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Wi-Fi Alliance to certify 802.11g WLANs

Wi-Fi Alliance to certify 802.11g WLANs

The Wi-Fi Alliance plans to start interoperability and certification testing of new wireless LAN products based on the still-evolving 802.11g standard, which offers 54M bit/second data in the 2.4-GHz band. That compares to 11M bit/second throughput for WLAN products that operate in the same unlicensed frequency band and use the better-known 802.11b.

Atheros Communications and Intersil have both developed 802.11g chip sets while manufacturers such as Cisco Systems and Proxim plan to sell WLAN access points and cards incorporating the high-speed 802.11G standard. Several hardware vendors are already selling 802.11g products including Apple Computer, NetGear and D-Link Systems. Those products are out, even though ratification of the 802.11g standard by the Institute of Electrical and Electronics Engineers has not yet occurred.

That decision was expected between June and August, chairman of the Wi-Fi Alliance, Dennis Eaton, said.

But analysts and Symbol Technologies, a key supplier of WLAN equipment to a number of vertical markets including transportation and retail, wonder whether 802.11g is ready for prime time this year.

In order to receive certifications from the Wi-Fi Alliance, 802.11g products must be backward-compatible with the 802.11b standard and support simultaneous operation of both 802.11b and 802.11g clients, Eaton said.

That presented manufacturers with a tough technical challenge, he said, since the “b” and “g” standards used entirely different modulation schemes — Complementary Code Keying for “b” and Orthogonal Frequency Division Multiplexing for “g”.

Since a “g” access point cannot hear a “b” client due to the different modulations, the “g” protocol included technology that allowed the access point to determine whether there was a channel clear of traffic in the 2.4-GHz band on which it could transmit, Eaton said.

Vice-president of the network systems group at Symbol, Ray Martino, said the forced sharing by “b” and “g” clients of the same frequency band meant enterprise customers with a large installed base of 802.11b WLANs would pass on installing 802.11g access points.

Martino also cited potential conflicts between older “b” clients and the new “g” gear in environments where enterprises also used Bluetooth short-range communications devices that operated in the 2.4-GHz band. In such installations — for example, United Parcel Service sorting hubs where UPS used Bluetooth scanners and 802.11b WLANs — the conflicts in the 2.4-GHz band could be difficult to manage and work around.

Enterprises that want higher data rates instead should opt for the 802.11a standard which offered the same 54M bit/sec. data rate as “g”, but in totally different 5-GHz unlicensed frequency bands.

Martino called this a “much cleaner” approach to offering 54M bit/second data rates on WLANs. However, 802.11a hardware wasn’t compatible with 802.11b hardware.

Gartner analyst, Phil Redman, said his company recommended that enterprises stick with the 802.11b standard due to its maturity and the wide variety of interoperable products.

Eaton said the Wi-Fi Alliance could certify 802.11g products within a matter of weeks after the IEEE approved the standard.

He said 802.11g WLAN clients and access points could initially carry a 20 per cent to 30 per cent price premium over 802.11b gear. That differential would quickly erode as manufacturing, sales and demand picked up.


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