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					    Mobile Communications
           Overview


Lecturer:   Michael O'Grady
Course:     MSc Ubiquitous & Multimedia Systems
Unit:       Context Sensitive Service Delivery
Lecture:
               Outline

 Introduce some basic wireless concepts
 Describe the evolution of cellular
  telecommunications networks
 Reflect on the services supportèd by
  cellular networks
 Consider the issue of standardization in
  wireless communications
                 Recall: PSTN

Public Switched Telephone Network

“Concatenation of the interconnected Networks operated by
the various telephone companies (telcos) and public utility
companies (PTTs) throughout the world”

       Originally -   human operated (plugboards), analogue
                      signal
       Later -        Electromechanical switches

       Today -        Automated, digital

But ……                the so-called “last mile problem”
           Recall: PLMN

Public Land Mobile Network (PLMN)

   Operated by either government agency or
    government appointed company.
   Objective is to deliver services to those
    members of the public who are mobile.
   May be considered an extension or an
    integral part of the PSTN.
   Uses Wireless technologies.
     Advantages of Wireless

   Constant connection
   Access to up-to-date information
   Minimum installation issues
   Freedom to roam
   Scalability
   No cables
   Extensibility e.g remote areas with
    satellite
    Disadvantages of Wireless

   Careful planning of network essential
   Environment generally hostile
   Security
   Safety
   spectrum licenses
   poor data rates
   cost (domain dependant)
Some Historical Developments

Origins debatable but ….
   1887 - Hertz demonstrates EM waves
   1896 - Marconi demonstrates wireless
    telegraph apparatus
   1901 - First radio signal across the Atlantic
    (Cornwall to Newfoundland)
   1914 - First wireless voice transmission
   1946 - PSTN augmented with wireless
   1947 - Cellular Network proposed
                   Why Cellular?

Originally proposed by D. H. Ring in an
 unpublished paper.
Why?
      Potential for existing systems to expand
       was severely limited.
How?
      Reuse frequencies so as to maximize the
       use of the available radio spectrum thus
       improving scalability.
Note: This issue will be revisited when the GSM architecture is discussed.
           Standardization

Advantages include
     accelerates the availability of new equipment and
      services
     lowers costs through increased competition
     ensures reliability of supply
     ensures interoperability
De Jure
     defined by industry groups or government agencies
De Facto
     established as the result of a product dominating
      the market
      1G - Characteristics

Analogue transmission technology
Pioneered semiconductor and
 microprocessor technology
Focus on voice
Data services almost non-existent
Incompatible standards
   Different frequencies and signaling
   International roaming impossible
Inefficient use of the radio spectrum
               1G - NTT

Nippon Telephone & Telegraph (NTT)
  Now NTT DoCoMo
1979
Tokyo
World’s first operational cellular system
          1G - NMT-450

Nordic Mobile Telephone 450
1982
Sweden
First wireless communications standard
 deployed in Europe
Pioneered the use of light portable
 handsets
Supported international roaming
             1G - AMPS

Advanced Mobile Phone System (AMPS)
1982
USA
Mandated (FCC) as the standard to which
 all operators in the USA had to adhere to.
             1G - TACS

Total Access Coverage (TACS)
1985
UK
Adaptation of AMPS
Complies with frequency allocation in
 Europe
1G - Network Access Technique

Frequency Division Multiple Access
 (FDMA)
Subdivides the available spectrum into a
 number of frequency slots
Each user is assigned a separate
 frequency.
            1G - Services

Standard voice
No data services
No supplementary services
     Call barring
       The 1G Landscape

A series of incompatible networks
Limited capacity for expansion
Limited support for roaming
Susceptible to interference
Poor security
No support for wireless data
No third party applications
            Solution: 2G

Digital techniques rather than analogue
Increased flexibility
   error control
   compression
More efficient use of available bandwidth
Increased compatibility with the fixed
 component of the PSTN
Increased quality of service
Possibility of wireless data services
              2G - GSM

 Global System for Mobile Communication
  (GSM)
 Conceived in 1982
 Deployed in 1992 in Europe
 European Telecommunications
  Standards Institute (ETSI)
 Most successful 2G system
   863 million users in 197 countries
            2G - D-AMPS

Digital Advanced Mobile Phone Service
 (DAMPS)
   Also called IS-54 (Interim Standard 54)
1991
Dual mode terminals ensuring backward
 compatibility
IS-136 introduced in 1996
Telecommunications Industry Association
 (TIA) TR-45 Committee
              2G - IS-95

   Interim Standard 95 (IS-95)
   Also called cdmaOne
   1993
   USA
   Qualcomm Inc.
   Pioneered the use of the network
    access technique CDMA
                2G - PDC

Personal Digital Cellular (PDC)
1991
Japan
Two modes
   Full-rate
   Half-rate
12% of global digital subscriptions in
 1999.
2G - Network Access Technique

