Telefonaktiebolaget Lm Ericsson (publ)

Tommy E Svensson

Tonu Trump

Gunnar A Eriksson

Erik L Jansson

Gunnar Eriksson

A single two-ended echo canceller is provided that uses an adaptive FIR filter to model the impulse response of the echo path and cancel the echo originating from the PSTN side of the connection, and a non-linear processor controlled by input signal levels to cancel the echo originating from the mobile phone side of the connection. Since the linear processing function is not used for cancelling echoes of the mobile phone side, the algorithms directed to estimating and cancelling echoes on the two sides of the connection can be executed in a single DSP, with all of the attendant advantages.

Method and apparatus for controlling echo on both sides of a connection

A PCM codec for converting between PCM words and analog signals has at least one element which is used for both types of conversions even though the clock pulse frequencies of the incoming and outgoing PCM words are different; a timing unit for generating time intervals wherein a first and second number are needed at the very most to carry out the respective conversion operations, the shorter of the period lengths determined by the two clock pulse frequencies includes at least the sum of the two numbers of time intervals; and a control unit for receiving the clock pulses in order to indicate the respective conversion type and for generating conversion type signals by means of which each of the time intervals is associated with one of the two conversion types. In order to control states where a type signal is generated delayed with respect to a notification pulse, the codec includes information memories to store the influenced information. And in order to control states where the control unit interrupts the present conversion operation of one type due to the priority of the other type, the codec includes a result memory to store such intermediate results which make it possible to continue the interrupted operation after the termination of the priority operation.

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Skarholmen, Sweden

Tommy E Svensson