摘要

IEEE 802.11e has been introduced to support quality of service (QoS) in WLANs by allocating different traffics to four access categories. Cross-layer design is a method to improve the transmission quality of multimedia over wireless networks. However, when the fragmented packets of a single frame are allocated to different AC queues, out-of-order delivery may occur. Then the receiving node requires more buffer space to absorb the out-of-order packets. Therefore, even with a significance classification mechanism, the quality of the video transmission may still be limited due to the occurrence of out-of-order delivery and the transmission of information that becomes useless to the receiver. Therefore, this work developed a novel mapping mechanism (NMM) to improving the quality of MPEG-4 video delivery over IEEE 802.11e networks. The NMM considers the action that was taken on packet of the video frame that had been previously transmitted to resolve the out-of-order delivery by allocating them to the same AC queue as the previously process if possible. Furthermore, the proposed mechanism NMM takes more aggressive scheme to protect more important frame packets from being dropped. In order to evaluate the quality of MPEG-4 video delivery over IEEE 802.11e networks by the proposed mechanism, this work adopted two evaluation metrics, which is called Peak to Signal Noise Ratio (PSNR) and the ratio of frames loss. The simulation results demonstrate that, in terms of both PSNR and the ratio of frames loss, the proposed scheme outperforms exiting schemes such as EDCA (Enhanced Distributed Channel Access) and adaptive mapping.

  • 出版日期2017-2