Content for  TS 22.179  Word version:  19.3.0

For MCPTT Users, one of the most important performance criteria is the MCPTT Access time (KPI 1). The MCPTT Access time is defined as the time between when an MCPTT User requests to speak (normally by pressing the MCPTT control on the UE) and when this user gets a signal to start speaking. This time does not include confirmations from receiving users. The Mouth-to-ear latency (KPI 3) is the time between an utterance by the transmitting user, and the playback of the utterance at the receiving user's speaker. Figure 7.11.1.1-1 illustrates the MCPTT Access time and Mouth-to-ear latency.

An MCPTT User is able to join or leave an already ongoing MCPTT Group Call. Late call entry is the activity when an Affiliated MCPTT Group Member joins an MCPTT Group Call in which other Affiliated MCPTT Group Members are already active. The Late call entry time (KPI 4) is the time to enter an ongoing MCPTT Group Call measured from the time that the user decides to monitor such an MCPTT Group Call, to the time when the UE's speaker starts to play the audio. The performance requirements for Late call entry time only applies to when there is ongoing voice transmitted at the time the MCPTT User joins the call. In a Late call entry there might be an initial lost audio of the voice burst sent to the new Receiving MCPTT Group Member.