Research And Design On Transmission System Of Wireless Multimedia Cross-Layer Protocol

With the development of the technologies on communication, computer, digital multimedia and wireless networks, wireless multimedia transmission becomes a hot research topic.Due to the limited band, time-variability and fallibility of wireless channel, the efficiency of traditional layered protocol is low, which can't adapt to the fast fading of channel. The cross-layer protocol design,which have been widely recongnized and studied, can optimize performance of the whole system.Based on the idea of cross-layer design, the real-time compression, transmission, decoding and playing are achieved.At the same time, the platform of practical wireless multimedia video cross-layer transmission is set up in this paper. The main contents are as follows:Firstly, we introduce the standard of H.264, which is the new generation video image coding standard. Then the basic structure and the key technology about encoding and decoding are analyzed, and the realization of the compression encoding in Linux operating system is emphasized. Meanwhile, the code rate control technique of multimedia transmission in wireless environment which can improve the efficiency of network is presedted.Secondly, the principle and process of RTP/RTCP protocol are introduced.The simple packing rules based on NAL and the packing/partition policy used in this paper are analyed. In addition, we implement the real-time multimedia transmission based on JRTPLIB, and the real-time acquisition of channel throughput based RTCP.Thirdly, in Linux operating system, two rate adaptive algorithms of ARF and AMARF are implemented in commercial wireless network card. We made performance test of several rate adaptive algorithms in office environment. The result showed that the AMARF performed better than others in fast fading channel.Finally, the platform of wireless multimedia video cross-layer protocol transmission is set up, which can achieve the acquisition, the real-time compression and transmission of multimedia video. The acquisition of the video is analyzed emphatically. In addition, the acquisition of channel throughput and the adjusting of QP, which ensures the high quality of multimedia transmission, are explained in detail.