Preparing for the Death of CDPD

By Eric Griffith

December 19, 2003

The city of Aurora, Colorado, has unleashed one of the largest municipal wireless networks ever for use by public safety as they get ready for the planned disbanding of the older CDPD network.

Cellular Digital Packet Data (CDPD) is a cellular-based, wireless specification that lets users get onto the Internet and other packet-switched networks. It's been used for a while by police and fire officers in a number of locations to get real-time data at 19.2Kbps while in the field.

And now it's going away. AT&T specifically is shutting down its PocketNet CDPD networks as of June 2004. And that's leaving a number of places in the lurch.

Aurora, Colo., a suburb of 275,000 just east of Denver, would have been one of them. City officials, specifically public safety systems manager Michael Bedwell, started looking at new possibilities for the same or better services months ago. Working with Denver-based integrator/reseller Anyware Network Solutions, the city decided to go with a mix of Wi-Fi and GPRS cellular to get the bandwidth and the coverage they need.

NetMotion Wireless's Mobility was chosen by the city and Anyware as the best method for increasing speed with compression, getting inter-network roaming, and for security features such as virtual private network (VPN) tunnels. NetMotion also happens to be the preferred VPN service by AT&T's for helping customers move from CDPD networks to faster networks like GPRS or CDMA2000.

Eric Hermelee, vice president of marketing at Wavelink, says "We've had other deployments that looked like this, but never in this way with the public safety environment."

Wavelink's management software is helping run all the public safety hotspots using Wi-Fi, in a way similar to how its software would be used to run hotspots in a series of café. The Wavelink software is deployed in the Aurora network operating center. The wireless LAN aspects of the network run on Cisco hardware. Officers in the field have ruggedized Panasonic Toughbook laptops they use in their cruisers to get data.

Data officers can access will run the gamut from Department of Motor Vehicles records to criminal records to full mug shots (the latter used to take several minutes to receive on CDPD). 300 mobile police and fire units will be using the service.

As cruisers move from place to place in this 145 square mile area, they'll travel in and out of Wi-Fi hotspots -- for example, there will be one at the city refueling stations where all the cops go to gas up a vehicle. While they're stationary at the hotspot, the laptop will automatically connect to the access point and use the higher bandwidth connection to download everything that's pegged policy-wise as requiring the extra bandwidth, from work data to new virus definitions to full software upgrades.

When they leave the hotspot, the laptop will trip over to the slower but much longer range GPRS network. The NetMotion Mobility client software helps maintain the session persistence so the laptop's network switch is seamless.

According to Bedwell, "if they drive off before they complete the download, it will bookmark and complete the download the next time they arrive" at a hotspot. In the past, such a task would have taken hours, having to be done by hand, with officials hoping every laptop would make it in to get an effective upgrade.

The network policy manager run by Wavelink ensures that only certain things happen when under the Wi-Fi connection.

Perhaps even more important is making sure the laptops don't connect to the wrong access point.

"We don't want our officers, police and fire, to be going down the street and have them associate with the network of every access point that sees them," says Bedwell. "We have to be blind to every network but our own."

The total cost for setting up this network to support 300 mobile clients will be between $100,000 and $200,000. One hundred units are already outfitted, the rest will be by the end of the year.

Hermelee says his company and NetMotion Wireless saw this as an opportunity for the two to integrate tightly together as far back as six months ago.

"As municipalities move off of CDPD they increasingly want to use Wi-Fi as a piece of the network," he says. "They see it as another way to connection and get high speed at a low cost...[but] it's not just for public safety. It could be used wherever it's natural for workers to move in and out of hotspots, like utility technicians, package delivery, and other field services. "

Comment and Contribute
(Maximum characters: 1200). You have
characters left.