Estimating the transmission grade-of-service of telephone connections with multiple echo paths

Provides a methodology for estimating the subjective performance of telephone connections with multiple-talker or multiple-listener echo paths. This work is relevant to the performance assessment of voice-grade channels using in-service, nonintrusive measurement devices. The methodology is based on two attributes of existing echo/delay transmission rating models, which enable the dominant echo paths to be identified and all echo paths to be combined into a single path. Thus, as applied to multiple-talker echo paths, the method is more complete than the approach used in the current IEEE voiceband standard. The method, which is illustrated by an example, can also be applied to multiple-listener echo paths. The analysis of multiple echo path problems can be related to balance procedures and to measures of return loss commonly used in the telecommunications industry