The Effect of Waveform Substitution on the Quality of PCM Packet Communications

Missing packets are a major source of impairment in packet voice networks. While it is easiest to allow these gaps in received information to appear as silent intervals in reconstructed speech, subjective quality is improved by filling the gaps with estimates of the transmitted waveform. We have investigated several estimation techniques for packets containing 16 ms of speech in a pulse code modulation format. The simplest method, packet repetition, extends from 2 percent to 6 percent the acceptable ratio of missing packets.