IEEE 802.16 spec could disrupt wireless landscape
By Loring Wirbel, EE Times
May 30, 2003 (4:06 PM)
URL: commsdesign.com
COLORADO SPRINGS, Colo. — The IEEE Standards Authority on Wednesday (Jan. 29) approved the 802.16a specification for wireless metropolitan-area networks (MANs) in the 2- to 11-GHz range, giving a seal of approval to technology that one executive said could enable a disruptive change in communications.
Roger Marks, chairman of the 802.16 committee and a wireless director at the National Institute of Standards and Technology's labs in Boulder, Colo., said industry discussions are inevitable as to whether 802.11 and 802.16 wireless specs are complementary or whether they overlap.
In an ideal world, Marks said, 802.16a can serve as a backbone for 802.11 hot-spots. Still, some wireless LAN advocates promote 802.11's use as a MAN, even though its medium-access control protocol is fundamentally optimized for shorter-range topologies. At the same time, Marks said, others have talked of using 802.16a within the enterprise as an adjunct to 802.11a or 802.11g. If the 802.11e working group has trouble providing true quality-of-service prioritization for wireless LANs, then it might make sense to take 802.16a directly to an end user, Marks said. Otherwise, "it's more efficient and more cost-effective to look for the ways 802.11 and 802.16 complement each other."
The 802.16 MAN, which won approval in 1999 as its own study group in IEEE, has suffered and benefited from both the telecom collapse and the belated craze over WLANs. In its early days, the wireless MAN work was centered on licensed services in higher frequency bands, though this work has been swamped by lower-frequency efforts that come closer to bridging wireless LAN services into the metro area.
The 802.16a standard specifies three physical layers for services: a single-carrier access method which was retained for special-purpose networks; a 256-carrier orthogonal frequency division multiplexed (OFDM) multicarrier for mainstream applications; and a special "OFDMa" standard with 2,048 carriers, which can be used for selective multicast applications, and advanced multiplexing options in tiered metro networks.
The 802.16 Task Group C on interoperability for 10- to 66-GHz frequency ranges still is proceeding with useful work for higher-frequency services evolving from LMDS and point-to-point 50- to 60-GHz radio. Compliance and test documents for 802.16c were published in April 2002, and implementation profiles were published in mid-January. But the task group with the heaviest participation right now is 802.16e, which seeks to add some level of mobility to wireless MANs.
Defined interests
When outsiders hear of such mobility goals, many assume that 802.16e is going after any broadband wireless metro market that might have been served by nascent 3G cellular services. In reality, Marks said, the task group has no interest in high-speed handoff in an automotive environment. Instead, 802.16e specs are aimed at the slow-speed, lightly mobile user who wants to maintain some level of roaming within metro access points. The task group hopes to have a first draft of mobility completed in July.
Wireless MANs now are supported by a coalition named the WiMax Forum, which develops interoperability tests based on the profiles developed by the 802.16 task groups. As important as the forum, however, has been public statements from Intel Corp. and other vendors saying they expect 802.16 to be every bit as revolutionary as 802.11. |
