Multimedia Transmission Strategy In 3G And WiFi Networks

The development of Internet, as well as the existing of other hetergeneous networks, makes multimedia communication among these networks become increasingly important. Although there are many optimal algorithms aiming at improving performance of multimedia transmission, the communication between different networks is still a bottleneck, specially the performance and quality of packet transmission over IP networks.Therefore, this thesis mainly focuses on the optimization and control of multimedia transmission, as well as the performance and quality, in 3G and WiFi networks. More details of our contributions can be described as follows:(1) A Moving Average strategy based on Neighbor Graph (NG) is proposed between different WiFis. Through employing background scanning to collect signal strength of current Access Point (AP), the strategy dynamically calculates the mean value of signal strength. It then decides to handoff to the candidate AP according to the mean value. In order to decrease the loss of data packets, the strategy forces the packets to be transmitted to candidate AP by querying the NG of current AP.(2) A Gradient Prediction Scheme (GPS) is proposed based on the characteristics of handoff between 3G networks and WiFi. GPS starts the procedure of handoff through computing the first derivative value of the received signal strength. The combination of MAFS and GPS improves the efficiency of vertical handoff and abbreviates the disconnecting time.(3) For the purpose of improving quality of voice and video transmission and networks bandwidth utility, this thesis analyzes the related work of loss recovery technology and proposes Binomial Probability Model (BPM), which is based on Forward Error Correction (FEC) Reed-Solomon codec technology and interweaving loss recovery technology. BPM calculates the number of redundant packets according to the feedback from the receiver. By using interweaving technique to transmit mixed-packet of voice and redundancy, BPM can save bandwidth effectively.To sum up, the data propagation among the heterogeneous networks owns a great range of applications. Therefore, the work aiming at ensuring and improving the quality and performance of the transmission also shows great significance. Based on this background, this thesis has proposed some handoff algorithms between different networks and validates them through experiments. This thesis will mainly focus on improving the robustic and security of these handoff algorithms and data treansmission in the future work.