Application-aware retransmission design for VoIP services in BWA networks

To improve the user-perceived quality of service (QoS) performance of voice over Internet protocol (VoIP) services, a retransmission of a packet experienced an error is needed in broadband wireless access networks. This means that the number of wireless resources to successfully transmit a packet can be increased by the retransmitted packet. For this reason, there can be a trade-off between the QoS performance improvement and the wireless resource efficiency enhancement with respect to the maximum number of retransmissions. This paper has formulated the cross-layer optimization problem to maximize the wireless resource efficiency with a constraint of the user-perceived QoS performance. This paper has driven the R-value for the user-perceived QoS performance because it includes most of impairments that can be generated during transmitting a voice frame from mouth to ears. Due to this feature, we can directly assess the QoS performance of VoIP services from a viewpoint of users. In addition, we can clearly design the optimal maximum number of retransmissions that can provide the satisfied quality of a VoIP service. By the numerical results, the optimal maximum number of retransmissions to provide the fair quality of a VoIP service under given conditions for G.711, G.729 and G.723.1 are 1, 3 and 4, respectively.