Public Service

Project 25 Streamlines Emergency Interoperability

By James T. McKenna | July 1, 2008
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Vendors are working hard to support airborne law enforcement units seeking communications gear that meets new requirements for interoperable communications.

The industry/government Project 25 initiative is forcing police air units throughout the United States to upgrade their aircraft communications suites with radios that meet higher standards for digital encryption, interoperability and frequency separation. The U.S. government no longer permits its airborne law enforcement units to buy analog radios. Sheriff’s departments across the country are refitting their aircraft with new radios; there are 25 in Florida alone doing so. The California Highway Patrol recently put out a solicitation bid for upgrades of its airborne radios.

Nor are we at the end of the new requirements. Having completed Phase 1 of Project 25, the working groups on the project — which include avionics manufacturers, operators, and government agencies — are turning their attention to Phase 2. A key element of that will be specifying the technical requirements that must be met to permit law enforcement radios to handle traffic on frequencies that are separated by just 6.25 KHz. Phase 1 reduced the separation from 25 KHz to 12.5.


A whole host of trade and user groups have been collaborating on the work. They include the Telecommunications Industries Assn, the Assn of Public Safety Communications Officials International, the National Assn of State Telecommunications Directors, as well as selected federal agencies and the National Communications System. They set up Project 25 as a steering committee for selecting voluntary common system standards for digital public safety radio communications.

P25-compliant radios (as the units that meet Project 25 standards are known) are designed to communicate in analog mode with legacy radios and in either digital or analog mode with other P25-compliant radios. The changes are designed to allow a high degree of equipment interoperability and compatibility.

Specifically, according to the group, P25 systems can be maintained and upgraded cost effectively during the system’s life cycle. This helps police agencies satisfy their requirements and maintain the security of operational communications. Another goal was to foster competition among communications vendors, thus achieving cost-effective emergency/safety communications solutions.

Time and again, disasters and terrorist attacks in the United States have demonstrated the absolutely critical need for interoperability among first responders.

The P25 suite of standards covers digital land-mobile radio systems and services for local, state and federal public safety organizations and agencies. The standards are enforced by the National Telecommunications and Information Administration (NTIA) or Federal Communications Commission (FCC). But use of such equipment is not limited to public safety, according to the steering committee, and P25 equipment has also been selected and deployed in private system applications. For example, railroads use radio systems based on the standards to control rolling stock, personnel and support vehicles.

Vendors are shipping Phase I P25-compliant systems. According to the steering committee, these systems involve standardized service and facility specifications, ensuring that any manufacturer’s compliant subscriber radio has access to the services described in such specifications. Abilities include backward compatibility and interoperability with other systems across system boundaries, regardless of system infrastructure. In addition, the P25 suite of standards provides an open interface to the radio frequency subsystem to facilitate interlinking of different vendors’ systems.

P25 Phase 2 implementation involves time and frequency modulation schemes (e.g., TDMA and FDMA), with the goal of improved spectrum utilization, the steering group says. Significant attention is being paid to interoperability with legacy equipment, interfacing between repeaters and other subsystems, roaming capacity and spectral efficiency/channel reuse. In addition, Phase 2 work involves console interfacing between repeaters and other subsystems, and man-machine interfaces for console operators, which would facilitate centralized training, equipment transitions and personnel movement.

The evolving nature of emergency response communications will enhance the capabilities — and challenge the budgets — of airborne law enforcement units for years to come.

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