The rocky road to LTE

12 Nov 2008
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Earlier this year, the Wimax Forum held court at the Mobile World Congress in Barcelona and declared that Wimax, despite the naysayers, was here to stay.

'We went from having virtually no products here in Barcelona last year to having over 40 companies with real products on their stands, so Wimax is here and it's real,' Wimax Forum president Ron Resnick said at the time.

By that standard, if 2008 was the year Wimax proved itself to be a player, then 2009 could prove to be a similar key year for LTE. At an HSPA/LTE conference in Hong Kong last month, LTE was declared an official reality - not least by the Long Term Evolution/System Architecture Evolution (LTE/SAE) Trial Initiative (LSTI), currently comprising 21 vendors and eight operators, which was created in May 2007 to validate LTE/SAE's capability and facilitate interoperability to bring it to market faster.

'A year ago, the saying was that Wimax is real and LTE is not,' said Julius Robson, chairman of the LSTI Proof Of Concept Group, Nortel, 'but we can now say that LTE is out there in the field, there are trials, and it's real.'

That's no mean feat, considering that the original evolution path to LTE set a commercial trial availability target of 2011 at the earliest. But the wireless data market has changed considerably in the last couple of years. Wireless data usage has grown dramatically, driven partly by optimized trendy handsets like the iPhone, but also by laptops capable of replicating the Web user experience in a way handsets never could. And with Wimax designed from scratch to address that very market - and HSPA unable to keep up with growing demand for long - operators began clamoring for LTE to arrive sooner. Even CDMA operators decided they wanted it, forcing the CDMA Development Group to officially renounce its own 4G technology (UMB) and back an LTE migration path.

The good news is that LTE is living up to the hype in initial tech trials. According to LSTI's Robson, the group's proof-of-concept tests show LTE has surpassed the technical requirements outlined by the 3GPP, achieving a peak downlink rate of 154 Mbps field in a drive test using 2x2 MIMO. Another test using a 4x4 MIMO configuration yielded downlink peak rates close to 250 Mbps. Robson adds that LTE doesn't suffer much throughput loss under additional factors like differing RF conditions between users and application overhead, and that it also meets the 3GPP's latency requirements of 10 milliseconds for the air interface, 20 milliseconds end to end, and 100 milliseconds for the control plane.

But for all the hoopla over LTE's imminent arrival, that won't equate to massive rollouts any time soon. The standardization process is still ongoing, and apart from some early rollouts in the US and Japan (where NTT DoCoMo has already begun deploying its pre-LTE standard 'Super3G' technology) in 2010, even the most optimistic projections don't see serious LTE commercial rollouts before 2011.

That's not to say that LTE equipment won't be available before then. A number of vendors say they'll have LTE hardware ready next year. NSN plans to deliver LTE-ready base station hardware to over ten 'major mobile operators' in Europe, Asia and North America by the end of this year, with the promise that standardized LTE will be just a software upgrade away.

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