A Cross Layer Mechanism for H.264 Video Streaming over IEEE 802.11e WLANs

• Main Authors: Bing-ran Liao, 廖柄然
• Other Authors: Chie Dou
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/68374608028145609470

碩士 === 雲林科技大學 === 通訊工程研究所碩士班 === 96 === Recently, with wireless network largely development and video compression techniques maturity, to combine wireless network with multimedia applications is widely considered as one important part of the wireless communication techniques. However, after multimedia video are encoded, it often results in different types of coded data with different degrees of importance. When the network becomes congested, equal error protection to all video packets will degrade the video quality significantly. In this thesis, we propose a cross layer mechanism to improve the quality of H.264 video streams over the HCCA（HCF Controlled Channel Access）of the IEEE 802.11e WLAN. We use the data partition technique provided by the error resilience tools in H.264/AVC application layer to discriminate different degrees of importance of video data. In the proposed cross layer mechanism, a video stream is separated into four HCCA TSPECs（Traffic Specifications）according to different significance of data partitions. MAC layer retransmission represented by the Surplus Bandwidth Allowance （SBA）parameter in each TSPEC is specified differently to preserve the required frame error rate（FER）of the video data governed by that TSPEC. We calculate the SBA value for each TSPEC under the given MAC layer delay bound and the given channel error probability to maintain the required FER. The calculated SBA can be converted to the number of retries for the retransmission of MAC frames sending through the corresponding TSPEC. The results derived in this thesis are further applied to develop the admission control and scheduling policy of real coded video streams over 802.11e MAC in 802.11a PHY environments.