But the eagerness of vendors to access the dollars of chief backer China Mobile, as well as others like Reliance Infotel in India and Clearwire in the US, has accelerated their R&D roadmaps and the technology is close to full commercial availability.
It is particularly being eyed as a standard which can be adapted more flexibly than FD-LTE to take advantage of underused spectrum, including unlicensed frequencies and the 3.5GHz band, and to support new business models, such as machine-to-machine and data-intensive services for business.
One way to extend LTE into bands where it does not sit comfortably in its current forms is to use license exempt spectrum. Deploying LTE in such bands is increasingly discussed as a way to maximise capacity and simplify data offload from licensed networks. As regulators in the US and Europe become friendly towards one of the (mainly) licence exempt options, the white spaces in TV bands, Huawei has produced a TD-LTE system for the frequencies from deep in its laboratories.
The vendor said it had been working on the technology for two years but had not publicized it. However, supporters of the TDD version of LTE – which will underpin China Mobile's 4G roll-out in future, among others – see an opportunity to extend its influence by pushing it into unconventional bands, even if FD-LTE remains dominant in the “classic‟ mobile broadband frequencies such as 1.8GHz, where most spectrum is still being allocated on a paired basis.
Huawei's trial platform is called TVWS (TV White Space) LTE TDD and it is now embarking on field tests, particularly with an eye to interference problems with incumbent broadcasters or wireless microphone users. The trial is scheduled to be completed in mid-2012.
“The LTE TDD system can take full advantage of TVWS bandwidth and enhance spectrum efficiency,” said Tan Zhu, director of Huawei's wireless strategy department, in a statement. “This LTE TDD system will benefit network and service providers by offering a combination of strong operation and management capability, a mature industry chain, and variety of deployment scenarios.”