Dueling standards bodies eye the broadband wireless ring

When the IEEE finalized the 802.16 standard for fixed and mobile wireless access earlier this year, it was done to much applause. Sriram Viswanathan, director of Intel Capital's Broadband and Wireless Networking Investments group, commented that the newly ratified IEEE 802.16 standard for wireless broadband networks will be "the next big thing," after wireless LANs. Viswanathan's enthusiasm derived from his perception of 802.16 as a back-hauling scheme for Wi-Fi hotspots.

But Viswanathan's group is also an investor in broadband equipment vendor, Navini Networks (Richardson, TX), Sai Subramanian, vice president of product management and strategic marketing, makes no bones about the problems he sees with 802.16. Citing everything from lack of operator involvement and a lack of real-world data from which to establish the standards, to an almost zealot-like obsession with orthogonal frequency division multiplexing (OFDM), Subramanian instead vouches for the nascent IEEE 802.20.

Anointed the wordy title "Standard Air Interface for Mobile Broadband Wireless Access Systems Supporting Vehicular Mobility — Physical and Media Access Control Layer Specification," that standards effort was announced in February this year. Over the next two years the group will focus on creating an air-interface that will boost ubiquitous real-time data transmission rates in wireless metropolitan area networks from the the theoretical hundreds of kilobits/s of 2.5 G cellular phones to a rate 1 Mbit/s or more, based on cell ranges of up to 15 km or more.

"The IEEE 802.16 effort is a key component for widespread adoption of broadband wireless, and we're in full alignment," said Subramanian, "but in our opinion it was a bit before its time in that there wasn't significant operator involvement when the standards effort started." Subramanian's argument is that next-generation technology hadn't been trialed so it "ended up being a lot of paper arguments over what to do."

According to Subramanian, that resulted in the four air interfaces and multiple media access control (MAC) layers that got rolled into that standard. While the 802.16 group argues that this allows for technical differentiation, Subramanian doesn't buy it. "Providing for everything and so diluting the whole effort, raises questions of interoperability," he said.

To address the interoperability issue, the IEEE 802.16 group aligned with WiMax (Worldwide Interoperability for Microwave Access) Forum to certify standards compliance and test product interoperability for 802.16-based devices. "That's laudable," said Subramanian, "but one key thing missing — operator involvement and learning from what's deployed today," again lamenting the lack of real-world trial data.

"Without that, we end up playing the same game as IEEE 802.14," he said. IEEE 802.14 formed the first standard for cable modems. "It died because it didn't have operator support — they [the operators] just ignored it and went with Docsis (Data over Cable System Interface Specification) instead." According to Subramanian, 802.20 has the support of Sprint, DoCoMo, "and others." Navini itself has already trialed is RipWave line with Sprint (Houston); BellSouth (Daytona), IBAX (Italy); IntroWeb (The Netherlands); Liberty Technologies (Panama) and Rioplex Wireless (Rio Grande Valley).

OFDM obsession

Subramanian's biggest issue with the current 802.16 standard is what he calls its "obsession" with OFDM modulation. "It's a good scheme with many benefits in the face of multipath but it fails on frequency-selective fading and spreading gain, and you pay the peak-to-average [power ratio] price so you need a bigger amplifier," he said.

As far as he's concerned, there are four fundamental features a broadband solution must have: It must be truly broadband. "A few kilobits/s is no use to us. Also, it must be plug and play, have an evolution path to portability and mobility and have wide area coverage.

"For plug and play and wide-area access, the issue is link budget," he said. "You need 10 to 20 dB more link budget to make it penetrate a wall and other obstacles and overcome scattering. That won't be solved through modulation."

Instead, Navini went with phased-array smart antennas and power combining "to get 18 dB over and above a standard systems." The company may also implement adaptive beamforming in the near future.

For modulation, Navini opted for multicarrier CDMA. "We aren't religious and opted for a compromise," he said. "Our scheme has the multipath benefits of OFDM — without the PA drawbacks — as well as the spreading gain of CDMA."

With the standards backdrop as it stands, this week's In Focus contributors offer their views on the after effects of the ratification of IEEE 802.16 and its impact on new products in fixed broadband wireless.

John Liebetreu, chief technologist in Broadband Wireless Access at Intel Corp., details the 802.16a 'differentiators' while Aperto Networks' Dean Chang and Subir Varma, provide practical coverage on the interoperability guidelies.

Exclusive online coverage also includes a piece from Flarion Technolgies' Peter Carson on how 802.20 will unlock existing market potential — complementing both 802.16 and 3G. Nigel King, co-founder of Orthogon Systems, delves into the unresolved problems with non-line-of-sight (nLos) systems and what needs to be done for high availability, high throughput connections over longer ranges and Allan Klein, vice-president of technology at SR Telecom, discusses the growing popularity of 802.11b for high-speed Internet service hot spots. He explains how 1xEV-DO, a spectrally efficient air interface, will offer substanial benefits.

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