User-Equipment-Transcoding-Based Sharing Technique For Adaptive-Bit-Rate Video

With the rapid development of wireless communication technologies and the widespread application of mobile intelligent terminal devices,multimedia data,like high-definition network video,urban security surveillance video is growing rapidly and will become the absolute subject of future wireless traffic.In order to cope with the tremendous pressure brought by this kind of fast-growing high-bandwidth services to mobile network operators,caching technology is an effective technical solution universally recognized by the academic community and industry.By deploying caches at key network nodes,the distance between the content and the user can be shortened,which effectively reduces the delay for the user to obtain the content;at the same time,the repeated transmission of the same content in the network is reduced and network load is reduced to some extent.However,the newly emerging Adaptive Bit-Rate(ABR)technology provides differentiated services for devices which have heterogeneity in performance and link rate by providing multiple bit rate versions of the same video content.This technology,while improving QoE(Quality of Experience),also doubles the storage space required for caching the same video content.In the event that the storage space of the cache system cannot expand exponentially,the application of this technology will cause cache hit-rate drop significantly,which will seriously affecting the performance of the caching system.In order to solve the above problem,this paper studies the caching system in the ABR service scenario.The main research contents of this paper include:We design and implement an ABR video experiment platform based on MPEG-DASH protocol with which,we conduct experiments on 4G and Wi-Fi wireless network environments respectively.Some key user experience metrics,such as average video bitrate and playback stall time,are compared between ABR technique and traditional technique.The experimental results verified the positive effect of ABR technology on user experience enhancement in a wireless network environment with large fluctuations in bandwidth.At the same time,the limitations of traditional cache system in ABR video service scenario is analyzed through simulation experiments.We propose an ABR video sharing technique based on transcoding of user equipment.Users can obtain pre-cached content or corresponding content transcoded to a lower bit rate version from other user equipment using Device-to-Device(D2D)communication.For the above service scenario,we models user distribution,video request behavior;take the user device power budget,cache size and cell communication resources and other constraints into consideration,and formulate an optimization problem which aims at minimizing the backhaul traffic of the base station.Taking business processes in real scenarios and the complexity of problem solving into consideration,we later divides the original problem into two sub-problems: content presetting and user request scheduling.An on-line low-complexity content presetting strategy is proposed to solve the first sub-problem,and the optimal user request scheduling strategy under known cache condition is given by converting the second sub-problem into an integer linear programming problem.A large number of simulation experiments show that the proposed ABR video transmission framework based on user equipment transcoding can effectively improve the cache hit ratio and significantly reduce the backhaul overhead of the base station compared to the traditional distributed cache solutions.