Right now, 24 police cars and three Fire Department vehicles are equipped with the new technology, including vehicle-mounted modems, laptop computers with wireless cards, cameras and printers. Once the network is fully built out, more than 200 emergency vehicles, mostly police cars, will have access to it, says Charles Hewitt, Providence’s chief information officer.

Mug Shots and Traffic Videos

The system will be used, for example, to transmit mug shots and suspect profiles to police cars and let the officers transmit reports from the vehicles – allowing the officers to spend more time in the field rather than behind a desk. Fire commanders in the field can receive data about hazardous materials, blueprints, floor plans and other information that can help save lives.

The network carries only data, and not voices, but it allows police and firefighters to communicate with one another and to share a common database with the city’s Emergency Management officials and emergency dispatchers. They can also receive live traffic video feeds from the Rhode Island Department of Transportation.

Video applications are still limited today by insufficient backhaul – as Hewitt says, “we can’t put a lot of video on this [network] without putting it on its knees” – but Providence police may be able to make more use of video in the future. In Ripon, Calif., where a similar network is in use, police view live video feed from surveillance cameras as they ride to an incident. In crowds, they can stay on foot and monitor the situation by controlling the pan, tilt and zoom of their cars’ cameras while they view video feed on their PDAs. Patrol officers can also share video feed with headquarters or with dispatchers to help determine needs for backup.

A portion of the network’s funding came from the U.S. Department of Homeland Security, and Providence Mayor David N. Cicilline said that the system would also help public safety officials respond faster and more efficiently to crises.

Building the Mesh Network

The mesh network is based on Motorola’s Mesh-Enabled Architecture technology as well as on a cable-based data communications service from Cox. Although it uses the same 2.4GHz radio frequency used by consumer-grade WiFi networks, its designers took steps to reduce interference from consumer networks. “So far it has run like a champ,” Hewitt says, adding that the only network interruption occurred when two access points were forced offline by a power failure.

In a mesh network, every device acts as a router and each data packet is dynamically routed along an optimal path from one device to another until it reaches its destination.  The Providence network comprises between 50 and 60 access points mounted on electric utility poles – which are owned by the local utility, National Grid – and on street light fixtures, as well as more than 450 other router devices attached to vehicles and PCs.

A city like Providence, Hewitt says, offers plenty of technology hurdles for the builders of a mesh network. Because it is architecturally dense (with nearly 10,000 residents per square mile) and hilly, and has relatively few straight shots down streets, the city “presents a reasonably challenging radio environment.” Yet the biggest hurdles didn’t involve technology but securing permission to use utility poles. “A project like this is really not a technology project, it’s a construction project,” Hewitt says.
 

Robert Calem is a freelance writer specializing in technology.