On QoS constraints and joint source-channel coding for real-time cooperative multimedia communications

Cooperative diversity exploits the broadcast nature of wireless channels by allowing users to relay information for each other so as to create multiple signal paths. This technique could be used together with joint source-channel bit rate allocation to transmit conversational multimedia traffic. This paper studies, following a methodology that avoids the use of high or low SNR approximations, the interaction between joint source-channel bit rate allocation with AF and DF cooperation. Furthermore, the effect of QoS constraints on performance is studied. In addition to the advantages of user-cooperation at medium and low source-destination channel signal-to-noise ratio, the results in this paper point at the fact that significant extra performance gains could be obtained by careful selection of the relay node. Guidelines for choosing the relay are also discussed.