Time Division Multiple Access (TDMA)
   Users share a frequency band by multiplexing
    their transmissions in time
In practice ..
   Available spectrum is divided into frequency
    channels (recall FDMA!)
   Each frequency channel is further subdivided
    into cyclic timeslots (1,2,3,1,2,3,1,2,3 …)
   A call is assigned a time slot
            2G - Services

Depends on
   Network standard
   Operator policies
Improved standard telephony (speech)
Basic wireless data
Additional services
   Call barring
    Example: GSM Services

Teleservices
     Speech
     Emergency calls
     Short Message Service (SMS)
Bearer Services
     Telefax
     Basic data (9.6kb/s)
Supplementary Services
     Call forwarding
     Call barring
   2G - 3G Transition Driver?


Higher data bandwidth requirement
     anticipated subscriber demand for
        •   audio/Video streaming
        •   other multimedia services
        •   collaborative services
        •   location services

Possibility of third party applications
 being developed
    Recall: Circuit v Packet
           Switching

Circuit Switched ..
   A dedicated channel is established for the
    duration of a call
Packet Switched …
   A message is subdivided into packets which
    are sent individually and may follow
    different routes to their destination. The
    packets are then used to reassemble the
    original message.
   3G - Migration Strategies

Migrate straight to 3G
   This approach is being take by some
    operators in Japan (PDC) and the USA (IS-95)

Migrate incrementally to 3G
   Operators progressively and incrementally
    incorporate a number of technologies into
    their networks
   This approach is taken by operators in both
    Europe and the USA
   This strategy is sometimes referred to as 2.5G
      2.5G - HSCSD (GSM)

High Speed Circuit Switched Data (HSCSD)
Uses existing GSM infrastructure and
 interface
Data rates of up to 57.6 kb/s (4 channels @
 14.4 kb/s)
Inefficient for certain types of application
       2.5G - GPRS (GSM)

General Packet Radio Service (GPRS)
Introduces packet switching to GSM
“Always-on”
Uses multiple timeslots (channels)
  14.4 kb/s per channel
  Maximum of 115.2 kb/s
Dynamic resource allocation
Supports IP
Billing per KB, NOT per sec.
       2.5G - EDGE (GSM)

Enhanced Data rates for GSM Evolution
 (EDGE)
Maximum 384 kb/s
8 Phase Shift Keying (8PSK)
  Send more bits down the line
  3 fold increase over GSM
Two classes of handset:
  Class A (EDGE only on downlink)
  Class B ( EDGE on uplink and downlink)
   2.5G - D-AMPS (IS-136+)

Two phase migration path
   IS-136+
      Integrate GPRS
      Note: packet switching already supported by
       Cellular Digital Packet Data (CDPD)!
   IS-136 High Speed Outdoor
      Integrate EDGE


Subscribers can roam between IS-136HS
 and GSM networks supporting EDGE
      2.5G - IS-95B (IS-95)

Enhanced version of IS-95
Already supports packet switching
 (CDPD)
Maximum of 115.2 (8 channels @
 14.4kb/s)
Realistically …
   28.8 kb/s to 57.6 kb/s on downlink
   14.4 kb/s on uplink
          2.5G - Services

 Standard services that can use packet
  switching:
    WWW browsing
    email
    file downloading e.g. mp3
   Multimedia Messaging Service (MMS)
 3G - The IMT2000 Initiative

Conceived in 1986
Sought to define a single world-wide
 standard for accessing the global
 telecommunications infrastructure from
 both terrestrial and satellite mobile
 systems
Problem: backward compatibility
So five standards approved for the air
 interface!
3G - Air Interface Standards I

    IMT-DS (Direct Spread), also known as
     Wideband CDMA Frequency Division
     Duplex (W-CDMA-FDD).
    IMT-TC (Time Code) or W-CDMA Time
     Division Duplex (W-CDMA-TDD).
    IMT-MC (Multi-Carrier) or CDMA2000.
    IMT-SC (Single Carrier), also known as
     EDGE or UWC-136.
      IMT-FT (Frequency Time), for cordless sytems
       e.g. DECT
3G - Interface Standards II


 Radio-Interface Standard             Cellular Network               Standards Organisation
         IMT-DS                          GSM, PDC                               3GPP
         IMT-TC                            D-AMPS                               3GPP
        IMT-MC                           IS-95, PDC                             3GPP2
         IMT-SC                      Any TDMA Network                           UWCC
             Table 1: 3G interface standards for the predominant 2G networks.
3G - Principal Requirements - I

 Support for voice quality comparable with
  fixed line networks;
 Support for both circuit-switched and
  packet-switched data services;
 Support for roaming between different
  IMT-2000 operators;
 Support for greater capacity and improved
  spectrum efficiency;
3G - Principal Requirements - II

 A data rate of 144 kb/s for users moving
  quickly e.g. moving vehicles;
 A data rate of 384 kb/s for pedestrians;
 A data rate of 2 Mb/s in a low mobility
  or office environment.

