Test Capabilities for First Responder and Emergency Workers Networks
What is MCPTT?
Mission Critical Push To Talk (MCPTT) is the vital service used regularly by first responders worldwide to quickly keep in touch. MCPTT service is delivered over 4G/LTE networks and provides conferencing through Push to Talk (PTT). In order to prove and verify essential performance of the new MCPTT service operated over FirstNet and other 4G/LTE networks for emergency workers, the Public Safety Communications Research (PSCR) agency, a part of the Department of Commerce, has specified four Key Performance Indicators (KPIs).
Mouth-to-Ear (M2E) Latency
- the time it takes audio to get from transmitting user to receiving user (read Teraquant’s blog post, “Measuring Mouth-to-Ear Latency” for more information)
End-to-End Access Time
- the time between PTT button press and receiving user hearing intelligible voice, i.e., access delay plus M2E latency
- the ability to establish call and the ability to retain call
MCPTT KPIs can be used to measure:
- equipment in the lab
- drive testing with MOS
- field testing of wireless voice/MCPTT service
- rapid transmission of audio, i.e., latency
Good results for all four measurements will give confidence that the MCPTT system will:
- be responsive
- provide timely access and retention to communication channels
- provide good voice quality using measures such as PESQ/POLQA scores and voice or speech intelligibility
For more information on making all these measurements with fully supported calibrated test equipment, view Teraquant’s multiDSLA solutions page.
Accurate and Specific Implementation of the Four KPI Measurements
The PSCR Mission Critical Voice (MCV) department leverages the 3GPP standard shown below. For example, accurate measurement requires the detection of start and end of grant tone.
Full ETSI Tests for First Responder Apps & Networks
The only system to fully test all 4 x MCPTT metrics defined in 3GPP TS 22.179 M2E Latency and Access Time MCPTT.
- Floor Access Time (KPI 1) to a grant tone
- Time for Voice Path Establishment
- Mouth-to-Ear Latency
- Time for third participant to join conference call
The following two images show sample results from Opale MultiDSLA Grant Tone and Test-Tone. The first screenshot is for the transmitting device which shows the grant tone. The second screenshot shows the receiving audio. The time marker placed at the beginning of the audio sample on the second screen shows 816 msec which is the end-to-end access time measurement.
The Opale MultiDSLA is uniquely capable of measuring all four PSCR MCV KPIs. This is because of its flexible capability:
- to generate and accurately detect multi-tones, DTMF, Sel-Cal (Selective Calling/PTT Grant Tones), and voice samples with a dynamic range beyond that of any voice/PTT system (read more about PESQ/POLQA test scores)
- of providing voice or speech intelligibility rating scale and testing over the full human voice frequency range
- of unmatched linearity and resolution