TDD LTE gaining momentum in 4G push, says ZTE
Some carriers could move from FDD
The Frequency Division Duplex (FDD) flavour of LTE will face increasing competition in favour of Time Division Duplexing (TDD), according to Chinese telecoms infrastructure giant ZTE.
Far more operators currently have FDD networks either in operation or trialing than TDD, as can be seen on this handy interactive map.
FDD's benefits are that it handles interference well and fits more neatly with the way many legacy networks were architected, ZTE’s VP of Wireless Sean Cai. That's all well and good, but TDD is more cost effective and efficient in the way it handles traffic, he says.
"TDD is gaining momentum," Cai told The Reg on a visi to HK this week. "TDD is becoming the trend."
“It’s not all about the technology but also the politics and regulations of individual countries.”
FDD LTE has been the natural choice for many operators in Europe and beyond who previously ran FDD 2G and 3G networks. However, by requiring paired spectrum the standard has been criticised for being inefficient, with downlinks becoming swamped while uplinks are wasted, Cai explained.
TDD transmits the up- and downlink traffic in the same unpaired frequency band, maximising available bandwidth, and incurs lower power costs. Another trump card is that an FDD set-up can be converted to TDD but not the other way around, said Cai.
"We're not able to predict when and how [some companies redeploy fdd spectrum to tdd] but we know it's going to be a long time," said Cai, stressing political and regulatory issues play a big role in operator strategy.
However, it could be 10 or 20 years before the LTE standards shake out and in the meantime ZTE has been promoting their co-existence in base stations by building the first dual-mode LTE network in the world for operator 3 in Sweden.
Cai was less willing to predict the end of the 3G TD-SCDMA which, despite technically being an international standard, is virtually unheard of outside of China.
The standard has caused China Mobile some headaches – Apple has never released an iPhone which supports it, for one – yet Cai feels the firm will have the edge when it comes to upgrading to TD-LTE as the process requires very little work.
In this context, far from backing the Betamax of 3G standards, China Mobile – the largest operator in the world with over 700 million subscribers – may have played a canny long game.
Cai was speaking ahead of Mobile World Congress, which opens later this month, when he said ZTE would be making some announcements on Radio Access Network technology. The firm has apparently worked hard in this area, with the goal of making the network more efficient by ensuring it can adapt dynamically to user behaviour.
Spectrum sharing, carrier aggregation, small cells and white space technology will also become vital in the coming years to coping with the flood of data and diminishing bandwidth, argued Cai. ®