When it comes to Project 25 digital radios, cost still is a significant barrier to entry. While the standards suite—more than two decades in the making—finally is fulfilling the promise held for it regarding interoperability, the ability to mix and match subscriber units has not yet resulted in the dramatic price reductions that many imagined would result from increased vendor competition.

But there are other challenges. One concerns maintaining radios from several different vendors, said Karl Larson—public-safety project manager for the city of Portland—who participated in a P25 panel discussion last month during the International Wireless Communications Expo (IWCE).

“Competition, particularly for the subscriber units, is very important,” Larson said. “But since we maintain all of the public-safety radios in Multnomah County … when you have nine different radios, the radio shop is concerned about the number of templates, how long it’s going to take to do all of that, and how they’re going to maintain all of that.

“So, what we’ve done is split our RFP process into two processes,” he continued. “We have an infrastructure RFP that I’m reviewing right now, and then—in 2014—we’ll be issuing a subscriber RFP that will get more into that competition. We want to structure it somehow so that we don’t have nine [radio types], but maybe a top tier, middle tier and lower tier, so that we can limit the number of maintenance problems that we might have at the shop.”

Tom Sorley, deputy director in charge of the city of Houston’s radio communications system, said he’d like to see future iterations of the standard include a common template that all vendors would use. Short of that, Sorley encouraged vendors to create troubleshooting databases that would ease the maintenance burden.

“Come up with use cases or known scenarios—create a knowledge base—so that when a person who owns a Harris radio system and they program an Icom radio, if they get this problem—whatever this problem is—they can go to the database to find out what the trigger was the last time someone had this issue,” Sorley said. “In order to religiously encourage competition, I’ve got to be able to support it.”

Another step in the right direction would be to add a component to the Inter-RF Subsystem Interface (ISSI)—the interface that connects disparate P25 systems by establishing roaming between authenticated users—that would address system migration.

“You have systems that have had multiple revisions from the same manufacturer,” said Steve Devine,  interoperability program manager for the Missouri Department of Public Safety. “So there really is a need for a standard system interface, whether it’s between two vendor systems, or even within a single vendor system that happens to be at different revisions.

For example, the city of Joplin, Mo., uses the same Motorola P25 system that the Missouri statewide network is using, but the latter system operates at a different software revision. Because each revision has different features and capabilities, incompatibilities result that negatively affect interoperability, Devine said.

"So, there needs to be something in the ISSI that would promote intersystem [migration between] multiple vendors, as well as within the same vendor at different revisions—that would really be helpful,” he said.

When upgrading, it is vital that system operators ensure that operability isn’t compromised, Sorley said.

“One of my neighbors upgraded to an newer version of the operating system on their radio, and the ability for a certain type of roaming that they used for the other vendors would no longer work,” Sorley said.  

“Not only did they break the other manufacturers’ radios, they broke their own. They would still operate in a basic functionality mode … but if you have a feature that’s not basic functionality, but is a primary feature that makes your system usable, [breaking] it can have some big issues.”