Research And Implementation Of 5G NR Cell Search And Random Access

The 5th Generation Mobile Communication Technology(5G)has completed the formulation of the Release 15 and Release 16 protocol standards,and has been put into commercial use in 2018.However,the research on 5G,B5G and 6G wireless communication technology is still the focus of the communication field.In terms of radio access technology,3GPP has defined a new radio access standard called New Radio(NR)for 5G.Similar to Long Term Evolution(LTE),cell search is the first step for a terminal to access a base station.However,compared with the LTE system,the 5G system has changed in terms of frequency band,synchronization information block and synchronization sequence selection.Random access is the first step for the UE to establish a connection with the BS wireless network,and it is also a key step for uplink synchronization.Therefore,it is of great significance to study 5G NR cell search and random access.The main contents of this thesis are as follows:(1)According to the properties of the primary synchronization signal(PSS)and the secondary synchronization signal(SSS)in the 5G NR synchronization information block(SS/PBCH Block,SSB),the cell search coarse timing synchronization,frequency offset estimation and precise timing synchronization is studied and simulated.For PSS coarse timing synchronization,an improved algorithm is proposed in this paper.The algorithm enhances the anti-frequency offset performance by presetting the normalized frequency offset of the local PSS sequence and then performing cross-correlation.To reduce the amount of calculation,the correlation value is calculated by frequency domain multiplication and the received signal is segmented.The simulation results show that the algorithm has good anti-frequency offset and anti-noise performance,and has the advantage of complexity compared with the traditional algorithm.For the SSS detection in cell search,this thesis proposes an improved SSS detection algorithm,which reduces the complexity of the SSS detection algorithm to that of the traditional detection algorithm by sequentially detecting two cyclic shift values in the SSS sequence generation formula,and the complexity is 40%of the traditional SSS detection algorithm.The simulation results show the effectiveness of the proposed SSS detection algorithm.For 5G NR Random Access Channel(PRACH)preamble detection,this thesis adopts the frequency domain correlation preamble detection algorithm,and proposes a noise estimation algorithm suitable for multipath channels.The simulation results show the effectiveness of the noise estimation algorithm.(2)Implementation and simulation verification of NR physical layer.The design of the physical layer is the core part of NR,and the performance of the physical channel determines whether the entire test platform can run normally.This paper firstly studies and implements the general processing process of NR uplink and downlink physical channels,including the research and implementation of CRC adding and checking,Polar coding and decoding,LDPC coding and decoding,modulation and demodulation,channel estimation and equalization.Then based on the NR general process,the uplink and downlink physical channels are realized.In order to verify the performance of the realized physical channel,the link-level simulation of the NR uplink and downlink physical channels is carried out.In order to verify the performance of the realized physical channel,link-level simulation of the NR uplink and downlink physical channels is carried out,and the wireless channel used in the simulation is a tapped delay line multipath channel.The simulation results show that the realization of the physical layer meets the performance requirements of the test platform.(3)On the basis of cell search and random access related algorithm research and physical channel implementation,this paper implements 5GNR cell search and contentionbased random access based on the Universal Software Radio Peripheral(USRP)platform under Linux system.The test platform adopts a combination of software and hardware architecture,the hardware adopts USRP,and the software part is implemented on a general purpose computer(GPC)and is implemented on the BS side and the UE side,including the simplified implementation of the radio resource control layer,the media access control layer and the physical layer of the BS and the UE,as well as the realization of the interaction interface between the layers.Finally,the implemented cell search and random access platform is tested.The test results show that the test platform can operate normally in the actual wireless channel,subsequent cell search and random access related studies can be used for real wireless channel testing on this platform.