Finally, a real breakthrough

Aug 1, 2008 12:00 PM, By Lynnette Luna

Interoperability testing of P25 radios expected to begin soon

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More than 15 years ago, U.S. governmental and standards organizations began to develop the Project 25 standard for the public-safety community. The primary objective: to create a set of standards for high-quality interoperable digital radio voice and data communications.

Today, although all of the standardization work isn't done, end users in theory should be able to buy P25-compliant networks, purchase digital radios from any P25 vendor for cost savings and operate those devices on their networks without any complications. But that isn't always the case.

Like all standards, including the all-IP-based WiMAX standard, P25 lets vendors add their own application-layer features — such as encryption software — as long as they don't interfere with interoperability. However, such additions often compromise interoperability, leading critics to say that manufacturers are diminishing the effectiveness of P25 by including proprietary hooks in their products.

“The dominant manufacturers appear to subscribe to the philosophy that measures should be taken to restrict competition when P25 radio systems are initially sold,” said Daryl Jones, owner and president of Telecommunications Engineering Associates, which manages public-safety systems throughout the San Mateo, Calif., area. “This is done by introducing proprietary variants and special features that other manufacturers cannot provide and results in limiting interoperability. This allows the manufacturer to sell system enhancements and subscriber radio equipment for extremely high, non-competitive prices by controlling the client's ability to purchase other brands.”

Steve Rauter, executive director of the Western Will County Communications Center in Plainfield, Ill., is ruffling feathers by asserting that manufacturers are embedding certain features in P25 that conflict with the goals of the InterRF Subsystem Interface, or ISSI, which is a component of P25's second phase. The ISSI is designed to connect disparate P25-compliant systems by establishing roaming between authenticated users, including both individual and group calls, via an IP-based software protocol stack that can reside in the users' handsets or in a gateway device.

“I've stumbled across an issue with the roaming dataset,” Rauter said. “What I'm finding out is that off-brand radios may not be able to read the brand signature of the manufacturer that is hosting the infrastructure, so a device may not roam correctly.”