The use of a computer model to assess telephony performance

Abstract

This thesis describes the formation of a computer model which can be used to aid the planning of, and future developments in, telephone speech transmission networks. The model is named TCAM (Telephone Connection AssessmentModel). It is comprised of 6 stages. Stages 1 and 2 form the main body of the model and are described fully in this thesis. Stages 3 to 6 form the subjective parts and are implemented by D.L. Richards. These are described elsewhere. The system is of modular construction and is run on a microcomputer. It is implemented in BASIC computer language. Also described is an investigation into the suitability of the modulation transfer function (MTF) method for objectively assessing the quality of a telephone channel. The method was however, found to be unsuitable in this particular case. A study into the preferred listening level (p.1.1.) of speech was made, concentrating on the effects of p.1.1. on speech bandwidth and the type of noise present with the speech. Relationships between random (Gaussian) noise and speech correlated noise (as found in PCM systems) were found. The results from these investigations can now be incorporated into Stage 5 of the model.