【作者】 陈博；

【导师】 阔永红；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2016， 硕士

【摘要】 由于无线频谱资源的匮乏,多媒体数据传输时大带宽、低时延的要求为现有的无线通信系统带来了巨大挑战,研究高效视频传输方案变得至关重要。将终端直通D2D(Device-to-Device)技术和多播技术相结合的D2D协作多播,在提高无线通信的资源利用效率、减少系统能耗等方面有着巨大的潜力。现有的基于D2D通信的视频多播方案大多是以提高网络吞吐量、频谱效率、能量效率等作为提高用户视频接收质量的手段。在实际应用中,由于会有重复和无法解码的视频帧在D2D阶段传输,上述方案带来的效果并不十分理想。针对这个问题,本文根据视频信息编解码结构的特点和用户需求,对需要重传的视频帧设置优先级:对于解码顺序靠前、用户需求量大的视频帧设置较高的优先级;对于解码顺序靠后、用户需求量小的视频帧设置较低的优先级。在D2D阶段根据视频帧的优先级顺序进行重传,保证了在有限的时频资源内,用户得到更多的有效解码信息。为进一步优化视频接收质量,本文以最小化一个视频帧的传输时间为目标,在不同的频谱接入方式下,分析该传输模型下的资源分配和中继选择问题。当D2D多播以Overlay的频谱共享方式进行时,本文提出一种基于CQI(Channel Quality Indication)矩阵的最优中继和分组策略;在Underlay模式下,本文联合考虑信道分配、中继选择和分组问题,在采用复杂度较高的遍历算法得到最优结果后,进一步从用户角度出发,提出一种复杂度较低的次优启发式算法。仿真结果表明,在Overlay模式下,本文提出的算法能传输更多的有效视频帧,同时兼顾公平性,解决了小区边缘区域用户体验差的问题。另外,本文在Underlay模式下提出的启发式算法不仅复杂度大大降低,与最优算法相比,其偏差也在可接收范围内。更多还原

【Abstract】 Due to the lack of radio spectrum resources,the explosion of multimedia services and the requirements of large bandwidth,low latency have brought a huge challenge to the existing wireless communication systems.It is crucial to research efficient video transmission schemes.Device-to-Device(D2D)cooperative multicast technology has huge potential to improve the utilization ratio of wireless resources and reduce the energy consumptions of the systems.Most of the existing video transmission schemes based on D2 D technology are aiming at improving the network throughput,spectrum efficiency and energy efficiency.These schemes pay no attention to the transmission contents.In practical applications,increase the transmission rate blindly,repeated and invalid frames are transmitted in the D2 D phase.To solve this problem,a mechanism which rank this video frames firstly,and then multicast them based on D2 D communication is proposed.In this thesis,according to the characteristics of video coding structure and user requirements,the priority of the retransmission video frames are set: the video frames which decode earlier and have larger userrequirements are set higher priority and vice versa.It ensures that users can get more efficient decoding information in limited time-frequency resources.Further,based on the different spectrum access methods,the problems of resource allocation and relay selection are analyzed.In overlay mode,an optimal relay selection and group partition strategy based on channel quality indication(CQI)matrix is proposed.When the network load is high,underlay mode is the more reasonable choice.In underlay mode,the problems of channel allocation,relay selection and group partition are jointly considered.Firstly,the optimal relay selection and group partition result is obtained by the traversal algorithm.Next,a sub-optimal heuristic algorithm is proposed from the users’ point of view.The simulation results show that the proposed algorithm can transmit more effective video frames and improve the video resolution in the overlay mode.At the same time,users’ fairness is guaranteed.In underlay mode,the heuristic algorithm proposed in this thesis not only reduces the complexity greatly,the deviation from the optimal algorithm is in the range of acceptable.更多还原