April 7, 2009 by Isybel Harto
IP-based mobile transport networks first appeared in backbone bearer networks. IP/MPLS (multi-protocol label switching) routers over the wave division multiplexing (WDM) system efficiently bear mobile softswitch services. China Mobile, BT, Vodafone, and Etisalat, have all seen greater profits and consumer satisfaction after building IP backbone bearer networks. Mobile base stations are gradually adopting ALL IP technology and the air interface rate has been increasing rapidly, for example, from 144Kbps in GPRS to 14.4Mbps in HSPA, and to 100Mbps in Long-Term Evolution (LTE). As a result, transport bandwidth required by mobile backhaul networks has been booming. The forecast for 2010 is that the growth of data services will quadruple the demands on mobile backhaul bandwidth. In this scenario, an IP-based mobile backhaul is inevitable for future mobile transport networks.
To improve transport efficiency and reduce transport costs, an IP mobile transport network has
to satisfy the following requirements:
ALL IP architecture:
Packet requirements of transport networks can be mostly attributed to the rapid growth of data services that have uncertain and unexpected traffic. The transport network should be designed and deployed on the basis of a pure IP-based kernel to guarantee the highest level of efficiency.
Multi-service transport capability:
Recent developments have shown that a unified transport network must adapt to various mobile network technologies, including GSM, WCDMA, CDMA2000, WiMAX, HSPA+ and LTE. The transport network should be able to transport services of multi-mode radio access networks (RANs) in a unified way. Traditional 2G networks are based on time division multiplexing (TDM); 3G R99/R4 network adopts the asynchronous transfer mode (ATM) protocol; 3G/WiMAX/LTE networks evolve into ALL IP. During the evolution of mobile networks, services based on TDM, ATM and packet will coexist in the same network for a long time. The transport network should be able to support unified transport of multiple services, including TDM, ATM and Ethernet services. This can be realized with the pseudo-wire emulation edge-toedge (PWE3) technology.
Multi-scenario access and networking capability:
As different access resources are allocated to different base stations, no single access technology can cater to all requirements. Base stations in Asia-Pacific like China have relatively rich optical fiber access resources. In Europe, the microwave access mode is mostly adopted, plus there are some leased lines and small quantity of twisted pair cables. When a mobile network is extended from wide coverage to indoor microcells and hotspot access points (APs), the transport network must provide customized multi-scenario access and networking capabilities. The network has to support multiple combined access technologies involving optical fibers, microwave and copper cables.
Precise IP clock transfer capability:
Clock synchronization is a key demand for mobile networks. Traditional transport networks transfer clocks through SDH and the global positioning system (GPS). ALL IP transport networks need precise clock synchronization capabilities to handle mobile service roaming and handover.
3G services include data and voice services, which place different requirements on network reliability. Transport networks must offer carrier-class protection on services. By using the QoS
strategy and the network protection mechanism, transport networks can offer differentiated services to reliably handle voice, video and data services.
As data services develop quickly, mobile data services and mobile traffic will boom. Transport networks should have fine flexibility and scalability regarding interface types, transport bandwidth, and network scale.
End-to-end management capability:
The provision of mobile 3G services and wide network coverage will drive transport network evolution into multi-service bearer networks. End-to-end management capability can efficiently decrease network operations and maintenance costs.