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Mission Critical Voice QoE Access Time Measurement Methods


Jaden Pieper, Jesse Frey, Chelsea Greene, Zainab Soetan, Tim Thompson, Stephen Voran, Donald Bradshaw


Access time generally describes the time associated with the establishment of a talk path upon user request to speak and has been identified as a key component of quality of experience (QoE) in communications. NIST's Public Safety Communications Research (PSCR) Division developed a method to measure and quantify the access time of any push-to-talk (PTT) communication system. This measurement method is a follow-on development to the mouth-to-ear (M2E) latency measurement system presented in Ref. [1]. Here, a broad definition of access time is created that is applicable across multiple PTT technologies.

In this paper, a speech intelligibility-based access delay measurement system is introduced. This system measures the Modified Rhyme Test (MRT) intelligibility of a target word based on when PTT was pushed with a predefined message. It relies only on speech going into and coming out of a voice communications system and PTT timing, so it functions as a fair platform to compare different technologies. Example measurements were performed across the following land mobile radio (LMR) technologies: analog direct and conventional modes, and digital Project 25 (P25) direct, trunked Phase 2 modes.

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Created October 22, 2019, Updated December 4, 2020