LTE Architecture: Flat or Not so Flat?

'Migrating to Flatter, All-IP Wireless Networks' claims this article in converge digest. People have been talking about this Flat architectures for some time now and I decided that it was time i clear my understanding on this.

While searching my library of infinite resources i finally hit the jackpot. Qualcomm presentation from LTE 2007 has an answer.


The flatness of an access network can be measured by the depth of its link layer-specific network element hierarchy.

Going back to the article mentioned earlier:

Despite the growth of carrier networks and the evolution of standards, voice and data communications have not evolved in synch. Carriers have historically added data communications as an afterthought to voice network architectures originally conceived in the circuit-switched era, resulting in complex hierarchical networks that support both voice and data.

This type of architecture is expensive, leading to high operating and capital expenditures for service providers and significantly lowering margins in a highly competitive industry. In addition, networks employing cobbled-together voice and data communications systems simply do not have the capacity to provide the rich multimedia services and omnipresent Internet access that today’s wireless customers demand.

To address these limitations, service providers are moving toward emerging all-IP wireless technologies that promise to reduce complexity, simplify the wireless core, and decrease service providers’ operational and capital expenses.

Currently there are several initiatives that operators are considering for building wireless IP networks:

· WiMAX End-to-End Network Systems Architecture: Defined by the WiMAX Forum Network Working Group (NWG) and leveraging the IEEE 802.16e WiMAX interface.
· Long Term Evolution (LTE): Being defined by the Third Generation Partnership Project (3GPP) and targeted as a successor to GSM-based technologies.
· Ultra Mobile Broadband (UMB): Being defined by the Third Generation Partnership Project 2 (3GPP2) and targeted as a successor to CDMA-based technologies.

All three of these architectures are similar in that they leverage a flat, user-plane, all-IP network architecture with fewer nodes that enables mobile operators to integrate the core with the access network, providing real-time multimedia and broadband IP services from the core to the mobile station. This flatter architecture results in reduced latencies and thus optimizes performance for real-time services such as voice and video.

So going back to the Qualcomm presentation and checking if the LTE part is as flat as claimed.

We can see that the LTE Network Architecture is Lumpy rather than flat. Even though it is an improvement from the Release 99 (or rather Release 6) its not as flat as claimed.

Sure this would be something to consider in case of 4G (IMT-Advanced).