 Note how a network using GPRS and
  EDGE meets most of these criteria!
3G - Network Access Technique

Code Division Multiple Access (CDMA)
    Signal is modulated with high bandwidth
      spreading waveforms called signature
      waveforms or codes. Subscribers may
      submit at the same frequency and time but
      signal separation is facilitated via the
      signature waveform
 In contrast with TDMA
    More robust
    Less susceptible to fading & interference
         3G Networks



2G Network   3G Successor
GSM          UMTS
PDC          CDMA2000
IS-95        CDMA2000
DAMPS        IS-136HS or UMTS
Example: 3G Services (UMTS)

Universal Mobile Telephone System
 (UMTS)
  Four QoS classes of services
    Conversational Class
       • Voice, video telephony,video gaming
    Streaming Class
       • multimedia, video on demand, webcast
    Interactive Class
       • WWW browsing, database access, online gaming
    Background Class
       • email, SMS, file downloading
      Quality of Service (QoS)

“the collective effect of service performances which
   determine the degree of satisfaction of a user of a
   service”… ITU G1000 specification

 Telecommunications World
   QoS encapsulates all aspects of a service that determine the
    degree of satisfaction with that service.


 IP World
   QoS implies guaranteed bandwidth

Pronunciation check: QoS == kwoz
  QoS: Network v Customer

Network performance
  Packet loss, transmission delay, bit error
   rates, call set-up times, etc
But customer interpretation?
  Thus Q.800 suggests:
       • Focus on effects as perceived by customer
       • No assumptions about network design
       • All aspects of the service considered (from customer
         perspective)
       • Network independent terms used
       • Can be assured to a user by a service provider
                  3.5G

UMTS
 High Speed Downlink Packet Access (HSDPA)
   14 Mbps (but 1 Mbps per subscriber!)
   Incremental upgrade
   More functionality in Node B
   Backward compatible with W-CDMA
 High Speed Uplink Packet Access (HSUPA)
 Other Technologies
   OFDN, WiMAX, etc, etc
    4G- Some Speculations

Global Mobility
Increased data rates..100Mbps?
All IP network
When?
     Standardisation - ITU

Founded in 1865 in Paris by 20 European
 countries
    interconnection issues
    equipment standardization
    uniform instructions for operating equipment
    accounting procedures and rules
Today, affiliated with the UN
500 new or revised recommendations every
 year!
      Structure of the ITU

Telecommunications Standardization
 (ITU-T)
    specifications for systems networks and services
Radiocommunications (ITU-R)
    specifies technical characteristics of terrestrial
     and space based wireless services and systems
Telecommunications Development (ITU-
 D)
    reports, guidelines and recommendations for
     developing countries
   Wireless Standardization

Recall IMT2000 vision
Two global partnerships comprising a
 number of traditional standardization bodies
   Third Generation Partnership Project (3GPP)
     Concerned with EDGE & UMTS advancement
   Third Generation Partnership Project 2
   (3GPP2)
     Concerned with CDMA advancement
Note that membership not mutually
 exclusive!
3GPP - Organizational Partners


                 Organisation                  Region              URL
    Association of Radio Industries and        Japan    http://www.arib.or.jp
            Businesses (ARIB)
      China Wireless Telecommunications        China    http://www.cwts.org
            Standard Group (CWTS)
    European Telecommunications Standards      Europe   http://www.etsi.org
                Institute (ETSI)
              Committee T1 (T1)                 USA     http://www.t1.org
   Telecommunications Technology Association   Korea    http://www.tta.or.kr
                     (TTA)
   Telecommunications Technology Committee     Japan    http://www.ttc.or.jp
                    (TTC)
3GPP2 - Organizational Partners


                 Organisation                  Region                URL
       Association of Radio Industries and     Japan    http://www.arib.or.jp
               Businesses (ARIB)
      China Wireless Telecommunications        China    http://www.cwts.org
            Standard Group (CWTS)
    Telecommunications Industry Association     USA     http://www.tiaonline.org
                     (TIA)
   Telecommunications Technology Association   Korea    http://www.tta.or.kr
                     (TTA)
   Telecommunications Technology Committee     Japan    http://www.ttc.or.jp
                     (TTC)
             Summary

 Introduced wireless communications
 Described the evolution of the various
  generations of cellular networks
 Described the services supported by the
  various networks and the issues
  effecting their deployment
 Briefly introduced the issue of
  standardization
       Review Questions

Compare and contrast the three
 generations of mobile networks.
Trace the evolution of services from 1G to
 3G.
Identify the advantages and disadvantages
 of circuit switched and packet switched
 data services from both an operator and
 subscriber perspective.
What benefits do standardization bring to
 network operators? Subscribers?
The End

				
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