easier selection
                         of the measurements you need at a particular time. BSC measurements are indepen-
                         dent of each other even though they are handled via the same user interface.
                         You can find more information on the measurements and observations of the BSC in the
                         Counters/performance indicators section of the BSC documentation set.


                 3.2     Data and messaging services
                         General Packet Radio Service (GPRS)
                         GPRS gives customers the benefits of instant IP connectivity on-the-move and of being
                         continuously connected. GPRS provides the possibility of being charged only for trans-
                         ferred data in addition to more efficient use of limited air interface resources.
                         GPRS provides packet radio access for a GSM/GPRS mobile. The benefit of GPRS is
                         that it can use the same resources as circuit-switched connections by sharing the
                         overhead capacity. This means that one mobile uses the resources only for a short
                         period of time, that is, when there is data to be sent or received. The sharing of
                         resources together with a very fast method of reserving radio channels makes the air
                         interface usage even more efficient. GPRS coding schemes CS1-CS4 are supported.

                         EDGE
                         Enhanced Data rates for GSM Evolution (EDGE), introduced in GSM/GPRS standard
                         Release 99, boosts GSM/GPRS network capacity and data rates to meet the demands
                         of wireless multimedia applications and mass market deployment. Nokia Siemens
                         Networks EDGE Solution includes GPRS/EDGE for packet switched data.
                         EDGE uses 200 kHz radio channels, which are the same as the current GSM channel
                         widths. From a technical perspective, EDGE BSS allows the GSM and GPRS core
                         network to offer a set of new radio access bearers. EDGE is designed to improve
                         spectral efficiency through efficient link utilisation with GMSK and 8-PSK modulation
                         schemes, which can be alternated on the same radio slot according to radio channel
                         conditions. With new modulation, EDGE increases the radio interface data throughput
                         threefold on average compared to GPRS.
                         EDGE Modulation and Coding Schemes MCS1-MCS9 provide optimal performance in
                         all radio conditions. In good radio conditions MCS9 provides up to 59.2 kbit/s through-
                         put. In four timeslot multislot allocation 236.8 kbit/s throughput can be achieved.
                         With Dynamic Abis functionality, the Abis resources for packet data are reserved
                         dynamically depending on the needed user throughput.




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Functionality of the Flexi BSC                                                    Product description of Flexi BSC



                         Multipoint Gb Interface
                         Multipoint Gb Interface enables one packet control unit (PCU) or PCU pool to be con-
                         nected to several SGSNs. This enhances the resilience of the system and provides the
                         possibility of distributing the traffic load between the SGSNs. Different users in the same
                         PCU can be connected to different SGSNs according to their load conditions.
                         A PS pool area defines a group of PCUs, where an MS may roam without the need to
                         change the serving SGSN node. This reduces the need for signalling when, for example,
                         a MS moves between the city centre and suburban areas within a single pool area.
                         Multipoint Gb Interface improves scalability and fault protection in the core network and
                         thus leads to savings in capital expenditure. In case of failures in the GPRS core, the
                         network remains operational with reduced SGSN capacity. Multipoint Gb Interface also
                         facilitates easy core network element upgrades and helps the operator to maintain
                         revenue and increase end-user service quality.

                         Dual Transfer Mode
                         Dual Transfer Mode (DTM) provides mobile users simultaneous circuit switched (CS)
                         voice and packet switched (PS) data services. This means that users can, for example,
                         share a video call or send and receive email during an ongoing phone call. The CS con-
                         nection is always a single slot connection, whereas the PS connection can also be a
                         multislot connection. The BSC supports full rate (AMR/FR, EFR, and FR) CS connec-
                         tions in dual transfer mode. Simultaneously obtained packet data rates can be up to 118
                         kbit/s for GPRS/EDGE and 40 kbit/s for GPRS.

                         Extended Dynamic Allocation
                         Extended Dynamic Allocation (EDA) allows an MS to use more than two timeslots in the
                         uplink direction. With EDA the number of uplink timeslots per uplink TBF is up to four,
                         which enables the following maximum uplink bitrates:
                          •   GPRS with CS1/CS2, up to 48 kbit/s
                          •   GPRS with CS3/CS4, up to 80 kbit/s
                          •   EDGE, up to 236 kbit/s

                         High Multislot Classes
                         High Multislot Classes increases the EDGE peak throughput value from 236.8 kbit/s to
                         296 kbit/s. The combined downlink and uplink transmission throughput also increases.
                         Together with DTM it makes symmetrical (equal number of downlink and uplink TSLs)
                         allocation possible, enabling good quality video transmission. One TSL is used for CS
                         voice and two downlink and uplink TSLs are used for PS video transmission.

                         Downlink Dual Carrier
                         Downlink Dual Carrier makes it possible to allocate radio timeslots in two separate
                         downlink carriers for one MS in the same cell. One of these can be, for example the
                         BCCH carrier and the other a traffic channel with frequency hopping. This means that
                         peak downlink throughput can be doubled to up to 592 kbit/s.
                         In the uplink direction the MS may dynamically alternate between the carriers to
                         maximize the utilization of uplink resources.

                         Extended Cell for GPRS/ EDGE
                         Extended Cell for GPRS/EDGE enables the use of GPRS/EDGE traffic in the extended
                         radio coverage area of an extended cell. Traffic for a mobile station is supported so that



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                         the mobile station can move between coverage areas of the cell without breaking data
                         connections. Depending on the configuration of the cell, packet services can be
                         provided up to 70 km distance from the BTS site.

                         Network-Controlled Cell Re-selection
                         Network-Controlled Cell Re-selection (NCCR) introduces the possibility for the network
                         to order a cell re-selection instead of the autonomous selection done by the mobile
                         station (MS) itself. With NCCR, the network triggers the cell change and selects the
                         target cell.
                         Cell re-selection is a basic cellular radio network operation, where an MS moves from
                         one cell to another. Cell re-selection is performed by the MS.
                         NCCR includes the following criteria:
                         •   Power budget pushes GPRS/EDGE-capable mobiles to operator-defined data layer
                             or cells preferred for data usage.
                             In gradual EDGE network deployment power budget algorithm can be used to direct
                             EDGE capable MSS to EDGE cells and non-EDGE capable MSS to GPRS cells.
                             With power budget NCCR, the operator can also effectively reduce the number of
                             unnecessary cell re-selections, especially ping pong cell re-selections at the cell
                             borders.
                         •   Quality control triggers NCCR when the quality of the serving cell transmission
                             drops, even if the serving cell signal level is good.

                         Network-Assisted Cell Change
                         Network-Assisted Cell Change (NACC) reduces service outage time to less than one
                         second when a GPRS/EDGE mobile moves between GPRS/EDGE cells. It improves
                         both autonomous and network-controlled cell change.
                         Outage time is reduced because the network is allowed to assist MSS before and during
                         the cell change. The network sends neighbour cell system information to the mobile via
                         the source cell on packet associated control channel (PACCH) while it is still camping
                         on the serving cell. Neighbour cell system information messages sent to the MS contain
                         a set of system information messages needed to perform packet access in the new cell.
                         When all required messages are sent to the mobile, the MS can perform packet access
                         and use PACKET SI STATUS procedures for the acquisition of the rest of the system
                         information messages.

                         Circuit Switched Data services
                         The BSC supports the following bearer services, including both transparent and non-
                         transparent data services, defined in GSM Specification ETS 300 904 with applicable
                         ETSI/3GPP specifications:
                         •   Data Circuit Duplex (300-14400 bit/s) transparent/non-transparent
                         •   High Speed Circuit Switched Data
                         •   14.4 kbits/s Data Traffic Channel
                         •   Telefax Automatic Group 3, Transparent
                         •   Short Message Service Functionality

                         High Speed Circuit Switched Data
                         High Speed Circuit Switched Data (HSCSD) application software provides accelerated
                         data rates for end-user applications. HSCSD supports both transparent and non-trans-




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                         parent data services. A multiple set of basic resources is reserved for one HSCSD call,
                         and up to four time slots can be used for an HSCSD call.
                         HSCSD can be combined with 14.4 kbit/s data service for higher data speed rates.

                         Multimedia Message Service (MMS) and Short Message Service (SMS)
                         The BSC forwards mobile originating and mobile terminating messages transparently.

                         Cell Broadcast Messages (CB)
                         Cell Broadcast provides the BSC with the short message service cell broadcast
                         (SMSCB) capabilities defined by GSM recommendations. The SMSCB is a basic
                         teleservice that is used for broadcasting short messages to mobile stations in a specified
                         area within the PLMN. The input is MMI, local, or remote. Optionally CBC can be used
                         as the input for CB messages.


                  3.3    Operability, capacity, quality and value added services
                         GSM-UTRAN interworking
                         To provide seamless coverage in areas where WCDMA is not available, for example in
                         rural areas, inter-system handovers provide a method of extending the radio network
                         coverage area by making a handover from the WCDMA network to the GSM network.
                         Additionally, in situations where the WCDMA network and GSM network overlap, an
                         inter-system handover from GSM to WCDMA can be made to relieve the traffic load in
                         the GSM system. Inter-system network controlled cell re-selection is also supported.
                         Inter-system handovers provide seamless coverage extension for 3G with existing GSM
                         network (or vice versa) as well as capacity extension for GSM with load sharing between
                         3G and GSM.
                         Both the circuit-switched (handover and MS-controlled cell re-selection) and packet-
                         switched (MS- and network-controlled cell re-selection) modes are supported.
                         The BSC also provides support for incoming handovers from the TD-SCDMA radio
                         network and circuit-switched and packet-switched cell re-selection from GSM to TD-
                         SCDMA.

                         MS Location Services
                         MS Location Services (LCS) allows a GSM subscriber and/or valid mobile equipment to
                         be positioned. Positioning may be initiated by the subscriber, the network, or an external
                         party utilising the Mobile Positioning Function. Positioning is subject to various restric-
                         tions based on, for example, capability, security, and service profiles. LCS allows the
                         location of a GSM mobile station (MS) to be determined at any time while the MS is
                         within the radio coverage area of the GSM HPLMN or VPLMN. Important applications
                         of Location Services are, for example:
                          •   Government applications:
                              • Emergency calls (E911 requirement by FCC in US)
                              • Electronic surveillance
                          •   Operator applications:
                              • Home zone calls
                          •   Commercial services:
                              • Fleet management, tracking packages
                              • Information on the nearest hotel, petrol station and so on



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                             •     Car navigation
                             •     Emergency roadside service
                             •     Search for stolen property
                         Different MS Location methods have different benefits and drawbacks. No single
                         method is suitable for all applications. The BSS provides support for Cell ID with timing
                         advance (CI+TA) method for legacy phones. That means that in addition to CI data also
                         additional information will be used to improve legacy MS location accuracy. The method
                         includes location calculation using air interface measurements. Lb+ interface support for
                         Stand-alone SMLC also enables the use of the Assisted GPS location method.

                         Adaptive Multi Rate Codec
                         The BSC supports Full Rate (FR), Half Rate (HR) and Enhanced Full Rate (EFR)
                         speech codecs. Adaptive Multi Rate Codec (AMR) introduces a set of codecs and an
                         adaptive algorithm for codec changes which together can provide significantly improved
                         speech quality and more capacity on the air interface. With AMR it is possible to achieve
                         very good speech quality in FR mode even in low C/I conditions; or increase the speech
                         capacity through using the HR mode while still maintaining the quality level of calls.
                         The Adaptive Multi Rate codec consists of a family of codecs (source and channel
                         codecs with different trade-off bit-rates) operating in the GSM FR and HR channels. The
                         idea behind the AMR codec concept is that it is capable of adapting its operation opti-
                         mally according to the prevailing channel conditions.
                         Enhanced operation with power control and handover algorithms together with improved
                         quality measurements (FER Measurement) provide extended benefits and interworking
                         with the Nokia Siemens Networks advanced capacity software solutions, including Intel-
                         ligent Frequency Hopping (IFH). Power control for AMR is enhanced through AMR Pro-
                         gressive Power Control and Robust AMR Signalling provides reliable operation of the
                         control channels (FACCH/SACCH) in poor radio conditions.

