Last month's LTE conference in Hong Kong offered plenty of updates from cellcos on their plans for LTE, but little in the way of new topics to talk about - with two exceptions. One was the concept of LTE as ADSL substitute and possibly FTTH challenger (see this month's "First Mile: LTE to take on FTTH in Japan").
The second was TD-LTE. Which is astounding.
I say this because TDD has always been the stepchild of the 3G world. It had two standards under IMT-2000 and gave cellcos that acquired unpaired spectrum during 3G license auctions something to do with it - like, say, offer fixed-line broadband substitution in unserved areas much like Wimax is doing now. Only they didn't, of course. Cellcos were focused on FDD-based W-CDMA, and despite the efforts of a handful of companies like IPWireless and InterDigital, TD-CDMA (the UMTS version of TDD) never caught on.
Delay tactics
China's version, TD-SCDMA, generated even less love. TD-SCDMA carried too much political baggage that became increasingly noticeable as China's MII continuously put off issuing 3G licenses in an apparent plan to wait until TD-SCDMA was ready for commercial prime time - and, more importantly able to compete against W-CDMA and EV-DO.
Almost a full decade after the ITU approved it for IMT-2000, TD-SCDMA went live in 2008 (in extremely limited quantities), and China Mobile has already slashed its end-of-2009 subscriber target by 70%. Meanwhile, critics have piled on China for obstinately backing a technology that would only serve to isolate it in a 3G world, as no one in the world was ever going to seriously adopt TD-SCDMA.
Oh how they laughed.
They're not laughing now.
Well, all right, they're laughing a little. But they're paying a lot closer attention to its possibilities, especially now that TD-SCDMA is primed to evolve into a global standard: TD-LTE.
Granted, TD-LTE's sales pitch is not all that different from its ancestors - i.e. making use of unpaired spectrum to boost capacity in urban environments where FDD macro networks get overloaded. What is different this time around is a bigger ecosystem of vendors developing it - admittedly for just a single market at the moment, but also the biggest single mobile market in the world.
The other key difference is that TDD has always been primarily a data play. But from 2001 up to 2008, 3G cellcos were still primarily in the voice business, and FDD allowed them to continue milking that cash cow. That worked fine when 3G data usage was still mostly ringtones, wallpapers and other walled-garden content.
Then the iPhone happened. Smartphones got smarter and data usage skyrocketed so high that E1 backhaul links became the new bottlenecks. If ABI Research is to be believed, by 2014 mobile users will be transmitting a total of 1.6 exabytes a month (compared to 1.3 exabytes for all of last year).
Hence all the interest in LTE, as well as related technological tricks to offload data traffic and maximize RAN capacity like spectrum refarming in the 900- and 1800-MHz bands and femtocells. TD-LTE is another tool in the toolbox, and by the time we start hitting monthly exabyte levels in five years, its predecessor in China will have been put through the ringer enough to qualify as "seasoned" if not "mature".
Of course, all that depends on a ton of factors over the next five years. Still, TDD is a lot closer to realizing its potential than it was at the start of the decade.
If nothing else, TD-LTE may have the novel distinction of being the quietest evolution the cellular world has yet seen. That will depend on how much progress Qualcomm and other chipset vendors make with dual-mode FDD/TDD chipsets, but once devices are capable of roaming seamlessly between both, TD-LTE may be the first RAN acronym that won't need to be marketed to end-users who don't give a toss what it's called anyway.
Which will make a nice change.