Report: Clearwire best served by moving to TDD-LTE

Clearwire's (NASDAQ:CLWR) decision to launch LTE trials this fall shook the wireless world. However, a new research report suggests the company may have a difficult time implementing an FDD-LTE network, and would be better served deploying a TDD-LTE network.

Click here for a detailed look at Clerawire’s spectrum position.The report, by wireless research firm Tolaga Research (headed by analyst Phil Marshall), found that despite Clearwire's significant spectrum holdings, the company "lacks adequate resources" to deploy FDD-LTE in many of the areas where it holds spectrum.

Clearwire said it will test LTE technology in both TDD and FDD configurations in the 2.5-2.6 GHz band. Clearwire said the Frequency Division Duplex tests will use 40 MHz of spectrum, paired in 20 MHz contiguous channels, which will produce download speeds up to 70 Mbps. (Verizon Wireless (NYSE:VZ) is working with 10 MHz channels in the 700 MHz band for its LTE buildout, which likely is using FDD-LTE.) Clearwire also said its Time Division Duplex test will run in a 20 MHz configuration, which the carrier noted is twice the channel size currently used in its WiMAX deployments.

Essentially, the report argues that Clearwire's spectrum holdings vary significantly across markets, which makes it difficult to employ FDD-LTE on a nationwide basis. "Of the major markets in the U.S., we believe that Clearwire is incapable of deploying FDD-LTE with 20 MHz duplex channels in Chicago, Detroit, Cincinnati, Orlando, Tampa, Fla., Portland and Columbus Ohio," the report said. "A hybrid network architecture that incorporates both FDD and TDD-LTE is necessary for Clearwire to offer nationwide service."

A Clearwire spokeswoman, Susan Johnston, said that the company believes it is "difficult to offer a definitive analysis of a given spectrum position due to the large number of assumptions that need to be made on a specific deployment and the competitively sensitive nature of this information." 

"Clearwire is fortunate that our deep spectrum position, all-IP network and technology agnostic approach gives us the flexibility consider several options for further evolving our 4G network to meet customer demand," she told FierceWireless.

The report concludes that even though Clearwire has significant spectrum resources, its allocations are "fragmented and suboptimum for FDD channel structures."

"Between 50 and 60 percent of its markets lack resources for FDD allocations, and a TDD technology overlay will be required to ensure nationwide coverage," the report said. "We believe that a competitive advantage with Clearwire's spectrum assets will depend on the long-term prospects of TDD as opposed to FDD-LTE."

The report also said that Clearwire might opt to deploy FDD-LTE in major markets where it has adequate spectrum--including Atlanta, Boston, Los Angeles and New York--while maintaining a long-term strategy to migrate its entire network to TDD-LTE, if and when, dual-mode FDD/TDD-LTE devices become widely available.

For more:
- see this Tolaga Research site

Related Articles:
WiMAX Forum confident in the face of operators' LTE flirtations
A Clearwire LTE switch won't bring wireless harmony overnight
Clearwire to begin testing LTE, promises speeds of 20-70 Mbps
WiMAX 2: The WiMAX Forum's response to TD-LTE

Article updated Aug. 23 with a comment from Clearwire.