Multiplex communications – Wide area network – Packet switching
Patent
1984-12-10
1987-11-17
Rubinson, Gene
Multiplex communications
Wide area network
Packet switching
379410, H04B 323
Patent
active
047078243
ABSTRACT:
A method and apparatus cancels an echo by using an echo replica generated such that a tap coefficient of an adaptive filter is sequentially updated, the echo being received from a transmitting end to a four-wire side through a two/four wire converter and being obtained such that a pulse signal having positive and negative polarities is fed into a receiving end, wherein a difference signal (error signal) between the echo replica and a reception signal is calculated; a correlation value between a signal representing a polarity of the error signal and a signal representing a polarity of the echo replica is calculated; when the correlation value is smaller than a predetermined value, a first of two types of tap coefficients which belong to each of a plurality of taps is updated based on at least the error signal and is set as the tap coefficient of the adaptive filter during a period in which the pulse signal is set in the positive polarity, and a second type of tap coefficient is updated based on at least the error signal and is set as the tap coefficient of the adaptive filter during a period in which the pulse signal is set in the negative polarity; and when the correlation value is larger than the predetermined value, the first and second types of tap coefficients are updated irrespective of the polarity of the transmission pulse on the basis of the error signal.
REFERENCES:
patent: 3787645 (1974-01-01), Ochiai et al.
patent: 4007341 (1977-02-01), Sourgens et al.
patent: 4334128 (1982-06-01), Snijders
patent: 4539674 (1985-09-01), Carlqvist et al.
patent: 4621172 (1986-11-01), Kanemasa et al.
"Large-Scale Integration of Hybrid-Method Digital Subscriber Loops", IEEE Transactions on Communications, vol. COM-30, No. 9, Sep. 1982, pp. 2095-2108.
NEC Corporation
Rubinson Gene
Vaas R.
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