Research On Key Technology Of Multimedia Transmission Of 3G High-Speed Wireless Broadband Network

With the rapid development of 3G wireless network transmission technology, the application of wireless multimedia transmission has gradually entered the lives of common people and provided a lot of help to improve the efficiency of social production and people's living standards. However, the wireless multimedia transmission often cause packet loss and delay time due to the constraints of wireless channel bandwidth, transmission delay, chip processing capacity etc. In order to further improve the reliable and real-time video data transmission, it mainly studies from two aspects of wireless transmission technology and wireless mobile terminal in this paper.The wireless transmission technology:first, this paper introduces the characteristics of 3G wireless networks and analyzes the respective advantages and disadvantages of TCP protocol and UDP protocol in the transmission of 3G wireless network. In order to meet the needs of wireless multimedia applications in 3G wireless network, this paper firstly proposes a hierarchical video frame transmission mechanism based on mixed TCP/UDP protocol. It uses different channels to achieve hierarchical transmission according to the different types of video frame produced by the sender. Among, it uses TCP protocol to transmit key frame data as the 0-level transmission channel, ensuring the video playback quality and reliable transmission. UDP protocol is used to transmit non-key frame data as the 1-level transmission channel. The receiver compares delay time of packet in 0-level channel with the packet lifetime threshold once at regular intervals, then generates data packet with control information and feeds back to the sender according to the comparison result. The sender determines whether to start to discard non-key frame data in 1-level transmission channel according to the feedback information. Through this mechanism, it can effectively alleviate the channel congestion, reduce the video delay time, and ensure the real-time playback of the streaming media. Besides, it also proposes an adaptive-weighted-average rate transmission control mechanism in this paper. According to the amount of data transmission channel received by the receiver, it uses a weighted average bitrate control algorithm to dynamically adjust the encoding bitrate of the sender, in order to make the streaming media transmission adapt to the change of 3G wireless channel bandwidth. By combining these two transmission mechanism in this paper, we not only ensure the reliable transmission of video data, but also effectively control delay time of video data.The wireless mobile terminal:in order to improve playback quality of the multimedia audio and video and the system stability, the paper designs and realizes an embedded 3G wireless audio and video transmission system based on GM8128. The system uses a high-definition video processing chip ADV7181C as video interface, and uses USB Hub chip uPD720114 and HuaWei EC3372 module for 3G wireless channel which is scalable. It designs a streaming media transmission control method which supports multiple bundled wireless channels, and achieves the reliable packet-oriented real-time audio and video transmission that adapts to the characteristics of 3G wireless data communications. The system has reliable structure, stable transmission, low power consumption and flexible channel expansion capability. It has a promising future in the future 3G/4G wireless streaming media application.By studying these two aspects above in the paper, it makes the multimedia operation smoother and more stable in 3G wireless network.