Carriers hold key to TD-LTE's out-of-the-gate performance

The TD-LTE ecosystem is ramping up quickly, but it is unclear if this nascent technology will burst out of the gate with the robust performance that characterized early products supporting the FDD flavor of LTE, according to Nigel Wright.

FDD LTE devices quickly ramped up in terms of performance, in part, because U.S. operators such as Verizon Wireless (NYSE:VZ) and AT&T Mobility (NYSE:T) were driving that technology's deployment, and "North American operators have a huge track record of pushing back on their supply chain to get it right," said Wright, vice president of wireless product marketing at test and measurement products vendor Spirent Communications.

"I do believe a successful piece of the successful rollout of FDD LTE was that the leading North American carriers were involved," he said.

In the United States, TD-LTE is being backed by Clearwire (NASDAQ:CLWR), which doesn't have the financial ballast to make it a heavyweight when it comes commanding vendors to up the quality of their products. Another TD-LTE backer is China Mobile, which certainly has influence as the world's largest mobile operator but isn't known for prodding its vendors on performance standards, at least not as assertively as North American operators, said Wright.

However, he said China appears dedicated to making TD-LTE a success since its homegrown TD-SCDMA technology had only limited regional success. Last month, Spirent announced that China Telecommunications Technology Labs, a national-level telecom research institution of China's Ministry of Industry and Information Technology, selected the Spirent VR5 HD Spatial Channel Emulator for use in TD-LTE testing. Since one of its core functions is testing and certification of telecom products, CTTL will likely play a key role in the commercial readiness of TD-LTE.

Further, there is growing competition among vendors that want to play in the TD-LTE space. Wright noted there are at least 15 chipset vendors chasing down TD-LTE. Many of them, such as Sequans Communications and Altair Semiconductor, previously dedicated their efforts to WiMAX.

Early TD-LTE deployments might be role models for future rollouts. Softbank's TD-LTE network in Japan "provides a lot of insight into how these networks might be structure going forward, with lots of microcells," Wright said. He envisions operators using FDD LTE in macrocell networks and supplementing those with TD-LTE in microcells

TD-LTE, because it requires synchronization between base stations, offers advantages in terms of interference mitigation that might make it attractive in a small cell environment, said Wright. This is particularly true in place such as Europe, where operators won FDD spectrum for WCDMA along with TDD spectrum that has largely sat unused.

Given the fact that there is considerable effort being applied to TD-LTE development worldwide, "it doesn't seem unreasonable to think that in the next three or four years it really could be 25 percent of the global market," said Wright. "So we're planning accordingly because that's a pretty significant opportunity."

He said TD-LTE could become popular in markets where device cost is critical. It is cheaper to build a single-mode TD-LTE device because it doesn't  requires a lot of complex RF components that FDD needs, such as a duplexer to avoid interference in an FDD system. "In TDD, you just need to switch between the transmitter and the receiver," Wright said.

One market to watch is India, which mandated TD-LTE as the technology to use with Broadband Wireless Access licenses. Since 3G hasn't taken off in India, there really is no need to offer more expensive multimode devices that include 3G, Wright said.

"TD-LTE's future depends on adoption in large markets such as China and India," he added.

So far, Spirent's TD-LTE efforts have been largely focused on conformance testing. "As the device ecosystem starts to ramp up, we expect to see much more demand for performance testing," said Wright, adding "We will be adding TD-LTE to pretty much all of our device testing solutions."

TD-LTE testing efforts are ramping up quickly. Last week Huawei announced it had established open TD-LTE interoperability testing labs in Xi'an and Shenzhen. "The labs were established to cooperate with chipset, device and application partners for the purpose of creating an open and win-win LTE ecosystem while driving end-to-end TD-LTE maturation and commercialization," said Huawei.

In April of this year, Huawei and Intel established another joint interoperability testing lab in Beijing to promote the development of the TD-LTE ecosystem.

For more:
- see this Huawei release

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