Means of optical access fiber-to-floor; in addition to fiber to the home (FTTP / FTTH) cable has been extended to the home or business; FTTO, FTTC ... fiber-optic broadband network in a variety of transmission media in an ideal it is characterized by a large transmission capacity, transmission quality, low loss, long distance relay.
Huawei Communicate Optical access network trends New trends like network structure flattening, increasingly intelligent management and maintenance, integrated bearing of convergence services, even higher network security and reliability, make it critical for the optical access network to adapt both on the network and equipment layers. By Ao Li MAY 2009 . ISSUE 49 14 Expert’s Forum Expert’s Forum will deliver our promise “Batelco’s NGNDeputy Director of Institute of Communications Policy Research, China Academy of Telecom Research (CATR), Ao Li, Ministry of Industry and Information Technology all Vice to bring affordable broadband access to(MIIT);of Chairman of Transport and Access Network Technical Committee, and Head of Access Network Workgroup, China Communications Standards Association. Bahrain’s households, making them among the best connected in the world. A s a result of telecom structure of the wired access network. challenges and must consider the following restr ucturing, the time is T h e l a r g e c a p a c i t y, h i g h a c c e s s issues comprehensively. near for China’s three major bandwidth, high reliability, and multi- telecom operators to launch full-service operations. As a basic bearer service QoS support capability features of the optical access network enable the Construction, operation network, the access network has to bear access network to evolve towards a unified, and maintenance multiple services such as voice, data, video, converged and efficient bearer platform. enterprise access and backhaul services of The optical fiber broadband access By substituting fiber for copper cable, the radio base station. network was deployed on a considerable operators can reinforce the effectiveness Tr a d i t i o n a l c o p p e r w i r e d a c c e s s scale in China during 2007. The future of overall planning for access optical fiber, networks are constrained by attenuation development strategy of China’s FTTx OLT, ODN and system devices during in signal transmission, so the coverage of has set a clear objective for operators FTTx network construction. an end office is usually within 3km and a to “vigorously advance the substitution It is necessary to strengthen the linkage large number of end offices are deployed of fiber for copper cable, deploy access between front-end and back-end devices, in the network. This poses a challenge networks of optical fiber, realize FTTB power supply assurance, IT support, for operators to build equipment rooms (fiber to the building) and FTTV (fiber project construction, operation and and auxiliary facilities and to control to the village) in newly built areas and maintenance and to quickly transform the OPEX. The dispersed distribution of end strengthen renovation of existing metro access capability into service capabilities. offices requires adding a metropolitan areas.” The actual situation indicates that convergence layer. Consequently, there are Current statistics show that more than FTTx deployment now faces numerous more network layers in metropolitan areas, 4.5 million Chinese homes are passed problems that arise due to the lack of the structure is complicated and network by FTTx. The network has been built adequate capability and experience on the OPEX gets higher. by taking FTTB/C as the predominant part of the operator in the construction, The introduction of the optical access mode and FTTH as the supplementary operation and maintenance of the network with a coverage of 20km ensures mode. In actual network construction, the optical fiber access network, especially in that optical line terminals (OLTs) can be optical access network also faces multiple operation and maintenance. advanced to the traditional metropolitan convergence nodes at the initial stage of optical access network construction. It simplifies the network structure of the convergence layer for the access network and reduces the number of end offices. This is important not only for the network upgrades of traditional fixed operators, but also for the new networks from emerging broadband operators who lack equipment room resources. While accelerating optical fiber access applications, operators should pay attention to setting up OLTs in a centralized manner under unified planning to realize “large capacity and fewer nodes deployment” and to optimize the network 15 MAY 2009 . ISSUE 49 Huawei Communicate First, the deployment, configuration, board bus bandwidth, uplink port capacity In the FTTB/C mode, as the remote and upgrade of devices is a complicated of OLTs, and the system’s switching device of the PON, the optical network and cumbersome affair. The types of capacity all need to be increased. This unit (ONU) should meet network devices and the quantity of network trend is reflected in the emergence of large- and service needs in functionality and elements are increasing and their capacity OLTs (with 800GB switching performance. PON ONU devices management and maintenance are capacity, eight PON ports per board and support the switching between VLAN complicated and laborious. Multi-service 10GB uplink ports). 1:1 and n:1 and cross-VLAN multicast configuration and service provision involve When network layers are simplified, it replication, meet the requirements for multiple devices and multiple back-end is preferential that OLTs should be directly QoS deployment and support the queue support systems and operation is very connected to the upper-link BRAS/SR dispatching based on 802.1P and priority. complicated. equipment. In addition, the growing OLT The ONU will provide the built-in voice Second, the number of remote nodes capacity and the increasing number of function based on service development requiring maintenance and management users covered in the future will impose an needs. has doubled along with the gradual increasingly higher requirement on FTTx Different building and application devolution of optical fiber. As remote network reliability. environments have different requirements devices are removed from the equipment One primary requirement for PON for the ONU port density. Generally, room, the operating environment of the devices is to fully consider protecting the configurations of 8, 16, 24 and 32 device is poor and the fault rate is on the the key components of OLTs (such as ports can cover requirements in various rise. The devices are widely dispersed, redundancy protection for the power scenarios. leading to a significant amount of panel, main control board, and uplink The narrowband to broadband (NB-BB) troubleshooting workloads. board). For networking protection, ratio of the ONU is specified based on These issues have imposed very the OLT needs to provide dual uplink the service penetration rate. To guarantee high requirements for FT Tx device protection to key customers or critical long-term operating performance, the management, device deployment, service services, avoiding any single-point fault