Evaluation of Joint Admission Control and VoIP Codec Selection Policies in Generic Multirate Wireless Networks

Multirate wireless networks in general share a common problem for the transmission of VoIP traffic, since the rate changes of some of the flows affect the transmission of all others, which causes an unacceptable voice quality degradation. In this paper, an admission control algorithm is combined with a codec selection block to mitigate this negative effect. This centralized admission control is able to block or drop calls in order to maintain the system stability, despite rate changes. Moreover, the integrated codec selection block is able to select the most adequate VoIP codec for each incoming or already active call based on the channel rate used and according to a number of optimization policies. Several such policies are designed and evaluated in this paper.