P25 radio communications are the gold standard in terms of interoperability and radio advancement. But if your coverage isn’t adequate or your signal is weak, your gold standard may be sounding a little tarnished. What are the main indicators of P25 quality and how is coverage and reliability measured?

Quality Indicator – DAQ

DAQ, or ‘Delivered Audio Quality,’ is the common measurement used to assess signal quality. The DAQ scale includes a scale ranging from 1 to 5, with 1 being unusable audio output and 5 being perfect.

A DAQ rating of 3.4 is the threshold rating considered acceptable for P25 radios in a public safety system. At this level, speech is understandable, with minimal repetition necessary and only some noise or distortion present.

Predicted Reliability

Another important consideration to ensuring quality P25 radio coverage is predicted reliability. This calculation involves determining two things:

  1. How much of the network area receives coverage.
  2. What percentage of the time the system performs to the expected level.

So to determine reliability, you need to assess how much of the coverage area receives signal at the projected DAQ and how consistently this signal is present. For instance, if the P25 radio system delivers a DAQ of 3.4 to 90% of your coverage area, 90% of the time, then your coverage statement would be: 90/90 @3.4DAQ.

Public safety agencies should strive for a system that is designed to provide reliable coverage 95% of the time.

If your current radio system is producing inconsistent audio quality or spotty coverage, it may be time to upgrade system components or invest in new equipment. Contact your Relm representative to address your department’s specific needs.