In case you haven't heard, the wireless LAN industry is now up to "s" in the alphabet soup of 802.11 technical standard extensions.

802.11s aims to define a MAC and PHY for meshed networks that improve coverage with no single point of failure. In such networks, 802.11 cellular WLAN access points relay information from one to another, hop by hop, in a router-like fashion. As you add users and access points, you add capacity. So, as in the Internet, adding nodes becomes a scalable and redundant endeavor.

Meshed networks can serve as indoor or outdoor networks run by wireless ISPs or enterprises with large outdoor deployments. For example, municipalities might wish to extend their fiber networks wirelessly, using fiber-to-wireless gateways. 802.11 meshes might also serve the outdoor portions of campus networks or all-outdoor enterprises such as construction sites.

Among the vendors that make products for these applications are BelAir Networks, Firetide, Nortel and Tropos Networks. Another company, RoamAD, also makes outdoor products, but currently sells them exclusively to the service provider market.

For its part, Tropos' outdoor system behaves like a wireless routed LAN. The company has developed its own wireless routing protocol, called Predictive Wireless Routing Protocol (PWRP), which is analogous to traditional wired routing protocols such as Open Shortest Path First (OSPF).

However, says Tropos president and CEO Ron Sege, PWRP doesn't use routing tables or rely on hop-count only to select transmission paths. Rather, it compares packet error rates and other network conditions to determine a best path at a given moment, he says.

If you are interested in deploying any of these systems, find out from the vendor what versions of 802.11 are supported and what security mechanisms are used. Also, some of the vendors note that their meshed products may not be limited to 802.11 in the future.

BelAir, Firetide, Nortel and Tropos also have 802.11 products to cover the interior of enterprises, though they do so in different ways. BelAir, for example, uses an environmentally hardened, outdoor device that beams signals into buildings from outdoors. Nortel resells the thin access point/WLAN switch combination from Airespace. And Firetide and Tropos sell indoor meshed networks.