ITU-T P.1305 PDF

This Recommendation has the primary purpose of describing the impact of echo-free transmission delays on telemeeting quality of experience (QoE). Delay is special amongst communication impairments in that it can have a major impact on how well the users interact, but very often without them being explicitly aware of its presence. Typically users comment on its impact (e.g., "we kept on interrupting each other") or assume a delayed response is due to the other participants taking a long time to respond. Consequently its impact is not always captured in conversational-opinion tests. Crucially the impact has been shown to be highly dependent on the task or activity being undertaken

The focus in this Recommendation is therefore on the human factor – its purpose is not to define specific quantitative limits or values, discuss the sources of delay or to discuss methods of delay measurement or methods to reduce its impact

Before discussing the impact of the delays, it is useful to first consider how people behave when conversing in an ideal environment. Since this has been well studied in the linguistic discipline of conversation analysis (CA), a short discussion of conversations in that context and a discussion on the impact of delay from a CA perspective is included. Some analysis based on the alternative technique of conversation surface structures is also included.

A secondary purpose of this Recommendation is to provide guidance on appropriate testing methods. A number of these have already been described in Annex D of [ITU-T P.1301] and will not be repeated here. However, there have been a number of new developments since that recommendation came into force and it is appropriate to expand on that knowledge.