Research On The QoS Support Of Multimedia Streams In Wireless IP Networks Based On Packet Loss Distinction

With the development of the wireless wideband network techniques, people expectappearance of new wireless multimedia services, especially video services on wireless network.In this thesis, we propose two kinds of congestion control algorithms for multimediatransmission, one of which is based on the end to end congestion control algorithm namedASMTP-X(Auto Switch Multimedia Transmission Protocol -X), the other one namedTFRC-QoS is based on the lower layer information. The main contents of the study aresummarized as follows:First, for multimedia streaming over the wireless IP network, in order to distinguish the reasons of packet loss effectively, ASMTP-X, automatically switches to the corresponding lossdifferentiation algorithm based on the state of the transmitter. With the help of a wireless channelmodel, ASMTP-X can get the congestion and bit error status by sending big packet and smallpacket alternately. An update factor K is added to adapt the algorithm to the network statequickly. When sending fixed -length packets, ASMTP-X adjusts the thresholds according to thestate of network, to improve quality of service and the throughput of multimedia transmission inwireless networksSecondly, in order to improve the quality of multimedia services more effectively, we candistinguish the packet loss reasons from the information of lower layers. TFRC-QoS cancontrol the maximum number of retransmissions reasonably based on wireless channel statisticsand link quality. Besides, TFRC-QoS can distinguish the packet loss types through the number ofretransmissions, which makes the sender better control transmission rate, thus reducing thenetwork congestion level and conflict, and increasing the packet delivery rate.Finally, we carry out NS-2 simulations to compare several algorithms. The experimentsshow that the algorithms proposed in the thesis can improve the throughput and reduce thecongestion loss rate, while remaining friendly with TCP flow even if there are competing flows.Besides, it can control QoS parameters like delay,jitter and loss rate at an acceptable level andmeet the QoS requirements for media delivery.