Pseudorandom generator of crosstalk transmission functions for modeling of multi-quad metallic cables

Crosstalk, and mainly far-end crosstalk (FEXT), is one the most serious source of disturbance in present xDSL lines (Digital Subscriber Line). It mostly limits the maximum achievable transmission speeds. It is necessary to implement new transmission techniques and modulations, such as VDMT modulation (Vectored Discrete Multi-tone Modulation), for reducing the crosstalk influence. However, the reduction of crosstalk by VDMT modulation is not possible in present systems due to its overall complexity and demands on computational units in DSLAMs. This paper presents the possibility of using space selection of disturbing sources among the metallic cable, which would allow the use of VDMT modulation only for a limited number of the most disturbing pairs. The new far-end crosstalk model, called advanced FEXT model, which is based on cable internal structure and parameters, is proposed here. The presented generator of crosstalk transmission functions is based on advanced FEXT model and provides accurate and realistic simulations and calculations of crosstalk characteristics.