Page 186 7750 SR OS Services Guide
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. Due to the
relatively low bit rate of existing handsets, most cell sites use 2-10 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 Alcatel-Lucent applications, the
circuit emulation would currently be performed using the 7250 SAS. This could be performed by
the 7505 SAR or DMXplore at the cell site. However, a large number of cell sites aggregate into a
single switching center. Book-ending 7250 SAS nodes would require a very large number of
systems at the switching center (Figure 33). Therefore, a channelized OC3/STM1 solution is much
more efficient at the switching center. Due to the lower capacity requirements for mobile network
infrastructure, the 7710 SR is well positioned for these applications. However, some customers
will have scaling and deployment time frame requirements that necessitate the use of the 7750 SR.
With the introduction of a channelized OC3/STM1 CES CMA/MDA in the 7710 SR and 7750 SR,
Alcatel-Lucent can provide a converged, flexible solution for IP/MPLS infrastructures for 2G/
2.5G/3G mobile networks supporting both the CES (by CES CMA/MDA) and ATM/IMA
transported traffic (by the ASAP MDA).
BR: Border Router
Table 6: Mobile Infrastructure Definitions (Continued)
Cellsite Backhaul Type CSR Role Transport Acronyms
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