Research And Implementation Of LTE Protocol Stack Based On RRC For C-RAN

Through centralized deployment,the cloud access network C-RAN reduces the number of base stations.In addition,by adopting collaboration and virtualization technologies,C-RAN achieves the function of resource sharing and dynamic scheduling.It is an effective method to solve the problems of high energy consumption caused by large number of base stations and low utilization rate of base stations due to tidal effect in traditional access networks,which is of great significance in research.This thesis is based on the project “Research and Development of Low-Power General-Purpose Processor Platform for C-RAN”,which is proposed by the Institute of Computing Technology,Chinese Academy of Sciences.By studying and designing the LTE protocol stack Radio Resource Control(RRC)layer system for C-RAN,the thesis studies how to make the computing resources of RRC layer intelligent and controllable,so to support the dynamic migration of signal carriers.The purpose of this thesis is to implement a RRC subsystem with complete functions,high stability and supporting for statistical multiplexing of protocol stack computing resources.Firstly,based on research and analysis of service and functional requirements in RRC layer,this thesis presents a system architecture of the RRC layer for C-RAN.In this architecture,the RRC layer independently manages its own memory resources and entity information.By adopting the unified interface communication mode within the protocol stack,the coupling between other layers and RRC is released.This decoupling can better support parallel processing of the protocol stack,thus improve the overall processing performance of LTE.Secondly,aiming at the above architecture,this thesis firstly studies the memory management module in the RRC layer,and presents a new mechanism of memory partition management in the RRC layer.The mechanism is based on the protocol stack migration mechanism and different characteristics of the storage data function of the RRC layer.The RRC layer memory is divided into inter-layer interactive memory area,heap memory area and state information memory area.In the inter-layer interaction memory area,following the kernel network structure skb,a full array design is used to provide an inter-layer message processing mechanism(LteLb).In the heap memory area,the traditional memory pool and the Silicon Graphics Inc Standard Template Library(SGISTL)memory pool are used for reference.A RRC layer custom memory pool(MCMempool)adapted to the current protocol stack is stored;the RRC running context information is stored in the status information memory area.Finally,modules of the RRC layer is implemented,including RRC layer Radio Resource Management(RRM)state machine,RRC connection establishment,Access Stratum(AS)initial security activation,RRC connection re-establishment,and RRC reconfiguration.Finally,the performance of the MCMempool memory pool is tested on the system development platform.The test result shows that compared with the system default memory management mode,the MCMempool memory pool performs better in time consumption.For 100000 operations,the time performance of MCMempool increases of about 38.6%.Based on the prototype verification system for C-RAN develop by the project team,the software and hardware of the RRC layer are tested.The result verifies the protocol consistency and functional completeness of the RRC layer subsystem.The successful migration of the protocol stack indicates that the RRC layer can support the statistical multiplexing of computing resources in the protocol stack.