Project 25

What is Project 25?

Efforts to develop industry-wide standards have been underway since the late 1980’s. Project 25 (P25) is an industry-wide effort to develop a voluntary standard for uniform digital two-way radio for public safety organizations. P25 Standards are a benchmark in Public Safety Radio Communications for First Responders. P25 is defined in the published ANSI/TIA102 documents enabling migration from today’s radio systems to desired levels of interoperability directly impacting first responders. It is the first standard of its kind, driven by users, to allow graceful, scalable migration to standards based interoperable systems.

Why is P25 relevant now?

The events in the United States and around the world since September 11, 2001 have spurred popular interest in Public Safety communications interoperability. Growing concern has driven many country’s governments - including the US Federal Government - to reorganize to create focused positions to address Homeland Security. Long before these events, Public Safety and the land-mobile radio industry created an interoperability solution. Published by TIA and approved by Federal, State/Province and Local Public Safety users, the P25 standards enable a feature-rich, scalable digital radio technology. The availability of radio equipment compliant to P25 standards is now providing a basis for conventional radio communications interoperability that is necessary for First Responders.

Is P25 an accepted standard now?

The P25 standard has been adopted by the National Telecommunications and Information Administration (NTIA), which manages spectrum for the federal government. In addition, NTIA also specified use of P25 narrow band by the year 2005 for the VHF Hi bands (162-174 MHz), and by 2008 for all other bands. Many US government agencies (e.g. Treasury, Interior, Departments of Defense (DoD) and Justice) have specified P25 for procurements of new radio communications systems and equipment.

P25 compatibility has become a significant purchasing factor for users of state and local public safety and public service radio communication systems. As state and local Public Safety users change or upgrade their existing analog systems to comply with new FCC regulated bandwidths, demand for P25 compliant digital public safety systems increases. This is partly due to the ability of P25 systems to be configured for compatibility with older analog mobile and portable radios, allowing adopters of the P25 standard to purchase new system equipment without replacing all of their subscriber radios.

The 8 Interfaces:

A commonly misunderstood aspect of P25 is that it is comprised of a single standard. Instead, it is a suite of standards that specify the eight interfaces between the various components of a land mobile radio system (hand held to hand held, hand held to mobile unit, mobile unit to repeater, etc.):

1. Common air interface: This interface defines the wireless access between mobile and portable radios, and between the subscriber (portable and mobile) radios and the fixed or base station radios;
   
2. Subscriber data peripheral interface: This interface characterizes the signaling for data transfer that must take place between the subscriber radios and the data devices that may be connected to the subscriber radio;
   
3. Fixed station interface: This interface describes the signaling and messages between the radio frequency simulation system (RFSS) and the fixed station by defining the voice and data packets (that are sent from/to the subscriber(s) over the common air interface) and all of the command and control messages used to administer the fixed station as well as the subscribers that are communicating through the fixed station;
4. Console interface: This interface is similar to the fixed station interface but it defines all the signaling and messages between the radio frequency simulation system (RFSS) and the console, the position that a dispatcher or a supervisor would occupy to provide commands and support to the personnel in the field;
5. Network management interface: This interface to the radio frequency simulation system (RFSS) allows administrators to control and monitor network fault management and network performance management;
6. Data network interface: This interface describes the RF subsystem's connections to computers, data networks, external data sources, etc.;
7. Telephone interconnect interface: This interface between the RFSS and the Public Switched Telephone Network (PSTN) allows field personnel to make connections through the public switched telephone network by using their radios rather than using cellular telephones;
8. Inter RF subsystem interface: This interface permits users in one system to communicate with users in a different system, from one jurisdiction to another, from one agency to another, from one city to another, etc.

Until this past January, the last fifteen years had resulted in only one of the above P25 interfaces, the Common Air Interface that deals with the functions of the hand held units (i.e., walky-talky), being advanced to a level where it would help satisfy one or both of the goals of P25. The remainder of the interfaces had either remained undefined, or lacked enough specificity to allow for a common implementation of the interface; in other words each manufacturer’s implementation of the interface would be different and proprietary thus resulting in systems that would not meet "interoperability" requirements.

