Realization Of Physical Random Access Channel In 5G Mobile Communication System

With the gradual introduction and optimization of the 5th generation cellular communication,the requirements of e MBB,m MTC and URLLC will gradually be met.After the base station completes the downlink synchronization with the terminal,the terminal initiates random access to the base station to access the network,and the physical random access channel is the first step of random access.In view of the multi-scene and multiservice situation of 5G,it is necessary to design a physical random access channel that can meet the requirements of multi-format and high speed.Under the support of a project,this paper analyzed the protocol specifications related to physical random access channel,analyzed and designed the baseband transmitter and receiver of physical random access channel through the provisions of the protocol,and completed on FPGA.Firstly,starting from the standardized protocol of 5G NR,we studied various provisions on the sequence of physical random access channel in NR,including its position in time and frequency range.At the same time,We introduced the advantages of the new version of two-step random access over the old version of four-step random access,and briefly described the whole access flow between the user and the base station.Then,according to the requirements of 3GPP for NR protocol specification,we analyzed the generation method and application scope of each format of the PRACH sequence in the standard protocol and generated sequences according to protocol standards.And we completed the simulation design of the transmitter and receiver of physical random access channel,the transmitter proposed the ZC frequency domain sequence generation algorithm,and proved the advantages of the algorithm through complexity analysis and resource consumption analysis.In the filtering part of downsampling rate and upsampling rate,the existing filtering technology was combined with the hierarchical polyphase filter and half-band filter to reduce the resource consumption and improve the performance.We also compared the performance of the fixed threshold detection algorithm and the comprehensive threshold detection algorithm,and finally chose the comprehensive threshold algorithm with better performanceThen we complete the logical design,simulation and test of transmitter and receiver of physical random access channel based on VCU 118 FPGA evaluation board.According to the specific hardware characteristics,we set the frequency domain ZC sequence generation parameter lookup table at the transmitter to improve the performance of the system,and paralleled part of the circuits at the transmitter and receiver,which improved the efficiency of the system.This paper also optimized the FPGA application of polyphase filter for this design platform.And we also designed the corresponding soft core test system according to the transmitter and receiver two baseband modules,and compared the test results with the simulation results of MATLAB,to ensure that the hardware design meets the requirements.