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Mobile backhaul offload could affect Evolved Packet Core design

Part two of our analysis of 4G network offload strategies looks at the implications of moving mobile backhaul traffic to the metro network, and how it could affect the design of LTE’s Evolved Packet Core.

(Continued from: 4G network offload: Radio access network solutions)

Operators can’t escape carrying wireless traffic on their metro networks unless they don’t have any wireless traffic in the first place. 

So 4G network offload strategies that use the mobile backhaul network are focused on moving traffic to its destination at the lowest possible cost. Internet traffic is the primary mobile backhaul focus because operators get the lowest return per bit on IP, and they need to make sure that services that consume the expensive wireless infrastructure are the ones that bring in high revenue per bit.

Mobile backhaul strategy could change Evolved Packet Core design. The architecture for 4G Long-Term Evolution backhaul is defined by the evolved packet core and

Offload strategies for 4G networks are highly sensitive to the operators’ business goals and to the regulatory frameworks in which they provide services.

Tom Nolle, President, CIMI Corp.

how its components relate to the rest of the metro network. The Evolved Packet Core can be visualized as tunnel-managed connectivity between the LTE serving gateway (SGW) and the public data network gateway (PGW). The Evolved Packet Core can handle Quality of Service (QoS), but it will likely present premium costs for the ability to offer traffic-handling options. If the majority of 4G network traffic is regular IP rather than premium wireless traffic that brings in more revenue, it makes sense to move the two gateways closer together (or combine them into a single device), which would shunt traffic onto the metro network near the wireless network edge, thus reducing custom EPC equipment and handling costs.

Moving 4G gateway boundaries can help with network offload. Compressing SGW/PGW boundaries reduces the area of the metro network where the Evolved Packet Core has to manage QoS, which means that the “new” PGW must be able to move premium traffic onto metro routes already designed to handle traffic like applications under service level agreements (SLAs), for example. If the metro network already carries other premium services traffic and supports classes of service, it may make sense to add 4G network offload traffic there rather than manage an EPC-based set of handling options for wireless traffic in addition to the QoS options already available for wireline services on the metro network.

As an option, many equipment vendors support a combination of integrated SGW/PGW at the radio access network (RAN) edge for offload, combined with a separate PGW at the service edge to create a true Evolved Packet Core and EPC-based management for premium traffic.

The specific decision on how the premium mobile traffic should be handled will likely depend on a number of factors, including the operator’s 3G migration strategy, existing management and QoS options in the metro network for wireline services, and even enterprise service offerings that require premium handling.

DPI could play 4G network offload role, if regulation permits

In addition to technical mobile backhaul decisions, global issues with net neutrality and country-by-country differences in how wireless and wireline Internet traffic are treated for regulatory or commercial reasons are making some deep packet inspection (DPI) concepts applicable to wireless Internet traffic. A logical place to use DPI is in the PGW function that forms the 4G network offload point, whether it’s integrated with the SGW or not. The use of DPI in the PGW can help an operator manage bandwidth to control heavy users, where permitted, by better analyzing traffic. The use of DPI can also offer premium handling for Internet services, where permitted, without requiring that some services be carried by the Evolved Packet core while others must be offloaded.

4G network offload strategies in flux

4G network offload strategies are highly sensitive to operators’ business goals and to regulations where they provide services. The most important consideration in any 4G network offload strategy is to have maximum flexibility to accommodate the shifting relationships between business goals and regulation as new Internet applications and wireless devices drive change in the market.

Back to Part 1: 4G network offload: Radio access network solutions

About the author: Tom Nolle is president of CIMI Corporation, a strategic consulting firm specializing in telecommunications and data communications since 1982. He is the publisher of Netwatcher, a journal addressing advanced telecommunications strategy issues. Check out his networking blog, Uncommon Wisdom.

This was last published in February 2011

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