Developing a Test Solution
A Historical Perspective
In the examination of their current and future needs, public safety communications agencies identified several factors that pointed to the need to develop advanced digital two-way communications to replace aging and spectrally inefficient analog systems.
The growing scarcity of available radio spectrum
Better voice quality over greater areas
The growing demand for the integration of new, bandwidth intensive, data functions
The Project 25 initiative, has brought together a wide array of local, state, and government agencies with support from the U.S. Telecommunications Industry Association (TIA) to evaluate and develop a new standard for digital two-way radio.
Co-chaired by APCO International and the National Association of State Telecommunications Directors (NASTD), a steering committee was given the job of evaluating the plethora of technologies. Several sub-committees, in-turn, provide the technical expertise to research a number of specialized areas. Aeroflex, through its association with the Telecommunications Industrial Association, has been a key contributor to researching and defining testing parameters for the new standard.
The principle guiding the work of the steering committee was to establish an open narrowband digital radio standard so that multiple vendors could compete for contracts to supply compliant networks with interoperable products. Secondary principles include achieving maximum radio spectrum efficiency and simplifying P25 equipment.
The final documents establishing the Project 25 Standard were signed in Aug. 1995. The basic characteristics of Project 25 radios are these:
- Phase I—Emission designator 8K10F1E (C4FM, compatible four-level frequency modulation) in a 12.5 kHz channel.
- Phase II—Emission designator of 5K76G1E (CQPSK, compatible quadrature phase shift keying) in a 6.25 kHz channel.
- Common receiver for both C4FM and CQPSK to ensure full interoperability.
- Encryption—As defined in the U.S. Data Encryption Standard (DES) algorithms.
- Improved Multiband Excitation vocoder—Providing 4400 bits/s of digitized voice, 2800 bits/s of voice error correction on the voice, and 2400 bits/s of signaling overhead, for an aggregate bit rate of 9600 bits/s.
The first true P25-compliant system is expected to be the state-wide P25 trunked system of the Michigan State Police.
AvComm Leverages P25 Standard Expertise To Develop a Project 25 Test Solution
A long-time provider of test solutions serving the SMR marketplace, Aeroflex had a great deal of interest and expertise to contribute toward developing a new SMR digital standard. Beginning in 1995, Aeroflex employees, through their membership in TIA’s TR8 Standards Committee, have been actively lending their expertise to several sub-committees working to develop the P25 standard.
It was through the exposure in the Project 25 development sub-committee that the platform that would later become the 2975 was born. Designed as a brand new platform, the core concept was to build a platform that could easily handle the phased implementation of the standard, as well as other testing requirements.P25 History
Click to see Project 25 Technical Diagrams