Distortion optimized rate allocation in wireless video multicast

Layered multicast transmission has been proposed as a solution to video content delivery over Internet. Existing schemes are usually based on layered video coding and perform rate control on end systems by using adaptation at the receiver's side and performing rate allocation at the sender's side. When considering video multicast in wireless context, mobile devices usually cannot afford to the cost of complex algorithm for rate controlling and layered encoding/decoding due to the stringent resource and power constraints in mobile device, limiting the apply of existing schemes in mobile environment. In this paper, we show that such computation cost and protocol overhead can be minimized by employing dynamic rate allocation in multicast designated router (DR) instead of mobile client. Specifically, DR keeps track of the wireless link state to mobile receivers and uses video quality as optimization criteria for rate allocation of each multicast group session. This optimal rate allocation benefits from lowering bandwidth cost while wireless link degradation is detected and hence proactively avoids network congestion; also in this scheme TCP-friendliness is easily achieved because flow-isolation is implemented in routers. We simulate a multiparty wireless video conference scenario in NS-2 to evaluate performance; the result shows that the proposed scheme can decrease the average packet loss ratio in each video stream and hence improve the overall video quality in mobile clients.