Cross-layer quality enhancement scheme for video transmission over multi-hop wireless networks

Wireless networks have a varying channel quality and a limited bandwidth. Therefore, ensuring a satisfactory video quality over wireless networks is extremely challenging. Most existing studies for enhancing the received video quality over wireless networks consider only single-hop transmission environments. Consequently, when applied to multi-hop wireless networks, such as wireless mesh networks, VANETs or wireless sensor networks, the video quality is typically rather poor. Accordingly, this study proposes a cross-layer mechanism for improving the video transmission quality in multi-hop wireless networks. The proposed scheme considers both the video frame type and the output interface queue length at the intermediate nodes while determining the drop probability during the packet forwarding process. Besides, in the event of transmission failures, the number of retransmission attempts is varied adaptively in accordance with the network conditions and the relative priority of the corresponding frame. Furthermore, the forwarding probability at each node is increased in accordance with the number of hops previously traversed by the packet. Thus, the proposed scheme improves video delivery quality by means of providing unequal protection for frames of different importance. The NS2 simulation results show that the average PSNR results obtained with the proposed scheme have significant improvements compared to that obtained with the traditional IEEE 802.11 mechanism, thereby confirming the effectiveness of the proposed scheme.