Patent ID: 8447000
Filing Date: 2013-05-21
Classification: H04L

Abstract:
1. A transceiver system comprising (a) a primary transmitter for providing a primary symbol-information-carrying output signal and (b) a primary receiver for receiving a primary symbol-information-carrying input analog signal that includes an echo of the output signal, the receiver comprising: analog echo-cancelling circuitry for operating on the input analog signal, or on a first intermediate analog signal generated from the input analog signal, to produce an echo-reduced analog signal in which the echo is reduced; an analog-to-digital converter for converting the echo-reduced analog signal, or a second intermediate analog signal generated from the echo-reduced analog signal, into an initial digital signal; digital echo-cancelling circuitry for adaptively operating on the initial digital signal, or on a first intermediate digital signal generated from the initial digital signal, to produce an echo-reduced digital signal in which the echo is further reduced; and an output decoder for decoding the echo-reduced digital signal, or a second intermediate digital signal generated from the echo-reduced digital signal, into a stream of symbols, the digital echo-cancelling circuitry having echo-filtering characteristics that are adaptively adjustable in response to information provided by operating on the echo-reduced digital signal or on a further digital signal generated from the echo-reduced digital signal, the information for adaptively adjusting the echo-filtering characteristics of the digital echo-cancelling circuitry comprising an error signal generated by decoding the echo-reduced or further digital signal, the digital echo-cancelling circuitry comprising (i) an echo filter responsive to the error and output signals for generating an echo-estimate digital signal and (ii) an adding/subtracting element for generating the echo-reduced digital signal by substantially subtracting the echo-estimate digital signal from the initial or first intermediate digital signal, the echo filter comprises echo filtering circuitry that operates substantially according to a transfer function where z is a time-related variable, j is a general running integer, k is a time-index integer, ζ k,j is an adaptable jth coefficient at the kth time index, and L is a selected positive integer, the echo filter adaptively updating coefficients ζ k,j substantially according to: where μ EC,j is an adjustment parameter for the jth coefficient ζ k,j , sign (Tx k−j ) is the algebraic sign of the value of the output signal at the (k−j)th time period, and e k is the value of the error signal.