The Covariance of Near End Crosstalk and Its Application to PCM System Engineering in Multipair Cable

The near end crosstalk (NEXT) model proposed by Cravis and Crater [1] is analyzed to give the covariance of NEXT, with good agreement between theory and measurements on multipair cable. The covariance of NEXT is then used to estimate the variance of the meansquare NEXT interference between PCM systems operating under the same cable sheath. These results are used to derive the required minimum mean NEXT loss as a function of the number of PCM systems , the NEXT loss standard deviation σ, and pertinent PCM system parameters. Comparisons with the minimum mean NEXT loss proposed in [4] and [5], , and that proposed in [1], , show that: dB, for and , while dB, for and , for all pertinent PCM system parameters.