Research On Transmission Technology Of Wireless Network Based On C-RAN

C-RAN(Cloud Radio Access Networks)is a centralized,cloud-based architecture,which has been considered as the solution for future mobile communication with high density and high capacity.To solve the problem of low transmission speed and insufficient network capacity,this dissertation studies uplink interference suppression,D2D(Device-to-Device)communicationand load balancing technology based on the development of C-RAN prototype in National Science and Technology Major Project.The main contributions are as follows:Firstly,the interference cancellation problem in C-RAN architecture network is studied.It is observed that the interference from the system of the C-RAN is correlated with the transmitted signals in the system,that is,these interferences carry useful information,and the mean value of the background noise apartfrom the C-RAN is zero.According to this characteristic,a matrix transmission model suitable for C-RAN architecture network was proposed.On the basis of this model,the information carried from the system internal disturbances is transformed into the diversity gain of the transmission signal by applyingthe functional method.Thus,the interference in the C-RAN Architecture network is reduced.The resource allocation strategy aiming at the minimum interference between users was investigated,which can reduce the interference between the uplink users.Simulation results show that this method can furtherreduce the bit error rate(BER)compared with the method of only usinginterference cancellation matrix.Secondly,this dissertation established a downlink cooperative transmission mode in the C-RAN wireless network,and proposeda cooperative RRU selection algorithm based on the multicast users received signals and the load conditions of RRUs.The resourceallocation is jointly optimized by channel capacity and resource utilization.Simulation results show that under the premise of improving the throughput and the fairness of multicast users,the QoS(Quality of Service)requirements of multicast users are guaranteed without increasing the bit error rate of multicast users.Thirdly,the D2 D mechanism of DiffServ with different priority in C-RAN network was proposed,which provides a method to guarantee the QoS of the users with priority in D2 D discovery.And this mechanism dynamically constructedthe discovery resource allocation information of the next discovery cycle according to the number of the high priority D2 D userswhich sent the emergency request information.Then,according to the failed number of low priority D2 D users to select the discovery resource,the mechanism switch between multi-channel time slot ALOHA access mechanism and energy aware multi-channel ALOHA access mechanism.Finally,the mechanism judges whither the D2 D partner has been found according to the SINR of the D2 D users.Simulation results show that adopting the above direct communication scheme in C-RAN can improve the throughput and the number of user connections by 7.2% and 6.4%,respectively,compared with that in conventional cellular networks.Lastly,we proposed a load balancing method by mutually transforming the load between C-RAN and nearby femto-cell.According to the femto-cell's characteristic of small coverage,large delay and low cost,under the condition of high traffic in C-RAN,the method can switch the load from themacro-cell to the femto-cell by using the C-RAN's centralized scheduling,and can jointly optimizes the network load balancing between femto-cell and macro-cell.Simulation results show that the proposed approach greatly improves the satisfaction rate of users and the resource utilization rate by 4% as well asreduces the blocking rate and dropping rate.The above works and achievements were completed under the auspices of the national science and technology major project.As part achievements of the project,all these works has passed the project acceptance of government in 2015.The project provides a strong support for the promotion of C-RAN to become one of the key technologies of 5G in 2016.