With operators worldwide evaluating the migration to 4G radio access based on Long Term Evolution (LTE) technology, defining the target network architecture and its real-world implementation is critical.

A key part of that process is identifying to what extent it’s realistic for operators and suppliers to consolidate 2G, 3G, and 4G applications on common hardware and software platforms, finds the recent report from Heavy Reading, "Flat IP Architectures in Mobile Networks: From 3G to LTE."

Arguably, it's in the mobile packet core, and the interfaces with the radio access network, where the issue of consolidating platforms and aligning the evolution of today’s equipment with tomorrow’s architecture first hits home.

The intent is to develop network architectures that reduce latency and complexity by minimizing the number of nodes in the data path, performing fewer protocol conversions, and using equipment that is simpler to configure and manage.

The implementation of Direct Tunnel is one area where there is considerable scope for alignment across generations of technology. In 3G High Speed Packet Access networks operators see clear benefit from separating mobility management traffic from the user-plane traffic, especially, where there’s data-intensive use of laptops in low-mobility scenarios. The idea is for the serving GPRS support node (SGSN) to become a predominantly control-plane node that can be evolved to support integrated mobility management across 2G, 3G, and 4G networks and become a combined SGSN/Mobility Management Entity (MME).

The challenge is that, while almost the entire industry is on board with the basic concept -- Ericsson AB (Nasdaq: ERIC - message board) and Nokia Siemens Networks already have live customers for Direct Tunnel -- there’s debate about how exactly to achieve it, and how much of the legacy base it is really practical to upgrade. Some suppliers, such as Starent Networks Corp. (Nasdaq: STAR - message board), argue that, with newer technology platforms, a “FastPath” architecture is preferable.

Deeper in the core there’s less interest in repurposing existing GGSN (GPRS gateway support node) equipment for “4G” packet gateways (comprising serving gateway and packet data network gateway functions) -- the sheer volume of traffic generated by LTE/4G radio access may make this impractical. Instead, some operators anticipate introducing new gateway equipment to support LTE, with a view to perhaps transitioning the GGSN application to this new platform over time. Longer-term there’s also an expectation, especially among larger operators, that packet gateways will be deployed closer to the radio access network, with control-plane functions (SGSN/MME) centralized at a national or regional level.

This raises the question of what type of platform is suited to 4G packet gateway applications, with two broad approaches emerging.

One group of vendors -- Ericsson, Alcatel-Lucent (NYSE: ALU - message board), Cisco Systems Inc., Juniper Networks Inc., Huawei Technologies Co. Ltd. , and to some degree Motorola Inc. -- anticipate the serving gateway and PDN gateway functions being implemented on edge router platforms. Another group -- Nokia Siemens, Starent, Nortel Networks Ltd., and WiChorus Inc. -- see SAE gateways as a high value-add network element that is best implemented on service-aware, computing-type platforms deployed on top of a routed core network.

The caveat to this coarse characterization, however, is that both platform types will align over the longer term as routers add service awareness (DPI, etc.), and mobility-specific nodes increase their packet forwarding capability.

Source:LightReading