Realistic Modeling of Far-End Crosstalk in Metallic Cables

Crosstalk and especially far-end crosstalk (FEXT) represents the most serious source of disturbance in today´s digital transmission systems. It mostly limits the information capacity of current xDSL digital subscriber lines and local data networks with unshielded or shielded twisted pairs. The elimination of FEXT will require implementation of advanced methods for its modeling to obtain required predictions of its behavior. The standard FEXT model and ITU-T model gives only average results based on the sum of crosstalk in the entire cable, which is usually sufficient in case of summarizing FEXT contributions. However, the implementation of VDMT modulation would require individual modeling of FEXT crosstalk between all subscriber lines in a cable. That is why a new method for modeling of FEXT was developed and is presented here. The results of the model are also compared with measured characteristics for a typical UTP cable and several other cables. The proposed advanced FEXT model with minor modifications is applicable for any metallic cable to provide realistic FEXT characteristics.