Interview: UMTS Forum Talks LTE, the Future of 3G

Gordon sits down with the UMTS Forum chairman and communications manager to learn about this imminent 160Mbit standard.

”As 3G becomes a staple part of every dumb and smartphone worth its salt the question has started to arise: what’s next? The short answer is ‘LTE’ or ‘Long Term Evolution’ and the first commercial roll-out has already begun in Sweden.”

”The premise is phenomenal: the theoretical maximum of HSDPA will be raised from 7.2Mbit to LTE’s remarkable 160Mbit – and that’s just the first iteration. That said, there is much confusion about what this exciting successor can and can’t do and when it might arrive to a wider audience. Consequently, I sat down with Jean-Pierre Bienaimé, chairman of the UMTS Forum, and Chris Solbe, communications manager at the UMTS Forum, to try and definitively sort fact from fiction.”

”’Jean-Pierre, Chris the talk about LTE is starting to build. What should people expect?”’

CS: “As you say LTE is what people are beginning to talk about and rightly so. It is interesting in on lot of levels as delivery proposition broadband experience – we will finally get proper megabits on move and that’s when mobiles get interesting with audio and video streaming experiences. LTE also has much better latency than 3G, it will bring another jump forward in terms of the user experience.”

JPB “We prefer speaking of a typical average data rate than theoretical peak rates, HSDPA can go up to 14.4Mbits but it never delivers and LTE will begin at up to 160Mbits but what is interesting is to get the typical minimum rate and that will be reached by the customer.”

”’I think this is where the excitement comes from. With so much more bandwidth available surely we should get a base speed that will reliably handle most things and perhaps better coverage?”’

CS “(Regarding coverage) Not in itself but so much more comes with the LTE experience to make it better. For instance LTE can be used over lots and lots of different frequency bands which make it a very flexible technology. GSM or 3G operate in much narrower bands.”

JPB “When you look at the trials, the tests by which networks measure throughputs and users per cell. Just one user on a cell would get 160Mbits but this has to be divided by the number of users. Most important is that the minimum is insured for the customer. Say 2Mbit is ensured with an average of 4/5Mbit all the time, not the 160Mbit you will get in ideal conditions. What is very important is the end to end communication.”

This is the issue. If HSDPA really ran at 7.2Mbit there would be no worries, if Wireless G actually produced 50Mbit there’d be no need for Wireless N. You need a bigger pipe. Will LTE scale as HSDPA did from 1.8Mbit to 3.2Mbit to 7.2Mbit?

JPB “Yes, there are several levels, 300Mbit is the theoretical top. With this type of technology beyond that you begin to hit the limits of physics. For full performance LTE needs the widest bandwidth possible. The benefit is its spectrum efficiency and spectrum flexibility. It can operate all the way from 1.4MHz up to 20MHz.”

CS “It’s a big chunk of contiguous bandwidth which means more users can get a better quality of service. If you’re an operator you want the biggest amount of spectrum space possible and the beauty of LTE is it scales so you can prioritise it differently for speed or coverage depending on whether you are in a city or more rural area. And don’t forget LTE can help decongest the 3G network by moving away the heaviest users so the benefits can be two fold in both the new standard and for the existing one.”

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