Research On Wireless Transmission Of Video Based On IEEE 802.11n

Nowadays, High-Definition video has become a hot point in electronic consumer field and got more popularity, which requires higher bitrate in wireless transmission technology. IEEE 802.11n of Wi-Fi Alliance has improved its highest bitrate to 600 Mbps, which make its main application focus on the transmission of High-Definition videos. However, such a high bitrate still can’t meet the transmission of uncompressed HD videos. It is inevitable to use compression technology before transmitting HD videos. Taking the figures of compressed HD videos into account, there are two aspects need consideration. The one is each bit in a video stream plays different roles during the reconstruction, so it is necessary to apply UEP (Unequal Error Protection) to the stream according to the importance of each bit. The other is the compression scheme needs adjusting dynamically with the change of the transmission environment to reduce the waste of resources and the instability of the system performance. As a result, just pursuing the bitrate improvement is not enough for the transmission of compressed High-Definition videos. It is necessary to make some effort on compression strategy and transmission technology according to the characteristics of the video stream to get a satisfied video quality and ensure the reliability of the wireless video transmission.In this paper, some researches are made on the optimization technology of the transmission of high-definition videos based on IEEE 802.11n through both the Unequal Error Protection and the cross-layer optimization aspects. First of all, hierarchical modulation is applied to IEEE 802.11n system. UEP is deployed to MSB (Most Significant Bits) and LSB (Least Significant Bits) in order to improve the total quality of the received videos. Secondly, since IEEE 802.11n supports multiple MCS (Modulation and Coding Scheme) and part of which contains different modulation method, an ordered modulation is proposed. MSB utilize the low-level modulation to get stronger protection, which will enhance the video quality significantly. On the basis of ordered modulation, different MCSs with the same bitrate are compared to choose the best one for video transmission. Finally, a cross-layer optimization scheme is proposed. QP (Quantization Parameter) from VCL (Video Coding Layer) and MCS from PHY (Physical Layer) are adjusted adaptively according to the change of channel condition. This will ensure the video quality maintain within the acceptable range, even though the SNR (Signal-to-Noise Rate) varies in a large range.