A high-speed pursuit along the 101 Peninsula ends in a San Mateo neighborhood where the suspect abandons his car and disappears on foot. A San Mateo police officer responding to the call runs the suspect's plates and brings up a photograph on his dash-mounted Panasonic  Tough Book.

The California Highway Patrol officer who started the pursuit identifies the suspect from the picture. Then the San Mateo Police Department officer blasts the image to all patrol cars on duty, and the suspect is picked up off the streets 5 minutes later.

Until July, the SMPD's dash-mounted computers could only download small amounts of text, painfully slowly, over a data radio network. And forget about mug shots, photos from the state Department of Motor Vehicles or other bandwidth-heavy images. For those, officers had to return to the station and download them off wired computers.

"We used to get only get text messages - 'white male, five-foot-eight, 180 pounds.' That's not very helpful," says Lt. Wayne Hoss, IT director for the SMPD, who received a $450,000 grant that financed the Wi-Fi  hot zone. "Now from our cars, we can put together a photo lineup of potential criminals, show the lineup to victims at the site of the crime, and print it as evidence for later on."

The officers have a square mile of wireless Web access in and around the municipal and entertainment districts on the El Camino Real. By year-end that range will about double.

When they're in range of the Wi-Fi hot zone, patrol officers (and soon, foot and bike patrols over PDAs) have wireless  VPN access to the state's Department of Motor Vehicle databases, arrest records and mug shots, missing children reports, the sex offender registry and emergency dispatchers.

Cell hopping

In the first phase, 17 enhanced 802.11b Wi-Fi access points, being protected from the elements in a cast-aluminum casing, are placed about two blocks apart in a grid pattern and plugged into the photo adapters atop the city's light posts. In the next phase, the deployment will make use of newer-generation Wi-Fi cells, with a more powerful 1-watt radio unit, so the SMPD will need only 10 boxes to cover three-quarters of a square mile. The Wi-Fi cells are produced by start-up Tropos Networks .

A hot zone is not to be confused with a hot spot, says Sri Srikirishna, founder and CTO of Tropos. A hot spot is a small-area 802.11b wireless network that plugs into fiber, such as those used in cafe's, airports, hotels, Starbucks and, soon, McDonald's. A hot zone spreads the coverage by using a more-powerful radio, and then hopping signals from cell to cell until they reach a backhaul into the wire, a process called cell hopping.