Settling the confusion of WiMAX duplexing method: TDD or FDD or both?

There has been a lot of confusion lately about what duplexing method is used by WiMAX. Duplexing refers to the way the downlink and uplink data is arranged in a simultaneous transmit and receive transmission system (wireless or wireline). For wireless, the downlink carries information from a Base Station (BS) to Subscriber Stations (SSs). The uplink carries information from a SS to a BS.

Most WiMAX deployments support only TDD, There are several reasons why: TDD uses half of FDD spectrum hence saving the bandwidth, TDD system is less complex and thus cheaper, and WiMAX traffic will be dominated by asymmetric data. The WiMAX Forum first release of Fixed WiMAX profiles support both TDD and FDD, while Mobile WiMAX profiles only include TDD.

“Contrary to any of the unofficial statements made recently, the WiMAX Forum has not made any Board-approved policy or determination of when FDD mobile WiMAX system or certification profiles will be created,” said Ron Resnick, president and chairman of the WiMAX Forum.

Here's an excellent reference:
http://www.conniq.com/WiMAX/tdd-fdd.htm

To the best of our knowledge, no BS vendor has a combined Fixed WiMAX FDD/TDD system and there are none even contemplating combining Mobile WiMAX with LTE in the same BS platform. However, Ericsson has demonstrated LTE with FDD and TDD in the same BS platform while China Mobile and VZW are trialing LTE with both FDD and TDD duplexing methods.

Does anyone know something I missed?

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Permalink Reply by Rubens Kuhl on June 12, 2009 at 1:19am

Alvarion has a combo FDD/TDD 802.16d CPE, so one can change the BS without replacing every subscriber CPE.
Curious thing is that their FDD 802.16d is WiMAX Forum certified, but their TDD BS and CPEs are not.

TDD is required for some advanced antenna systems to work, but some bellheads seem to be fond of FDD, which is probably why LTE vendors are trying to please them all.

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Permalink Reply by Alan J Weissberger on June 12, 2009 at 12:28pm

I believe that cellular carriers like FDD because it's compatible with their existing 2G and 3G cellular networks.

Curious thing: I did not know that WiMAX Forum even had a program to certify FDD equipment (BS and CPE). Any other WiMAX FDD gear certified? Are you sure the Alvarian CPE is not also TDD certified?

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Permalink Reply by Rubens Kuhl on June 17, 2009 at 1:07am

Alan J Weissberger said:
Curious thing: I did not know that WiMAX Forum even had a program to certify FDD equipment (BS and CPE). Any other WiMAX FDD gear certified? Are you sure the Alvarian CPE is not also TDD certified?
The 16d FDD certification program was ready before the 16d TDD certification program, at least on 3.5 GHz.

The only WiMAX 16d FDD certified gear I know of is Alvarion, which doesn't mean there are no others.

Yes, Alvarion informed us that the TDD operation of the CPE was not certified and likely to not interoperate... which made us not buy 300 more units from them, so my guess yes they are right about this.