Abstract:
The invention relates to a far-end crosstalk (FEXT) canceling circuit for a digital subscriber line transmission system, said transmission system comprising a plurality of line termination modems receiving digital multitone symbols from corresponding network termination modems over a plurality of transmission channels. The invention proposes to estimate the modulated data Si(fj) actually transmitted by the NT modems from the frequency components (Ri) of the DMT symbols received by the LT modems i and to evaluate the FEXT as a linear combination of these estimates. FEXT cancellation for all the LT modems is also proposed in a centralized manner.
Abstract:
The invention relates to a far-end crosstalk (FEXT) canceling circuit for a digital subscriber line transmission system, said transmission system comprising a plurality n of line termination (LT) modems (Mi) transmitting discrete multitone (DMT) symbols Si to corresponding network (NT) termination modems (Mc(i)) over n transmission channels. The invention proposes to multiply the vector S = (Si) i = 1 to n, before transmission, by a precompensation matrix M such that the matrix product H*M is diagonal, H being the transfer matrix of the n downstream transmission channels defined by R = H*S where R = (Ri), i = 1 to n, is the vector of the DMT symbols Ri respectively received by the modems Mc(i).
Abstract translation:本发明涉及一种用于数字用户线传输系统的远端串扰(FEXT)消除电路,所述传输系统包括多个n个线路终端(LT)调制解调器(Mi),将离散多音(DMT)符号Si传输到对应的网络 (NT)终端调制解调器(Mc(i))。 本发明提出在传输之前将矢量S =(Si)i = 1乘以预先补偿矩阵M使得矩阵乘积H * M为对角线,H为由n个下行传输信道定义的传输矩阵 R = H * S其中R =(Ri),i = 1至n,分别是由调制解调器Mc(i)分别接收的DMT符号Ri的向量。
Abstract:
L'invention concerne la transmission de données entre des noeuds d'un réseau, par multiplexage multiporteuses à répartition de codes. L'invention consiste à allouer à chaque noeud au moins une matrice d'étalement, un ensemble de données d'au moins une donnée à transmettre par un noeud (N) étant multiplié par la matrice d'étalement qui lui est associée et le produit étant ensuite transmis sur un groupe de porteuses en au moins un ensemble prédéterminé d'échantillons constituant au moins un symbole OFDM (S) ; à former des symboles à transmettre ayant tous la même durée quel que soit le noeud d'émission ; et à adjoindre à chaque symbole transmis un préfixe cyclique (PF) et un suffixe cyclique (SF) représentant un nombre prédéterminé d'échantillons, respectivement de la fin et du début du symbole.
Abstract:
A digital subscriber line transmission system comprising an IFFT circuit (14) generating successive outgoing time domain symbols (S) on a subscriber line from respective groups of digital frequency domain coefficients; an FFT circuit (18) generating groups of digital frequency domain coefficients from respective incoming time domain symbols (S') received on the subscriber line, a current incoming symbol being delayed with respect to a current outgoing symbol by a predetermined time interval (δ); and means (82) for, during an end portion of a current incoming symbol, subtracting from the signal (IN) received on the subscriber line an estimated echo obtained by a filter (84) from a signal portion (Xn+1) following the end of the current outgoing symbol, and adding thereto, through said filter, a beginning portion (Xn) of the current outgoing symbol, wherein said portions have a duration at least equal to said predetermined time interval.