Industry momentum behind Time Division LTE continues to grow with news that a number of major operators and vendors are working with the 3GPP to allow the standard to be deployed in the USA, using the 2.6GHz spectrum band. Clearwire and its partners own the majority of that spectrum. Most of Clear’s 2.6 GHz spectrum goes unused.
Light Reading Mobile notes that China Mobile, Clearwire, Sprint Nextel, Motorola, Huawei, Nokia Siemens Networks, Alcatel-Lucent and Cisco Systems are asking for the 2.6GHz spectrum (2496MHz to 2690MHz) to be defined as a TDD band for LTE.
Outside the United States, part of the band (2570MHz to 2620MHz) is already specified for TDD. The new work will extend this compliance. The report adds that specifications for the US 2.6GHz band for TD-LTE is scheduled to be completed by March 2011.
Sprint and Clearwire may like the idea of TD-LTE because finding spectrum pairs for resale to cellular carriers could be problematic. Time Division LTE and WiMAX/WiMAX 2.0 might co-exist without stepping on each others spectrum.
The presence of Clearwire in the consortium of operators and vendors backing the US move indicates that the WiMAX service provider is keeping a very close eye on LTE.
Only last week the head of Clearwire called for greater integration between competing WiMAX and LTE standards. Clearwire is sitting on a spectrum bonanza. Selling or leasing spectrum for Time Division LTE makes good sense. It could also work with international TDD-LTE phones and devices that use the 2.6 GHz spectrum.
TD-LTE (the unpaired ‘version’ of the more common Frequency Division LTE), is in its infancy, but recent industry moves suggest it could become an important technology.
LTE pioneers TeliaSonera, NTT DoCoMo and Verizon Wireless, will all use different frequency bands for their respective LTE networks, explains TechWorld. So for roaming in the U.S, Japan and Europe to work, modems will have to support 700MHz, 2100MHz and 2600MHz, with more bands to be used in the future. That will be a challenge for roaming, says Light Reading.
- TeliaSonera’s LTE network began commercial operation in Stockholm and Oslo in December 2009, and will continue to expand in 2010. TeliaSonera plans to offer LTE in the 25 largest municipalities in Sweden alongside the four largest municipalities in Norway. It uses the 2.6 GHz band and (two) 20 MHz wide channels, using FDD-LTE. TeliaSonera uses an LTE modem from Samsung for its networks in Stockholm and Oslo. Support for roaming will be a natural next step, according to Tommy Ljunggren, head of system development at TeliaSonera.
- NTT DoCoMo, Japan’s largest cellular provider, plans LTE service this year. DoCoMo’s LTE service will operate in the 2.1GHz band, which is one of two radio bands it currently uses for 3G service. The company has set a launch date of December 2010 for the FDD-LTE service.
- Verizon plans FDD-LTE service this year in the 700MHz band (which AT&T will also use). Verizon says they’ll start with 25 to 30 markets in 2010, covering approximately 100M people; and extend the footprint to cover their current 3G users in 2013.
- AT&T now plans to begin field trials of LTE this year, and announced plans to establish Innovation Centers to drive development of next-generation devices, applications and equipment.
Limited spectrum is the main problem with LTE in the 700 MHz band. There is also the issue of self-interference, limiting practical range and speed. AT&T and Verizon have a total of 20 MHz to work with. Clearwire has close to 150 MHz.
WiMAX advantages include data-centric Time Division channels (10 or 20 MHz wide), upgradability to WiMAX 2.0 with 100+ Mbps (and backward compatibility with Mobile WiMAX), unlicensed use in the 5 GHz and 3.65 GHz bands, and a more open infrastructure with a highly defined specification for plug and play compatibility between different vendors.
One of the biggest advantages of LTE (besides backing by cellular operators) is the Time Division variant. In a data-driven world, symmetrical pipes can be a waste of space. Compatibility with overseas TD-LTE devices on the “premier” 4G band – 2.6GHz – would also be a big plus for Clearwire.
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Related LTE stories on Dailywireless include; LTE-TDD & WiMAX: Two Peas in a Pod?, Indian 3g/4g Auction: Qualcomm Bidding TD-LTE, LTE Migration White Paper, LTE: Wait For ItBlowback on 2.6 GHz, LTE: Cox Cable Calling, LTE Phones to be Showcased at MWC, T-Mobile USA Merger? and Houston WiMAXed.