MIMO Systems in the Subscriber-Line Network

We consider multi-tone modulation (DMT, Discrete Multitone, OFDM, Orthogonal Frequency Division Multiplex) over cable bundles and present a compact mathematical description of the transmission line. Both, nearand far-end crosstalk (NEXT, FEXT) are taken into account and a new method for removing far-end crosstalk is derived. Keywords— MIMO, Multiple-Input-Multiple-Output, FEXT-Cancellation, NEXT-Cancellation, DMT, Discrete Multitone, xDSL I. MULTI-INPUT/MULTI-OUTPUT SYSTEMS AND THEIR MATHEMATICAL DESCRIPTION In this paper, we consider a transmission system, which consists of several loops from one dedicated point to another (e.g., from the central office to the cabinet). We assume that these loops are used for bidirectional data transmission. Let denote the number of loops which are used for transmission from point A to point B and the number of loops which are used in the opposite direction (from B to A). This MIMO channel can be described using a matrix and a matrix of time-discrete impulse responses. Let and ! denote the transmitted symbol sequences from point A to point B on loop " and from point B to point A on loop # . Then the received symbol sequence $&% on loop ' is given by (c.f., Fig. 1)