Design And Implementation Of Medium Access Control Layer In 5G System

The 5th Generation Mobile Communication(5G)technology aims to provide mobile communication services with high capacity,high rate,high reliability and low latency,so as to provide better services to the coming era of artificial intelligence and the internet of everything.In order to meet 5G's service requirements,5G uses the wireless access technology called New Radio(NR)which is based on the wireless access technology of Long Term Evolution(LTE),but has made a lot of improvements.As an important part of NR protocol stack,Medium Access Control(MAC)layer also makes a lot of improvements to adapt to service requirements of 5G,so it is necessary to research the MAC layer with new characters.Relied on the scientific research item “the R&D and Application of 5G Terminal Simulation Equipment” and based on the 3rd Generation Partnership Project(3GPP)R15 version protocol,the MAC layer of 5G terminal is designed and implemented.The main research contents include: random access process,resource application and resource allocation,multiplexing and demultiplexing,Hybrid Automatic Repeat re Quest(HARQ)and scheduling function,the improvements and the reason of improvements of these functions in 5G compared to LTE are emphasized during the research.At the design section,based on the architecture of protocol stack,interface primitives are designed for MAC layer to interact with the upper layer and the lower layer,and the state machine is designed for MAC layer according to the function of MAC layer and the terminal service process,the process flow of each function of MAC layer is designed.On the basis of analysis and design,this paper proposes a detailed implementation scheme of MAC layer,including function modules and processing functions.In the implementation part,according to the requirement and characteristics of the project,the multi-core Digital Signal Processor(DSP)is choosed as the hardware development platform.With the help of hardware interrupt,inter core communication and high computing ability of DSP,the MAC layer functions of 5G terminal side are implemented by using Code Composer Studio 5.5 software.In order to verify whether the random access,resource request,resource allocation and scheduling functions of MAC layer meet the protocol requirements,test cases are designed for each function to test.The specific test method is to test whether the processing result of MAC layer meet the protocol requirements through the primitive interaction between layers.After continuous improvement and optimization,the test results show that the MAC layer can complete random access correctly,request and allocate resources to the network according to the amount of data to be transmitted and the parameters to be configured,schedule at the specified time-domain location,etc.,and the pass rate of test cases reaches 100%,which verifies that the proposed MAC layer implementation scheme and code meet the protocol consistency.