WHAT REALLY IS 4G?

The fourth generation wireless technologies are considered to be the next logical step for the ever evolving wireless business and the customer. A lot has been stated, discussed and argued about LTE and WiMax and how they are will compete with each other (at least in the USA). Many companies in different parts of the world are making claims about the download speeds under each of these technologies and are running towards the finish line to be the first to reach the consumer. But the question is that how many of us actually understand what is 4G and what sort of bandwidth it is supposed to provide us? Is it what the network operators and the media are telling us or is it something more than that?

LTE and WiMax, both theoretically and practically, are evolution to 4G and not 4G themselves. Calling them 3.5G could be more appropriate. ITU-R, the apex body for radio communications standards in the world, prefers to use the term ‘IMT-Advanced’ for 4G. IMT-Advanced according to them, should be able to provide average downlink speeds of 100 Mbps to the high mobility users, and up to 1 Gbps for local access or low mobility scenarios. Also the radio interface technology should support a scalable bandwidth up to and including 40 MHz and preferably, service providers should consider channel allocations of 100 MHz. The ITU-R recommendations also specify criteria for latency, capacity and spectral efficiency. The key candidate technologies for IMT-Advanced are 802.16m and LTE-Advanced.

Going back to WiMax and LTE for a moment, here are the kinds of speeds coming out of different field tests. WiMax has shown peak download speeds of up to 10 Mbps with an average speed of 3 to 6 Mbps. For LTE, the peak is around 50 Mbps with an average of 5-12 Mbps in real world scenarios. The world’s first commercially deployed LTE network in Scandinavia showed variable average speeds between 16 and 32 Mbps depending on geographic location. It is not that greater speeds are not achievable. But operators want to move one step at a time. They do not want to create too much supply before understanding the demand. Also they intend to keep an upper cap on the bandwidth per user in order to adjust more subscribers within a given backhaul network. Another constraint is the lack of spectrum, especially in USA. The FCC, as part of the National Broadband Plan, intends to make 500 MHz of spectrum available to mobile broadband service providers in the next 10 years. The FCC realizes that the country lags in both broadband speeds and adaption despite being on top of most global technological developments. The ratio of bits per second to dollar remains one of the lowest in the world here. This can be attributed to various factors, but the fact remains that Internet has become such a vital part of life, that the demand for bandwidth is ever increasing.

As I wrote earlier, 802.16m and LTE Advanced are two disruptive technologies that could be considered as being next up in the wireless communication generation. 802.16m can be seen as the advanced version of 802.16e. Promising features such as advanced multiple antenna architectures, uplink and downlink OFDMA, multihop relay architecture, reduced latency and multi channel/carrier access through aggregation of channels would help 802.16m in achieving peak data rates of up to 120 Mbps for highly mobile users. LTE Advanced is expected to be an evolution of LTE and should share the same frequency bands. Key features of this technology would be higher spectral efficiency, greater capacity (about 3xLTE), higher average cell throughput by using advanced antenna techniques, coordinated multipoint transmission reduced latency and multi-carrier support. LTE Advanced claims to achieve peak downlink data rate of 1 Gbps. It also requires 100 MHz transmission bandwidth which is much higher as compared to LTE. Interested readers will notice the similarity between 802.16m and LTE Advanced. They have similar attributes which points out to the possibility of merging the 4G standards into one technology in the future.

Such high download data rates have been demonstrated by various companies under ideal situations. At the 2010 GSMA Mobile World Congress in Barcelona, Ericsson showcased 4G with a speed of 1 Gbps in the downlink. In the commercial world, the deployment of these actual 4G technologies is a few years away with the main bottleneck being lack of enough spectrum. In a nutshell it can be stated that while WiMax and LTE will significantly enhance user experience in terms of speed and reliability, the big leap that will bring a disruptive change to the user perception is still some time away and that will be the ‘real’ 4G.

About the Author: Gunjan Indrayan
Gunjan Indrayan is a telecommunications professional with more than four years of experience in the wireless consulting industry. He has a wide understanding of technical, business and policy aspects of the wireless communications industry. His current job profile mainly involves frequency planning, spectrum management, wireless network analysis and interference resolution. Gunjan holds an MS in Telecommunications from University of Colorado, Boulder where he performed research in the field of mobile ad hoc networks.
Connect with him on LinkedIn - http://www.linkedin.com/in/gindrayan
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