                         Wideband Adaptive Multi Rate Codec
                         Wideband Adaptive Multi Rate Codec (Wideband AMR) is a family of speech codecs
                         designed to achieve improvements in speech quality by extending the speech band-
                         width. The sampling rate used by Wideband AMR is twice the rate of current voice
                         services in mobile and fixed line telephony. The higher sampling rate, combined with
                         improved transcoding algorithms, enhances the audio frequency band to 50 Hz - 7000
                         Hz, which is a significant increased compared to the 300 Hz - 3400 Hz frequency band
                         for existing voice services.
                         The Wideband AMR codec set supported by the BSS consists of 12.65, 8.85 and 6.60
                         kbps codec modes, which are currently the same as in WCDMA RAN.
                         Like in AMR, the codec mode can be chosen based on the radio conditions, yielding to
                         optimal audio performance through rate adaptation. The codec mode can be changed
                         every 40 ms in GSM. The codec also includes a source controlled rate adaptation mech-
                         anism, which allows it to encode speech at a lower average rate by taking speech inac-
                         tivity into account.
                         Wideband AMR requires support for end-to-end Tandem Free Operation, because
                         downsampling in transcoding would invalidate the improved properties of sound.

                         A5/3 Ciphering
                         A5/3 is a more secure 3GPP-standardized ciphering method that is based on the same
                         core algorithm used in WCDMA. While the actual ciphering is performed by the BTS, the



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                         BSC selects the ciphering algorithm based on the information received from the MSC
                         and the information on the allowed and supported algorithms in the BSS and MS.

                         Dual Band GSM operation
                         The BSC supports the Dual Band network. The Dual Band operation supports dual band
                         mobiles able to perform handovers between the GSM 900 and GSM 1800 bands,
                         between 800 and 1900 bands as well as GSM/EDGE 800/1800 during a call.

                         Extended GSM 900 Band
                         The Extended (E)GSM 900 Band (Tri Band) supports the use of the ETSI-specified GSM
                         900 frequency band extension, the area of 880-890 MHz uplink and 925-935 MHz
                         downlink where available. This means that a total of 50 radio frequency channels are
                         included in this E-GSM 900 band. For a GSM operator, the E-GSM 900 extension band
                         can represent the most cost-effective way of adding capacity to his system if the Primary
                         GSM spectrum is used.

                         Common BCCH
                         There is an option that allows GSM 900 and GSM 1800 TRXs to share the same BCCH
                         in the same cell. This functionality can be considered a progression from the integrated
                         dual band BTS and EGSM 900 frequency band support (Tri Band). Common BCCH is
                         also supported for GSM/EDGE 800/1900 frequency bands.

                         Intelligent Underlay-Overlay
                         The Intelligent Underlay-Overlay (IUO) allows the operator to reuse frequencies more
                         intensively and hence achieve a higher radio network capacity. In IUO the operating
                         spectrum of a network is divided into regular frequencies and super-reuse frequencies.
                         The overlay network uses regular frequencies and offers a continuous coverage area.
                         The underlay network uses the super-reuse frequencies which are reused very inten-
                         sively to provide the extended capacity.

                         Intelligent Frequency Hopping
                         The Intelligent Frequency Hopping (IFH) provides the benefits of IUO and frequency
                         hopping at the same time: the operator can enjoy powerful radio spectrum efficiency and
                         the quality benefits of frequency hopping, avoiding frequency-dependent fading in the
                         radio path.

                         Advanced Multilayer Handling
                         Advanced Multilayer Handling (AMH) concept is used to redistribute traffic to the appro-
                         priate layer or frequency band according to the prevailing load of the network. AMH
                         provides the network operator with the tools to relieve the load of the congested cells
                         and smooth out the load over the network. In other words, it provides the operator with
                         both improved quality and capacity.

                         Dynamic Frequency and Channel Allocation (DFCA)
                         Dynamic Frequency and Channel Allocation (DFCA) is a new channel assignment
                         scheme, which uses interference estimations derived from mobile downlink measure-
                         ment reports to dynamically assign a timeslot and frequency in the establishment of a
                         new call or incoming handover.
                         The purpose of this channel selection is to provide satisfactory quality, so that each con-
                         nection meets its quality of service requirements, and to minimise the interference to




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                         other connections. These lead to a significant capacity gain as the usage of valuable fre-
                         quency resources is dynamically optimised.
                         DFCA is a completely automated functionality, and it removes the need to make a fre-
                         quency plan for the non-BCCH TRXs configured for the functionality.

                         Extended Cell
                         Extended Cell Two enables the use of two cells cells, that is, inner and outer cells, with
                         different timing advance ranges. An inner cell has a regular coverage area and an outer
                         cell has an extended radius of the coverage area. Based on the timing advance, the
                         BSC triggers a handover when the mobile station is approaching the inner cell while still
                         being served by the outer cell.

                         Multipoint A interface
                         Multipoint A Interface enables one BSC to be connected to several core network
                         elements (MSCs or MSC Servers). Even if one of the core network elements or connec-
                         tions fails, it is still possible that the network remains operational (but with a reduced
                         capacity).
                         Multipoint A interface improves network performance in terms of scalability and makes
                         capacity upgrades smoother. Network load can be distributed among the serving enti-
                         ties.

                         SIGTRAN
                         SIGTRAN is a standardised way to carry SS7 signalling over an Internet protocol (IP)
                         backbone. The same IP backbone can be used for all kinds of traffic (management,
                         user, and control plane).
                         SIGTRAN offers easy scalability of the signalling network capacity and can provide cost
                         savings compared to a TDM infrastructure. Parallel usage with old SS7 transport
                         network provides extra resilience for transfer period.

                         Multi-operator BSS
                         Multi-operator Base Station Subsystem (MOBSS) enables two or more network opera-
                         tors to share a BSS. This BSS sharing would typically occur in a network roll-out phase
                         in order to derive CAPEX / OPEX advantages or in a phase where the 2G network is
                         being scaled down due to 3G networks.
                         Operators can share one or more physical BSCs and BTSs between themselves. They
                         can have both shared BSS as well as their own dedicated BSS networks, and either own
                         or shared BTSs within the shared BSS area.

                         Energy Saving Mode for BCCH TRXs and 2G TRX Automatic Power Down
                         Energy Saving Mode for BCCH TRXs introduces a new configurable power saving
                         mode for BCCH TRXs in Flexi EDGE BTSs and UltaSite BTSs, which can reduce energy
                         consumption throughout the day. 2G TRX Automatic Power Down enables the operator
                         to shut down a dual TRX during periods of low traffic, thus reducing energy consumption
                         during the night-time, for example.

                         File-based plan provisioning
                         File-based plan provisioning enables the operator to download radio network configura-
                         tion plans by using the file transfer protocol (FTP).
                         File-based plan provisioning improves the performance of the configuration change pro-
                         cedure. The performance improvement is needed because of increased network



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                         element capacity, increased number of radio network objects, and growing network
                         sizes.




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                   4 Architecture of the Flexi BSC
                         The Flexi BSC is based on a modular software and hardware structure. Because there
                         are exact specifications for the interfaces between different modules, new functions can
                         easily be added without changing the architecture of the system. Thus, the Flexi BSC
                         can have a long operational life span and still always have up-to-date functionality.
                         The distributed architecture of the Flexi BSC is implemented by a multiprocessor
                         system. In a multiprocessor system the data processing capacity is divided among
                         several computer units, each of which has a microcomputer of its own.
                         Call handling capacity depends on the number of call control computer units. The
                         capacity of the BSC can easily be increased by adding more call control computer units.
                         Figure Architecture of Flexi BSC shows the block structure of the Flexi BSC. The most
                         important functional units of the BSC are:
                         •   Bit-oriented Group Switch is used for switching speech and data, and connecting
                             signalling circuits.
                         •   Base Station Controller Signalling Unit (BCSU) handles the BSC signalling func-
                             tions.
                             The optional Packet Control Unit (PCU) is included in the BCSUs, when the
                             GPRS/EDGE service is implemented. It handles the GPRS/EDGE packet control
                             functions in the BSC.
                         •   Marker and Cellular Management Unit (MCMU) controls and supervises the Group
                             Switch and implements radio resource management (RRM) functions, being
                             responsible for cells and radio channels.
                             The MCMU also acts as a BSC system maintenance unit in case of OMU failure.
                         •   Operation and Maintenance Unit (OMU) serves as an interface between the user
                             and the BSC, but also works as a system maintenance unit of the BSC and automat-
                             ically supervises the BSC
                         •   Ethernet-based Message bus (EMB) interconnects the functional units of the BSC.
                         •   LAN Switching Units (SWUs) are connected to the interface units (CPUs and PCUs)
                             with internal Ethernet subnetwork established with duplicated cable connections.
                         •   Ethernet Exchange Terminals (EET) enable IP connectivity towards the Abis, Ater,
                             and A interfaces, for example.
                         •   SDH/Sonet Exchange Terminals (SET) connect external optical (STM-1/OC-3)
                             interfaces.
                         •   Exchange Terminals (ET) enable traditional E1/T1 connectivity.
                         •   Clock and Synchronisation Unit (CLS) generates the clock signals for the BSC.
                         •   Transcoder submultiplexer (TCSM), although a separate network element and
                             usually installed on the MSC site, is normally viewed as a functional unit of the BSC.




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                         Figure 2      Architecture of Flexi BSC
                         For a more detailed description of hardware, see Engineering for Flexi BSC.
                         The functional units and cartridge types used in the Flexi BSC are described in the fol-
                         lowing sections, which provide the information on both the basic configurations of the
                         functional units (or cartridges) and the extension possibilities.
                         Each microcomputer of the functional unit has two duplicate Ethernet interfaces: an
                         internal message bus interface via a dedicated LAN switch pair to other microcomputers
                         and an external LAN interface via integrated LAN switches (SWUs) towards other
                         network elements. The LAN switch pair for message bus is located in the same car-
                         tridges with MCMUs. The LAN switches for external interfaces are located in the LANU
                         cartridges.


                  4.1    Bit Group Switch
                         The Bit Group Switch in the Flexi BSC consists of eight pieces of SW256B plug-in units
                         having 2048 pcs of 2 Mbit/s internal PCMs (GSW2KB). The Flexi BSC uses two identical
                         cartridges for redundancy. The Bit Group Switch switches on 8, 16, 32, and 64 kbit/s
                         levels.
                         The Bit Group Switch conveys the traffic passing through the BSC and switches the
                         tones to the subscribers of the exchange and to the trunk circuits. The Bit Group Switch
                         also establishes the necessary connections to the signalling units and the internal data
                         transmission channels, and is responsible for the submultiplexing functions of the BSC.
                         The Bit Group Switch of the Flexi BSC is a fully digital, one-staged, and non-blocking
                         time switch with full availability. Its great advantage is its simplicity. After the Bit Group
                         Switch has identified the correct time slots, it can always connect them in a uniform
                         manner without using a special search path.
                         The operation of the Bit Group Switch is controlled and supervised by the Marker and
                         Cellular Management Unit (MCMU). The MCMU performs all necessary connecting and
                         releasing functions.


