In late February 2004, emergency agencies responded to a catastrophe at San Francisco's landmark Golden Gate Bridge. First to the scene was the Marin County Office of Emergency Services, followed by the San Francisco Fire Department, and ultimately other agencies, including the National Park Service, California Highway Patrol and US Coastguard.
All these agencies use a variety of different radio systems which usually can't communicate. But this time they were equipped with a new type of data link allowing them to coordinate on laptops, PDAs and tablet PCs with video links, real-time resource maps and multimedia messaging, among other applications.
The three-hour session was a simulation by the Golden Gate Safety Network, comprised of 11 California emergency bodies, trialling an emerging wireless networking technique known as mesh. In this case, technology from PacketHop, a Silicon Valley start-up, set up an ad-hoc broadband wireless network linking workers with different varieties of off-the-shelf equipment on the bridge, on land and on the water. There was no central server, no single point of failure, and the nodes were able to maintain their network connections without being in range of an access point -- each node acted as a repeater and router for the nodes around it.
The next step for wireless
Tech industry heavyweights such as Cisco and Intel believe mesh techniques are the logical next step for the wireless networks that are increasingly ubiquitous in offices, homes and public places. Enterprises could use mesh to quickly create new wireless networks or extend existing WLANs without needing a wired connection to each base station. Mesh-enabled base stations are good at load balancing because they can choose the most efficient path for data. Industrial users can quickly deploy networks of sensors and controllers with embedded wireless mesh radios.
Start-ups and established vendors are selling modified wireless local-area network (WLAN) kit incorporating mesh ideas. Standards groups are working on building mesh into the families of standards in use today, such as 802.11, and those coming down the line, such as 802.16 (also known as WiMax). On the embedded side, mesh technologies are feeding into nascent standards like ZigBee.
A fine mesh
In essence mesh is something very familiar -- wireless mesh networks are really just applying the basic principles of the wired Internet to the wireless world, says Scott Burke, vice president of engineering for PacketHop: "The fixed Internet we have today can be thought of as a large fixed mesh network."
Each device on a mesh network receives and transmits its own traffic, while acting as a router for other devices; intelligence in each device allows it to automatically configure an efficient network, and to adjust if, for example, a node becomes overloaded or unavailable. The advantages include ease of setup, the ability to spread wireless access over a wide area from a single central wired connection, and the inherent toughness of such networks.
