Non-P25 Digital for Public Safety: Why Not?
Wednesday, February 19, 2014 | Comments

Proponents of Project 25 (P25) cite interoperability as a primary advantage of the protocol. However, consider a very common scenario — a particular community uses UHF P25, while the neighbor on one side uses VHF P25 and the neighbor on the other side uses 800 MHz P25. How does using the same digital protocol help any of these communities? It doesn’t — it only helps the vendor they purchased the system from.

When it comes to interoperability, analog remains the industry standard. Digital Mobile Radio (DMR) is an advanced and open standard that retains analog functionality for interoperability while offering many advantages over P25.

DMR offers two-slot TDMA technology, simulcast and cross-band communications at low cost, as well as high-level encryption from at least one vendor at no additional charge. P25 offers two slots per channel with Phase 2, but with a tight budget, this is an expensive proposition. Why wait for two-slot capabilities when increasing capacity requirements demand it now, and DMR is significantly more cost effective?

For example, take a congested area where a fire department uses one channel for paging and dispatch. If we installed two-slot DMR, the fire department doubles its capacity and retains analog paging. This new channel can be used to patch cross-band to any other band or protocol for interoperability, using IP gateways, audio bridges, back-to-back radios or dispatch consoles.

The DMR protocol allows for GPS, man-down, ambient listening, text messaging and Tier 3 trunking with or without simulcast. DMR IP67-rated radios with five-year warranties can be purchased for less than $650.

Several vendors are concentrating on production of sub-$1,000 P25/DMR dual-protocol radios. This is great news for public safety — whichever technology you choose, the future promises increasing digital interoperability. The only question is how much money do you want to spend getting there?

If I had the choice and bandwidth, TETRA is the best protocol for public safety, having four slots per channel and robust data; unfortunately, narrowbanding put a stop to that, with some exceptions.

Any way you slice it, software-defined radio (SDR) is the way to go. May the best, lowest cost and most efficient protocol win. Open standard DMR is a European Telecommunications Standards Institute (ETSI) standard on Tiers 1, 2 and 3 and provides the best choice for competition and price.

For the counterpoint opinion on why non-P25 digital technologies hurt interoperability efforts, click here.

Bruce S. Marcus is a 45-year veteran system designer and two-way radio expert, advising vendors and clients throughout the industry. Marcus keeps his fingertips on the latest technology solutions in his role as chief technology officer (CTO) of Marcus Communications in Manchester, Conn. He can be reached at

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