As LTE gains momentum, there are calls for more support for unpaired TDD spectrum

The focus of 4G competition is moving from coverage to higher data speeds and increased capacity, according to a new report from Strategy Analytics. The firm says that leading operators are now not only exploiting new frequency bands to deploy additional LTE carrier channels but also re-farming existing spectrum. They are also exploring new spectrum to support future traffic growth.

However, it recommends that to fully leverage the unified LTE standard, the industry must create a harmonised ecosystem, supporting products and solutions that conform to both modes of LTE – FDD and TDD.

“The unified global 3GPP LTE standard provides significant technical commonality and a good foundation for commercial harmonization between both modes, but the ecosystem for [unpaired] LTE TDD does not yet quite match its [paired] FDD counterpart,” said Sue Rudd, Director Service Provider Analysis at Strategy Analytics. “The industry needs to pursue commercial products and solutions that support both TDD and FDD to achieve global scale economies.”

As a duplexing mode of the 3GPP LTE standard, LTE TDD shares the same network architecture, protocol stack and common physical layer technologies with LTE FDD systems. Strategy Analytics says this enables seamless interworking that should enable operators who implement an integrated FDD/TDD operation to reduce operating costs and provide users an enhanced experience.

Strategy Analytics says the 3.5GHz bands look to be a good candidate in near term where LTE TDD can provide either fixed or mobile broadband access. However, there’s very little support from device manufacturers for these bands (42 and 43), with on 15 devices available according to the Global mobile Suppliers Association (GSA). Contrast that with 493 devices available for the 2600MHz FDD band 7.

Whilst the vast majority of terminals are designed for operation in the FDD mode, the GSA reports that 304 products can operate in the LTE TDD (TD-LTE) mode, which is almost double that of a year ago. Over 10 per cent of commercial LTE networks have deployed the LTE TDD mode. The GSA said in February that 28 LTE TDD systems are commercially launched in 21 countries, including 13 operators who use FDD and TDD modes in their operations.

“We learned that over half of the latest LTE device announcements included support for 1800MHz (Band 3), which is the most commonly used spectrum globally in LTE network deployments,” said Alan Hadden, President of the GSA. “Very soon 1800MHz will have the largest device ecosystem. Support for LTE TDD (TD-LTE) devices has also significantly strengthened.”

Strategy Analytics cites the Spark programme from US operator Sprint as proof that LTE TDD offers an efficient solution for mobile operators to increase their broadband capacity using higher frequency bands, while re-farming lower frequencies with LTE FDD to provide good coverage and spectral efficiency.

“Hybrid LTE FDD and TDD networks deployed in multiple frequency bands can help operators rapidly achieve a good balance between network coverage and capacity,” said Guang Yang, Senior Analyst for Strategy Analytics Wireless Networks and Platforms. “For operators with more limited access to paired spectrum, TDD provides a good option to deploy 4G LTE while still leveraging common LTE networking equipment and devices, as long as deployment bands are globally or at least regionally harmonised.”

A total of 274 operators have commercially launched LTE service in 101 countries, and the GSA forecasts there will be over 350 LTE networks in service by end 2014. Over 130 manufacturers are producing LTE devices.

North America leads the way in global LTE subscriptions, with 101 million as of Q4 last year, according to the GSA. This represents 50.5 per cent of the global total of 200.1 million. Asia Pacific follows with 77.8 million, and Europe adds another 16.4 million. A total of 125 million new LTE subscriptions were added during 2013.

“LTE subscriptions percentage growth in 2013 was easily the highest for any mobile technology, achieving an 166 per cent increase,” said Hadden. “This was over seven times more than any other technology.”

Incidentally, the GSA reports that the total number of subscriptions across all mobile communications technologies increased by 399 million net to reach 6.78 billion by end 2013, representing 6.25 per cent annual growth.