Research On Air Interface Multicast Technology Based On Local Cache

With the exponential growth of mobile devices and various mobile applications,wireless network operators are facing the challenge of blowout-type mobile network data traffic transmission in mobile network,of which three-quarters of data traffic is video traffic.However,The inherent characteristics of video service such as the large bandwidth and the high probability of the user repeatedly requesting the same content bring huge challenges to the existing mobile network.In order to meet this challenge and reduce the pressure on the operator's network,there are two effective solutions.One is to sink the content into the local mobile communication network to realize local breakout for data traffic and reduce the huge backhaul cost between the base station and the source server.The other is to use multicast and broadcast to transmit broadband and video services in the mobile network.After deeply analyzing the problems and challenges of joining a local cache server,this thesis presents an optional network architecture.Based on the above architecture,the process of acquiring context information in wireless network is analyzed.Finally,in order to enable the user to obtain the content cached by the local cache server,three kinds of service selective acceleration solutions are proposed.According to different source of context information that assisted user to get the required content,the solutions are divided into three types,which are based on the user assisted?network assisted and server-assisted local caching solution.The above three solutions meet the 3GPP technical standards and solve the technical problem of how the user obtains content after joining the local cache server,and provide technical support for the subsequent research on the local cache.In order to verify the effectiveness of the local caching technology solution,this thesis combines theoretical analysis and simulation to verify the system performance gains brought by adding a local cache server.In addition,this thesis analyzes the existing defects of multicast and broadcast transmission methods in current mobile networks,and proposes a new radio air interface multicast transmission solution for IPTV service transmission in the WTTx environment.This solution is based on the existing LTE network architecture to transmit live service by multicast.And then we compare the performance of new radio air interface multicast transmission with the SC-PTM(Single Cell-Point to Multipoint)and MBSFN(Multicast Broadcast Single Frequency Network)of eMBMS(Evolved Multimedia Broadcast Multicast Service)service.Simulation results show that the spectrum efficiency of the proposed new air interface multicast scheme is close to that of SC-PTM,and is superior to the performance of MBSFN when the number of users is small.Based on the above research results and the technical difficulty that the video on demand service cannot use the multicast transmission method,this thesis combining the local caching technology and the multicast transmission method proposes an air interface multicast transmission solution for video on demand services.The solution caches video files of a certain time length on the local cache service,so that when a user requests a file within a certain period of time,the data flow can be transmitted by multicast.It can improve resource utilization efficiency while ensuring the quality of user services.In order to obtain the optimal cache space allocation scheme for the local cache server,this thesis modeled the above question as a multiobjective optimization problem,then transformed the problem into a single-objective problem,and obtained the optimal cache space allocation scheme through simulation.