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Part 2 – LTE and WiMAX: An apples-to-apples comparison

Cisco Employee

Now that we understand one another's genealogy (as discussed in Part 1 of this series), before we dive in a system-level comparison of LTE and WiMAX, let's look at the two 4G standards in terms of why we want them in the first place. The answer is simple: data, data, data.

And that means being able to support large number of data users, bandwidth-hungry data applications like video-streaming, video conferencing, etc. So the question is how to achieve it. While the answer has any facets one of the most important is improving spectral efficiency (that is how many bits of data you can send reliably for one unit of frequency). (The other obvious answer would be providing more spectrum. However, as Will Rogers famously said about real estate is also true of RF spectrum: they're not making any more. ) The quest for improved efficiency has led to very similar design choices in LTE and WiMAX

  • OFDMA as the fundamental access technology to support multiple users simultaneously and provide high degree of resiliency to multipath interference even at high data rates
  • Multiple Antennas (MIMO) on the base station and the end-device utilize multiple signal paths between transmitter and receiver to significantly improve throughput on a given channel
  • Higher Modulation and Coding Schemes: Increase the coding efficiency to 64 QAM (Quadrature Amplitude Modulation).

A combination of the above techniques have increased the efficiency 2-3 times on average and increased the peak rates by over 5 times. Another aspect of LTE and WiMAX has been that it can operate in a range of spectrum bandwidths (such as 5/10/20 MHz). This is different from 3G technologies which operated in fixed (and much narrower bandwidths).  So a combination of improved spectrum efficiency and more spectrum gives significant throughput improvements over existing 3G technologies.

In addition to radio-level commonality between LTE and WiMAX there is commonality in the network/system architecture. Both systems are all IP systems and devoid of any network element to carry circuit-switched voice. 3G networks have a split (circuit-packet) network architecture with the circuit network carrying voice and packet carrying data. LTE and WIMAX provide a significant departure from this architecture. They are an entirely IP-based network.  More importantly, voice and data service are carried on the same physical network leading to reduced costs, complexity, and management.  Looking into the commonalities further: 

  • LTE and WiMAX have a flat architecture consisting of a Base Station and an Access Gateway. (Unlike 3G networks, there is no Base Station Controller and that function has been absorbed mostly in the Base Station.)
  • LTE and WiMAX enable the Base Stations to communicate with each other directly to enable fast handovers.
  • LTE and WiMAX use an IP tunnel to transport packets between the Access Gateway and the Base Station. (This enables leveraging existing IP network for efficient packet delivery between the two elements)

The main point I was trying to communicate that at a fundamental design level the two networks reached very similar choices. As with all things designed by independent bodies (even if working on identical requirements) implementations differ. So LTE and WiMAX are not identical implementations: for example they use very different protocols, etc.  However, I hope to have convinced you they are very similarly designed.

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