                  4.2    Call control computers
                         In the Flexi BSC, the call control functions are executed by the call control computers,
                         MCMU and BCSU. The call control computers have an identical Central Processing Unit
                         (CPU), which is based on the most suitable commercially available Intel microproces-
                         sors. The CPU board contains a microprocessor and a local Random Access Memory




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                         (RAM). Each call control computer also contains the additional units that are required
                         for performing specific tasks.
                         All plug-in units of each call control computer are interconnected by a Compact PCI bus
                         through the cartridge backplane.


                4.2.1    Marker and Cellular Management Unit (MCMU)
                         The Marker and Cellular Management Unit (MCMU) controls and supervises the Bit
                         Group Switch and performs the hunting, connecting, controlling, and releasing of the
                         switching network circuits. The range of the tasks it handles makes up a combination of
                         general marker functions and radio resource management functions.
                         The hardware of the MCMU consists of a microcomputer and a Switch Control Interface.
                         Dedicated LAN switch unit for Ethernet-based Message Bus is also located in the same
                         cartridge with the MCMU. When the MCMU performs the marker functions, it exchanges
                         messages with other call control computers via the message bus.

                                                          GROUP
                                                          SWITCH




                                       MCMU               control
                                                          interface



                                                                 COMPACT PCI BUS

                                                        micro-
                         LAN                            computer



                                                       message bus
                         Figure 3     Structure of the MCMU
                         The Switch Control Interface writes the required connections into the switch control
                         memory and reads its contents. The switch control interface also performs various tests
                         on the switching network, defined by the microcomputer, and generates the required
                         timing signals.
                         The MCMU has centralized cellular management functions for controlling cells and radio
                         channels for BSC. The MCMU reserves and keeps track of the radio resources
                         requested by the MSC and the handover procedures of the BSC. The MCMU also
                         manages the configuration of the cellular network.
                         One Flexi BSC always includes two MCMUs that are permanently connected to the
                         duplicated pair of the Bit Group Switches, the active MCMU to the active GSWB and the
                         passive MCMU to the passive GSWB.
                         Redundant Ethernet interfaces connect the MCMU to the duplicated LAN switch units.




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                4.2.2    BSC Signalling Unit (BCSU)
                         The BSC Signalling Unit (BCSU) is a TRX-capacity unit of the Flexi BSC. It performs
                         those BSC functions that are highly dependent on the volume of traffic. One BCSU can
                         handle traffic in a maximum of 500 transceivers (TRXs). The BCSU consists of two
                         parts, which correspond to the A and Abis interfaces.
                         The BCSUs 1-6 are housed in cabinet-wide cartridges. The BCSU 0 is housed in a car-
                         tridge of its own. The optional Packet Control Units (PCUs) are housed in the same car-
                         tridges.
                         The A interface part of the BCSU is responsible for the following tasks:
                          •     performing the distributed functions of the Message Transfer Part (MTP) and the
                                Signalling Connection Control Part (SCCP) of SS7
                          •     controlling the mobile and base station signalling (Base Station Subsystem Applica-
                                tion Part, BSSAP)
                          •     performing all message handling and processing functions of the signalling
                                channels connected to it.
                         The Abis interface part of the BCSU controls the air interface channels associated with
                         transceivers (TRXs) and Abis signalling channels. Every speech circuit on the Abis inter-
                         face is mapped one-to-one to a GSM-specific speech/data channel on the air interface.
                         The handover and power control algorithms reside in this functional unit.
                         The hardware of the BCSU consists of the following modules:
                          •     a microcomputer
                          •     a preprocessing unit for multichannel signalling
                                 • A LAPD (Link Access Protocol on the D-Channel) interface
                                 • A LAPD interface for control of the ET
                                 • an SS7 interface
                          •     the Packet Control Unit(s)

                                                                 Group Switch


                                    BCSU               00 55
                                                        -
                                                      00--5
                                                      PCUs-5
                                                       PCUs
                                                       PCUs
                                                        PCUs

                                                                              SS7/LAPD
                          LAN                                                 interface
                                                         Compact PCI bus

                                                      micro-
                                                      computer


                                                   message bus
                         Figure 4        Structure of the BCSU
                         The interface unit for the SS7 and the LAPD protocols are connected to the switching
                         network via PCM connections. Similarly, redundant Ethernet interfaces from the micro-
                         computer connect the BCSUs to the duplicated LAN switch units. The LAN interface
                         from the PCU is used for Gb over IP functionality and LAN interface from the microcom-
                         puter can be used for BSC-BSC interface (DFCA) or SS7 signalling over IP (SIGTRAN).



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                         There are two preprocessor units for multichannel signalling equipped to the BCSU unit
                         for LAPD and traditional SS7 signalling (CCS7). For detailed information on the signal-
                         ling capacity, see Configurations, capacity and performance of the Flexi BSC.
                         A preprocessor unit for multiprocessor signalling in the BCSU includes LAPD interfaces
                         for signalling towards the BTSs and towards the ETs and SETs for both Abis and Ater
                         interface directions. The bit rate of a single link can be either 16 kbit/s, 32 kbit/s, or 64
                         kbit/s. The layer 2 LAPD functions are performed by the signalling unit, but application-
                         specific messages are handled by the microcomputer of the BCSU. The signalling is
                         semipermanently connected to the time slots used for signalling.
                         According to the N+1 redundancy principle (see section Reliability of the Flexi BSC),
                         there is one extra BCSU compared to the number set by the dimensioning rules. The
                         additional unit is used only if one of the active units fails.

                         Packet Control Unit (PCU)
                         The PCU unit is an independent processing unit, which is embedded in the BCSUs and
                         which takes advantage of BSCs O&M and redundancy mechanisms. The PCU unit
                         performs all the data processing tasks related to GPRS/EDGE traffic. It implements both
                         packet switched traffic oriented Gb and Abis interfaces in the BSC. Additionally, the PCU
                         unit provides flexible choices for the transport method between BSC and SGSN; both IP
                         and Frame-Relay are available as transport alternatives for the Gb interface.
                         The PCU includes microprocessors and digital signal processors integrated in the same
                         plug-in-unit to handle the tasks. The PCU controls GPRS/EDGE radio resources and
                         acts as the key unit in the following procedures:
                         •   GPRS/EDGE radio resource allocation and management
                         •   GPRS/EDGE radio connection establishment and management
                         •   Data transfer
                         •   Coding scheme selection
                         •   PCU statistics
                         In the Flexi BSC, the PCUs can be flexibly configured and activated in the BCSUs
                         according to the traffic requirements. There can be up to five PCU2-E units per TRX
                         capacity step (BCSU). One PCU2-E provides capacity for 1024 (16 kbit/s) Abis chan-
                         nels. Asymmetrical PCU HW configuration optimises the used PCU2-E hardware con-
                         figuration, enabling PCU2-E hardware installation in granularity of one and according to
                         the traffic requirements. The installed PCU2-E units are flexibly software-activated in
                         four steps with 256 channel licenses.
                         PCU2 pooling enhances the operability related to the Gb and Abis interfaces and allows
                         for more efficient usage of available PCU resources. Activated PCUs can be grouped
                         into a PCU pool belonging to one Network Service Entity (NSE). From the SGSN point
                         of view a PCU pool looks like a single PCU.


                 4.3     Operation and Maintenance Unit (OMU)
                         The Operation and Maintenance Unit (OMU) is an interface between the BSC and a
                         higher-level network management system and/or the user. The BSC can provide full-
                         scale traffic capacity even when O&M interface towards NetAct is disconnected.
                         The OMU can also be used for local operations and maintenance. The OMU receives
                         fault indications from the BSC. It can produce local alarm printouts to the user or send
                         the fault indications to NetAct.



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                         In the event of a fault, the OMU automatically activates appropriate recovery and diag-
                         nostics procedures within the BSC. Recovery can also be activated by the MCMU if the
                         OMU is lost.
                         The tasks of the OMU can be divided into four groups:
                          •     traffic control functions
                          •     maintenance functions
                          •     system configuration administration functions
                          •     system management functions
                         The OMU consists of a microcomputer similar to the call control computers. In addition,
                         the OMU contains I/O interfaces for local operation.

                                                      GROUP          EXTERNAL
                                                      SWITCH          ALARMS




                                    OMU              X.25, PCM         alarm
                                                     interface         interface

                              LAN
                                        micro-
                                        computer
                                                                                COMPACT PCI BUS
                                                    disk units and    peripheral
                                                    USB memory        device
                                                    interface         interface




                                  message bus
                                    (EMB)
                         Figure 5   Structure of the OMU
                         The alarm interface module connects internal wired alarms to the OMU from, for
                         example, the BSC cartridges, power supply and air conditioning equipment. This
                         module provides both input and output interfaces for external alarms to NetAct. The
                         OMU communicates with the call control computers of the BSC via the message bus.
                         The CPU controls the peripheral device interface module (SERO), which is used to
                         connect visual display unit and printer to the OMU. A mirrored pair of hard disk units,
                         and one USB memory stick can be controlled by the OMU. The disk units are installed
                         in the same OMU cartridge using a dedicated plug-in unit adapter.
                         The visual display unit and printer interfaces are standard asynchronous serial inter-
                         faces complying with the ITU-T Recommendation V.24.
                         The optional digital X.25 PCM-based O&M interface module (AS7) is used for the
                         network management interfaces implemented in time slots. This module provides an
                         X.25 connection via the A interface time slot.
                         The LAN interface provides an Ethernet interface according to IEEE802.3. Redundant
                         LAN interfaces from the CPU are interconnected to the duplicated LAN switch units
                         (SWUs).



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                         OSI over TCP/IP introduces TCP/IP protocol support for all traffic that comes via the
                         Ethernet interface. This removes the need for using ISO IP routers in the DCN networks
                         and therefore simplifies the IP configuration of the BSC site.


                 4.4     Ethernet-based Message Bus (EMB)
                         The Ethernet-based message bus enables significant capacity of the network element
                         while reducing its physical size. The LAN switches for the EMB are installed in the
                         MCMU. They provide a 1 Gbit/s connection to all central processors.
                         The EMB LAN switches are integrated in the network element's LAN configuration.
                         Functionalities such as centralised management of the LAN switches, connection super-
                         vision, diagnostics, and statistics can be utilised also in the EMB LAN. The LAN switches
                         in the EMB are ready to transport EMB traffic immediately after they have been powered
                         on and initialised themselves; therefore they do not need any configuring. For more
                         information, see Ethernet Based Message Bus feature description.
                         The LAN topology used in the EMB is a switched LAN: every computer unit has a point-
                         to-point connection to all the other computer units through a LAN switch. Point-to-point
                         signalling enables a very high messaging capacity as the different computer units can
                         be transmitting messages at the same time.


                 4.5     Ethernet Exchange Terminal (EET)
                         The Ethernet Exchange Terminal represents a functional unit of the physical Gigabit
                         Ethernet interface, a port in ETIP1-A plug-in unit. The ETIP1-A plug-in unit provides one
                         active and one protecting Gigabit Ethernet interface. The interfaces are implemented by
                         hot-pluggable optical or electrical SFP modules that can be ordered separately.
                         The EET units can be configured with transmission or equipment protection. Equipment-
                         protected EET units are configured so that the active and standby EET units are on dif-
                         ferent ETIP1 plug-in units (the active EET on the active ETIP1 and the standby EET on
                         the protecting ETIP1). Transmission-protected EET units are equipped so that the active
                         and standby EET units are on the same ETIP1-A plug-in units. Transmission protection
                         is the default and equipment protection optional.
                         The exchange terminal for the IP transmission unit ETIP is a functional unit representing
                         the ETIP1 plug-in unit. A maximum of 8 active interfaces can be achieved by 8 plug-in
                         units or with 16 plug-in units in equipment protection case. The Pseudo Wire capacity of
                         a ETIP1-A plug-in unit is either 126 E1s or 168 T1s.


