Study And Realization Of Selective Retransmission Technology For Guaranteeing The Quality Of Video Communications

With the development of video compression technology, the high-levelcompression can be obtained by applying the inter-frame temporal correlation andimage spatial correlation, thus promoting the transmission efficiency, however, it alsosuffers greatly from the error propagation. Meantime, the factors such as the bandwidthof the network environment, packet loss rate and bit error rate can affect theperformance of video communications, for example, the packet loss in some frames willaffect the quality of this frame itself as well as those frames with the same intra-framecode, which makes the video recovery quality dramstically decrease. Therefore, it isimperative to use the appropriate error control mechanism for the video bitstreamtransmission.This thesis has proposed an adaptive selective-retransmission control algorithmbased on the video context. A retransmission control model has been set up by means ofthe distribution model of packet importance and the network parameters likeround-trip-time, packet loss rate, sending rate and so on, which can efficiently managethe retransmission process in heavy loaded network and make sure the quality of thevideo transmission. The experiment results show that the proposed strategy in this thesiscan reduce traffic overhead caused by retransmission, almost functioning as theall-retransmission method.And then, it has also presented a Quality of Service (QoS)based hybrid selective automated request retransmission. When there is no packet loss,it will not increase the redundancy or increase a smaller one, which has escaped fromthe unnecessary bandwidth. In the case of a severe packet loss, the need of adjusting theforward error correction (FEC) protection and the selective retransmission protectionwill be determined by the video service quality, guaranteeing the video service quality.Finally, based on the above mentioned selective retransmission control, this thesishas illustrated the specific process of realizing the selective hybrid automatedretransmission request (HARQ). In comparison with the selective retransmission andonly forward error correction coding, the proposal in this thesis can promote subjectiveand objective quality and guarantee the QoS of video communications.