IEEE group accepts wireless LAN mesh proposals


The IEEE group charged with creating a standard for wireless LAN mesh is rounding up about 15 proposals at this week’s 802.11 meeting in San Francisco.

Members of the 802.11s task group hope to have a draft standard completed in 12 to 18 months. Today's wireless LAN mesh networks use proprietary algorithms and are typically deployed outdoors. With a IEEE mesh standard implemented by WLAN vendors, it's possible that in the future every wireless LAN would also be able to configure itself as a mesh network, similar in concept to the Internet.

A wireless mesh uses a radio to interconnect the access points and route wireless packets over the best available route. Mesh benefits include potentially higher performance and more reliable nets.

Today's 802.11 wireless LANs use a star topology: users link wirelessly to an access point which then links via Ethernet cable to a LAN switch.

An array of companies - including BelAir, Nortel, Tropos, and Strix - are already selling mesh access points for 802.11 wireless LANs. Many, such as BelAir and Tropos, have focused on creating very large outdoor nets, which can blanket a community with a WLAN for public safety applications or for Internet access.

The Wi-Mesh Alliance is a group of hardware, software and other vendors that is submitting a technology proposal to the 11s task group. There are about five complete proposals and about 10 partial proposals being filed this week, according to WMA member Nortel. Other Alliance members include Accton Technology, InterDigital, NextHop, Thomson and others.

The key elements in the proposals concern the algorithms for auto-discovery and for routing, says Bilel Jamoussi, director of strategic protocols and standards for Nortel, Brampton, Ontario. There may be some hardware elements to support quality of service in unicasting and multicasting, he says. Both of these transmission types let a mesh create a subset of access points, optimizing bandwidth and routing. "When you enlarge the network's geography, and are streaming multimedia over it, multicasting lets you do that efficiently by sending [the stream] only to those access points that are interested in it," Jamoussi says.

As with conventional wireless LANs, 802.11s mesh nets will base their security on the IEEE 802.11i standard. Jamoussi says a number of extensions to 11i will be needed for key management and data encryption requirements in a mesh.

One controversy that some vendors have been arguing about is how many radios are needed to create efficient wireless backhaul connections among the access points in a mesh. "The Alliance proposal supports both single- and multiple-radio configurations," Jamoussi says.

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