Delivering on a promise

A spate of major disasters over the past decade highlighted the radio incompatibility issues that have plagued the public-safety sector for a very long time. But the aftermath of the terrorist attacks on Sept. 11, 2001, during which the New York City police and fire departments were unable to communicate with each other because they were using disparate radio systems, brought these issues in to sharp focus. More importantly, this event more than any other was the catalyst that caused public safety to finally place a much heavier emphasis on rolling out Project 25–compliant systems citywide, statewide and nationwide, under the banner of homeland security.

“Public safety, [even] without the D Block and without funding, has come a long way since 9/11, since we now have regional and statewide systems that were never there before,” wireless industry analyst Seybold said. “We have the start of 700 MHz narrowband interoperable systems and IP bridges between VHF and UHF. Have we solved [all of] the problems? No. But we’ve made a lot of progress.”

Related story: How to test a Project 25 system

Today, P25 finally is delivering on some of its promise — though it took much longer than anyone had hoped — as equipment compliancy and interoperability have taken a quantum leap forward from that fateful day 10 years ago.

The P25 concept has been around for more than two decades as an effort to make interoperable gear for police, fire and other emergency responders on all levels of government a reality. Since 1989, public-safety officials and the land-mobile radio industry have worked side by side on the standards that would enable such interoperability so that public-safety agencies could communicate with each other using wireless devices — regardless of the equipment that they use.

It also was hoped that P25 would allow public-safety agencies mix and match subscriber equipment, with the resulting increased competition amongst radio vendors driving down the cost such equipment. But despite the good intentions of the standards committees, the goal of better pricing largely has remained elusive.

However, Charles Werner, fire chief in Charlottesville, Va., who also is a member of the International Association of Fire Chief’s Communications Committee and vice chair of SAFECOM‘s executive committee, noted that the introduction of the Inter-RF Subsystem Interface (ISSI) standard, a component of P25’s second phase, has propelled public safety significantly closer to the equipment interoperability goal.

The ISSI enables two or more trunked P25 networks to be connected at the network layer to enable roaming across multiple networks, while also allowing dispatchers to communicate with users outside of their home network coverage areas. Products based on the ISSI offer even more benefits to the public-safety community because they allow networks and radios from various manufacturers to interconnect via a common standardized interface.

“The big leap forward was in ISSI, as it shows a new way to connect systems,” Werner said. “And I think the really good news is that there has been a real engagement of public safety into the P25 standard as to where there is more direct involvement.”

More good news: The ISSI has been followed by development of the Console Subsystem Interface, or CSSI, which allows the integration of consoles and recording devices from disparate vendors, and the Digital Fixed Station Interface, or DFSI, which makes communications between a fixed station and a P25 RF subsystem possible.

A further boon is the compliance testing program that was established by the Department of Homeland Security a couple of years ago. The P25 Compliance Assessment Program (CAP) is a voluntary program managed by the National Institute of Standards and Technology’s (NIST) Office of Law Enforcement Standards in partnership with a coalition of emergency response agencies and communications equipment manufacturers. To complete the P25 CAP compliance process, manufacturers’ radios must be tested for performance, conformance and interoperability using laboratories that were winnowed through a rigorous and objective assessment process based on internationally accepted standards. P25 equipment suppliers must then release summary test reports and suppliers’ declarations of compliance based on this testing.

It’s a big deal. The burden always has been on the buyer to determine that the equipment being purchased does what it’s supposed to do in the field. While manufacturers may have built their products according to the standard, they have in the past conducted little to no interoperability testing with other P25 products. Complicating matters is that some vendors have added proprietary components to the P25 radios in order to differentiate themselves; the net effect is that such radios, though technically built to the standard, are unable to fully interoperate with radios that lack those proprietary components, defeating P25’s purpose.

The public-safety sector and its vendors are now entering the next phase of conformance testing and are working to develop more detailed processes in order to bring interoperability to the next level, so that various radios, switches and base stations can work together.

All of that said, true interoperability is a lofty goal that may never be accomplished entirely, according to Stephen Devine, interoperability program manager at the Missouri Department of Public Safety.

“We’ve made progress, but I don’t know how much more progress we can make with increasing the degree of interoperability within P25, knowing there is a different technology that will address voice and data in the coming future,” Devine said. “What are the things we should try to accomplish in what may be a short timeframe?”

Devine, of course, is referring to the advent of the mobile broadband technology dubbed Long-Term Evolution, or LTE, which will provide the foundation for the next generation of communications technology for the public-safety sector. While public safety is a long way from running their critical voice communications over LTE infrastructure, Seybold predicted that devices capable of running both LTE and LMR would come to market in the next three years.

Eventually, the public-safety community will have to decide where it will place the majority of its development effort and investment. But one thing is for sure: When it comes to LTE for public-safety, the sector has plenty of lessons to draw from the evolution of the P25 standard.

— Lynnette Luna