Cheannel Capacity of Twisted Wire Pairs in Multi-Pair Symmetric Copper Cables

Crosstalk is caused by electromagnetic coupling between neighbouring wire pairs in multi-pair copper cables. In this contribution the channel capacity of a twisted wire pair in an unidirectional driven multi-pair cable is calculated, where only far-end crosstalk is present. Thereby two scenarios are considered: Firstly the far-end crosstalk from neighbouring wire pairs is interpreted as disturbance, which affects the transmission in the considered wire pair. Secondly the far-end crosstalk paths are viewed as additional transmission paths, which together with the wanted signal path convey the signal from the near to the far cable end. In the former case the channel capacity is decreased compared to the transmission with only noise disturbance, whereas in the latter case the channel capacity is increased due to the utilization of additional transmission paths. In particular for short cables the effect of far-end crosstalk is very strong and with rising number of neighbouring wire pairs the far-end crosstalk impact increases