                 4.6     Exchange Terminal (ET)
                         All 2.048 Mbit/s (in the ETSI environment) or 1.544 Mbit/s (in the ANSI environment)
                         interfaces for the MSC, the SGSN and the BTSs are connected to the Exchange Termi-
                         nals (ETs). The ETs adapt the external PCM circuits to the Group Switch and synchro-
                         nise to the system clock. Synchronisation is included in the bit frame.
                         Each ET is connected to the switching network and the Clock Unit of the Flexi BSC via
                         permanent, wired connections. The ETs are also connected to the LAPD interface via a
                         LAPD link. Two types of connectors, symmetrical and coaxial (75/120 SL), are available
                         for the ETs.
                         In the incoming direction, the ET decodes the 2.048 Mbit/s (ETSI) or 1.544 Mbit/s (ANSI)
                         signal of a circuit into data signals. The decoder decodes the line code (HDB3 in the



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                         ETSI environment, B8ZS or AMI in the ANSI environment) into binary form. At the same
                         time, the ET is synchronised to the bit rate of the incoming signal.
                         In the outgoing direction, the ET receives a binary PCM signal from the switching
                         network, generates the PCM frame structure and inserts the alarm bits. The resulting
                         signal is converted into a line code (HDB3, B8ZS or AMI) and transmitted further onto
                         the 2.048 Mbit/s (ETSI) or 1.544 Mbit/s (ANSI) circuit.
                         ET16 plug-in units contain 16 separate ETs.


                  4.7    SDH/Sonet Exchange Terminal (SET)
                         The SDH/Sonet Exchange Terminal represents a functional unit of the physical STM-
                         1/OC-3 interface, a port in the ETS2 plug-in unit. The SET units can be configured with
                         transmission or full equipment protection. Equipment-protected SET units are config-
                         ured so that the active and standby SET units are on different ETS plug-in units (the
                         active SET on the active ETS2 and the standby SET on the protecting ETS2). Transmis-
                         sion-protected SET units are equipped so that active and standby SET units are on the
                         same ETS2 plug-in units. Transmission protection is the default and equipment protec-
                         tion optional.
                         The STM-1/OC-3 functional unit STMU is a functional unit representing the ETS2 plug-
                         in unit.
                         The ETS2 plug-in unit contains up to two active and two redundant optical STM-1/OC-
                         3 interfaces. A maximum of 16 active optical interface can be achieved with 8 plug-in
                         units, if two active interfaces per unit are used or with 16 plug-in units if one active inter-
                         face of each unit is used.
                         The interfaces are implemented by hot-pluggable optical SFP modules that can be
                         ordered separately. The required number of SFP modules per each plug-in unit is 2
                         when using equipment protection and 4 when using transmission protection.
                         The ETS2 plug-in unit is responsible for framing, mapping, and multiplexing of PCMs
                         into channelised way in optical interfaces (VC12). One STM-1 interface consists of 63
                         E1s (ETSI) and one OC-3 interface consists of 84 T1s (ANSI). PCMs are handled in the
                         same way as ETs in the ET16 plug-in unit.


                  4.8    LAN Switch Units
                         The integrated LAN switch (SWU) provides access to the operator's IP network as a
                         first-level LAN switch. The preferred external equipment is multilayer (L2/L3) LAN
                         switch. Another possibility is to use a router as the external first connection. The con-
                         nection is established via the Flexi BSC connector panel.
                         The SWU collects data from the computer and packet control units and sends it further
                         to external equipment via 100 Mbit/s copper or 1Gbit/s optical (or copper) connections.
                         Redundant SWUs provide ports of 10/100Base-Tx (or 1000Base-T) interfaces with
                         RJ45 connectors or 1000Base-Sx with duplex LC connectors via the Flexi BSC connec-
                         tor panel.
                         The redundant hardware implementation of SWUs contains LAN switch (ESBxx plug-in
                         unit) pairs situated in redundant cartridges. One LAN switch pair is dedicated to collect-
                         ing data from computer units and two pairs to collecting user-plane traffic from packet
                         control units. Figure LAN topology of Flexi BSC clarifies the LAN connection principles
                         in the Flexi BSC.



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                         Figure 6     LAN topology of Flexi BSC


                 4.9     Clock and Synchronisation Unit (CLS)
                         The Clock and Synchronisation Unit (CLS) distributes timing reference signals to the
                         functional units of the Flexi BSC. It can operate plesiochronously or synchronously with
                         the timing references it receives from the digital PCM trunks.
                         Four PCM reference inputs with priority order are provided for the timing reference
                         signals. The oscillator of the CLS is normally synchronised to an external source, usually
                         an MSC, through a PCM line. Up to three additional PCM inputs are provided for redun-
                         dancy.
                         The processor chooses the highest-priority interface which is in order, for the phase lock
                         from the six synchronisation inputs. The options are the following:
                         •   A maximum of four 8 kHz synchronisation signals are received from the Exchange
                             Terminals. The interface with the Exchange Terminal is symmetrical and current-
                             controlled.
                         •   A signal n x 4 kHz (n = 2, 3,..., 4 096) is received from up to two frequency standards.
                             The interface with external frequency standard is separated by a transformer and
                             both a balanced and unbalanced synchronisation signal can be connected to it.
                         The Clock and Tone Generator (CL3TG) plug-in unit meets the requirements of the ITU-
                         T Q.500 Series Recommendations with respect to the Time Interval Error (MTIE), the
                         output jitter, the jitter and wander tolerance, and the transfer function. In the plesiochro-
                         nous operation mode, the frequency shift of the CL3TG is 5 x 10-9 within each 24-hour
                         period, if the temperature of the environment does not vary.




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                         CL3TG with external synchronised input is available by using the external synchronisa-
                         tion input connector from the CPRJ45 panel. It can be implemented either by symmet-
                         rical or asymmetrical PCM connection (120-Ohm RJ45 or 75-Ohm BNC connector).


                4.10     Accessories
                         The peripheral devices of the Flexi BSC are:
                          •     hard disk units
                          •     USB memory stick
                          •     printer
                          •     visual display unit
                          •     external alarm unit
                         Other accessories:
                          •     cable conduit for raised floor installations
                          •     cabling cabinet for PCM connections

                         Disk units
                         The BSC has a duplicated system disk unit. The software can be loaded locally to the
                         BSC by using a USB memory stick.
                         The system disk units contain the operative software as well as fallback software of the
                         BSC and BTS including the BTS hardware database. Traffic measurements are also
                         stored on the system disks. All the disk drives are connected to the OMU, which controls
                         the system disk units.

                         USB memory stick
                         The Flexi BSC deliveries contain a USB memory stick (USB2.0) with a capacity of at
                         least 4 GB. It is the recommended solution for software backups and for other additional
                         storage, because it is small, lightweight, removable, and rewritable.

                         Printer (optional)
                         A printer can be connected to the OMU. The interface complies with the ITU-T Recom-
                         mendation V.24. There are three V.24 interfaces and one V.11 interface available for the
                         printer on top of the equipment cabinet.

                         Visual display unit (optional)
                         In the BSC, a visual display unit is used as a user interface. With a VDU terminal, the
                         user can perform normal operational functions with MML commands and diagnostic
                         tests on various units.
                         Visual display units can be connected to the OMU in the same way as printers by using
                         interfaces that comply with the ITU-T Recommendation V.24. There are three V.24 inter-
                         faces and one V.11 interface available for the visual display unit on top of the equipment
                         cabinet.

                         External alarm unit (optional)
                         The optional external alarm unit (EXAU) provides a visual alarm of the fault indications
                         of the BSC. The EXAU panel is located in the telecommunications site rooms, outside
                         the network element. It is easy to install to all wall materials.




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                         Cabling cabinet for PCM connections (optional)
                         A cabling cabinet is used to the right side (seen from the front) of the Flexi BSC cabinet,
                         if there is a need for over 48 PCMs (E1/T1)
                         The cabinet can be used in equipment rooms with or without raised floor. A cabling
                         cabinet can be used for both PCM and power lines. The side cable conduit (SCC) can
                         be used for power lines if there are special requirements for separating them from the
                         PCM lines.

                         Side cable conduit (optional)
                         In equipment rooms with raised floor, the SCC can also be used with each BSCC
                         cabinet for cabling external cables. The SCC can be installed on either side of the
                         cabinet (see Figure Flexi BSC cabinet with optional cabling cabinet in section The
                         mechanical design and power supply of the Flexi BSC).




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                    5 Interfaces relating to the Flexi BSC
                          The policy of open standard interfaces has been adopted for the design of the Flexi
                          BSC. The Flexi BSC provides interfaces for the MSC/MGW, NetAct, the Base Trans-
                          ceiver Stations (BTSs), the Serving GPRS Support Node (SGSN), the Cell Broadcast
                          Centre (CBC), and towards other BSCs. There is also the Lb interface to stand-alone
                          SMLC.


                  5.1     A interface
                          The A interface between the MSC/MGW and the BSC is implemented according to the
                          GSM standards. Because the A interface is open, the Flexi BSC can be used with any
                          switching centres supporting the ETSI/3GPP standardised A interface.

                          Layered interface structure in A interface
                          The interface is defined in accordance with the Signalling System No.7 (SS7), which is
                          similar to the layered OSI protocol model. The Message Transfer Part (MTP) and the
                          Signalling Connection Control Part (SCCP) provide the signalling network functions
                          required to carry the messages of the Base Station Subsystem Application Part
                          (BSSAP) layer.
                          OSI Layer 1 represents the physical layer. It is a digital interface at 2048 kbit/s (ETSI) or
                          1544 kbit/s (ANSI), based on the ITU-T Recommendation G.703. This interface is
                          normally used as the A interface between the MSC/MGW and the BSS, providing a 64
                          kbit/s transmission rate on each channel. Additionally, wide SS7 links can be configured,
                          if the NSS supports them.
                          OSI Layer 2 is based on the MTP level 2 of SS7. The MTP level 2 provides a mechanism
                          for reliable transfer of signalling messages between the MSC/MGW and the BSS. At
                          least two signalling links are normally provided between the BSS and the MSC/MGW for
                          both capacity and reliability reasons.
                          OSI Layer 3 of the signalling network includes the SCCP and MTP level 3. Together, the
                          MTP and the SCCP functions provide both connectionless and connection-oriented
                          network services. These services are used to transfer circuit-related and non-circuit-
                          related signalling information and other types of information between the MSC/MGW
                          and the BSS.

                          Functions of the application parts of the A interface
                          The Base Station Subsystem Application Part (BSSAP) provides procedures for the A
                          interface, which are in accordance with GSM standards.

                          SIGTRAN
                          Signalling transport over IP (SIGTRAN) is a standardised way to carry SS7 signalling
                          over an Internet protocol (IP) backbone. It allows flexible capacity allocation that is not
                          tied to a fixed bandwidth such as 64 kbit/s or 2 Mbit/s.
                          SIGTRAN can be configured with a resilience functionality like SCTP multihoming
                          together with heartbeat mechanism. Usage of redundant routes and duplicated
                          backbone elements provide resilience for QoS-aware IP network. Signalling is assigned
                          to high priority class for IP routers and sufficient amount of transmission capacity must
                          be ensured for this high priority class in IP backbone.




