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From Mobile Data Solutions to Next Generation Wireless

When the Maine Department of Public Safety (MDPS) was told it had until June 31, 2004 to migrate the Maine State Police (MSP) in-vehicle wireless solution from the soon-to-be obsolete Cellular Digital Packet Data (CDPD) technology to the faster, next generation General Packet Radio Service (GPRS) technology, it was one step ahead of the game.

While implementing the MSP’s original solution in 2002, the MDPS Information Systems (IS) team was notified of AT&T Wireless’ planned phase-out of its CDPD service. The IS team, working with wireless systems integrator TransCOR, had already begun preparing for the migration during the initial CDPD deployment.

On the advice of TransCOR, the MSP’s initial in-vehicle communications solution was deployed using the AirLink PinPoint NGE rugged wireless modem. The NGE (Next Generation Enabled) version of the PinPoint modems provided a built-in upgrade path from CDPD to GRPS, allowing MSP to easily migrate its CDPD solution to GPRS at a future date. The AirLink modem was one of many integral pieces of the migration process that allowed the MDPS to successfully and cost-effectively adopt the newest wireless technology.

The MDPS initially implemented a wireless solution for the State Police to address two major issues: 1) timeliness of event reporting, and 2) the need for real-time communications.

The size and remoteness of Maine provides a unique challenge for law enforcement. The patrol area for many troopers is more than 100 miles from their station, making it difficult for them to return to the station on a daily basis. Often times it took several days after an event before an incident report was finally filed. This sort of delay resulted in reduced operational efficiency and customer service. The right wireless system would allow for reports to be filed in a far more timely and efficient manner.

Also, because of the vast patrol distance covered, state troopers—who are assigned their own vehicles for daily use—do almost all of their work in their cars. Explained Network Manager Emile Poulin, “A wireless solution was a way to provide officers with access to critical applications, such as location mapping, vehicle license checks and email, from home or on the road—two places where they spend more working hours than in the station.” With mobile access, troopers can perform on-line inquiries to the National Crime Information Center, enabling them to check license plates, vehicle registrations and driver’s licenses for wants and warrants, parole violations and more.

New Technology

The initial CDPD deployment provided MSP with a solution that met all of their needs. Equipped with a rugged laptop, in-car printer and wireless modem, about 50% of the 300 trooper force was efficient and in-touch. Concerned that a move to a new wireless network technology could disrupt that service, the MDPS gave itself six months to work on its CDPD to GPRS migration. The migration project was divided into three phases: planning, field-testing and implementation.

The planning phase lasted approximately two months with MDPS IS and MDPS Radio Repair teams conducting such tasks as equipment research, bench testing, wireless coverage analysis, network interface preparation and deployment logistics. They researched and selected newly required high-gain vehicle-mounted antenna, mapped out necessary cable upgrades and conducted extensive state-wide drive testing, identifying both GPRS coverage and blackout areas.

During this process, the MDPS IS group began installing new GPRS networking capabilities in the data center, including an additional Frame Relay interface specifically designed to support GPRS planning and testing. As planning moved forward, the IS team began coordinating new component acquisition and logistics with TransCOR, who would ensure that all solution components would be scheduled for delivery to the multiple deployment and installation locations.

The next phase, testing, took about six weeks to complete. It included a pilot test group of about 10 troopers equipped with a fully upgraded GPRS wireless solution in each of their vehicles. The troopers acted as field beta testers, using the new GPRS solution in their daily routine and providing detailed feedback to the IS and Radio Repair teams. Their experiences and feedback were used to help MDPS uncover and work through any technical issues that may arise when deploying the final solution.

The final phase, implementation, involved the coordination and replacement of in-vehicle solutions for 150 wireless equipped vehicles. Radio Repair team members worked out a schedule for each trooper to bring a vehicle into one of several deployment locations to both remove the existing CDPD PinPoints and configure and install the new AirLink GPRS units. Proper planning was essential during this phase, as each trooper was required to be separated from the patrol vehicle and patrol route, something that every police force tries to avoid.

