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www.wi-fiplanet.com/columns/article.php/3072471
September 4, 2003 With WiMax poised to usher in the second coming of fixed wireless
broadband, two Institute of Electrical and Electronics Engineers (IEEE)
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."
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