Project 25 (P25)

P25 (Project 25) is a set of design standards developed to provide interoperable digital radio communications, spectral efficiency, integrated voice and data, as well as improved security .

 

The development of the P25 standards started in late 1989 and is just now starting to demonstrate it's true potential. While the road from idea to widespread implementation has been long, one of the challenges of standards based solutions, the positive benefit of P25 is the range of vendors who are competing to provide equipment, based on the P25 standard.

 

Radio manufacturers who could not compete with proprietary trunking have now introduced a full line of P25 radios, including some who now produce 700/800 MHz P25 radios. With the migration to IP based radio system connectivity, new console solutions have been introduced that provide feature rich radio system interfaces.

 

Many system operators will find new P25 systems more expensive to operate. P25 brings new capabilities, greater monitoring, better integration, all of which increase complexity. Systems being replaced are often 15 to 20 years old and have been in care taker mode for some time. The change from really old, to brand new, high functionality IP based systems, increases support costs as new systems need to be  maintained at new system levels.

 

With digital radio, everything is data, including voice, providing the opportunity to implement and manage encryption. P25 supports AES 256 bit encryption, the Public Safety standard with support for FIPS 140-2. Many radios also support software encryption, which is much less secure, using a short manually entered key, but provides an opportunity for public works and utilities to gain some privacy from anyone monitoring the radios.

Implementing a P25 system does not guarantee interoperability with partners. P25 greatly improves the opportunities and possibilities, but there are still some laws of physics, costs and  personalities that can get in the way.

The best solution is a large area shared P25 system, which has all partners operating on the same system. The frequency band and coverage is the same across all the partner service areas. This requires multiple agencies to work together, providing reduced operating costs and greater functionality. However having everyone on the same system is only the technical part of Interoperability. Making interoperability work, "intertalkability", still requires the other 4 lanes of the Interoperability continuum.

If a single shared system is not possible, then the next best solution is independent systems, on the same frequency band, linked together through an ISSI connection. With the same frequency band, single band radios can transition from one system to the other, so coverage is maintained for all users over the combined service area.

Interoperability where partners are on different frequency bands with different coverage areas, can create challenges. The systems can be linked together, but there are areas where agency A has coverage and agency B does not, or vice versa, creating areas where one agency cannot talk to the other.

There are options like dual band radios that can overcome different frequency band issues, but this increases cost per radio, something that may not fit the budget. Implementing dual band radios for specific users, such as supervisors can help reduce the number of dual band radios required, while providing some degree of interoperability.

Click here for more information on Interoperability.

System Size: Small P25 systems can be cost prohibitive, due to the costs to purchase and operate the common infrastructure. Cost savings and interoperability are driving factors for large shared communications systems serving entire Cities, Provinces or States. The concept of each agency operating their own independent radio system can limit interoperability options and can exceed available funding.

Radios: The cost of P25 radios is more than a cheap analog radio and in most cases is still more than a radio from one of the other digital radio technologies. Radios for P25 systems must support the standard and the standard provides a lot of flexibility to meet the needs of different Public Safety users.

With more vendors making P25 capable radios, and as  agencies get more experience with P25 systems, competition is driving down the cost for P25 radios. The full benefit of this may not be fully evident, until a few years down the road when it comes time to replace the portable radios purchased with new systems.

There is a lot of confusion about interoperability and some people have been led to believe that if a partner agency has not implemented P25, then interoperability is not possible. This is not true.

Interoperability between P25 and non P25 systems is possible and will be required in most jurisdictions. The interconnection  between independent radio systems will be done using the same methods that were used in the past. Options include using a tone interface on each system, with a 4 wire circuit between them, or attaching a radio from one agency onto the system of the other agency. These are standard options used today to link proprietary systems as well as for linking with conventional analog systems.

In many cases, agencies will use these same methods for linking P25 systems as well, because it meets their functionality and budget requirements. Not all interoperability partnerships can justify the costs of a dedicated network to network connection.

While the P25 standard includes the Inter Sub System Interface (ISSI), allowing systems to be connected together for interoperability and roaming, it is not without some costs. Systems may require additional hardware and software to implement the ISSI and there is an ongoing cost for the network connection between the ISSI gateways. Agencies will have to make value/risk/cost decisions for each Interoperability partner.

For partners that work together regularly, the ISSI is an excellent solution, providing maximum benefit from the P25 standard. For occasional use, the connection of a  radio from one system, onto a base station interface port of another system, may provide the capabilities required, at a cost that  can be supported year over year.

Not all Interoperability partners with Public Safety are Police, Fire and EMS. Local hospitals, Municipalities and Utilities may have independent radio systems and may have interoperabilty with Public Safety agencies and/or with each other.

Having a mix of P25 and non P25 systems as part of an interoperability plan is a reality and is an area that needs improved connection options. One way to improve interconnection options would be using Software Defined Radios (SDR) with true digital interfaces. This could greatly improve the capabilities and audio quality when linking P25 and non P25 systems together.

Click here for more information on Interoperability Options.