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Building a better evolved packet core for 4G LTE networks

4G LTE networks address wireless bandwidth issues for mobile operators, but to really make it work, an Evolved Packet Core architecture is essential to address today's traffic onslaught and tomorrow's signaling and scaling issues. ACG Research analyst Bill Rubino tells you how.

The explosion of smart phones and the data and videos that can be downloaded to them has wireless service providers wringing their collective hands and looking for alternatives to ease the pressure these

The goal is to provide reliability that is five 9s, not nine 5s, without additional equipment expense while doing it.
Bill Rubino
Principal AnalystACG Research
devices are putting on their wireless networks and infrastructure. Long-term Evolution (LTE) with its higher bandwidth and all-IP infrastructure is being heralded as one of the solutions to this overload problem.

LTE addresses the bandwidth issue, but without high performing networks, the problem might be, to paraphrase Monty Python, "not dead yet." As carriers migrate from a 2.5/3G infrastructure to a 4G/LTE network infrastructure, the Evolved Packet Core (EPC) must be constructed with devices that can handle problems service providers currently face in their networks, as well as accommodate tomorrow's bandwidth signaling requirements.

Here are the key elements that must be built into the evolved packet core to address this explosion and future growth.

  1. Signaling capabilities for now and later. Signaling traffic can account for more that 70% of a subscriber's traffic. And with devices like the Droid®, which allows the user to ping pong back and forth between e-mails, Twitter and checking the baseball scores, stock market quotes or news headlines, data traffic and the signaling needed to support these applications adds up fast. Even an idle smart phone will generate signaling traffic.

    Think of this traffic growth in terms of the millions of users e-mailing, twittering, surfing and downloading, coupled with the continued popularity of the smart phone, which means more users with more applications that will generate more signaling and data traffic. This, in turn, puts more pressure on service providers to evolve their networks. Evolved packet cores must not only have headroom built into the signaling capability to handle signaling demands made by today's devices but plan for tomorrow's smart phone.

  2. Scaling for simultaneous EPC sessions. Sessions refer to the number of simultaneous sessions that can be established per EPC. A service provider can have the best EPC with great performance and signaling capacity, but if it cannot scale to a large number of simultaneous sessions, throughput and signaling are pointless because the EPC will be dropping sessions if it is over capacity and reaches the ceiling for the maximum number of simultaneous calls. As with signaling, headroom built into the session capability of the EPC will address this issue.
  3. Throughput while using Deep Packet Inspection. The EPC must support the performance needs and the high bandwidth requirements for 4G, at least throughput of 30Gbps or greater. Throughput while using Deep Packet Inspection (DPI) is another crucial element to address. When a carrier uses DPI, the question is, what's performance hit is when it is enabled? DPI is a processor intensive application because all packets that flow through the EPC have to be inspected right up the OSI layer stack. This will affect overall throughput. Taking a serious performance hit of 40% or greater when DPI is enabled, could cause problems for an operator.
  4. Architecting the EPC for redundancy. All carriers want redundancy built into their networks. The concept of five 9s (99.999%) reliability originated from the requirements of the old analog networks and is still relevant for today's carrier networks. The evolved packet core must have some level of redundancy to provide reliability, however. Carriers need an EPC architected with a redundancy scheme that isn't going to break the bank in terms of deployment. Having a primary and secondary EPC device where the secondary device sits dormant until the primary fails is an expensive deployment scenario. EPC devices that have 1:N redundancy will help because a carrier will not need dormant secondary devices or have dormant secondary slots or blades that take up space within a chassis as with 1:1 redundancy. The goal is to provide reliability that is five 9s, not nine 5s, without additional equipment expense while doing it.

As consumers continue to buy and aggressively use new applications and services across smart phones, laptops and other mobile devices, network traffic, and, by extension, congestion will continue grow regardless of bandwidth expansion, thus making the evolved packet core a strategic component in the transition to the next-generation system architecture and LTE. Providers will need to concentrate on integrated EPC product development and develop strategic network deployment models that take into account their current networks, the underlying packet transport domain, policy control and service delivery layer to make an effective transition.

About the author: Bill Rubino is a principal analyst at ACG Research specializing in service provider mobile network infrastructure. He has worked in the telecom industry for more than 20 years and previously was senior product manager at Motorola responsible for its wireless broadband product line. He also worked at Nortel, Sycamore Networks, Bay Networks, Wellfleet Communications and Proteon. Rubino has also been involved in different networking technologies, including wireless broadband, intelligent optical switches and core routing technologies. He has worked with the IETF and the IEEE. He also has received two routing and switching patents. He can be reached at brubino@acgresearch.net.


This was last published in May 2010

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