Design And Implementation Of MAC Layer In 5G Terminal System

Fifth Generation Mobile Communication(5G),as a new generation of mobile communication technology,adopts a new network architecture.Based on the Long Term Evolution(LTE)technology,5G has Introduced a new air interface technology(New Radio,NR).The Media Access Control(MAC)layer belongs to the high-level protocol stack of NR.With the update of the 5G standard,it is continuously improved and perfected.This paper is based on the R16 version of the MAC layer 38.321 protocol issued by the Third Generation Partnership Project(3GPP),and relying on the scientific research project "R&D and Application of 5G Terminal Simulation Equipment",design and implement the functions of the MAC layer on the terminal side.The research contents and innovation points of this paper are summarized as follows:1.The terminal-side MAC layer studied in this paper includes: random access process,beam failure recovery process,MAC layer resource scheduling process,Hybrid Automatic Repeat Request(HARQ)process,etc.This paper analyzes the abnormal situation of the alignment failure of the connected beam pair,founds that there are some problems in the design of the existing solutions,this paper improves and proposes a new beam recovery scheme.At the same time,R16 version supports HARQ feedback of multiple physical uplink control channels(PUCCH)in the same time slot,which is also introduced and studied in this paper.2.In the design,the finite state machine model is designed based on the functions of MAC layer and the business process of protocol stack,considering that the communication link between the base station and the terminal is easy to be interrupted due to external factors,this paper improves the design of MAC layer in the connected state and adds the realization of beam fault recovery.In the development and implementation part,the digital signal processor(DSP)has accurate timing interrupt ability and high computing ability,so DSP is selected as the hardware development platform and the software platform Code Composer Studio 5.5(CCS v5.5)is responsible for the compilation of MAC layer functional modules and the verification and debugging of later functional modules.3.Build a test platform for function test.Referring to the description of MAC layer function consistency test in 38.523 protocol,test cases are designed for functional modules such as random access,beam fault recovery,data multiplexing and demultiplexing and so on.By comparing whether the actual operation results meet the conditions for passing the consistency test,analyze whether the function realization of MAC layer is correct or not.After hundreds of test case verifications and later functional module corrections,the verification results show that the designed MAC layer solution can correctly implement functions such as random access,beam failure recovery,data demultiplexing and multiplexing,and the pass rate of test cases is 100%,which verifies this set of MAC layer,which verified that this set of MAC layer scheme meets the requirements of protocol consistency.