Research On Bandwidth Allocation And Rate Adaptation Algorithm In DASH Based Video Streaming Transmission System

With the widely used mobile equipment,e.g.,smartphone,tablet,etc." and video applications,e.g.,video sharing,video chat,video broadcasting,etc,it is hard to deal with the huge bandwidth requirements of video users.Due to the limited network bandwidth,how to achieve higher Quality of Experience(QoE)is a challenging issue for video streaming system.In this thesis,we proposed two methods that can improve user QoE from the video server side(bandwidth allocation)and the user side(adaptive request)respectively based on MPEG dynamic adaptive streaming over HTTP(DASH).For the video server side bandwidth allocation method,we investigated the characteristics of the LTE-based wireless network that can support high-speed data transmission for mobile equipment.In a LTE network,the packet loss ratio is affected by the throughput which is observed as an independent variable.Furthermore,the transmission distortion is affected by the packet loss ratio.In this thesis,the end-to-end distortion model is first derived by taking throughput into account.Then,based on the derived end-to-end distortion model,the bandwidth allocation problem is formulated as a convex optimization problem and solved by Karush-Kuhn-Tucker conditions.Simulation results demonstrate the effectiveness of the proposed method.The rate distortion performance of the proposed method is better than the average bandwidth allocation method under different bandwidth utilizations,and is very close to the exhaustive search-based method.For the user side rate adaptation method,we proposed a novel algorithm based on non-cooperative game theory to optimally request video segments with appropriate bitrates so as to maximize their QoEs and guarantee fairness.The proposed algorithm is proxy-free.Specifically,a derived QoE model for users takes a variety of factors into account,like the received video quality,the reference buffer length,and user accumulated buffer lengths,etc.Then,the bandwidth competing problem is formulated as a non-cooperation game.And we proved the existence of Nash Equilibrium theoretically.Finally,a distributed iterative algorithm with stability analysis is proposed to find the Nash Equilibrium.Compared with state-of-the-art methods,extensive experimental results in terms of both simulated and realistic networking scenarios demonstrate that the proposed algorithm can produce higher QoE,and the actual buffer lengths of all users keep nearly optimal states,i.e.,moving around the reference buffer all the time.Besides,there is no playback interruption in the proposed algorithm.