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China Mobile Communications Corp. wants to start testing its so-called 4G technology TD-LTE soon, and through its demands for the technology, the operator has become one of the biggest driving forces behind the development of LTE worldwide.

The world's largest mobile operator by subscribers with 415 million customers is champing at the 4G bit. China Mobile's chairman and CEO Wang Jianzhou said today that he hoped to start trialling TD-LTE very soon, but that a lack of chipsets held those plans back. China Mobile champions TD-LTE, which is a time division duplex (TDD) version of LTE that will be backwards compatible with the home grown Chinese 3G standard TD-SCDMA. The TD-LTE specifications are scheduled to be completed by the end of this year along with the primary LTE/system architecture evolution (LTE/SAE) specifications.

China Mobile is pushing the industry and its vendors very quickly on TD-LTE. They're a hugely influential carrier. More significantly, China Mobile's TD-LTE will be compatible with the rest of the world's LTE, which is based on frequency division duplex (FDD).

China Mobile basically bridged the gap between TDD and FDD in LTE at the end of last year when it proposed what is now known as the "8+3 Proposal," which defined a new frame structure that would make a TDD version of LTE compatible not only with China's 3G TD-SCDMA, but also with FDD LTE. That proposal was the basis for today's TD-LTE spec that the 3GPP aims to complete by the end of the year.

The use of a single channel makes TDD much more spectrally efficient; however, operators have traditionally tended to favour FDD for voice. Unfortunately for the Chinese operator, TDD LTE development lags behind FDD LTE developments. It is expected that the first commercially available LTE equipment will support FDD. And equipment that supports both modes will follow. One industry estimate for commercial availability of TDD LTE terminals is mid-2010.

China Mobile recently unveiled plans to launch 3G services by the end of June next year in 38 cities. But the operator is clearly eager to move on to 4G technology. The major 3G vendors will have dual TDD and FDD functionality, but FDD will come first. To work on the dual TDD/FDD capabilities, China Mobile has joined forces with Verizon and Vodafone in their joint LTE trial. The equipment vendors participating in that trial are Alcatel-Lucent, Motorola, Nokia Siemens Networks, and Nortel Those trials are underway.

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