Alcatel

Armin Mann

Michael Walker

Hans J&uuml;rgen Matt

Holger S&ouml;hnle

Fritz Weinschenk

A compander circuit ( ) for echo cancellation in telecommunications apparatus with an estimator module ( ) for estimating an echo coupling and a delay of a line echo and a characteristic module ( ) with an associated multiplier ( ) for controlling the short-time output level of z (k) as a function of the short-time input level of z (k) is characterized in that at all inputs and outputs of the compander circuit ( ), a plurality of N communications channels are applied and outputted, respectively, at an N-fold clock rate as compared with a single communications channel; that all memory units in the compander circuit ( ) are designed as multiplexer-buffer-demultiplexer (MBD) units ( ); and that a modulo-N counter ( ) is provided which controls all MBD units ( ) so that in each of the MBD units ( ), always the same memory cell ( ) assigned to a particular communications channel is addressed.

Multichannel echo canceller with a compander

A process for suppressing total echoes comprising a plurality of partial echoes in telecommunications (TK) equipment such as terminals, transmission systems, or switching equipment by means of adaptive FIR (&equals;Finite Impulse Response) filters that simulate the total echo and subtract it from the echo-affected useful signal transmitted to the respective TK equipment, whereby n partial FIR filters are provided, which respectively simulate a partial echo, is characterized in that m parallel, mutually independent TK channels are provided with an echo suppression function and that for this purpose a variable sub-quantity of the partial FIR filters is assigned to a TK channel to be operated, respectively, as required depending on the number of partial echoes and the size of the occurring delay times between signal and echo. This permits effective echo suppression without significant memory space and computational effort even for a large number of m parallel, mutually independent TK channels, such as must be processed in switching equipment or gateways.

Process for echo suppression with adaptive fir filters

An equipment ( ) for the suppression of whole echoes composed of several partial echoes in telecommunications (TC) equipment, such as end devices, transmission systems or exchange equipment, with the help of adaptive FIR (&equals;Finite Impulse Response) filters, which reproduce the whole echo and extract it from the echo-laden useful signal and which has been transferred to the respective TC equipment, in which the homogeneous FIR filters or partial filters ( ), each of which are able to reproduce a whole echo or partial echo, are implemented on a single ASIC (&equals;Application Specific Integrated Circuit) ( ) for the m parallel and independent TC channels n to be served; and in which the whole echoes or partial echoes to be reproduced can be calculated in real time in the ASIC ( ) and in which a digital signal processor ( ) is designed to control the ASIC ( ) and set the filter settings, especially after the coefficient required to reproduce the echo is calculated on the ASIC ( ). This calculation is carried out in the digital signal processor ( ). This makes it possible to effectively suppress echoes in a large number of m parallel and independent TC channels, as they must be processed in exchanges and network hybrids, without requiring a large amount of memory space and computational effort.

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Stuttgart, Germany

Armin Mann