| With the rapid development of Internet,intelligent devices and wireless network technology,the application of video streaming service in wireless network has become the main driving force for the surge of global mobile data traffic in recent years.At the same time,video services are shifting from indicator-centric to user experience-oriented.However,due to users' demand for higher quality video content and the emergence of challenging live video application services,such as mobile video live streaming,telemedicine,augmented reality,and how to effectively guarantee the content delivery of low-delay and bandwidth-intensive video application services,this will bring new problems to the existing wireless network transmission.Based on D2 D communication technology,combined with the structural characteristics of video stream and the characteristics of MEC technology,this thesis aims to study the video transmission scheme with higher bandwidth,lower end-to-end delay and higher user experience.The specific research contents are as follows:Firstly,according to the exponential increase of video traffic and shortage of spectrum resources in wireless network,this paper summarizes the characteristics of D2 D communication technology and video multicast technology,and the great significance of the combination of these two technologies to alleviate video traffic overload and improve the quality of service of wireless network.In view of the differences between multicast channels,in order to ensure the quality of experience of multicast group users,this paper carefully considers the hierarchical structure of the video stream,uses scalable video coding to encode the video content layered,and flexibly adjusts the rates of different video layers to cope with the different fading channel characteristics between multicast groups.Secondly,considering that most of the existing studies are based on throughput to measure the effectiveness of video transmission schemes to improve video quality.For delay-sensitive video streaming services,the growth of this index is not a good measure of the gain to the video quality.Therefore,by deducing the formula of goodput,this paper proposes a D2 D cooperative video multicast transmission scheme based on SVC coding under delay constraints.Through system modeling and analysis,the optimization problem of rate allocation in different SVC video layers in D2 D network is given,and a two-stage heuristic algorithm is proposed to solve the problem,in order to maximize the effective throughput of the system.Finally,it is pointed out that the future development of 5G and even B5 G networks and emerging video applications will further lead to high quality of experience requirements for ultra-high quality and low latency video content delivery.Therefore,through the MEC technology which is closer to the user side,which has the ability of real-time insight into wireless network information and user location perception,this paper creatively puts forward the MEC-Enabled Goodput-Aware(MEGA)model.On the one hand,a traffic adjustment link state estimation algorithm based on path Chirp is proposed to monitor the current wireless network in real time and provide link state estimation results to ensure the full utilization of bandwidth resources on the wireless side.On the other hand,a rate allocation algorithm based on Gra Descent is proposed,and D2 D cooperative transmission is used to optimize the Qo E quality of users.Simulation results show that the proposed MEGA scheme can effectively improve the goodput and Qo E of real-time video applications,and significantly improve the end-to-end delay and effective loss rate. |
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