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                         Multipoint A interface
                         Multipoint A Interface enables one BSC to be connected to several core network
                         elements (MSCs or MSC Servers).
                         Multipoint A Interface introduces the concept of a pool area. A pool area corresponds
                         roughly to an MSC/MSS service area in that it is a collection of one or more BSC service
                         areas. However, a pool area is served simultaneously by multiple MSCs/MSSs which
                         share the traffic in the area. In addition, two or more pool areas may overlap whereas
                         service areas do not.
                         Service availability is increased as other core network elements can provide service in
                         case one MSC/MSS in a pool area fails. The amount of signalling required by roaming
                         mobile stations is reduced, because the pool area is larger than the service area of one
                         MSC/MSS.


                 5.2     Ater interface
                         The Ater interface is BSS internal interface between the BSC and the TCSM. In this
                         interface, 8 kbit/s, 16 kbit/s, 32 kbit/s, or 64 kbit/s capacity Transcoding and Rate Adap-
                         tation Unit (TRAU) frame channels are multiplexed onto 64 kbit/s time slots for optimised
                         transmission.
                         TRAU is an individual block of the TCSM and converts the 64 kbit/s traffic channels
                         arriving from the MSC into channels with a 16 kbit/s or 8 kbit/s rate. It also multiplexes
                         these channels to fit in the time slots of the trunk, towards the BSC. The other direction
                         (BSC to MSC) works according to the same principle (in reverse).
                         In some cases, the user may choose to implement the Multimedia Gateway (MGW) to
                         perform transcoding functionality instead of the TCSM. In such cases, the BSC commu-
                         nicates with the MGW using Ater interface. There is no O&M link between the BSC and
                         MSC, so the BSC has no control over the MGW. Ater can be transported over satellite
                         connection. For more information, see Multimedia Gateway (MGW) Functional Descrip-
                         tion in Multimedia Gateway product documentation.


                 5.3     Abis interface
                         The Abis interface telecommunication part between the BSC and the BTS is imple-
                         mented according to recommendations 3GPP 48.051, 48.052, 48.054. The Abis O&M
                         part is Nokia Siemens Networks proprietary and supports additional functionalities such
                         as the Site Test Monitoring unit, alarm consistency, remote transmission equipment
                         management, and BTS database management.

                         Layered interface structure in Abis interface
                         The interface between the Flexi BSC and the BTS is defined in accordance with the OSI
                         protocol model.
                         Layer 1 represents the physical layer. It is a digital interface at 2048 kbit/s (ETSI) or 1544
                         kbit/s (ANSI), based on the ITU-T Recommendation G.703. Submultiplexing is used on
                         the Abis interface as a standard solution, because each speech channel reserves only
                         16 kbit/s (FR channel or DR channel) or 8 kbit/s (HR channel) in the ETSI environment,
                         16 kbit/s in the ANSI environment.
                         Layer 2 is based on the LAPD protocol. The LAPD protocol is implemented to provide
                         the data link functions required to carry layer 3 messages. The Flexi BSC can handle
                         LAPD signalling links with the bit rates of 16 kbit/s, 32 kbit/s, and 64 kbit/s.


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                          A 32 kbit/s signalling link is needed for more than 100 000 pages per hour or more than
                          18 radio channels because of increased measurement reporting. A 64 kbit/s signalling
                          link is required for more than 200 000 pages per hour.
                          There are different transport options for the Abis interface. Abis can be transported over
                          satellite, and also auxiliary equipment for transporting Abis over IP can be used.
                          ISDN connections can also be used as the bearer for the Abis interface. The interface
                          between the BSC and the ISDN network is based on ITU-T's Digital Subscriber Signal-
                          ling System No. 1 (DSS1) Network layer Q.931 (03/93) and Data link layer Q.921. The
                          connection between the BSC and the BTS has to be unrestricted digital 2 x 64 kbit/s.

                          Functions of the telecom application parts
                          The following procedures are provided for the Abis interface:
                           •   radio link management procedures
                           •   dedicated channel management procedures
                           •   common channel management procedures
                           •   TRX management procedures

                          Functions of the O&M application parts on Abis Interface
                          The application parts of the Abis interface contain the following O&M functions:
                           •   fault management
                           •   fault reporting
                           •   BTS recovery
                           •   BTS test handling
                           •   configuration management
                           •   software configuration management
                           •   radio network management including extensions and parameters
                           •   performance management


                  5.4     Gb interface
                          The Gb interface between the BSC (PCU) and the Serving GPRS Support Node (SGSN)
                          is implemented according to 08.16 and 08.18 of GSM Recommendations. It is an open
                          interface connecting the BSS and GPRS core network.

                          Layered interface structure in Gb interface
                          The interface between the SGSN and the Base Station Subsystem (BSS) is defined in
                          accordance with the OSI protocol model. The protocol stack comprises BSSGP,
                          Network Service, and L1 layers. The Network Service layer further divides into two: Sub-
                          network Service and Network Service Control. The Sub-network Service uses Internet
                          or Frame Relay-based protocol.

                          Gb over IP functionality
                          The Gb over IP interface's subnetwork is constructed with a UDP/IP stack. When the Gb
                          interface is based on IP, an NS-VC is a pair of UDP/IP addresses: one UDP/IP address
                          in the BSS and one UDP/IP address in the SGSN. That is, an NS-VC is composed of IP
                          endpoint addresses, one IP endpoint address in BSS and the other IP endpoint address
                          in the SGSN.




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                         Sub-network Service Layer, Frame Relay
                         The physical layer is implemented as one or several PCM lines with G.703 interface. On
                         top of the physical layer in the Gb interface, direct point-to-point Frame Relay connec-
                         tions or intermediate Frame Relay network can be used.

                             GMM/SM                                                 GMM/SM
                              LLC                                                      LLC
                                                          Relay
                              RLC                   RLC       BSSGP                  BSSGP

                                                             Network                 Network
                              MAC                   MAC
                                                             Service                 Service
                             GSM RF               GSM RF        L1bis                 L1bis

                              MS         Um               BSS              Gb        SGSN
                         Figure 7     The protocol stack on the Gb interface
                         Network Service Control is responsible for virtual circuit management and GPRS-
                         specific addressing, which maps cells to virtual connections. BSSGP is a layer 3
                         protocol for delivering data packets and associated control information.

                         Multipoint Gb Interface
                         With Multipoint Gb Interface one packet control unit (PCU) or PCU pool can be con-
                         nected to several SGSNs. Multipoint Gb Interface provides the system with enhanced
                         resilience and with the possibility to equalise traffic load of the different SGSNs.
                         The maximum number of SGSNs (NSE) that can be connected to a PCU or PCU pool
                         is eight. Multipoint Gb Interface is only implemented over IP.


                 5.5     Lb interface
                         The Lb interface is used to connect a stand-alone SMLC to a BSC. Furthermore, the Lb
                         interface contains a controlling functionality for the allocation of location requests
                         between Position Based Services in BSC and the external stand-alone SMLC.
                         The Lb interface in the BSC is application software. Its optionality is controlled with the
                         2nd class parameter LB_USAGE.
                         For more details, see Location Services in BSC and BSC-SMLC Interface Specification.


                 5.6     O&M interface
                         Q3 interface
                         Q3 interface is the interface between NetAct and the BSC. The implementation of this
                         interface is based on the O&M framework of the ITU-T and the International Standards
                         Organization (ISO). The Flexi BSC provides the following types of Q3 interfaces,
                         depending on the network operator's requirements:
                         •    a digital X.25 connection via a semipermanent time slot on the A interface
                         •    a LAN interface, connected via the LAN Switch
                         •    OSI over TCP/IP (for more information, see Operation and Maintenance Unit (OMU)




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                          The X.25 software in the Flexi BSC can be configured to function as the data terminal
                          equipment (DTE) or data communications equipment (DCE). For PCM time slot-based
                          connection, the physical interface is G.703.
                          For the LAN interface, the physical interface supported is Ethernet IEEE802.3. OSI
                          Stack in Q3 implementation requires tunnelling to TCP/IP network in L3 level if OSI over
                          TCP/IP feature is not in use. File-based O&M traffic is supported with pure TCP/IP
                          protocol without tunnelling.
                          The connections can be made redundant as an option.
                          The upper layers of the OSI model, above the network layer, are implemented in the
                          Flexi BSC. The upper layers use the X.25 protocol or LAN as a sub-network. The follow-
                          ing protocols are implemented:
                           •   transport protocol, X.224 (TP0, TP2, and TP4)
                           •   session protocol, X.225
                           •   presentation protocol, X.226
                           •   association control service element (ACSE), X.227
                           •   remote operations service element (ROSE), X.229
                           •   file transfer, access and management (FTAM), ISO 8571
                           •   common management information service element (CMISE), ISO 9596
                          The FTAM protocol, using ACSE, is used for transferring files between the Flexi BSC
                          and NetAct. The CMISE protocol, using the ACSE and the ROSE, is used for network
                          management.

                          File based plan provisioning
                          File-based plan provisioning enables the operator to download radio network configura-
                          tion plans from NetAct to the BSC by using the file transfer protocol (FTP). If FTP is not
                          available, file transfer, access and management (FTAM) can be used.
                          Since file transfer is used, the operation and maintenance data traffic going via the Q3
                          interface is reduced.

                          Q1 interface
                          Q1 interface is used for managing Nokia Siemens Networks transmission equipment.
                          The Q1 service channels are asynchronous serial communication channels.

                          MML interface
                          MML commands are given through an MML terminal. The terminal can be either a local
                          terminal or a virtual terminal. The local terminal is connected to the BSC via a RS232C
                          connection and the virtual terminal is connected via a VT connection, either Telnet, ISO-
                          VT or PAD. Both local and remote sessions can be set using either one of these termi-
                          nals.
                          The security of the MML interface can be improved by utilising Secure Shell protocol
                          (SSH) in remote MML sessions.


                  5.7     CBC interface (BSC-CBC)
                          The BSC Cell Broadcast Centre Interface provides an interconnection between the BSC
                          and Cell Broadcast Centre (CBC). The implementation is according to GSM Specifica-
                          tion 03.41 and permits open interconnection between the BSC and CBC.




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                         In the BSC, the CBC connection is made through the OMU using the current Q3 inter-
                         face with digital X.25 interface plug-in unit AS7 or with Ethernet connection directly from
                         the CPU unit. The CBC connection shares the same transport media and functionalities
                         (such as OSI over TCP/IP) as Q3, and only a new logical connection is introduced. If a
                         non-redundant Q3 connection is used, more transmit capacity can be gained by using a
                         dedicated plug-in unit for the CBC.

                         Network interface
                         The interface between the BSC and the CBC is similar to the interface between the BSC
                         and NetAct.

                         Interface with OSI layer 4
                         The protocol used between the BSC and the CBC is the XTI-interface. The XTI-interface
                         uses the services of the OSI Transport Layer. The CBC Application can be developed
                         using the XTI Application Programming Interface (X/Open Transport Interface) to inter-
                         connect the application to the OSI Transport Layer.




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                  6 The Flexi BSC software
                         System software
                         In the Flexi BSC, each computer unit has common system software. The system
                         software provides a standard, easy-to-use operating environment for the application
                         software. The uniform operating environment facilitates the development and mainte-
                         nance of the application software and helps the user understand the operation of the
                         software.

