Wireless Systems Design

Whatever Happened To 802.20?

I've been writing about WiMAX and the 3G/4G cellular technologies lately and every now and then I see references to the IEEE 802.20 standard. In case you are not familiar with it, it is a mobile broadband wireless access technology that really does compete directly with mobile WiMAX 802.16e and the 3G/4G cell phone technologies. The IEEE established the 802.20 wireless mobile broadband group in 2002 and work began and progress was made. But the big question is: Whatever happened to this project? Now I know, so I can tell you about it.

WiMAX, or 802.16 broadband wireless technology, was intended to be a fixed service. And a fixed service was quickly developed and ratified in 2004. It was initially called 802.16d but is now referred to as 802-16-2004. In any case it is a fixed or nomadic service designed primarily for use in laptops and in fixed modems for home or small business broadband access. The overall goal was to create a broadband wireless service that could compete with cable TV and DSL. It would be ideal for rural and small cities that still don’t have Internet service faster than dial up. And it would make a great complement to Wi-Fi in laptops where no 802.11 hot spots were available.

Apparently the 802.16-2004 group was so successful that they decided to tackle a mobile version of the standard even though the IEEE designated 802.20 as the mobile broadband wireless standard. And they did a great job. The 802.16e-2005 standard was ratified in 2005 and already most of the networks are expected to accommodate both fixed and mobile services.

Fixed WiMAX is available right now. Basestation equipment is very affordable and already WiMAX is doing a good job implementing Wi-Fi and other back haul. In the US, licensed WiMAX spectrum is available in the 2.3- to 2.7-GHz bands. Unlicensed operation is also permitted in the 5.8-GHz band. Basestations can cover a radius of several miles and data rates can be as high as 10 Mb/s depending upon what the carrier provides. Right now, Clearwire and Sprint Nextel are building out a nationwide WiMAX network that should go into operation in 2008. Even AT&T is considering WiMAX.

The goal of the 802.20 group was to create an all IP based packet air interface that would deliver at least 1-Mb/s data rate in a metropolitan area network (MAN) in the spectrum below 3.5 GHz. The technology was to feature OFDM. This was to be a mobile technology that could maintain connection and data rate at speeds up to about 155 mph. They must have had high-speed trains in mind here. Pretty impressive performance if you can get it.

As often the case in these standards, deliberations hamstring productivity. Different technologies get consideration based on the IP from different companies. Once a couple of approaches have been chosen, the politics and positioning begin. In the case of 802.20 apparently two factions were created, one based on an Intel/Motorola proposal and the other coming from Qualcomm/Kyocera. The drafting, voting, revising, and ratification process is repeated many times to reach a consensus or what amounts to a 75% majority vote. But with the IEEE's unusual voting rules, things apparently got out of hand. That led to squabbling, disagreements, and accusations. Obviously this stalled development work and the 802.16e group got the inside track.

Standards’ problems seem to be relatively common these days. The work on the next generation 802.11 wireless LAN standard, called 11n, had similar problems when progress was brought to a halt. Last year an external group of companies formed the Enhanced Wireless Consortium to draft a workable standard. That draft was submitted to the 802.11n group and it was voted in. While a final ratified version of the standard is not expected until next year (some even say 2009), the Wi-Fi Alliance is already agreed to certify a pre-n or draft 2.0 version of the standard. You can already buy pre-n draft 2.0 chips and wireless LAN routers.

The ultra wideband (UWB) group 802.15.3a faced similar opposition. Two factions were made up, with Motorola (Freescale) on one side supporting direct-sequence-impulse type UWB, and everyone else backing the OFDM type. Again, a lopsided voting problem prevented the group from achieving 75% support. The group was subsequently abandoned. Outside, the OFDM group formed the WiMedia Alliance which went on to establish a standard that is used today. There is no IEEE UWB standard.

In any case, the IEEE finally stepped in and shut the 802.20 group down in 2006. But since then it reestablished the group with new leadership and progress is back on track. If you want to check up on its progress, you can go to the IEEE standards website (www.ieee802.org/20). I tried to talk to their chairman several times but never been received a call back. It would have been good to get an official word about their plans and progress.

My guess is that the work of the 802.20 group is too little too late. With both 802.16e-2005 and 3G technologies well on the way, there seems to be little need for 802.20 at this point, unless they come up with some unique feature or benefit that none of the others have. What could that be? Maybe we are in for a surprise.

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