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.
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.
The 802.16 effort got a major boost at the Wireless Communications Assoc. conference in San Jose in mid January. There, Sriram Viswanathan director of Intel Capital's Broadband and Wireless Networking Investments group, declared during his keynote that "802.11 is the first key disruption. 802.16 is the next." And he should know. He manages Intel's worldwide broadband and wireless networking investments where his team has made more than 40 equity investments, including the recently formed Cometa, as well as broadband wireless leader Navini.
Viswanatha n stands by his words today, arguing that in areas where no wired infrastructure is in place, 802.16 is "a viable last-mile solution. And for WLAN hotspots, 802.16 is appropriate for backhaul." Viswanathan identifies backhaul as a major hurdle to the widespread deployment of WLANs in the public.
Intel backed up Viswanathan's words by leading the Wi-Max forum, a similar-style group to the Wi-Fi Alliance. "We believe that all [the fixed wireless access companies] will be standardized and get universally adopted, and 802.16 is a step towards this." Intel's ultimate vision was spelled out at Viswanathan's keynote when he said that "All communications devices will compute, all computing devices will communicate."
Sriram did not point to any direct Intel involvement in product development for 802.16. However, along with its current investment in Navini, it will continue to actively search out companies "that show the ability to bring down the cost of 802.16 technology and get it deployed."
Sweet har mony
The debate over 802.11 versus 802.16 gets an added twist thanks to the inclusion within the newly ratified standard that provides for harmonization with the still-alive European-based HiperLAN-2 5-GHz WLAN standard.
The push for harmonization was led by Alvarion Ltd., a well- entrenched provider of proprietary fixed wireless access equipment. "We're a strong believer in standards," said chief evangelist at Alvarion, Patrick Leary, "having led the standardization of 802.11a for two years."
The ratification of the original 802.11b specification and the subsequent formation of the Wireless Ethernet Compatibility Alliance (now the Wi-Fi Alliance) interoperability group, was the driver behind the success that standard is currently enjoying.
"We fully intend to move our [proprietary] equipment over to 802.16, starting with the BreezeAccess5 which was designed from the ground up to be migratable toward the standard [when it became finalized]," said Leary. The BreezeAccess 5 uses OFDM in the 5-GHz band.
However, Leary did express disappointment that the standards group did not go along with Alvarion's push for more subcarriers in the OFDM physical-layer implementation, which according to Leary, would've provided an extra 6 dB in signal-to-noise ratio. "This would've led to larger cell sizes, but it didn't get through."