Source controlled semi-reliable multimedia streaming using selective retransmission in DCCP/IP networks

In the past few years we have witnessed an explosive growth in the usage of media streaming applications. The newly appeared audio/video applications are becoming increasingly popular in IP networks, while in mobile environment the limited bandwidth and the higher error rate arise in spite of its popularity. Retransmission-based error recovery is considered inappropriate for multimedia applications, because of its latency. This solution can be attractive because it requires minimal network bandwidth, processing cost and efficiently improves the stream quality. Despite its latency, retransmission can be used successfully in many cases, especially if playout buffering is employed. Only the successfully retransmitted packets will improve the quality parameters of the multimedia stream, therefore it is worth to examine which packets should be retransmitted. In this paper a source controlled selective retransmission algorithm is presented with a decision algorithm based on the actual RTT and sending rate determined by the TFRC. In our scheme the transmitter determines the playout delay caused by the playout buffer using the proposed Flood method. The needed information about the network congestion state and the network delay are provided by the TFRC (TCP Friendly Rate Control) algorithm. Our proposal does not need additional administration messages because the decision procedure and its inputs are at the transmitter. The obtained results show that significant quality improvement is possible with the proposed selective retransmission scheme.