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Just What Is LTE TDD Anyway?

Dan Jones
LR Mobile News Analysis
Dan Jones, Mobile Editor

If it gets more money, Clearwire LLC (Nasdaq: CLWR) could be one of the first operators in the world to deploy Long Term Evolution Time Division Duplex (LTE TDD), so we thought it was a good time to remind you what this 4G technology is and how it is different from today's Long Term Evolution (LTE) networks. (See Clearwire Goes It Alone With Faster 4G.) The basics
The key difference between LTE TDD, sometimes also known as TD-LTE, and the frequency division duplex (FDD) version more common today is in what spectrum the technology is deployed in and how the signal is transmitted. TDD technology uses a single channel and a timed signal to separate uploads and downloads. FDD systems have two channels of paired spectrum separated with a guard band for uploads and downloads.

Advocates of TDD technology suggest that the single channel makes the network more bandwidth-efficient. In the real world, however, operators tend to deal with the spectrum they were dealt through acquisition or auction. Therefore, Verizon Wireless is running FDD LTE on its 700MHz holdings, whereas -- as AnandTech points out -- Clearwire has enough 2.5GHz spectrum to consider various TDD deployment tactics while continuing to run its existing WiMax network. (For some history on this, see McCaw's Mystery Millions and A Clearwire Timeline .)

The devices
IP-based TDD devices are ideal for fast data downloads; indeed, Clearwire claims up to 120 Mbit/s down in tests in Phoenix. In the future, this will likely mean digital cameras, video recorders and MP3 players using the technology, as well as handsets, tablets and PCs. For now, vendors like Huawei Technologies Co. Ltd. are introducing multi-modal TD-LTE data cards that can support a variety of 3G and 4G technologies. (See Huawei Readies LTE TDD Device.)

The players
Huawei and other Asian vendors like Samsung Electronics Co. Ltd. (Korea: SEC) and ZTE Corp. (Shenzhen: 000063; Hong Kong: 0763) loom large as LTE TDD device suppliers now, largely because the technology has been spearheaded by China Mobile Communications Corp. and is being tested on the mainland and growing in popularity as a next-generation option in India. Alcatel-Lucent (NYSE: ALU), Ericsson AB (Nasdaq: ERIC) and Nokia Networks have all participated in various trials as well. (See China Mobile Trials LTE TDD With NSN and Market Spotlight: LTE TDD.)

The future
If it raises the $600 million it needs to deploy a TDD LTE overlay in the U.S., Clearwire could be among the first operators to bring the technology online in the world. ABI Research currently tracks 28 commercial FD-LTE networks, but says that no TD-LTE network has yet gone live. (See No TD-LTE Network has Gone Live Yet.)

— Dan Jones, Site Editor, Light Reading Mobile

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User Rank: Light Beer
12/5/2012 | 4:56:49 PM
re: Just What Is LTE TDD Anyway?

Verizon and ATT networks are built by bureaucrats and Clearwire network is built by network professionals.   The Telco bureaucrats still want 20 years service out of their equipment dispite the fact that everyone knows that IP equipment will be obsolete in 5 years. To expect to receive free equpment from every manufacturer and take 2 years to qualify hardware and short list their vendors, shows how incompotent and out of touch they are.  These guys are putting thier own suppliers out of business.  There is no longer a ma-bell with infinit resources to hand out free hardware, but they still expect it.  In 2 years that it takes to qualify hardware, the original equpment they have qualifid is already 2 years into its obsolecense cycle.   These guys want so many bells and whistles (including TDM support) in their equipment that not only drives the hardware equipment price high, it also makes them unstable.    Lets face it these guys put Nortel and Lucent out of business and Alcatel is on its last leg.   Google's venture in hardware is clearly a message to hardware providers, look, stop putting so many bells and whistles (not to mention TDM) on your hardware, we ain't paying for extra waisted  hardware.  The Telcos are currently in violation of the law because none of them delivers LTE speeds that they advertise and hopefully some attorney general will get the message and have them stop advertising their barely 3G network as 4G LTE.  Their networks are already collapsing under the weight of a few 4G devices that are running on their network.   We need investment in Clearwire to continue because they are the only viable option to building America's future wireless network infrastructure.  

User Rank: Light Beer
12/5/2012 | 4:56:47 PM
re: Just What Is LTE TDD Anyway?

Well, one direction investment *could* come from is vendor financing from Huawei or ZTE.

User Rank: Light Beer
12/5/2012 | 4:56:44 PM
re: Just What Is LTE TDD Anyway?

It's unlikely that US operators would get approved financing from Huawei or ZTE, that would (arguably) come from Chinese Government. However, if they would, then it might be unfair for other vendors that couldn't get such backup from their government (Ericsson, ALU, NSN), or at least, not enough. Unfortunately there is no worlwide regulator for this kind of practice, and most of the time country telecom regulators can't control proper competition and fair negotiations between operators and providers.  

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