A Model of the Switched Telephone Network for Data Communications

The error statistics from data-transmission field tests on the telephone network may be compactly represented by about one dozen parameters. These relate to a model of the telephone network in which there are three distinct channels. The errors in binary data on each channel are produced by a renewal process in which a bit-error is a renewal event. The mixture of three such channels allows a close fit to the error statistics for a large range of block lengths. It is not implied that the errors on the telephone network are actually produced by such processes, but merely that they may be conveniently and compactly represented by them. Use of this model simplifies the analysis of error-control systems and the determination of error rates for error-control codes. In this paper the model is applied to study the effect that interleaving (time division multiplexing) has on the effectiveness of error-correcting codes.