An Introduction to P25

APCO P25 LogoAs yesterday’s radio communications networks age and struggle to support new services demanded by today’s ever- changing public safety environment, decisions regarding critical communications networks need to be made sooner than expected. The decision is not only vital to the safety and productivity of today’s workforce, it’s a decision that must be far reaching enough to satisfy future needs over a 15-20 year useful life of the network infrastructure.

What makes P25 so special? Firstly, it was designed by public safety users in conjunction with radio manufacturers to provide real-world mission critical communications. It provides reliable and clear communications over a wide area. As an open standard it offers true interoperability which guarantees that users of this technology will always be able to talk to each other. It also guarantees a competitive market in which manufacturers strive to improve quality and cost-effectiveness of their products. Finally, the success of the standard can be judged by the fact that not only have P25 systems been deployed by public safety agencies globally, but that the standard has matched the needs of other industries such as power utilities and transport systems.

The P25 Standard and its benefits

P25 started life in 1989 as APCO project 25. APCO is the Association of Public Safety Communications Officials, a user organization representing police, fire, emergency medical and other public safety agencies. Among the various projects they initiated was project number 25 to define a digital radio technology for public safety users. The broad goals of this project were to:

  • get the best possible use out of radio spectrum,
  • allow effective and efficient communication within a public safety agency and between agencies,
  • ensure that a competitive market would exist in which different manufacturers could participate, and
  • create a technical platform for equipment that was easy to use.

With the active participation of radio vendors, the result of this initiative has been a dynamic and expanding suite of standards, driven by user needs, in tune with the rapidly evolving digital technologies of modern computer networks and voice over IP. This set of standards is administered by the TIA (Telecommunications Industry Association) as TIA 102, the official name for the P25 standards.

P25 is an open standard
P25 is a truly ‘open’ standard and is not proprietary to a single manufacturer. This means that competition is possible between manufacturers not only when a new system is purchased but over the lifetime of the system (e.g. each time new subscriber units are purchased). The P25 standards define conventional, trunked and simulcast systems.

What are the mandatory requirements of the P25 standard?
There is clear definition on P25 functionality, and in order for a manufacturer to claim P25 compatibility they must meet certain minimum functional criteria. At a minimum, to ensure interoperability between different manufacturers equipment, a P25 radio must meet two mandatory P25 Standard interface components:

  • The Common Air Interface (CAI) that defines the digital radio transmissions which are at the heart of P25.
  • The Improved Multi-Band Excitation (IMBE) or Advanced Multi-Band Excitation (AMBE) vocoder that converts voice to digital.

What are the standard options in the P25 standard?
There is also a range of defined ‘standard options’, which a manufacturer may choose to add to their product. However, if included, the option must operate as defined by the P25 standards. This ensures interoperability between different manufacturers who choose to include these features. For example, the various data services and encryption are standard features; equipment is not required to support them, but if it does, the implementation must follow the standard.

What are the manufacturers’ options in the P25 standard?
Beyond what is mandated and the range of standard options, there is a third category of features, which may be unique or proprietary to a manufacturer. These are known as manufacturers’ options. This means that although many manufacturers make P25-compliant equipment, not all P25 systems are created equal. Individual manufacturers are free to incorporate additional features and functionality into their products. Proprietary encryption technologies or proprietary schemes for interconnecting radio networks can be useful or add value at a lower cost, but also create an interoperability barrier since they generally cannot be used with other vendor’s equipment.

Stay tuned as we will be covering a lot more information on P25 in the coming weeks. Meanwhile, you can download this complimentary whitepaper to know why you should demand genuine P25 for your critical communications system.

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