Adaptive Codec Selection for VoIP in Multi-Rate WLANs

Abstract

Network Technologies and Strategies (NeTS) Research Group, Universitat Pompeu Fabra, SpainThis chapter introduces the problems caused to voice over IP calls on 802.11 networks due to the link adaptation mechanism of them. It provides an overview of all the components participating in this study with special emphasis on the multi-rate anomaly. Furthermore, it reviews the literature on recent works on the specific area of link adaptation and codec selection. The authors finally propose as a solution to the multi-rate problem a codec selection mechanism, which, by changing codec of some of the calls at the moment of the rate change, has as an objective to maintain delay and packet loss values in acceptable levels and provide the desired QoS for the voice flows.