Project 25 (P25 or APCO-25) is a suite of standards for interoperable digital two-way radio products. P25 was developed by public safety professionals in North America and has gained acceptance for public safety, security, public service, and commercial applications worldwide. P25 radios are a direct replacement for analog UHF (typically FM) radios, but add the ability to transfer data as well as voice, allowing for more natural implementations of encryption and text messaging. P25 radios are commonly implemented by dispatch organizations, such as police, fire, ambulance and emergency rescue service, using vehicle-mounted radios combined with repeaters and handheld walkie-talkie use.
Starting around 2012, products became available with the newer phase 2 modulation protocol, the older protocol known as P25 became P25 phase 1. P25 phase 2 products use the more advanced AMBE2+ vocoder, which allows audio to pass through a more compressed bitstream and provides two TDMA voice channels in the same RF bandwidth (12.5 kHz), while phase 1 can provide only one voice channel. The two protocols are not compatible. However, P25 Phase 2 infrastructure can provide a "dynamic transcoder" feature that translates between Phase 1 and Phase 2 as needed. In addition to this, phase 2 radios are backwards compatible with phase 1 modulation and analog FM modulation, per the standard. The European Union has created the Terrestrial Trunked Radio (TETRA) and Digital mobile radio (DMR) protocol standards, which fill a similar role to Project 25.
Suite of standards overview
History
Public safety radios have been upgraded from analog FM to digital since the 1990s because of an increased use of data on radio systems for such features as GPS location, trunking, text messaging, metering, and encryption.
Various user protocols and different public safety radio spectrum made it difficult for Public Safety agencies to achieve interoperability and widespread acceptance. However, lessons learned during disasters the United States faced in the past decades have forced agencies to assess their requirements during a disaster when basic infrastructure has failed. To meet the growing demands of public safety digital radio communication, the United States Federal Communications Commission (FCC) at the direction of the United States Congress initiated a 1988 inquiry for recommendations from users and manufacturers to improve existing communication systems. Based on the recommendations, to find solutions that best serve the needs of public safety management, in October 1989 APCO Project 25 came into existence in a coalition with: Association of Public-Safety Communications Officials-International (APCO) National Association of State Telecommunications Directors (NASTD) National Telecommunications and Information Administration (NTIA) National Communications System (NCS) National Security Agency (NSA) Department of Defense (DoD)
A steering committee consisting of representatives from the above-mentioned agencies along with FPIC (Department of Homeland Security Federal Partnership for Interoperable Communication), Coast Guard and the Department of Commerce's National Institute of Standards and Technology (NIST), Office of Law Enforcement Standards was established to decide the priorities and scope of technical development of P25.
Introduction
Interoperable emergency communication is integral to initial response, public health, community safety, national security and economic stability. Of all the problems experienced during disaster events, one of the most serious is poor communication due to lack of appropriate and efficient means to collect, process, and transmit important information in a timely fashion. In some cases, radio communication systems are incompatible and inoperable not just within a jurisdiction but within departments or agencies in the same community. Non-operability occurs due to use of outdated equipment, limited availability of radio frequencies, isolated or independent planning, lack of coordination, and cooperation, between agencies, community priorities competing for resources, funding and ownership, and control of communications systems. Recognizing and understanding this need, Project 25 (P25) was initiated collaboratively by public safety agencies and manufacturers to address the issue with emergency communication systems. P25 is a collaborative project to ensure that two-way radios are interoperable. The goal of P25 is to enable public safety responders to communicate with each other and, thus, achieve enhanced coordination, timely response, and efficient and effective use of communications equipment.