Project 25 (P25)
Mehmet Ulema · 2018
This chapter presents Project 25, a narrowband Land Mobile Radio (LMR) technology that provides voice and low-speed data communication capabilities for critical communication systems. It discusses in high-level Project 25's technical specifications, network architecture, interfaces and protocols, and services. The standardization process and its future are also discussed. A Project 25 digital radio system is composed of several open, standardized interfaces connecting a radio frequency sub-system (RFSS) to other components. However, Project 25 leaves it to the vendor to specify and build the interfaces inside RFSS. The common air interface (CAI) specifies the type and content of signals transmitted between compliant radios over a frequency division multiple access (FDMA) or time division multiple access (TDMA) channel at a maximum of 9.6 Kbps data rate. Digital encryption is an important, but optional, feature specified in Project 25 standards. Users can select this option when it is deemed necessary to have the transmission encrypted.