Clearwire LLC (Nasdaq: CLWR) is part of a group of operators and vendors that has asked the 3rd Generation Partnership Project (3GPP) standards body to start work on specs that would allow TD-LTE to be deployed in the US in the 2.6GHz spectrum -- which is now used for WiMax -- in a move that further exposes the operator's interest in the competing proto-4G standard.

The proposal to adopt the 2496MHz-to-2690MHz frequency band in the US for TD-LTE, which was first highlighted on the "LTE Watch" blog, was accepted at a 3GPP meeting earlier this month. The acceptance is significant because it will enable Clearwire and other spectrum holders to deploy TD-LTE, which is the time division duplex (TDD) version of LTE, in the US.

The move is the strongest indication so far that Clearwire is eying the proto-4G technology chosen by its competitors, AT&T Inc. (NYSE: T), T-Mobile US Inc. , and Verizon Wireless -- although they will deploy the frequency division duplex (FDD) flavor of LTE.

The development also comes hot on the heels of Clearwire CEO Bill Morrow's comments at the International CTIA Wireless 2010 show in Las Vegas last week about operators using the same technology sometime in the future. (See CTIA 2010: Hesse – LTE Will Be Bigger But We Are First, Clearwire Is a WiMax Company (For Now), and Clearwire Testing in Silicon Valley as LTE Looms.)

Power in numbers
Clearwire was not alone in asking for the 2.6GHz spectrum to be defined as a TDD band for LTE. Indeed, there was broad industry support for the proposal from other companies, including: Sprint Corp. (NYSE: S), NII Holdings Inc. (Nasdaq: NIHD), China Mobile Communications Corp. , UK Broadband Ltd. , Motorola Inc. (NYSE: MOT), Huawei Technologies Co. Ltd. , TD Tech Ltd. , WiChorus Inc. , ZTE Corp. (Shenzhen: 000063; Hong Kong: 0763), Chinese Academy of Telecommunications Technology , Nokia Networks , Cisco Systems Inc. (Nasdaq: CSCO), Sequans Communications , Alcatel-Lucent (NYSE: ALU), Alcatel Shanghai Bell Co. Ltd. , and Rohde & Schwarz GmbH & Co. KG .

Part of the 2.6GHz band is already specified for TDD, namely the 2570MHz-to-2620MHz band. The new work at the 3GPP will ensure that all of Clearwire's spectrum will have a definition for TD-LTE operation and will get the TD-LTE specs in line with Federal Communications Commission (FCC) requirements as well.

The specifications for the US 2.6GHz band for TD-LTE is scheduled to be completed by March 2011.

However, although the work at the 3GPP will make it possible to deploy TD-LTE at 2.6GHz in the US, Clearwire is committed to WiMax for now. (See Clearwire Can't Stray From WiMax 'Til 2011.)

"Clearwire intends to maintain our 4G leadership position, which requires us to future-proof our network and stay abreast of emerging 4G technologies and evaluate their potential when and if standards are reached," a Clearwire spokeswoman wrote in an emailed response to Light Reading Mobile.

Another boost for TD-LTE?
Beyond the implications for Clearwire's future network technology strategy, adding the US 2.6GHz band to the 3GPP LTE specs could potentially broaden the market for TD-LTE.

TD-LTE is the flavor of LTE that China Mobile will use, although it will deploy the technology at 2.3GHz. The operator is looking to gain support for TD-LTE outside China, so that it is not limited by low equipment volumes and relatively few device choices. (See China Mobile Fast-Tracks TD-LTE , Motorola's Shanghai Hope, China Mobile Selects Sequans for LTE Chips, and ZTE, China Mobile Test TD-LTE.)

For example, India has emerged as a new market for TD-LTE in the 2.3GHz band after Qualcomm Inc. (Nasdaq: QCOM) announced plans to participate in the upcoming spectrum auction in the country. (See Qualcomm Unveils LTE Plans for India, So Who's Pals With Qualcomm?, and India's WiMax Camp Wants Intel's Support.)

— Michelle Donegan, European Editor, Light Reading Mobile