Tropos Networks has updated its hardware and software to make it easier to build and run outdoor wireless mesh networks. Wi-Fi Cell System Release 3 will be able to manage five times as many nodes and will need 20 percent fewer access points to cover the same area.

The software upgrades, announced at the Wi-Fi Planet conference in Baltimore, also include features such as cross-subnetwork roaming and a revamped network management application, for its Tropos 5110 outdoor 802.11b nodes.

The vendor is one of several using 802.11 radios to create wireless LANs that span large areas, such as a downtown business district (see this news story). These companies have crafted mesh networking algorithms that let access points interconnect and route traffic over multiple paths, much like the wired Internet. The biggest name among the start-ups is Nortel Networks.

Wireless mesh networks are intended to extend Wi-Fi coverage beyond the LAN (see our feature), and are often aimed at local authorities. Tropos already has several meshes installed in US cities, including Milpitas California, which has 32 Tropos nodes on streetlight poles to create an 802.11b WLAN covering roughly 5 square miles, mostly along main roads. Thirty police cruisers, and soon 20 fire vehicles, have Wi-Fi enabled mobile computers, with exterior-mounted antennas.

The network acts like a broadband cellular network, says Bill Marion, information services director for Milpitas, thanks to cross-subnetwork roaming. In an earlier WLAN pilot, police cruisers could use the network only by parking at a stand-alone WLAN hot spot. When they drove to another one, they had to re-connect and re-authenticate. "With subnet roaming, a cruiser can come up on the net and stay on it, as long as we have coverage," Marion says.

The new version has a low-power option, running at 200 milliwatts instead of 1 Watt, which under US radio spectrum rules means it can be fitted with a broader range of antennas. Marion wants to put one on a tall building with a directional antenna. Another new option is battery back-up, which will keep each node running for six to eight hours if the power fails. The electrical outages that plagued California two years ago have made this backup much more important to the city.

The reworked Tropos Control net management software now users display each node on a detailed map of the city, and blue lines show the changing radio connections among the nodes.

The new version stays at the same price, from $100 to $200 per node, depending on volume. The company calculates node pricing based on the area being covered: typically $30,000 to $50,000 per square mile, depending on terrain and obstacles. The battery back-up option would be about $3,600 at the low end, in that case.