ONU should be able to work in the -10°C issuance, fault monitoring, and control and providing reliable access. to +55°C environment and have a solid capability on network security. At the initial stage of FTTx design for heat dissipation. The plug-in construction, uplink redundancy ONU can dissipate heat by using a fan protection can be realized for OLTs with a minimum service life of 50,000 Capacity configurations directly connected to the BRAS/SR by way hours. The integrated ONU can use a for PON OLT of link bundling or VRRP. The carrier- class Ethernet protection technology can natural heat dissipation design in lieu of a fan in consideration of the special stairway then be introduced to realize millisecond installation environment and the impact The large capacity, fewer offices and protection between active and standby on households. ONUs should also have network flattening trend implies an links of OLTs as well as the dual-homed superior lightning protection performance. increase in the number of users covered by configuration of BRAS/SR of the OLT. Power supply ports and DSL/POTS the OLT, which creates new requirements ports when equipped with 4kV lightning for OLT capacity. The number of passive protection capability can provide remote optical network (PON) ports per board, Requirements for PON ONU surveillance over temperature, municipal While accelerating optical fiber access applications, operators should pay attention to setting up OLTs in a centralized manner under unified planning to realize “large capacity and few nodes deployment” and to optimize the network structure of the wired access network. MAY 2009 . ISSUE 49 16 Expert’s Forum Optical access network trends power, battery and access control. The ONUs mainly use the local power supply directly open the SNMP MIB database to support the NMS of the IP MAN network Multi-service bearing of AC 220V or DC -48V and may use a and softswitch network and to configure impact on service backup battery or UPS as required. The and manage services such as VLAN, QoS height of ONUs needs to be low in order and voice access remotely. control to meet the installation requirements of Access devices with built-in voice under the narrow staircase environment. the FTTH mode can be managed by using The service access control layer consists The ONU is a terminal access device the ACS management system specified of two structures: single-edge and multi- that can also be connected to the BTS and in the TR-069, or by temporarily using edge. If all the services and traffic of a user support the private line access for small- the PON NMS. In principle, standalone are terminated in the same service access and medium-sized business users. In the NMSs will no longer be established for control device, it is a single-edge structure. substitution of fiber for copper cable FTTH voice access devices. As for the If different services of a user are terminated scenario, the ONU platform architecture built-in voice access devices under the in different service access control devices, supports smooth upgrades from the FTTB mode, NEs of different vendors it is a multi-edge structure. existing ADSL2+ to VDSL2 or LAN so can be managed by their respective The support capability of the FTTx as to support smooth upgrading of service NMS. A small number of new external network on integrated service bearing bandwidth. integrated access devices (IADs) can also will have relative impact on the service be incorporated into the vendor’s PON control layer of MANs. For important NMS. Access gateways (AGs) should be government and enterprise customers, SR FTTx device management managed by the softswitch NMS in a access shall be adopted. For public users, unified manner. small and medium-sized government/ New issues facing network management enterprise customers, single-edge structure and maintenance that come with the networking is used if BRASs of superior introduction of the PON system are: an Integrated service functionality and high performance are increase in the number of access points, the shift from single service to multiple services, bearer capability deployed in IP MANs. If the service volume is large and the BRAS cannot the greater granularity or refinement in support multi-service access control well, service management and an increase in the When constructing an FTTx network, multi-edge structure networking can be amount of maintenance workloads for the operators need to consider their ability to used. The same MAN can simultaneously optical cable network. As the number of meet the future requirements of bearing use the mixed networking of both single- ONUs increases significantly after mass integrated multi-services. The FTTx edge and multi-edge structures. deployment of the optical access network network can be equipped with customer To fulfill the requirements of multiple using the PON, the operation, management and service-differentiated bearing capability services such as IPTV, WLAN and VoIP, and maintenance of ONUs become quite for high quality access of voice and operators should consider introducing important. video services. The FTTx access network the dynamic host configuration protocol Under the FTTB mode, the should deploy the 802.1P-based QoS (DHCP) into the IP MAN and gradually management and maintenance of PON strategies and implement corresponding building the DHCP platform. The ONUs uses the combined management priority queues for OLTs and ONUs. In management system of the DHCP mode of OAM + SNMP (EPON) or addition, the FTTx must have service platform can be deployed in a centralized OMCI + SNMP. The OAM or OMCI traffic classification, priority marking, and way. is responsible for managing functions priority queue dispatching capability to The DHCP server function can be related to the PON protocols. The SNMP realize service packet forwarding based on enabled directly on BRAS/SR if the interface is responsible for functions service priority and assure the quality of requirements of the DHCP system for related with ports, protocols, and services. different services. security, reliability, and scalability are not Under the FTTH mode, the management In respect to WLAN functions, to high. Based on the actual needs of services, and maintenance of PON ONUs uses the adapt to the development trends of future the IPoE access authentication method joint management mode of OAM/OMCI networks, PON devices should support the capable of centralized management can + TR-069. VLAN stacking function. In particular, the be introduced in conjunction with the The PON OLT and ONU devices outer VLAN tag is used to identify services renovation of Radius and the related under the FTTB mode are managed and and represent OLTs. The inner VLAN tag support system, smoothly adapting to configured according to the network can be used to represent different users services that are always online and those management system (NMS) of PON or different services of the same user and with multicast requirements. devices by providing northbound to support the VLAN mapping function interfaces, or by allowing PON devices to between 1:1 and n:1. Editor: Xue Hua firstname.lastname@example.org 17 MAY 2009 . ISSUE 49
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