                         Platform architecture
                         The Flexi BSC is based on a fault-tolerant computing platform, which constitutes a base
                         for the switching and offers a wide range of cellular and fixed network applications. The
                         operating system is a platform for other system-level software and all the application
                         software.
                         The most significant functions of the operating system are:
                         •   scheduling the processor time
                         •   synchronisation of processes
                         •   exchange of messages between processes located in one computer or in separate
                             computers
                         •   time supervision
                         •   creation and deletion of processes
                         •   memory allocation and protection
                         •   observation of message traffic and processor load
                         •   initialisation of the operating system

                                             Base Station Controller
                                                  Application

                                          Common Switching Platform


                                       Fault Tolerant Computing Platform


                                    Modular and Scalable Hardware Platform

                         Figure 8      The Flexi BSC conceptual model

                         Layers
                         A layer is an up-level hierarchy level of the system platform. It divides the monolithic
                         platform into smaller modules. Layers can be developed relatively independently.

                         Databases
                         The base systems contain different types of data. In the case of the Flexi BSC the
                         database includes, for example, reduced routing and cellular data. The database also
                         includes data needed for the control and operation of the Flexi BSC.




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                                                                                                        Issue 1-3
Product description of Flexi BSC                                                         The Flexi BSC software



                         In this context, the files are RAM memory arrays. Some files are loaded from a disk unit
                         after restarting the control computer. Other files are updated on the disk when the
                         contents are changed.

                         Description and programming languages
                         In design and documentation of the Flexi BSC software, readability and visual quality of
                         the programs are enhanced by using special description languages in addition to the
                         actual programming language. These description languages also facilitate effective
                         software design and allow the use of automatic tools for development and testing.




DN70577137                                       Id:0900d805805912f0                                           39
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Configurations, capacity and performance of the Flexi                              Product description of Flexi BSC
BSC



                   7 Configurations, capacity and performance of
                     the Flexi BSC

                 7.1     Configurations
                         The Flexi BSC is available in a compact one-cabinet configuration for up to 3000 TRX
                         configurations. It can be equipped flexibly with a number of packet control units (PCUs)
                         and trunk circuits according to customer needs.

                          Flexi BSC
                          TRXs *              1...500   ...1000   ...1500   ...2000     ...2500   ...3000
                          BTS sectors         500       1000      1500      2000        2500      3000
                          (BTS)
                          BTS sites           500       1000      1500      2000        2500      3000
                          (BCF)
                          Active BCSUs        1         2         3         4           5         6
                          TCH for             5120      10420     15360     20480       25600     30720
                          GPRS/EDGE
                          **
                          GigE Ethernet       12        12        12        12          12        12
                          interfaces ***
                          STM-1/OC-3          16        16        16        16          16        16
                          interfaces ***
                          E1/T1 inter-        800       800       800       800         800       800
                          faces ****

                         Table 2           Flexi BSC maximum capacity steps in S14 hardware environment

                         * Software is scalable in 1 TRX steps with licence keys.
                         ** Abis 16 kbit/s channels for GPRS/EDGE.
                         *** Active interfaces. Doubled for redundancy: 12 + 12 or 16 + 16.
                         **** Above 48 requires a cabling cabinet.
                         For a description of the configurations, see Engineering for Flexi BSC.


                 7.2     Traffic handling capacity
                         With reference to the nominal model below, the maximum processing capacity of a Flexi
                         BSC is 18000 Erl, giving full support to 3000 TRXs.
                         The BHCA value varies heavily depending on the call mix. With the nominal call mix the
                         call processing capacity is 531 000 BHCA and with a call mix having a very short call
                         mean holding time and other supporting characteristics over 3 300 000 BHCA can be
                         reached.




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                                                                                                           Issue 1-3
Product description of Flexi BSC                               Configurations, capacity and performance of the Flexi
                                                                                                               BSC




                          Reference model of call traffic (call mix and
                          parameters):
                          Mean holding time                                   120 s
                          Proportion of MS originated calls                   70%
                          Proportion of MS terminated calls                   30%
                          Proportion of handovers                             1.5 per call
                          Proportion of location updates                      2 per call
                          Proportion of IMSI detaches                         0.1 per call
                          For terminating call attempts, the no-answer call   63%
                          attempts to paging requests
                          SMS call rate                                       1 req./subs./1 hour

                         Table 3       Circuit switched processing capacity of the Flexi BSC with nominal call mix

                         The above-mentioned traffic processing capacity of the BSC can be achieved with the
                         latest Flexi BSC hardware environment in a maximum capacity configuration. Some
                         new functionalities and network characteristics might, however, have an influence on
                         the capacity of the Flexi BSC. The maximum traffic processing capacity (18000 Erl) of
                         the Flexi BSC supports 3000 full rate TRXs or 1500 half rate TRXs. Connectivity for
                         3000 AMR HR TRXs is available as an optional Soft Channel Capacity functionality.


                 7.3     Connectivity
                         Different types of connections are provided with Flexi BSC as follows:
                         •   16 optical SDH/Sonet interfaces with fibre redundance (16 active and 16 redundant
                             interfaces)
                         •   800 E1/T1 connections used on external interfaces with ET units
                         •   12 Gigabit Ethernet connections are provided for the IP interfaces (1000Base-SX
                             optical or 10/100/1000Base-T/TX)
                         All needed interfaces can be connected with IP/Ethernet connections: user traffic from
                         the Abis and Ater interfaces with E1/T1 channelized in IP interface with ETIP1 plug-in
                         units and user traffic from the Gb interface with native-IP interfaces. All IP interfaces
                         support Gigabit Ethernet optionally with electrical 1000BaseT/TX or optical 1000Base-
                         SX Ethernet connections.


                 7.4     Signalling capacity
                         The GSM network has been originally specified (GSM 08.08) and designed to use 64
                         kbit/s CCS7 links in the A-interface. Due to various reasons, the CCS7 links can be con-
                         gested in the A-interface. The situation can be improved with higher capacity CCS7 links
                         on the A-interface between the BSC and MSC/MGW:
                         •   a maximum of 16 SS7 signalling links. Optionally wider 128, 256, 512 kbit/s or
                             2Mbit/s signalling links can be configured instead of the standard 64 kbit/s links.




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Configurations, capacity and performance of the Flexi                              Product description of Flexi BSC
BSC




                          Flexi
                          BSC
                          TRXs         1...500     ...1000   ...1500     ...2000    ...2500     ...3000
                          Maximum
                          number of
                          SS7 links
                          64 kbit/s    8           16        16          16         16          16
                          128 kbit/s   4           8         12          16         16          16
                          256 kbit/s   2           4         6           8          10          12
                          512 kbit/s   2           4         6           8          10          12
                          1024         1           2         3           4          5           6
                          kbit/s
                          2 Mbit/s     1           2         3           4          5           6

                         Table 4        Signalling capacity of the Flexi BSC

                         There shall always be configured at least two links in different BCSUs. The GSM stan-
                         dards limit the number of SS7 links to a maximum of 16.
                         SS7 signalling over IP is available as an optional SIGTRAN functionality. SIGTRAN
                         provides extended capacity compared to traditional SS7 links. There must always be
                         configured at least two links in different BCSUs.
                         LAPD signalling links can be configured to 16, 32 or 64 kbit/s speeds. A 32 kbit/s signal-
                         ling link is needed for more than 100 000 pages per hour or more than 18 radio channels
                         because of increased measurement reporting. A 64 kbit/s signalling link is required for
                         more than 200 000 pages per hour. The overload of the signalling link can be monitored
                         using the telecom LAPD link supervision with a possibility to set an alarm in an overload
                         situation. For more information, see BSS (BSC) Traffic Handling, Overload Protection
                         and Network Planning.
                         Introduction of HR enables TRX configurations of more than 18 radio channels, which
                         leads to increased load in measurement reporting. Because of this, the capacity of a 16
                         kbit/s signalling link is not sufficient in all cases. Therefore it is recommended that also
                         with HR the TRX configurations should be restricted to the maximum of 18 radio
                         channels if 16 kbit/s signalling links are used.
                         With TRX configurations of more than 18 radio channels, a 32 kbit/s LAPD link is highly
                         recommended for supporting the telecom signalling that half rate requires. The overload
                         of the signalling link can be monitored by the telecom LAPD link supervision with a pos-
                         sibility to set an alarm in an overload situation.


                 7.5     Packet handling capacity
                         In the Flexi BSC the packet handling capacity is provided by Packet Control Units
                         (PCUs):
                          •   packet handling capacity and connectivity per each PCU2-E unit is 384 BTSs, 1024
                              TRXs, and 1024 traffic channels (16 kbit/s, Abis) for GPRS/EDGE use
                          •   PCU2 software is scalable in 256 channel (16 kbit/s, Abis) steps with licence keys
                          •   maximum capacity of Flexi BSC with full configuration (30 PCU2-E units) is 1024 x
                              30 = 30720 traffic channels (16 kbit/s) per Flexi BSC for GPRS/EDGE use



42                                         Id:0900d8058080db1b                                            DN70577137
                                                                                                             Issue 1-3
Product description of Flexi BSC                        Configurations, capacity and performance of the Flexi
                                                                                                        BSC


                         The packet handling capacity mentioned above can be achieved with the new hardware
                         environment. However, some functionalities may have extra requirements for the
                         hardware or an influence on the packet handling capacity of the BSC.




DN70577137                                     Id:0900d8058080db1b                                        43
Issue 1-3
Mechanical design and power supply of the Flexi BSC                              Product description of Flexi BSC




                   8 Mechanical design and power supply of the
                     Flexi BSC
                        The information in this section pertains to Flexi BSC (new delivery only). Additional infor-
                        mation can be found in Engineering for Flexi BSC.
                        The mechanical structure of the Flexi BSC is hierarchical, based on plug-in units, car-
                        tridges and cabinet. The dimensions of different units and cartridges are in accordance
                        with the recommendations of the IEC (International Electrotechnical Commission). The
                        Flexi BSC is easy to install, operate, and maintain. Special attention has been paid to
                        thermal resistance and immunity to various types of interference.

                        Plug-in units
                        The Flexi BSC is constructed by using a total of 20 plug-in unit types, including the
                        DC/DC converters. The size of these plug-in units is 233 mm x 220 mm.
                        The printed circuit boards (PCBs) of plug-in units are multilayered. They are covered
                        with a protective coating that makes them easy to handle and protects the foils from
                        scratches. The connectors are of the Euro-connector, and 2 mm Hard Metric type.

                        ETP
                        ETP plug-in unit provides DX200 based network elements with Packet Abis over
                        IP/Ethernet interface (type E) and Packet Abis over TDM interface (type T) towards IP
                        BTSs. The plug-in unit is responsible for IP processing, TRAU frame handling, and TDM
                        conversion for interfacing with the Flexi BSC switching network (GSW). ETP has the
                        ability to convert up to 8000 CS channels or up to 128 Mbit/s PS traffic from Ater/TRAU
                        to Packet Abis packets and vice versa. For the Packet Abis over IP/Ethernet function,
                        the ETP unit provides two 1 Gbit/s Ethernet ports towards BTSs for connection to active
                        and redundant site switch. For the Packet Abis over TDM function, the ETP unit provides
                        two hotlink interfaces that are directly linked to an ETS2 (half) of the Flexi BSC to estab-
                        lish connection with the BTSs. The ETP plug-in unit implements the 1+1 card redun-
                        dancy protection scheme. ETP can be installed in GTx /ETCx cartridge types, and the
                        unit is compatible with the ET16 slot. ETP supports Synchronous Ethernet in the master
                        mode.
                        ETPE and ETPT functional units include the ETP plug-in unit.