While the wireless modems were being configured and installed, a team of IS staff members upgraded laptop software and configurations and tested each unit to ensure working order. At the same time, another IS team was also providing each trooper with training and hand-outs on the solution upgrade. This approach ensured that each trooper was up and running on the new system in minimal time.

Lessons Learned

Fundamental differences exist between CDPD and GPRS networks that must be considered in order to have a successful migration. First, as opposed to the single-band CDPD technology that runs on analog cellular networks, GPRS is a dual-band digital wireless technology that runs on two separate and distinct radio frequencies. This means that the existing radio antennas will be incompatible, and new dual-band antennas will have to be selected and installed.

In January 2004, when MDPS began planning the migration, an acceptable dual-band antenna did not exist. MDPS found a company called Austin Antenna was in development of a high-gain dual-band vehicle-mounted GPRS antenna. After some discussion, Austin agreed to accelerate its product development timetable to help ensure that MPS troopers would be able to outfit their vehicles with new antennas within the required timeframe. (Austin Antenna, as well as several other manufacturers, now offer an array of high-gain, dual-band antenna products for law enforcement agencies considering GPRS).

Another difference in the networks was in the area of coverage. In the case of the State of Maine, CDPD and GPRS network services were actually being deployed in different geographic areas. The MDPS IS and Radio Repair departments spent a great deal of time on the road testing and comparing coverage of wireless networks. The testing took a bit more time than expected, with many days and hundreds of miles of driving. Eventually the IS team was able to create a detailed coverage and signal strength map, which helped them to determine that GPRS coverage would meet the needs of the MSP patrol force.

Additionally, and within the same timeframe as the CDPD network phase-out, the state’s law enforcement agencies were required to comply with Criminal Justice Information System Security Policy standards of end-to-end 128-bit encryption for each mobile device. While the security upgrade added another level of complexity to the GPRS migration, the matter was quickly resolved. MDPS chose to deploy a software solution (Mobility XE) from NetMotion Wireless. With Mobility XE, troopers received both encryption and compression features to improve application security and bandwidth utilization.

Another aspect of the migration that proved deceptively time-consuming was the change in IP addressing from CDPD to GPRS. With CDPD, each device is assigned a single static IP address. This makes for planning a security solution fairly easy. GPRS networks, however, are slightly different. Instead of statically assigned addresses, GRPS devices are assigned dynamic IP addresses at the time they power-up. This shift in methodology required a great deal of reconfiguring of the MDPS local area network. New solutions and policies had to be employed in order to handle processing of IP addresses in this fashion.

Finally, MDPS learned that along with the data rate improvements of GPRS comes higher usage, a fact that has an impact on both backend systems and the cost of in-vehicle wireless data services. In order to choose the right GPRS service plan, MDPS found it critical to have an accurate measurement of network utilization. They needed to know just how often troopers were using their wireless connections and for what types of applications.

Since GPRS plans start at a higher price point than CDPD plans, MDPS anticipated an initial cost increase of about 10% from an equivalent CDPD plan. However, because of the increased data rates and greater coverage area provided by the GPRS network, MDPS has also seen wireless usage increase. When adding additional data transmission capacity, GPRS users can expect at least another 10% cost increase between plans.

Today with GPRS, MSP troopers are experiencing wireless data transfer rates at least double what they received with CDPD. GPRS coverage in Maine has also evolved and expanded into a more comprehensive area than what was offered by CDPD, creating a much bigger network footprint.

MDPS has a proven plan they can use to ensure their success. “Our migration team redefines the word ‘teamwork,’” Support Services Commanding Officer Major Robert Williams commented. “And the result of their commitment is a wireless solution that allows officers to access and deliver more timely and better quality information, enabling them to make better decisions and increase the safety of our citizens and of our state troopers.”

Brian McKeon is the Director of Technical Services for AirLink Communications. A retired Police Sergeant with 17 years of experience, he has been involved in public safety wireless applications since 1995. He can be reached at

Published in Law and Order, Aug 2005

Rating : Not Yet Rated

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