Research And Improvement Of Transport Protocols In The Mobile Video Broadcast System

The development of wireless network technology and the intelligent terminal technology haspromoted the coming of mobile Internet era. Carrying out real-time multimedia services in wirelessnetwork environment has become a hot field. Carrying out real-time multimedia services in wirelessnetwork is different from wired network in many aspects. The technologies of real-time multimediathat performs well in wired network may encounter challenges in wireless network.TFRC (TCP Friendly Rate Control) protocol is originally control technology designed forreal-time multimedia transmission in wired Internet, and the control protocol attributes packet lossto network congestion, that is, when packet loss occurs, the control mechanism determines thenetwork status to be congested. In wireless network environment, however, there may be continualwireless network link error, if the control mechanism could not distinguish the reasons of packetloss and just reduce the sending rate simply, it might cause to cause a decline in the throughput ofthe wireless network, and lower the wireless network bandwidth utilization.This thesis is to study for the problem described above, firstly, it introduces the technology ofmobile video broadcast system, focusing on multimedia real-time transmission of RTP/RTCPprotocol, and discusses how to conduct the rate control through feedback parameters by RTCP.Then,inspired by TCP Veno algorithm, we apply it to the wireless network environment, and ourthesis proposes the RTCP feedback based W-TFRC algorithm. Then we build NS2simulationsettings for verifying the performance of W-TFRC. Simulation results show that, in a wirelessnetwork environment, W-TFRC achieves higher throughput than TFRC does.In addition, a design of wireless voice and video broadcast system based on the open sourceoRTP library is proposed in this thesis. The overall structure of the system is given. Specifically,after describing the method iOS system uses to complete the collection of the voice and video, wefocus on the design ideas and procedures, and provide the critical section and the codes of key parts.Then the procedure that the client implements voice and video broadcasting is briefly introduced.Field test shows that the system can achieve better QoS performance and reliability in both WiFiand3G environment.