France Telecom

Etat Francais Represente Par Le Ministre Des Postes, Telecommunications

L'etat Francais Represente Par Le Secretaire D'etat

Andre Gilloire

Pascal Scalart

Albert Benveniste

Martin Vetterli

Christian Chaure

A method and a device adapted to hands-free mobile radiotelephony for the optimized processing of a disturbing signal during a sound capture, on the basis of an observation signal y(t) formed of an original useful signal s(t) and of this disturbing signal p(t), the disturbing signal is estimated as a signal p(t) and the useful signal as an estimated useful signal su. An optimal filtering of the observation signal y(t) is carried out on the basis of the signal p(t) and of a minimizing of the error e(su,su) between the useful signal su and the estimated useful signal su. The estimated useful signal su and the useful signal converge towards the original useful signal s(t) for a substantially zero error e(su,su).

Method and device for the optimized processing of a disturbing signal

An echo cancelling device for use between a line receiving an incoming signal and a line transmitting an outgoing signal, for cancelling out echo, comprising a plurality of processing channels connected in parallel relation and assigned to successive mutually adjacent sub-bands of the spectral band of the outgoing signal, each channel having: a first analysis band-pass filter receiving the echo-affected signal to be transmitted, whose output is connected to the additive input of a subtractor; a second analysis band-pass filter, identical to the first filter, receiving the incoming signal and feeding an adaptive filter delivering an estimated echo value in the sub-band to the subtractive input of the subtractor; and a synthesis filter, symmetrical with the analysis filters and whose output feeds the transmission line. Each processing channel receives an estimation of the aliasing component originating from another sub-band at least and that component is eliminated by adding it to the signal originating from the filter analyzing the respective incoming signal. Estimation may be made by synthesis using at least one adaptive cross-filter fed by the output of an adjacent channel.

Echo cancelling device with frequency sub-band filtering

A coding process for the adaptive prediction differential PCM type. An error signal e.sub.t is formed between a sample of signal y.sub.t to be coded and a prediction signal p.sub.t of said signal. The prediction signal p.sub.t is formed from restored signals y.sub.t and e.sub.t by two linear filtering operations, the first relating to N successive samples of y.sub.t and using coefficients A1.sub.t, A2.sub.t, . . . , AN.sub.t and the second relating to P successive samples of e.sub.t and using coefficients B1.sub.t, B2.sub.t, . . . , BP.sub.t, the coefficients A1.sub.t, A2.sub.t, . . . , AN.sub.t and B1.sub.t, B2.sub.t, . . . , BP.sub.t being sequentially adjusted at each time t so that the mean power of error signal e.sub.t is minimal. Instead of carrying out the prediction on the basis of signals y.sub.t and e.sub.t only according to the invention, use is also made of the real signal y.sub.t and the real error e.sub.t. A linear filtering of y.sub.t using the coefficients A1.sub.t, A2.sub.t, . . . , AN.sub.t, these coefficients affecting N successive samples of the signal y.sub.t, a linear filtering of e.sub.t using the coefficients B1.sub.t, B2.sub.t, . . . , BP.sub.t are performed. In addition, the quantities thus obtained are respectively weighted by two coefficients between 0 and 1 and not simultaneously zero.

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Lannion, France

Andre Gilloire