Wireless mesh network good as gold

When a coalition of emergency response agencies in the San Francisco Bay area built a wireless mesh network for a recent communications field exercise, the big surprise was how easy it was to use.The exercise was the first test of a new technology being commercialized by PacketHop Inc. of Belmont, Calif., that turns wireless devices into routing nodes in ad hoc networks.'PacketHop was able to achieve mobile broadband connectivity across tough terrain and over mobile, infrastructureless networks for 14 multijurisdictional agencies,' said Michael Griffin, assistant chief of the California Governor's Office of Emergency Services.Members of the Golden Gate Safety Network used PacketHop software on ruggedized notebooks and personal digital assistants with little or no training to share video, text and geospatial data.'We probably overestimated the amount of formal training needed' to use the tools, Griffin said.The immediate goal of the Golden Gate Safety Network is to create a playbook that will let federal, state and local agencies in the Golden Gate National Recreation Area in and around San Francisco communicate over existing systems in case of emergency. The February exercise showed that emerging technologies such as mobile mesh networking also could fit into the plans.Lack of interoperable communications systems is a big problem for first responders in many jurisdictions. The problem is compounded in the Bay area, where every bridge links two counties.The Golden Gate recreation area, which includes the Golden Gate Bridge, is served not only by multiple agencies in San Francisco and Marin County, but by state police, the Coast Guard and the National Park Service's police.The agencies formed GGSN in May 2002 following development of the Major Incident Response Plan for the historic Golden Gate Bridge.'The key thing we were lacking was timely communication and information sharing,' Griffin said. 'So we put together a coalition of first responders' to work out a communications plan.Replacing the existing infrastructures of 14 agencies was out of the question. The effort focused instead on finding ways to link them. The team established protocols for notifying member dispatch centers in the event of an emergency, and linking them through phone gateways and by activating the California Law Enforcement Radio System.The level of connectivity lets agencies communicate with one another but does not provide direct interconnectivity for users in the field.Soon after GGSN's formation, PacketHop approached the network team for advice on the mobile communication needs of first responders.PacketHop is a spin-off of SRI International in Menlo Park, Calif., created to commercialize research on mesh networks funded by the Defense Advanced Research Projects Agency.Wireless mesh networking creates ad hoc networks of wireless devices by turning each device into a routing node, eliminating the need for an infrastructure in the field.PacketHop's take on the technology is an all-software approach, independent of the type of wireless connection or the device used.'We're a software layer,' PacketHop CEO Michael Howse said. 'We're a routing stack that sits on any radio that can forward an IP packet.'The as-yet-unnamed product has four components:The quality-of-service feature routes traffic based on any combination of availability of nodes, congestion and even battery power of individual devices. Authentication is via digital certificates with either software or hardware tokens. The software allows over-the-air provisioning of certificates so new network users can be quickly approved.Field personnel had two dozen wireless devices'notebooks, PDAs and wearable computers equipped with PacketHop software and IEEE 802.11a and 11b network interface cards. A two-mile, 54-Mbps 802.11a link was established across the Golden Gate, letting users throughout the area share video, messages and GIS data.The mesh network linked to a secure Internet node at the Golden Gate Bridge Administration Building at the southern end of the bridge, creating a connection to the Office of Emergency Services in Sacramento, which became a node on the mesh.Video from cameras on the bridge also traveled across the network, giving real-time views of the area.'We were testing situational awareness to the supervisory and management level,' Griffin said.The network worked. In fact, it worked so well that when unscheduled observers showed up to see how the exercise was going, they were handed network devices and soon 'they were going through the maps and GPS and looking at the video' with no training, Griffin said.Using the mobile devices, supervisors in the field could select video, exchange messages and observe the location of all resources in the area. One unexpected benefit was a reduction of radio voice traffic, PacketHop's Howse said. Voice traffic dropped by an estimated 60 percent because of information available on the mobile mesh network.'The more devices are added, the more reliable they are' because more nodes become available for routing traffic, Griffin said.There were a few minor problems. 'It turned out to be a nice day, and some of the screens were difficult to see in direct sunlight,' he said. Maritime units also said their devices needed waterproofing.'It's a dynamic plan you're always going to be working on,' Griffin said. 'It's dangerous to say you're ready for the main event. It's a never-ending evolution.'Whether mobile mesh networking or some other form of wireless communication will be part of the network's future still is up in the air. 'We're exploring our next step now,' Griffin said.