P25 Compliance Assessment Program

Public safety demands that equipment claiming to be P25 compliant — or generally capable of its manufacturer’s claims — will communicate with other P25 radios. Unfortunately this is not often the case. Initial testing shows that often one manufacturer’s “P25-compliant radio” will not communicate with another manufacturer’s “P25-compliant radio.” The National Institute of Standards and Technology (NIST) is currently addressing this issue by developing a P25 conformance testing program in partnership with SAFECOM to ensure equipment meet the new P25 standards. National Institute of Standards and Technology (NIST), in cooperation with technical representatives from the Institute for Telecommunication Sciences (ITS) and industry representatives, has established a framework for the program and is moving into the first stage of testing. The safety of emergency responders will be enhanced when industry’s claims of P25 compliance can be measured objectively and independently. This initiative will also ensure federal grant dollars are being used appropriately to purchase equipment that is truly P25 compliant.

The Future State

Over the last year, through the concerted efforts of industry, public safety practitioners, and NIST, and the support of SAFECOM, the technical development of standards for the critical P25 interfaces has been greatly accelerated. Industry representatives, with key involvement by public safety practitioners, have dramatically increased the pace and scope of their standards development activities consistent with priorities set by Congress.
As a result, significant progress has been made through the formal P25/Telecommunications Industry Association (TIA) standards development framework established by the P25/TIA partnership in 1993. Specifically, the most critical P25 radio system interfaces have all been addressed. Basic protocol standards that specify the functionality and capability of these interfaces have now been completed and have been, or are on the verge of being published. The adoption of P25 standards is now occurring within a time frame acceptable to public safety users, NIST and its Federal partners, and the manufacturers.
As of the March 2006 the following has been achieved to add to the existing P25 Common Air Interface:

• Inter-RF Subsystem Interface (ISSI):

  On May 31, 2006 the TIA unanimously voted in favor of publishing the ISSI Messages and Procedures documents. The next step is for the TIA to formally publish this TIA standard during 2007. The public safety community can expect ISSI products to be available in 2007 (within approximately six months after publication of relevant standards in 2006 consistent with deadlines established by the P25 Steering Committee).
  
  

• Fixed/Base Station Subsystem Interface (FSSI):

    A completed FSSI standard was approved on January 11, 2006 for publication as a TIA standard.  The realization of a TIA standard for the FSSI is extremely important because this standard will result in the offering and procurement of interoperable multi-vendor equipment enabling direct control by the console and Radio Frequency Subsystem (RFSS) of fixed/base station equipment.  The console functionality provided by the FSSI substantially mitigates the urgency for completion of the CSSI.  The public safety community can expect FSSI products to be available in late 2006 (within approximately six months after publication of relevant standards in 2006 consistent with deadlines established by the P25 Steering Committee).
  
  

• Console Subsystem Interface (CSSI): 

  Completion in January 2006 of a new TIA standard for the FSSI that enables direct basic console control of fixed/base station equipment now serves as the foundation for more comprehensive CSSI standards to be developed in the future.  Further development of the CSSI will follow, upon continued development of the ISSI and FSSI throughout calendar year 2006.  The public safety community can expect CSSI products to be available in 2007 (within approximately six months after publication of relevant standards in 2006 consistent with deadlines established by the P25 Steering Committee).
  
  

• National Voluntary Laboratory Accreditation Program:

    NIST, with the support of SAFECOM and the P25 Steering Committee, is developing a P25 Conformity Assessment Program. NIST is preparing and documenting standardized test protocols for the most important aspects of the Common Air Interface Standard. The standardized test protocols will then be provided to NIST's National Voluntary Laboratory Accreditation Program (NVLAP), which can accredit laboratories interested in offering these testing capabilities. These test protocols would go a long way in assuring the public safety community that the equipment being purchased meets the P25 standard.
  

Conclusion

There are positive steps being taken by leaders within the public safety community, key federal programs, the Congress and industry to significantly change the current environment and move the state of standards for public safety forward. The last twelve months has seen significant progress in the development of critical P25 standards and the next twelve months will see even more progress made. In addition, by mid FY 2007, local, state, and federal agencies procuring P25 equipment will have a mechanism in place to ensure that the products they are purchasing truly do what is called for in the applicable standard.

See Larger Image (opens new window)

Project 25 Documents