MCV QoE Mouth To Ear Latency Measurement Data

Mouth to Ear (M2E) latency characterizes the time between speech input into one
communications device and its output through another, and has been identified as a key metric
of quality of experience (QoE) in communications. NIST's Public Safety Communications Research
(PSCR) division developed a method to measure and quantify the M2E latency of Push To Talk
(PTT) devices using MATLAB. Example measurements of the M2E latency of VHF and UHF Land Mobile
Radios (LMR) operating in both direct mode and in trunked mode were performed. M2E latency of
VHF and UHF handsets operating in Direct Mode measured over 200 ms whereas VHF and UHF
handsets operating in trunked mode measured over 400 ms. The measurements were performed using
land mobile radio (LMR) handhelds. The M2E latency was measured for these devices operating in
both direct and trunked modes. Direct mode communication is device to device and requires no
additional radio infrastructure. Trunked mode communication involves an LMR repeater which
processes the request to transmit by monitoring a control channel, then assigns a specific
frequency for the LMR to use to communicate with other LMR handsets. Both a single location
and two location measurement system were developed. The primary purpose of the two-location
measurement system was for use in future research and to demonstrate that the propagation of
the signal is generally a negligible contributor to M2E latency. The data provided contains
single- and two-location lab tests, with cabled RF between devices, as well as two-location
field tests, with devices communicating over the air. These tests demonstrate the consistency
of measurement results between the single- and two-location systems in a lab
environment.