Mobile Infrastructure

Packet infrastructure is required within 2G, 2.5G, and 3G mobile networks to handle SMS messaging, web browsing, and emerging applications such as streaming video, gaming, and video on demand. Within existing 2.5G and 3G mobile networks, ATM is defined as the transport protocol. Within existing 2G networks, TDM is defined as the transport protocol. Because of the relatively low bit rate of existing handsets, most cell sites use 2 to 10 DS1s or E1s to transport traffic. When using ATM over multiple DS1/E1 links, Inverse Multiplexing over ATM (IMA) is very effective for aggregating the available bandwidth for maximum statistical gain and providing automatic resilience in the case of a link failure. Also, multiple DS1s or E1s are required to transport the 2G voice traffic.

Typically, low-cost devices are used at the many cell sites to transport multiple DS1 or E1 using ATM/IMA and TDM over an Ethernet/MPLS infrastructure. In Nokia applications, the circuit emulation would currently be performed using the 7705 SAR. This could be performed by DMXplore at the cell site. However, a large number of cell sites aggregate into a single switching center. Book-ending 7705 SAR nodes would require a very large number of systems at the switching center (see Figure 1). Therefore, a channelized OC3/STM1 solution is much more efficient at the switching center. Table 1 defines the cellsite backhaul types, CSR roles, and transport acronyms used in Figure 1.

With a channelized OC3/STM1 CES MDA in the 7750 SR, Nokia can provide a converged, flexible solution for IP/MPLS infrastructures for 2G/2.5G/3G mobile networks supporting both the CES (by CES MDA) and ATM/IMA transported traffic (by the ASAP MDA).

Figure 1. Mobile Infrastructure