Cross-Layer Optimization For Cooperative Video Stream Transmission In Wireless Relay Networks

Recently, the demands of high-quality video stream applications are growing rapidly,while wireless frequency spectrum resources are increasingly going short. The expansionof wireless access points and mobile devices is explosive, which poses much pressure andmore challenges to video stream transmissions in wireless networks. Nevertheless, it alsoprovides a great opportunity for cooperative video stream transmission in wireless relaynetworks. Thus, it is paramount to optimize transmission mechanisms for video streamingin wireless networks, so as to increase the resource utilization ratio of wireless networksand improve the quality of services.A novel cross-layer transmission scheme for cooperative video stream in wirelessrelay networks is proposed to improve video transmission quality. A uploading scenario invideo surveillance applications is considered here, a typical three-node wireless relay networkand its hierarchical model is formulated. It takes into account of delay constraints at theapplication (APP) layer, relay node selection at the MAC layer and dynamic fading of wirelesschannels at the physical (PHY) layer in an integrated mode to improve the quality of videotransmission. At the PHY layer, a finite state Markov channels (FSMC) model is used to estimate thechannel states and a modified RTS/CTS scheme is proposed to facilitate the path selection at the MAClayer. The impacts of delay constraints and other factors at the APP layer are investigated. At the MAClayer, the source node can choose the proper path to transmit video data while considering video delayrequirements and wireless channel states simultaneously.The simulation experiments based on the Matlab7.0programming environment are carried out toevaluate the proposed scheme. An H.264encoder, x264, is used to encode the original video, andffmpeg codec is used to decode the received data frames with error concealment. The experimentalresults show that the proposed scheme could improve video transmission quality and achieve anear-optimal performance. The experimental results also reveal the impacts of some key factors, such as video rates, delay constraints and network loads to the video transmissionquality, and indicate that the types of lost video frames makes a relatively more significantcontribution to the ultimate quality of video transmission.