The Time-Division Duplex (TDD) variant of Long Term Evolution (LTE) technology will account for a quarter of all LTE connections by 2016, according to analyst firm Ovum.

When most people talk about LTE, they are referring to Frequency Division Duplex (FDD) LTE, which carries two separate signals – one for uploading and one for downloading. LTE FDD is what most mobile operators around the globe are using to upgrade their current 3G services.

By contrast, LTE TDD uses a single channel, and dynamically assigns bandwidth to each connection based on user requirements. This means that download capacity is maximised at all times, which is important because around nine times more data is downloaded than uploaded, and this is expected to increase 25 times over the next five years.

Developed by China Mobile in 2007, LTE TDD has now gained wide ecosystem acceptance from leading infrastructure and device vendors, and is used by operators including Softbank (Japan), Optus (Australia), Hi3G (Sweden and Denmark), and STC (Saudi Arabia).

“The biggest market opportunities for LTE TDD will come from its deployment to support mobile broadband services,” said Daryl Schoolar, a principal analyst in Ovum's Network Infrastructure practice. “Other opportunities will include its use as a fixed wireless broadband network and for small cell backhaul.”

Earlier this year, wireless company UK Broadband switched on a wholesale LTE TDD network in the London Borough of Southwark, to meet the growing demand for data capacity. The network, built using Huawei technology, will provide a platform for mobile operators to drop onto when capacity on their own networks becomes constrained.

UK Broadband’s 4G network will be delivered over six 20MHz channels of spectrum in the 3.5GHz and 3.6GHz bands, which became part of the LTE standard in March 2011. The company said that this would allow it to deliver LTE-Advanced speeds and enough capacity to deliver Next Generation Access superfast broadband speeds to a large number of users simultaneously.

Schoolar added that LTE TDD spectrum is cheaper that LTE FDD, meaning that savings can be passed on to end users. Thanks to multi-standard base stations, operators can also combine standards such as GSM and WCDMA/HSPA and LTE FDD/TDD, in order to increase the overall network capacity and increase quality of service.

“This is just a small part of it; the bigger opportunities lie in operators deploying it as their primary 4G network, such as Bharti Airtel in India and Mobily in Saudi Arabia,” he said.

Earlier this year, ABI Research predicted that at least half a million base stations will be installed or upgraded for the LTE TDD standard by the end of 2016. The company said that many WiMAX operators are now looking to upgrade to LTE TDD rather than WiMAX 2 – which was developed to provide higher data rates and increased capacity.