Q 1.12 What is the permitted latency for satellite communications recommended by the ITU?

ITU-T Recommendation G.114 should be consulted. The recommendation provides guidance about effects of end-to-end one-way delay (latency) on voice communication and recommends an upper bound for one-way network delay.

While G.114 recommends that latency of 400 ms should not be exceeded for general network planning, it cautions that highly interactive tasks (e.g., voice calls, interactive data applications, video conferencing) can be affected adversely by higher delays. The recommendation provides a curve derived from the E-model (ITU-T Rec. G.107) illustrating the effect of delay below 500 ms on conversational speech.

It should be recognized that in an end-to-end voice or data connection there are additional sources of delay such as voice codec, echo cancellers, packet assembly/disassembly circuits, modulation-demodulation processes, coding/decoding processes, trans-multiplexers and sub-systems in digital telephone exchanges.

One-way propagation delay associated with satellite systems are exemplified as follows: