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. . 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.