By Donald Root
Radio has been used to communicate with first responders in one form or another since the 1930s. Initially these communications were one way — telecommunicator to car — using broadcast AM band radio transmitters. In most cases, officers in the field would telephone into dispatch in response to a call for service or to summon additional resources. The onset of World War II saw a number of technological developments, including AM and FM two-way radios in military applications. Following World War II, two-way radio services were introduced into the civilian marketplace, with vehicle mounted radios providing analog FM communications between public safety telecommunicators and field units. This technology was adopted by public safety, businesses and industry users in what we now know as land mobile radio (LMR). During the 1950s and 1960s, improvements in technology provided radios with multiple channel capacities, along with handheld “portable” radios. Multiple companies produced LMR equipment, allowing for agencies to shop for the best deals to meet their needs when procuring equipment.
As more businesses and public safety agencies adopted radio, the radio spectrum available for LMR use became increasingly crowded. By the late 1960s radio frequencies to meet basic public safety agency needs in the larger metropolitan areas were very hard to find. During the 1970s, 1980s and 1990s the Federal Communications Commission (FCC) allocated additional spectrum for LMR use and implemented efficiency standards to increase the use of available spectrum. As additional spectrum for public safety communications systems have been allocated by the FCC, the efficiency requirements have also been increased.
As a result, technologies have been developed to increase frequency usage efficiency through technologies such as trunking. Trunking allows multiple groups of radio system users to share a pool of discrete frequencies by assigning a frequency from the pool to that user group when it is needed.
In the same time frame, a requirement for secure voice communications systems emerged for sensitive operations. Manufactures developed “scrambling” schemes to mask these communications. Two-way manufactures offered proprietary methods, while others manufactured aftermarket equipment that could be added to existing radios. One of the main problems was a lack of interoperable common methods, limiting effectiveness when multiple agencies worked together.
APCO Project 16
In response to the FCC’s opening new spectrum at bands including 800 and 900 MHz, APCO established Project 16 in 1977 to develop standards for public safety communications systems with significantly enhanced capabilities. The goal was to create a system concept that would satisfy the minimum needs of all potential users and permit more complex requirements by other users or in the future. The Project 16 effort addressed channel access times, automated priority recognition, data systems interface, individuality of system users, command and control flexibility, system growth capability, frequency use and reliability. The final document described a multi-channel mobile communications system that uses digital addressing techniques and frequency switching systems (Trunking).
After the Project 16 final report was released, three different manufacturer-specific trunking technology implementations were developed and marketed, each compliant with the Project 16 standard but not interoperable with the other two technologies. Agencies that procured one of these systems depended on that manufacturer for their subscriber radio procurements with the manufacturers free to set the pricing of the equipment. If a user needed to operate with an agency on another manufacturer’s radio system in their area, another user radio was required.
APCO Project 25
P25 was prompted by issues that public safety agencies at federal, state and local levels had with the incompatibility of trunking systems, as well as secure voice systems, supplied by the major vendors in the 1980’s. With the approach of digital communications and spectrum efficiency driven by the FCC, the public safety community wanted to ensure new public safety emerging technologies were developed under user-driven, interoperable and open standards that would meet their needs as well as FCC requirements.
In September 1989, an initial meeting of major public safety associations and federal agencies resulted in an agreement among APCO, the National Association of State Technology Directors (NASTD) and agencies of the federal government (the APCO/NASTD/FED agreement). APCO established the next sequentially available project number (Project 25) to implement this agreement.
The Project 25 Steering Committee was formed in 1990 to implement provisions of the agreement and oversee the process. The steering committee is comprised of representatives from APCO, NASTD, federal user agencies, and public safety officials and representatives.
The Steering Committee established a User Needs subcommittee to develop the “Project 25 Statement of Requirements.” Another subcommittee comprised of users and manufacturers developed interoperable standards. Memorandums of understanding were signed with the Telecommunications Industry Association (TIA), an ANSI-accredited standards development organization to lead the development of vendor-driven open standards. The Project 25 Compliance Assessment Program (P25 CAP) was established and managed by the Department of Homeland Security’s Science & Technology Directorate, through their Office for Interoperability and Compatibility (OIC) to ensure public safety users know which manufacturers have constructed radio equipment compliant with the P25 standards
TIA-TR8 Engineering Committees
The Telecommunications Industry Association’s Engineering Committee TR-8 formulates and maintains standards for private radio communications systems and equipment for both voice and data applications. The TR-8 Committee addresses all technical matters for systems and services, including definitions, interoperability, compatibility and compliance. Much of the TR-8 Committee work relates to the formulation of the TIA-102 Series standards for Project 25 equipment. These standards have been developed to provide digital voice and data communications systems for public safety applications. To date, TR-8‘s various subcommittees have developed more than 80 individual standards documents detailing all aspects of ensuring Project 25 radio equipment is interoperable among manufactures.
In addition to its P25 work, the TR-8 committee is responsible for the formulation of TIA-603 Series standards for analog FM systems, standards for portable radios operating in hazardous locations, TSB-88 wireless coverage guidelines for LMR and broadband systems and TIA-329 standards for communications antennas.
Project 25 Compliance Assessment Program (P25 CAP)
Congress legislated the P25 Compliance Assessment Program (P25 CAP) to ensure LMR equipment complies with P25 standards for interoperability across suppliers. The P25 CAP is a partnership of the DHS Office for Interoperability and Compatibility, P25 manufacturers, Testing Labs and public safety users of P25 technology.
The P25 CAP is a voluntary testing program for P25 manufacturers. The program started with a focus on the Common Air Interface, which allows for over-the-air compatibility between radios and base/repeater equipment. As the P25 standards continue to develop and refine, the program has added 2-slot TDMA (“P25 Phase 2”) and supplementary data testing of the common air interface, as well as testing of devices using the Inter Sub-System Interface (ISSI) and Console Sub-System Interface (CSSI) standards.
P25 CAP develops Compliance Assessment Bulletins (CAB) that outline specific test cases for P25 equipment. These test cases are taken from published TIA-102 Standards. P25 CAP testing must be performed by an accredited test lab that has been assessed for P25 equipment testing. The P25 equipment manufacturers submit the test case results to DHS OIC for review and posting on the DHS P25 CAP website as approved (grant eligible) equipment. Many federal grant programs encourage the purchase of P25 CAP compliant equipment that appears on this list.
Looking Forward
As public safety broadband networks adopt mission critical push-to-talk (MCPTT) applications, the ability to integrate users of P25 systems with users on a broadband network comes into play. The P25 program is working to make sure this integration is interoperable.
In summation, the Project 25 program provides public safety users with LMR equipment constructed to a suite of open standards. The standards embrace interoperability among manufactures while providing spectrum efficiencies and allowing for cost economies by allowing users to procure equipment that meets the user’s operational requirements, such as operating on P25 networks provided by a variety of manufacturers.
Donald Root is APCO’s P25 Program Manager. He has more than 40 years of experience in public safety communications at the state and local level. He can be reached at [email protected]
