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802.16e vs. 802.20

With WiMax poised to usher in the second coming of fixed wireless broadband, two Institute of Electrical and Electronics Engineers (IEEE) working groups are turning their attentions to mobile broadband so you can use that high-speed connection on the road.

The emerging 802.16e and 802.20 standards will both specify new mobile air interfaces for wireless broadband. On the surface the two standards seem very similar, but there are some important differences between them. For one, 802.16e will add mobility in the 2 to 6 GHz licensed bands, while 802.20 aims for operation in licensed bands below 3.5GHz.

More importantly, the 802.16e specification will be based on an existing standard (802.16a), while 802.20 is starting from scratch. This means that products based on 16e will likely hit the market well before .20 solutions -- a distinct advantage for the WiMax Forum, the group currently backing 802.16 and its permutations.

The IEEE approved the 802.16e standards effort in February with the avowed intent of increasing the use of broadband wireless access (BWA) by taking advantage of the "inherent mobility of wireless media." The amendment to 802.16, which is also called the wireless metropolitan area network (MAN) standard, will enable a single base station to support both fixed and mobile BWA. It aims to fill the gap between high data rate wireless local area networks (WLAN) and high mobility cellular wide area networks (WAN).

There could be a draft of the .16e standard as early as the middle of 2004, according to Brian Kiernan, the chair of the .16e Task Group. This would give it quite a head start over 802.20, which is still in the very early stages of development.

The IEEE actually established the 802.20 Working Group before it gave the go-ahead to 802.16e and indicated that it intended to have a standard in place by the end of 2004, but the group has been mired in conflict (a battle for the chairmanship is currently underway) and has made little progress.

The 802.20 interface seeks to boost real-time data transmission rates in wireless metropolitan area networks to speeds that rival DSL and cable connections (1Mbps or more) based on cell ranges of up to 15 kilometers or more, and it plans to deliver those rates to mobile users even when they are traveling at speeds up to 250 kilometers per hour (155 miles per hour). This would make 802.20 an option for deployment in high-speed trains. The 802.16e project authorization request specifies only that it will "support subscriber stations moving at vehicular speeds"; Kiernan said the group has achieved speeds of 120 to 150 kilometers per hour (75 to 93 miles per hour) in simulations.

There is clearly some overlap between the two standards, but the party line from companies involved in the 802.20 standards effort, including Navini Networks and Flarion Technologies, is that the two are not competitive. The IEEE would not ratify a group that has competing interests with an existing group, argued Sai Subramanian, vice president of product management and strategic marketing at Navini. "If they are so obviously in conflict, why did IEEE approve two standards tracks?"

Not everyone is buying that argument, though. "The bottom line is they're very similar," said Ed Rerisi, director of research at Allied Business Intelligence (ABI). "They do have some minor differences, but they both are aimed to serve similar users."

Essentially, 802.16e is looking at the mobile user walking around with a PDA or laptop, while 802.20 will address high-speed mobility issues, he said. One key difference will be the manner in which the two are deployed. "Our assumption is that the carriers are going to deploy .16e in their existing [.16a] footprint as opposed to deploying a more widespread footprint, like a cellular network, for example," said Rerisi. "802.20 is looking at more ubiquitous coverage ... and that will require a larger footprint."

Indeed, some argue that 802.20 is a direct competitor to third-generation (3G) wireless cellular technologies. Since mobile operators are spending millions to upgrade their networks in order to offer 3G services, it could be a tough sell to persuade them to invest in yet another network.

It doesn't have to be an either-or situation, though, said Ronny Haraldsvik, senior director of marketing strategy at Flarion Technologies, which has been heavily involved in the 802.20 standards process. He said that operators could deploy 802.20 as an overlay to their existing networks. "They don't have to walk away from what they have."

In the meantime, 802.16e's head start may actually work to 802.20's advantage by whetting users' appetites for mobile access, Rerisi suggested. "If 802.16e drives demand initially and people are getting thirsty for it, a .20 solution could be deployed on a widespread basis and take advantage of users wants and demands for high-speed data."

Ultimately, the fate of both standards rests with 802.16, he said. "I think that if there's success in the 802.16 market, it'll definitely portend good things for the 802.20 market."