| Along with the technological development of cellular system and mobile internet, high quality video multicast service is becoming an important value-added region, and need high band-width for large quantity of users. In cellular system, the wireless channel in the cells is the bottleneck of the band-width expanding. It is widely believed that the relay technique is an efficient approach to supply high band-width wireless channels as its ability to improve the channel capacity and throughput. The cooperative relay technique gain more attention by its convinence to deploy and lower cost. However, this technique had some drawbacks. How to maintain its advantages and overcome its disadvantages are highly significant for the development and application of cooperative relay technique.This thesis focuses on the problem of impact on the video multicast stream caused by the mobility of the relay nodes in cooperative relay network. After analyzing the characterization of the multicast traffic and the cooperative network in cellular system, a video layered cooperative relay multicast strategy is proposed by combining the video layering technique and cooperative relay technique. Then, aiming at the proposed strategy, the capacity and power allocation are studied. The theoretical analysis and simulation results show that the strategy and its research are efficient, and achieve the anticipated results. The main contributions of the thesis are listed as follows:1) Proposing a video layered cooperative relay multicast strategy. The strategy maintains the high band-width characterization of the cooperative relay channels and solve the problem that the instability of the relay link influences the video multicast stream. In the strategy, the video is encoded into base layer and enhanced layer(s). The base layer is broadcast to the whole cell to ensure the basic quality video service; meanwhile, the enhanced layer is transmitted via the relay channel to supply high quality video service to the terminals within its coverage. When the cooperative relay link is broken, the terminals can maintain continuous video display, with low video quality.2) Studing the capacity of the layered relay channel in the video layered cooperative relay multicast strategy. After constructing the abstract layered channel model, the wireless Gaussian layered channel model and the wireless fixed fading layered channel mode, their channel capacity bound is discussed obtained. And then, the capacity result is analyzed and simulated. The results proves the efficiency of the strategy and provides the basis for further power allocation research.3) Proposing a power allocation scheme to satisfy the proposed video layered cooperative relay multicast strategy. Because of the mobility of the relay nodes, the routing of the cooperative relay needs quick establishing and frequent refreshing. So the power allocation scheme ought to be quich and low-complexity. Based on the result of the layered channel capacity, a power allocation scheme is proposed by capacity calculating. Moreover, the implementation approaches are given for Gaussian channel and fixed fading channel.4) Proposing a improved cross-layer optimization scheme and a improved Ant Colony Optimization(ACO) scheme to satisfy the proposed video layered cooperative relay multicast strategy. Based on the result of the layered channel capacity, for cross-layer optimization, a pre-processing is added to determine the relay selecting zone in order to reduce the quantity of the participating terminals, and then, improve the convergence rate. For ACO, after determining the relay selecting zone, the serial number of the relay is encoded to conduct the artificial ants to creep from the base station to the edge of the cell, and avoid the invalid direction, such as reverse, transverse, skip, then, improve the convergence rate too.The research in this thesis has theory and practical value for existing and next genetation mobile networks, and has reference value to other wireless networks. |
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