Packet based echo cancellation for voice over Internet protocol

In today´s modern telephony network, VoIP is fast emerging as one of the main communication techniques. However, the performance and the quality of VoIP is affected by echo. In this paper, a packet based echo canceller (PBEC) is introduced, as a solution to cancel echo in the VoIP network. PBEC can replace the current echo cancellers, which are located in the public switched telephony network (PSTN) central switches. The operating principle of the PBEC is explained and its advantages highlighted. The performance of the PBEC operating using different speech codecs is also studied. Using the PBEC, a maximum ERLE of 37.39 dB has been achieved when used with the pulse code modulation (PCM) based speech codec. From the simulation results, it can be also shown that the performance of the adaptive differential pulse code modulation (ADPCM) clearly matches the performance of the PCM based speech codec.