| With the widespread use of wireless communication systems, the demand for multimedia services in wireless communications is increasing rapidly, such as voice and live video. Compared to the wired network, the wireless network has the defects of limited bandwidth, higher rate of transmission errors, and susceptibility to interference and so on. So it can’t meet the increasing requirement of stable, fluent and real-time to video transmission. There are several researches ongoing in this field. The continuous effort of increasing the transfer rate and reducing the bit error ratio for the wireless network for the video file to be transmitted, it has received a lot of attention. Also the video coding technology has undergone continuous improvement, which has made the encoded file has a higher compression ratio and has also made it more capable to dynamically adapt to various conditions of the wireless network. Thirdly in the wireless network transmission strategy, the video qualities of terminals have been improved by optimizing the strategy of video transmission in the wireless network.H.264/AVC is called the new generation of international video coding standard. As the extension of H.264/AVC, H.264/SVC provides temporal, spatial and quality scalable coding, and it allows a part of the video stream to be transmitted and decoded. The H.264/SVC stream can adapt to variety of terminals with different service requirements. It also inherited the ability of better compression efficiency and network adaptation of H.264/AVC. The concept of quality layer has been introduced in H.264/SVC in order to provide additional information that can be used for an optimized adaptation of a scalable bit-stream. The quality layers achieved a better scalability by a finer classification of the SVC video stream. Based on the Quality layer described in the H.264/SVC standard, some research was done on the details of the Quality layer assignment method. This paper presents one such breakthrough in the Quality layer assignment method. And then for the SVC stream transmission over the IEEE802.11e wireless network, a cross-layer algorithm is proposed that judges the importance of data packets according to their quality layer information.This paper is organized as follows:We begin by discussing the need for the transmission of video over wireless networks and the progress made in this research. Then there is an overview of the IEEE802.11e protocol standard. This section talks about the DCF, PCF and EDCA mechanisms, as well as some methods to support the quality of service. The next part of this paper gives a brief introduction to the H.264/AVC standard, and it focuses on its extension, H.264/SVC. The SVC stream’s temporal, spatial and quality bitstream scalability is described. Quality bitstream scalability is given the most detailed description. The quality layer of H.264/SVC is discussed in the next section, and the superiority of the quality layer on the bit-rate extraction is proved by experiment. Finally, this paper describes several cross-layer transport algorithms, compared with our wireless network transmission algorithm based on the quality layer of SVC, which achieved mapping adaptation in the MAC layer with the quality layer information in the application layer. We compared the algorithm proposed in this paper with other cross-layer mapping algorithms, using MATLAB and the NS-2simulation tool to simulate these algorithms, the results show that the quality layer based algorithm’s videos have better quality then the others. |
PDF Full Text Request