                        ETP-A
                        The ETP-A plug-in unit provides the DX200 based network elements with A over IP
                        interface towards the MGW. It is responsible for IP processing for interfacing with the
                        DX200 switching network elements such as GSW and SBMUX. In Flexi BSC, the ETP-
                        A plug-in unit can handle up to 8000 bi-directional A over IP connections. Internal con-
                        nectivity with the PCM switching is realized through two hotlink interfaces or thirty-two 8
                        Mbit/s PCM links (with TR3xs in TSCM3i). The path for control plane packets is through
                        the backplane Ethernet. The ETP-A plug-in unit provides two 1Gbit/s Ethernet ports
                        towards MGW for connection to the active and redundant site switch.
                        ETPA and ETPC functional units include the ETP-A plug-in unit. ETPC is located in the
                        TCSM3i. ETPC implements the 1+1 card redundancy protection scheme, and ETPA has
                        load sharing pool protection.
                        ETP-A can be installed in TC1C-A, TC2C-A, and GTx cartridge types, and the unit is
                        compatible with the ET16 slot.




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                                                                                                        Issue 1-3
Product description of Flexi BSC                           Mechanical design and power supply of the Flexi BSC



                         CP1D-A
                         The Central Processor of 1st Dual core generation (CP1D-A) is implemented using a
                         Penryn SP9300 processor with 1.6 GHz to 2.26 GHz frequency. It acts as the central
                         processing resource in the DX200 system.This plug-in unit provides the hardware?
                         required by the DMX and Linux operating systems and application software such as the?
                         boot memory, DDR2 SDRAM, real time clock, interrupt handling, process timing, and?
                         V.24/V.28 (RS232) based serial interfaces for service terminals. CP1D-A supports?
                         standard external interfaces such as three x4 PCIe interfaces, USB on the front panel,?
                         and four 10 Base-T /100 Base-TX / 1000 Base-T Ethernet on the back plane. The unit?
                         is also connected to the back plane CompactPCI bus. However, it can be used without?
                         the CompactPCI connection. This plug-in unit operates at forced cooling in the M98F2?
                         and M98A environments.The main features of the CP1D-A plug-in unit are:
                         •   Processor core speed of maximum 2.26 GHz
                         •   Memory size 8 GB (with 2 GB dims)
                         •   PCI 33/32, PCI Express x4
                         •   ETH 4x1000 Mbit/s
                         •   One USB 2.0 on the front panel
                         •   1 GB USB NAND flash module
                         •   CPCI 33 Mhz, 64 bits

                         Cartridges
                         Most of the functional units consist of one cartridge that contains a selection of PCBs. A
                         fixed cabinet position has been assigned to the cartridge of each functional unit.
                         The cartridges of the Flexi BSC are of the following types:
                         •   1/3 shelf cartridge (width: 200 mm)
                              • CC3C-B for BCSU 0
                              • DC3C-B for MCMUs
                              • CC3C-A for OMU
                         •   1/1 shelf cartridge (width: 800 mm)
                              • SGC1C-A for combined GSW2KB, GTIC, ETC and CLS
                              • BC1C-B for combined BCSUs and LANU
                         All cartridges have a height of 270 mm. Additionally, there is a marking rail at the upper
                         front edge of each cartridge, so the total height of the front of a cartridge is 300 mm.




DN70577137                                        Id:0900d80580721216                                           45
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Mechanical design and power supply of the Flexi BSC                                                                                                                                      Product description of Flexi BSC




                                                      Figure 9                                                                CC3C-B




                                                      Figure 10                                                               BC1C-B

                       GSW2KB-A 0 or                                                                                                                                                                                                         CLS 0 or
                       GSW2KB-A 1                                                                                              GTIC 0 or GTIC 1                         ETC 0 or ETC 2                         ETC 1 or ETC 3                CLS 1
                                                                       SW256B 5
                SW256B 0



                                                 SW256B 3
                                                            SW256B 4


                                                                                  SW256B 6
                                                                                             SW256B 7
                                      SW256B 2
                           SW256B 1




                                                                                                                                                                                                                                                      CL3TG
                                                                                                        Support mechanic 4T




                                                                                                                                                  Support mechanic 4T




                                                                                                                                                                                         Support mechanic 4T




                                                                                                                                                                                                                                Support mechanic 5T
                                                                                                                              ET16
                                                                                                                              ET16
                                                                                                                              ET16
                                                                                                                              ET16
                                                                                                                              ET16
                                                                                                                              ET16
                                                                                                                              ET16
                                                                                                                              ET16

                                                                                                                                                                        ET16
                                                                                                                                                                        ET16
                                                                                                                                                                        ET16
                                                                                                                                                                        ET16
                                                                                                                                                                        ET16
                                                                                                                                                                        ET16
                                                                                                                                                                        ET16
                                                                                                                                                                        ET16

                                                                                                                                                                                                               ET16
                                                                                                                                                                                                               ET16
                                                                                                                                                                                                               ET16
                                                                                                                                                                                                               ET16
                                                                                                                                                                                                               ET16
                                                                                                                                                                                                               ET16
                                                                                                                                                                                                               ET16
                                                                                                                                                                                                               ET16
                                                                                                                                                                                                               ET16




                   1          2          3          4          5          6          7          8        9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39
                DN70590345

                                                      Figure 11                                                               SGC1C-A




46                                                                                                                            Id:0900d80580721216                                                                           DN70577137
                                                                                                                                                                                                                               Issue 1-3
Product description of Flexi BSC                          Mechanical design and power supply of the Flexi BSC




                         Figure 12    DC3C-B




                         Figure 13    CC3C-A

                         Cabinet
                         The Flexi BSC cabinet is based on an indoor, ventilated cabinet variant IC209-A. The
                         frame of the cabinet consists of side rails, made of plated steel sheet, that support an
                         upper shelf and a lower shelf with adjustable legs.
                         The closed space in the cabinet configuration is surrounded by the side plates, the
                         doors, the upper cable conduit, and the baseboard. The doors are perforated to facilitate
                         cooling.
                         The height, width and depth of a standard Flexi BSC cabinet are (with cabling and doors)
                         is 2000 mm x 900 mm x 600 mm.




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Issue 1-3
Mechanical design and power supply of the Flexi BSC                                                               Product description of Flexi BSC



                        If more than one Flexi BSC is located on the same site, the cabinets can be connected
                        to each other. Each Flexi BSC constitutes a closed EMC-shielded space.
                        If there is a raised floor in the equipment room, the incoming and outgoing cables can
                        be placed under the floor and connected to the equipment racks either through a vertical
                        cable conduit SCC, which can be placed at either side of the Flexi BSC cabinet, or
                        through the cabling cabinet. The width of the side cable conduit is 75 mm and the width
                        of the cabling cabinet is 300 mm. The power supply cables must also be brought in
                        through the side cable conduit or through the cabling cabinet. The side cable conduit
                        does not belong to the EMC protection, but the cabling cabinet does.

                         BSCC
                                                                                                  CPGO/
                                  CPETx                        CPRJ45-A                                       CPETx
                                                                                                  CPETx

                                        PDFU 0                                           PDFU 1
                                          PDFU-B                                         PDFU-B
                          0
                              0                                             6



                                                                                                      CLS 0
                                  GSW2KB-A     GTIC                             ETC           ETC
                                     0          0                                0             1
                                                                                                              CPETx
                          1
                                  0           3                             6             9
                                                                                                      CLS 1




                                  GSW2KB-A     GTIC                             ETC           ETC                     0
                                     1          1                                2             3

                          2                                                                                   CPETx
                              0            3                                6             9
                                                                                                                      1
                                        FTRB 0                                           FTRB 1

                                                                                                              CPETx
                                                                                MCMU 1
                                                               MCMU 0




                                      BCSU                                                                            2
                                                                                              OMU
                                        0

                          3                                                                                   CPETx
                                  0                     4                   6             8
                                                                                                                      3
                                                      LANU 0




                                      BCSU                                      BCSU          BCSU
                                        1                                         3             5
                          4
                                  0           4                         6                  9
                                        FTRB 2                                           FTRB 3               CPETx
                                                      LANU 1




                                      BCSU                                      BCSU          BCSU
                                        2                                         4             6
                          5                                                                                           4
                                  0               4                     6                 9
                         DN70590321                                                           FRONT VIEW
                        Figure 14            Flexi BSC cabinet with optional cabling cabinet

                        Cabling
                        Standard-length cables are used for the internal cabling of the Flexi BSC. The internal
                        cables of the cabinet are installed at the factory. Within a cabinet, the cabling is installed
                        from each cartridge to the next one.



48                                           Id:0900d80580721216                                                                    DN70577137
                                                                                                                                       Issue 1-3
Product description of Flexi BSC                            Mechanical design and power supply of the Flexi BSC



                         The PCM trunks of the Flexi BSC enter the exchange room via a cabling cabinet or
                         cabling panels on top of the cabinet. Other station cables (external alarm, external syn-
                         chronisation, uplink LAN, and external peripheral cables) enter the cabinet via a connec-
                         tor panel on top of the cabinet. The power supply cables are terminated to the power
                         supply connector on top of the cabinet.

                         Structure of the power supply
                         Reliability, easy installation, and easy maintenance have been the main objectives in the
                         design of the power supply system of the Flexi BSC.
                         All the voltages required for the Flexi BSC are generated from the DC voltage by high
                         frequency transformers using chopper technique.
                         The input voltage is between 41.5 V and 72 V. Because the range is wide, the main
                         battery voltage of the Flexi BSC can be 48 V or 60 V. In both cases, it is possible to use
                         a direct floating battery.

                         Power consumption
                         Typical operating power consumption of the 4200 TRX Flexi BSC is below 1 W per TRX
                         and, besides the TRX capacity, depends on:

                          Capacity
                          steps (TRX)      500       1000     1500     2000     2500      3000
                          Base Configu-    1700 W    1800 W   1900 W 2000 W     2100 W    2200 W
                          ration
                          Full PS          2050 W    2325 W   2600 W 2875 W     3150 W    3425 W
                          Capacity

                         Table 5        Breakdown of the typical power consumption (in Watts) for Flexi BSC

                         Additional typical power consumption coming from packet control and external interface
                         units:
                         PCU               ~25 W per unit
                         ETIP1-A           ~21 W per unit
                         ET16              ~12 W per unit
                         ETS2              ~26 W per unit
                         ETP               ~120 W per unit (active, 50 W at idle for equipment protection)
                         ETP-A             ~83 W per unit
                         Site power distribution is recommended to be dimensioned as defined in Installation Site
                         Requirements for Base Station Controller and Transcoder.

                         Cooling of cabinets
                         The Flexi BSC includes forced cooling system to ensure optimum ambient temperature
                         for its functional units. Forced cooling is more effective than natural convection cooling
                         and allows higher heat dissipation.
                         The Flexi BSC cabinet is equipped with four Fan Trays (FTRB), each of which contains
                         five fans. Each FTRB is powered by a PFDU. The fans are n+1/L redundant, meaning
                         that if one of them fails, the remaining 19 fans automatically start to operate at maximum
                         speed, which is enough to provide sufficient cooling until a maintenance activity takes
                         place.



