P25 is an Open Standard
Project 25 (P25) is a set of standards produced through the joint efforts of the Association of Public Safety Communications Ofﬁcials International (APCO), the National Association of State Telecommunications Directors (NASTD), selected Federal Agencies and the National Communications System (NCS), and standardized under the Telecommunications Industry Association (TIA).
A P25 radio is any radio that conforms to the P25 standard in the way it functions or operates. P25 compliant radios can communicate in analog mode with legacy radios and in either digital or analog mode with other P25 radios. The P25 standard exists in the public domain, allowing any manufacturer to produce a P25 compatible radio product.
Although developed primarily for North American public safety services, P25 technology and products are not limited to public safety alone and have also been selected and deployed in other private system applications, worldwide. The Project 25 users’ process is governed by an eleven-member steering committee made up of nine U.S. federal, state and local government representatives and two co-directors.
Project 25 has four main objectives:
- Ensure competition in system life cycle procurements through Open Systems Architecture
- Allow effective, efﬁcient and reliable intra-agency and interagency communications
- Provide enhanced functionality and capabilities with a focus on public safety needs
- Improve radio spectrum efﬁciency
P25 has many various beneﬁts in performance, efﬁciency, capabilities and quality. Key P25 technology beneﬁts include:
Radio equipment that is compatible with P25 standards will allow users from different agencies or areas to communicate directly with each other. This will allow agencies on the federal state/provincial or local level (or any other agency) to communicate more effectively with each other when required (emergencies, law enforcement, etc.)
The P25 open standard will allow competing products from multiple vendors to be interoperable. This will allow customers of the P25 product to beneﬁt from multiple manufacturing sources (decreased costs, open bidding, non-proprietary systems).
A basic requirement for Phase 1 P25 digital radio equipment is backward compatibility with standard analog FM radios. This supports an orderly migration into mixed analog and digital systems, enabling users to gradually trade out radios and infrastructure equipment. By selecting products and systems that comply with P25 standards, agencies are assured that their investment in the latest technology has a clear migration path for the future.
The P25 standard includes a requirement for protecting digital communications (voice and data) with encryption capability. The encryption used in P25 is optional, allowing the user to select either clear (un-encrypted) or secure (encrypted) digital communication methods. The encryption keys also have the option of being re-keyed by digital data over a radio network. This is referred to as Over The Air Re-keying (OTAR). This capability allows the radio systems manager to remotely change encryption keys.
Improved Audio Quality
With 2800 bits per second of the total 9600 bits per second channel capacity allocated to error correction, P25 digital signals have improved voice quality over standard analog signals, especially at low or noisy RF carrier levels. The IMBE™ voice coder converts voice information into digital data and then the data is protected using error correction codes. The error correction is able to correct for small errors in the received signal. Since the audio is digitally encoded, the background noise typically present in analog systems is also removed.