July 25, 2016
In April 2016 the FCC issued a Report & Order that mandates use of analog FM for mutual aid and interoperability channels in the Part 90 VHF, UHF, and 800 MHz bands. This is an interesting development, in light of the massive effort by (and funding from) the U.S. Government to make APCO Project 25 the interoperability standard. Yet it’s not a surprise to us – we’ve been saying since 2013 that interoperability isn’t easy.
In March 2013 this blog stated “we’re farther away from interoperability than we were 20 years ago,” and referenced a presentation given at the Disaster Management Initiative hosted by Carnegie Mellon University – Silicon Valley that pointed out that “Not all P25 is interoperable.” Therein lays the basis of the FCC’s Report & Order.
Profits Over Interoperability
Interoperability wouldn’t be such an issue if strict adherence to the TIA-102 standard was mandated, but in an effort to lock customers into lucrative contracts and protect profit margins the radio manufacturers have tweaked P25 in ways that prevents interoperability. Figure 1 outlines the Homeland Security Interoperability Continuum.
Back in 2012 our product management team was contacted by a systems integrator seeking confirmation of field test results found during use of the P25 Bit Capture function in the LMR Master™ S412E. The captured data showed that the P25 Phase 1 uplink data from two different radio vendors did not match, even though each vendor claimed their equipment was standards-compliant. This is just one anecdote of many, and most readers of this blog very likely have similar experiences.
Fortunately, there’s a solution. Purchasers of P25 systems and equipment can and should insist on standards-compliance, and either independently verify compliance or require verification by the systems integrator and/or vendor. The LMR Master S412E Land Mobile Radio Modulation analyzer from Anritsu offers P25 analysis tools based on a strict interpretation of the TIA-102 standard, so that any variances found during testing can be recorded and documented as part of a corrective action order.
There are, of course, other reasons for this shift back to analog FM, not the least of which are ongoing issues with “voice codecs in high-noise environments” and issues with “digital cellular sites knocking digital public safety networks off the air.” Some fire departments have installed analog FM repeaters on incident command trucks because in some use cases analog has advantages over digital. The FCC’s Report & Order mandating analog will buy us some time to resolve these and other issues, but we also need to insist on standards-compliance supported by analysis and testing.
A library of technical documents outlining testing public safety networks and ensuring their operation has been published by Anritsu. You can access the full library here.