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Mechanical design and power supply of the Flexi BSC                            Product description of Flexi BSC



                        To make the forced cooling efficient enough, the empty cartridges have to be equipped
                        with cover plates. Correspondingly, in case there are empty slots in the cartridges, they
                        have to be covered with shim plates.




50                                    Id:0900d80580721216                                          DN70577137
                                                                                                      Issue 1-3
Product description of Flexi BSC                                                         Reliability of the Flexi BSC




                   9 Reliability of the Flexi BSC
                         The simplicity and the fast speed of the maintenance procedures are the prerequisites
                         for the availability of the Flexi BSC. Maintenance is improved by the modular structure
                         of the equipment, automatic fault detection procedures, and by the elimination of
                         downtime by using a hot standby unit in the event of a failure.

                         Fault management
                         The DX 200 system is a loosely coupled, fault-tolerant distributed system with some
                         centralised functions. The DX 200 system maintenance functions conform to the idea of
                         loose coupling of autonomous control computers. This means, for example, that state
                         control mechanisms do not depend on any centralised hardware, control computers
                         control their own software and are able to restart on their own by asking for the appro-
                         priate loading services, and an individual program block failure or an individual hardware
                         failure has a minor effect on the overall operation of the whole system. The fault situation
                         is hardly ever so bad or complex that the whole system has to be restarted.
                         In most cases, a restart in a program block, preprocessor, or a single control computer
                         is enough. The control computer states are controlled from a centralised point which can
                         be dynamically reallocated from the OMU to a pair of control computers when, for
                         example, an OMU with no redundancy fails. This means that this centralised function
                         has 3N redundancy. Only the control computers are autonomous as described above.
                         The preprocessors run under the control of a master computer.

                         Overload protection
                         The BSC overload protection handles excessive traffic or signalling load by limiting the
                         load level of the BSC's main CPUs and preprocessors, and also provides information of
                         excessive load, so that preventive actions can be taken. The main cause of this kind of
                         load might be related to special end-user behaviour and is mainly related to radio
                         network planning and dimensioning according to the required level.
                         For more information on BSS overload protection, see BSS overload protection in BSS
                         (BSC) Traffic Handling Capacity, Network Planning and Overload Protection.

                         Redundancy principles
                         When the Flexi BSC was designed, great attention was paid to the reliability of opera-
                         tion. The following redundancy methods are used for various units:
                         •   2N principle for duplicated units, including an active unit and a spare unit.
                         •   N+1 or N+m redundancy principle for provision of one or more units, active or
                             reserve, in addition to what is required by correct dimensioning.
                         All the critical parts of the switching system have an appropriate type of redundancy. The
                         Exchange Terminals of the PCM trunk circuits and the terrestrial channels are not criti-
                         cal, however, because the failure of a single terminal does not prevent service. There
                         are usually several PCM circuits available in each direction. Thus, the Exchange Termi-
                         nals are without redundancy.
                         The BSC's connection to the IP network is implemented by providing a redundant local
                         area network (LAN) connection. It is implemented with hardware and software that
                         enable transparent use of redundant Ethernet interfaces so that the CPU or PCU unit
                         may be connected to different switches through a pair of Ethernet interfaces working as
                         if there was only one connection. By implementing a secondary route, a single point
                         failure of the LAN connection can be avoided.



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Reliability of the Flexi BSC                                                        Product description of Flexi BSC



                           Power supply and the distribution of the basic timing signal are arranged so that the units
                           backing each other up get their supply from different or redundant DC/DC converters
                           and their basic timing signals from different distribution lines.

                           System availability
                           The Flexi BSC is designed to meet the availability requirements of the ITU-T. The fol-
                           lowing design objectives have been adopted to ensure that the unavailability of the BSC
                           is very low.

                           Flexi BSC System                              Mean Down
                           Configuration           Availability          Time              MTBFNE
                           Minimum configura-      0.999 9997            0.14 min/ year    3 800 000 h
                           tion (500 TRXs)
                           Medium configuration    0.999 9998            0.10 min/ year    5 400 000 h
                           (1500 TRXs)
                           Maximum configura-      0.999 9998            0.10 min/ year    5 400 000 h
                           tion (3000 TRXs)

                           Table 6      Flexi BSC system hardware availability

                           Note that the values above are predictions and cannot be used as guaranteed values in
                           contracts.
                           Simplicity and speed of the maintenance procedures are the prerequisites for the avail-
                           ability of the Flexi BSC. The maintenance is improved by the modular structure of the
                           equipment, automatic fault detection procedures, and elimination of downtime by using
                           a hot standby unit in the event of a failure. The following general design objectives have
                           been established for the maintenance of the Flexi BSC:
                           •   mean active repair time less than half an hour
                           •   fault localisation with the accuracy of a plug-in unit for 70% of the faults
                           •   fault localisation with the accuracy of four plug-in units for 95% of the faults
                           For more detailed information see Flexi BSC Availability Performance Prediction.

                           Planned downtime
                           The Flexi BSC is based on the DX 200 computing platform that makes it possible to
                           minimise the downtime caused by, for example, software upgrades. The Flexi BSC
                           software can be downloaded without any disturbance to user data traffic, but the activa-
                           tion of new software requires computer unit restarts. Thanks to the trial configuration,
                           the possible downtime can be minimised. The trial configuration means that first the new
                           software is loaded into spare units, then a unit switchover is performed, that is, the spare
                           units are switched into active state and vice versa, and finally the new software is loaded
                           into the primary units.




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Product description of Flexi BSC                                           The Flexi BSC operating environment




                 10 The Flexi BSC operating environment
                         The Flexi BSC can be located flexibly in the GSM network. It can be installed as stand-
                         alone, on the same site as the Base Transceiver Station (BTS) it controls, or at a remote
                         location, which can be either co-located or non-colocated with the MSC/MGW. Submul-
                         tiplexing can be used between the BSC and Transcoder Submultiplexer (TCSM) to
                         reduce transmission costs with locating the BSC near the BTSs it controls and install the
                         TCSM at the MSC site.
                         A common solution is to locate the BSC remotely from the MSC near the BTSs it controls
                         and install the Transcoder Submultiplexer (TCSM) at the MSC site. Submultiplexing can
                         then be used between the BSC and TCSM to reduce transmission costs.
                         A combined site installation option is available with TCSM3i. The TCSM3i for combined
                         BSC/TCSM installation provides optical SDH/SONET A-interface connectivity towards
                         the core network. With this configuration, Flexi BSC and TCSM3i are installed together
                         and maintenance of SDH/SONET connections is done by the BSC. Connectivity is
                         achieved by optional SDH/SONET Exchange Terminals. The TCSM3i in combined
                         BSC/TCSM installation can be shared with several remote BSCs. The IP connections
                         from the TCSM3i towards the A-interface can be achieved both with combined installa-
                         tion and with standalone installation.

                         Equipment room
                         The mechanical structure of the Flexi BSC does not place any special requirements on
                         the ceiling, the walls, or the floor. No raised floor is needed.
                         The height of the room should be at least 2500 mm. This ensures that there is almost
                         500 mm of open working space above the cable troughs on top of the cabinet(s).
                         The Flexi BSC cabinet can be located in many different ways in the equipment room.
                         However, take the following points into consideration when planning where to locate the
                         BSC:
                         •   future expansion of the BSC
                         •   location of other equipment on the same site
                         •   air-conditioning of the equipment room
                         •   sufficient working space around the cabinet(s)
                         Location of the cabinet is discussed in more detail in Engineering for Flexi BSC.

                         Environmental conditions
                         The internationally recognised and comprehensive description of the environmental
                         conditions is covered by the following ETS standards:
                         •   ETS 300 019-1-1, 1992, Equipment Engineering (EE); Environmental conditions
                             and environmental tests for telecommunications equipment Part 1-1; Classification
                             of environmental conditions, Storage
                         •   ETS 300 019-1-2, 1992, Equipment Engineering (EE); Environmental conditions
                             and environmental tests for telecommunications equipment Part 1-2; Classification
                             of environmental conditions, Transportation
                         •   ETS 300 019-1-3, 1992, Equipment Engineering (EE); Environmental conditions
                             and environmental tests for telecommunications equipment Part 1-3; Classification
                             of environmental conditions, Stationary use at weatherprotected locations




DN70577137                                        Id:0900d805805912fc                                          53
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The Flexi BSC operating environment                                                    Product description of Flexi BSC



                       Climatogram
                       Changes in temperature and relative humidity affect the reliability of the equipment. The
                       relationship between the availability, performance and the environment is defined in the
                       climatogram in figure Climatogram of the Flexi BSC. The functional ambient tempera-
                       ture is -5°C…+45°C. No start-up below 0°C temperature is allowed.

                                                                TEMPERATURE      °C

                                                                                 60

                            A    Nominal conditions: The equipment meets         50
                                 the functional reliability and life cycle
                                 requirements in accordance with the product     40
                                 specifications. These conditions must be        30
                                 maintained 85% of time.
                                                                                 20            A
                            B    Normal conditions: The equipment meets
                                 the functional requirements in accordance       10             B
                                 with the product specifications.
                                                                                  0                C
                            C    Exceptional conditions: The main functions of
                                                                                 -10
                                 the equipment are not jeopardised.
                                 The duration of these conditions is limited           0   20 40 60 80 100%
                                 to 1% of time or 48 hours consecutively.                  RELATIVE HUMIDITY



                       Figure 15        Climatogram of the Flexi BSC

                       Electromagnetic environment
                        •       EN 300 386, V1.3.2, Electromagnetic compatibility and radio spectrum matters
                                (ERM); Telecommunication network equipment; Electromagnetic compatibility
                                (EMC) requirements.
                        •       Code of Federal Regulations, Title 47 (CFR 47), Telecommunication, Revised Oct.
                                1. 2003, Federal Communications Commission, Part 15 (FCC 15), Radio Frequency
                                Devices (EMC).

                       Restriction of Hazardous Substances
                       The Flexi BSC complies with the European Union RoHS Directive 2002/95/EC on the
                       restriction of the use of certain hazardous substances in electrical and electronic equip-
                       ment. The directive applies to the use of lead, mercury, cadmium, hexavalent chromium,
                       polybrominated biphenyls (PBB), and polybrominated diphenyl ethers (PBDE) in electri-
                       cal and electronic equipment put on the market after 1 July 2006.

                       Product collection and disposal within European Union, WEEE directive
                       The products put on the market are compliant with the symbol indicating producer of the
                       product, separate collection for electrical and electronic equipment and the date of
                       placing on the market as described in the European Union directive 2002/96/EC
                       (WEEE). The markings follow the requirements defined in the WEEE directive and in
                       any relevant standards.




54                                       Id:0900d805805912fc                                               DN70577137
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Product description of Flexi BSC                                           The Flexi BSC operating environment




                          Product collection and disposal within the European Union
                                                         Do not dispose of the
                                                         product as unsorted
                                                         municipal waste. The
                                                         crossed-out wheeled
                                                         bin means that at the
                                                         end of the product's
                                                         life it must be taken
                                                         to separate collection.
                                                         Note: this is applicable only
                                                         within the European Union
                                                         (see WEEE Directive 2002/96/EC)

                                                                                DN0577953

                         Figure 16   Crossed-out wheeled bin
                         For the products marked with a symbol shown in the figure above, please follow the fol-
                         lowing: The crossed-out wheeled bin means that at the end of the product's life it must
                         be taken to separate collection. Do not dispose of the product as unsorted municipal
                         waste. Note that this is applicable only within European Union (see WEEE Directive
                         2002/96/EC).




DN70577137                                       Id:0900d805805912fc                                         55
Issue 1-3

				
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