Research And Implementation Of Cloud Access Network Supporting High-speed Mobile Terminals

Cloud-Radio Access Network(C-RAN)is an important method to address challenges such as explosive traffic growth and high base station maintenance costs by building a flexible network architecture through virtualization and collaboration.High-speed mobile terminals such as high-speed railways and high-speed vehicles have posed new challenges to the continuity and quality of cellular mobile networks.Using C-RAN's flexible network architecture to provide ultra-low latency and highly reliable communication services for high-speed mobile terminals is an effective way to solve these challenges.In this thesis,the C-RAN protocol layer is redistributed according to the Next Generation Fronthaul Interface(NGFI)division scheme,the physical layer functions are sunk,and a C-RAN semi-physical emulation platform supporting high-speed mobile terminals is built using virtualized software-defined radio technology.The C-RAN semi-physical simulation platform implements all protocol stack functions of 5th generation wireless system(5G)and supports access to user devices and core network.To better serve the high-speed mobile terminal business scenario,this thesis designs and implements the following three functions in the C-RAN semi-physical platform:1.To describe the communication environment of high-speed mobile terminals more realistically,this thesis designs a 5G channel model to support high-speed mobile terminals based on the 5G channel standard developed by the 3rd Generation Partnership Project(3GPP).This channel model applies to the communication system from 0.5GHz to 100GHz,supports the maximum bandwidth of 2GHz,and can realistically simulate the channel model of a high-speed mobile terminal communication scenario.Meanwhile,the channel model is implemented and verified on the C-RAN semi-physical simulation platform.2.To address the issue of communication continuity:The high-speed mobility would cause frequent handover among base stations,which leads to instability and high latency.To address this problem,we design a seamless handover mechanism based on precoding technology,which is implemented and validated on the C-RAN simulation platform.Performance results show that the impact of handover on the connectivity of the high-speed mobility is negligible adopting the proposed seamless handover mechanism.3.To address the issue of quality:Ultra-dense deployment of lightweight access nodes is an inevitable tendency for 5G development,which effectively solves the problem of the explosive traffic growth of wireless traffic.But,it also brings the problem of strong interference between cells.In this thesis,an adaptive joint transmission mechanism based on Coordinated Multi-Point(CoMP)is designed and implemented on the C-RAN semi-physical platform.Multiple cell nodes are grouped as collaborative clusters,providing joint transmission service for terminals,which effectively suppresses inter-cell interference and improves the communication service quality of the C-RAN system by transforming the base station interference signal to a useful signal.