Crosstalk noise and signal‐to‐noise ratio characteristics for digital symmetrical pair cable transmission system in synchronous clock operation

Abstract

AbstractIn the digital transmission system using a symmetrical pair cable, the following problems arise in the application to the communication network.(1) The transmission distance and the system accommodation rate in the symmetrical pair cable are limited by the crosstalk noise. Consequently, it is necessary to evaluate the crosstalk noise in pulse transmission with synchronized clock frequency and to provide system design based on the evaluation.(2) In the application of digital transmission systems to city links and subscriber loops, a highly efficient system accommodation in the existing cable is required. Then the signal‐to‐noise ratio (SNR) of the system in the multiple crosstalk environment must be evaluated accurately.For the first problem, it is noted that the crosstalk noise is a cyclostationary stochastic process. It is shown that the peak value of the instantaneous noise power, which is an ensemble average over multipairs, gives the worst evaluation of the crosstalk interference to the systems with synchronous clock operation. A new method for noise evaluation is proposed based on the result.For the second problem, a general case is considered. In this case, the crosstalk noise of the cable in SNR evaluation of multiple crosstalk is composed of more than one subpopulation. The principle of SNR distribution is analyzed, and a method of calculation for SNR is proposed based on the average and variance. It is shown that the proposed method of SNR valuation can be used in the design of digital transmission system in a crosstalk environment.