Packet communication applications cannot guarantee correct delivery of every packet. Congestions and interferences in the network lead to lost packets. However, real-time applications require timely delivery of data or information and always tolerate packet loss to achieve this aim. When some speech packets are lost, packet loss concealment (PLC) is used to replace the missing speech.

In this thesis, after investigating packet loss characteristics in realistic wireless networks and problems in existing PLC algorithms, we propose a new PLC scheme named adaptive PLC, which is composed of three algorithms: odd-even interpolation, waveform similarity matching and silence substitution. Adaptive PLC adjusts the algorithm to use depending on loss situations. Odd-even interpolation recovers the loss by interpolating odd or even samples in a packet. Waveform similarity matching estimates waveform segments from correctly received or already recovered packets. Silence substitution just fills in the missing part by zeros.

The adaptive PLC achieves improvements in speech quality relative to each single PLC algorithm and other existing PLC algorithms.
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