The Assessment And Optimization Of Video Quality Over Wireless Networks

Nowadays, with the rapid development of wireless communication,3G standards have matured and 4G standards have been formulated. Wireless communication has been involved in lots of fields. At the same time, the wireless video has been widely used. The video quality problem, which is aroused by the instability of the network and the limited spectrum resources, has attracted many researchers to study it. This paper focuses on the theory and simulation about the video transmission quality through WLAN, the objective evaluation of video quality and the mapping relations between QoE and QoS. It proposes the contribution in the following aspects:1) A full-reference blocking effects evaluation algorithm is proposed to give a quantitative analysis of the video with blocking effects. Compared with the PSNR of the damaged videos, the quality level which this algorithm presents is in accordance with the PSNR value.2) Based on the analysis of each video quality assessment algorithm and the correlation inside the video, a no-reference video quality assessment algorithm is proposed, considering the motion intensity and the character of wavelet analysis. The results of the objective and subjective assessment of a series of video sequence verify that the proposed quality assessment algorithm can well evaluate the clarity and fluency of video sequences.3) Based on the analysis of the definition and relationship of QoE and QoS, the testing platform is established. After access to the 3G wireless network, the platform can provide the network parameters when the video is being transmitted and the quality level of the video. That the network parameters are in different level is corresponding to different QoE level. Based on the analysis, the mapping relationship between QoS and QoE can be obtained. 4) An adaptive retransmission algorithm jointing application and data link layer is proposed, using the lost package gotten from M/M/1/K queuing model, which analyzes the overflow of the sending queue on MAC level and the performance statistical parameters of WLAN. Simulation results show that the cross-layer design in this paper can improve the video quality much better.