Method and device for reducing crosstalk interference

In a transmission system which makes use of frequency translated signals, particularly a discrete multi tone (DMT) modulated transmission system or an OEDM (Orthogonal Frequency Division Multiplex) transmission system, in which the modulation may be effected using a fast inverse Fourier transform (IFFT), a method for reducing crosstalk interference induced on a signal SN on a first line N by signals D1, . . . , DN−1, each on a respective line 1, . . . , N−1, comprising the steps of:

• (i) associating a coupling factor α′1—N, . . . , α′N−1—N with the respective line 1, . . . , N−1, said coupling factor α′j—N, 1≦j≦N−1, being a complex number and when multiplied by the signal Dj, 1≦j≦N−1, on its associated line j, 1≦j≦N−1, estimating the crosstalk interference Ij—N induced on the signal SN on the first line N by the signal Dj on its associated line j;
• (ii) reducing the crosstalk interference IN on the signal SN on the first line N by subtracting an estimated crosstalk interference I′N from the signal SN on the first line N, said estimated crosstalk interference I′N being computed from said coupling factors α′1—N, . . . , α′N−1—N, and said signals D1, . . . , DN−1 on the respective line 1, . . . , N−1;
• (iii) pre-rotating and scaling each of the signals D1, . . . , DN−1 on the respective line 1, . . . , N−1 according to the coupling factor α′1—N, . . . , α′N−1—N associated with the respective line;
• (iv) summing all of the pre-rotated and scaled signals D*1, . . . , D*N−1, obtained in (iii);
• and
• (v) multiplying the sum ΣD* obtained in (iv) by a single complex number βN, which product is used as the estimated crosstalk interference I′N in step (ii).

In a transmission system which makes use of frequency translated signals, particularly a discrete multi tone (DMT) modulated transmission system or an OFDM (Orthogonal Frequency Division Multiplex) transmission system, in which the modulation may be effected using a fast inverse Fourier transform (IFFT), a method for reducing crosstalk interferences induced by a signal DN on a first line N on signals S1, . . . , SN−1 on a respective line 1, . . . , N−1, comprising the steps of:

• (i) associating coupling factors α′N—1, . . . , α′N—N−1, . . . , α′N—N−1 with the first line N, each of said coupling factors being a complex number and when multiplied by the signal DN on the first line N estimating the respective crosstalk interference IN—1, . . . , IN—N−1 induced on each of the signals S1, . . . , SN−1 on the respective line 1, . . . , N−1 by the signal DN on the first line N;
• (ii) reducing the respective crosstalk interference IN—1, . . . , IN—N−1 on each of the signals S1, . . . , SN−1 on the respective line 1, . . . , N−1 by subtracting a respective estimated crosstalk interference I′N—1, . . . , I′N—N−1 from each of the signals S1, . . . , SN−1 on the respective line 1, . . . , N−1, said respective estimated crosstalk interference I′N—1, . . . , I′N—N−1 being computed from the respective coupling factor α′N—1, . . . , α′N—N−1, and the signal DN on the first line N;
• (iii) multiplying the signal DN on the first line N by a single complex number βN yielding a product D**N;
• (iv) replicating the product D**N for obtaining N−1 equal products D**N—1, . . . , D**N—N−1;
• (v) pre-rotating and scaling the respective product D**N—1, . . . , D**N—N−1 according to the respective coupling factor α′N—1, . . . , α′N—N−1;
• and
• (vi) using the respective pre-rotated and scaled products obtained in (v) as the respective estimated crosstalk interference I′N—1, . . . , I′N—N−1 in step (ii).