Research And Implementation Of MAC Layer For 5G Road Tester

With the large-scale deployment of the 5th Generation Mobile Communication(5G)networks,the workload of field experiment increases.As a basic instrument for measuring wireless signal quality and network coverage conditions,the 5G road tester will assess quality of 5G network and verify the commercial capability of terminal equipments by providing reliable data source and data analysis capability.As one of the core parts of 5G terminal protocol stack,the maturity of Medium Access Control(MAC)layer will affect the market competitiveness of terminal products.Therefore,a reasonable design of MAC layer can provide strong support for the construction,and optimization of commercial networks.Relying on the major theme special project "R&D and application of 5G road tester" in Chongqing,this thesis designs and implements the functional modules of MAC layer based on the 3rd Generation Partnership Project(3GPP)Release 15 protocol for NR technology.The details of the work are as follows:1.In-depth research on the key functions of MAC layer in 5G road tester.This thesis introduces the architecture of New Radio(NR)protocol stack from two perspectives,user plane and control plane respectively.Subsequently,this thesis focuses on the key MAC layer functions,which involve the random access,uplink scheduling,multiplexing and demultiplexing,and Hybrid Automatic Repeat Request(HARQ)process.2.A new access strategy is proposed for random access process in MAC layer.In5 G massive machine type communication scenario,the connection requests initiated by a large number of devices at the same time will aggravate the prreamble conflict,which will make the access success rate drop rapidly.To this end,this thesis proposes a dynamic back-off random access method based on clustering.First of all,the terminal devices are clustered according to the distance between devices and base station,and preambles are assigned proportionally based on the clustering results.Then,the access devices within the cluster are dynamically adjusted in conjunction with the Access Class Barring(ACB)and the back-off mechanism.The simulation results show that the method in this thesis can maximize the resource utilization while improving the access success rate.3.Design and implementation for the main functions of MAC layer in 5G road tester.This thesis firstly designs the interface primitives based on the protocol stack architecture.Simultaneously,a state machine containing six states is designed for MAC layer after taking into account the users' service process.Then,the detailed process for random access process,uplink scheduling,multiplexing and demultiplexing,and HARQ process in MAC layer are carried out.Finally,in order to verify the correctness of the design scheme and ensure that it meets the protocol consistency requirements,this thesis conducts a single-layer functional test of MAC layer,and transplants the code to multi-core digital signal processor(DSP).The generated data stream is analyzed by Wireshark software.