Wi-Fi Alliance to certify 802.11g WLans

The Wi-Fi Alliance plans to start interoperability and certification testing this summer of wireless Lan products based on the ...

The Wi-Fi Alliance plans to start interoperability and certification testing this summer of wireless Lan products based on the  802.11g standard, which offers 54Mbps data in the 2.4GHz band.

Atheros Communications and Intersil have both developed 802.11g chipsets, 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, even though ratification of the 802.11g standard by the Institute of Electrical and Electronics Engineers has not yet occurred - a decision is expected between June and August.

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 certification 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, said Dennis Eaton, chairman of Wi-Fi Alliance.

That presents manufacturers with a tough technical challenge, Eaton said, since the "b" and "g" standards use 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 includes technology that allows the access point to determine whether there is a channel clear of traffic in the 2.4GHz band on which it can transmit.

Ray Martino, vice-president of the network systems group at Symbol, said the forced sharing by "b" and "g" clients of the same frequency band means enterprise customers with a large installed base of 802.11b WLans will pass on installing 802.11g access points.

Martino also pointed out potential conflicts between older "b" clients and the "g" gear in environments where enterprises also use Bluetooth short-range communications devices, which operate in the 2.4GHz band.

The Wi-Fi Alliance could certify 802.11g products within a matter of weeks after the IEEE approves the standard. 802.11g WLan clients and access points could initially carry between 20% and 30% price premium over 802.11b gear, said Eaton. But that differential will quickly erode as manufacturing, sales and demand picks up, he added.

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