While TD-LTE remains very much the junior partner in the 4G world, at least until China Mobile announces firm timescales, a few operators are now going live with the technology. The latest is Hutchiso\'s Hi3G unit in Sweden, which has switched on a dual-mode 4G network in three major cities, working across FDD and TDD bands.

This highlights a pattern in LTE which will not be prominent for several years, but is still significant - carriers harnessing both FDD and TDD frequencies in order to maximize the capacity they have to support mobile broadband. In some cases they will create parallel, interworking macro networks, despite issues of interference; in some they will use the TDD band for a separate layer, perhaps of small cells, or for a specific service, such as smart grid.

Several European cellcos, in particular, plan to adopt such a plan in a second wave of build-out once their FDD capacity becomes overstretched - either they will acquire TDD spectrum or partner with current holders. Hi3G has taken this view at a far earlier stage than most of its peers and invested in both types of frequencies right at the beginning, seeking to steal a march on larger and more established rivals in the Nordic regions. It bought both types of licenses in Swede\'s 4G auctions and is now deploying services in Stockholm, Gothenburg and Malmo, using equipment from ZTE.

The Chinese vendors have harnessed their work with China Mobile; their experience with the other TDD technology, WiMAX; and their software defined RAN platforms, to put themselves in a strong position when the dual-mode trend gathers pace around mid-decade. Huawei supplies kit to the other live dual-mode LTE network, at Aero2 in Poland. The third publicly announced such contract is in Australia, for the NBN national broadband initiative.

Such deals take TD-LTE beyond its first customer bases, among WiMAX carriers looking to migrate to the newer standard, as well as a few cellcos with no FDD spectrum, like China Mobile. The Hi3G and Aero2 roll-outs point to the future when TD-LTE will also be part of the network mix for mainstream, traditionally FDD-focused cellcos.

Hi3G says its dual-mode network will eventually cover the whole of Sweden and that it is saving on cost of ownership by using ZTE\'s new generation of energy saving base stations. The carrier\'s CTO Jörgen Askeroth said in a statement, "This network fully indicates the practical use of the mature LTE multimode convergent solution. It allows us to extend the partnership with ZTE."

Source: Rethink Wireless