Research On Downlink Synchronization Technology Of 5G NR Communication System

At present,R16,the first evolved version of 5G,has been frozen,and application technology research with reference to protocol specifications has always been a hot topic in the communications industry.Downlink synchronization is a key process for the user to establish a connection with the base station.Only when the cell identity is obtained after the downlink synchronization is completed,can the user accurately identify the information sent by the base station.Compared with 4G,the frame structure and synchronization signal in the 5G NR system have changed.The protocol specification requires rapid wireless communication synchronization capabilities.In order to adapt to the evolving communication needs,this article will conduct research on the downlink synchronization technology of the 5G NR system.Firstly,combining the advantages and disadvantages of several current primary synchronization signal detection algorithms,a low-complexity superimposed segmentation correlation algorithm is proposed.The PSS sequence related to the received signal is reduced from the original three groups to one group,which greatly reduces the amount of initial blind detection calculations,and maintains good anti-frequency offset performance through segmentation.Experiments show that the improved scheme has better anti-frequency offset performance than sliding correlation,and better antinoise performance compared with differential correlation.Compared with the three algorithms of sliding,differential and segmentation,the original calculation is reduced the amount.The improved algorithm can reduce the computational complexity by66.65% on the basis of both good anti-frequency offset performance and anti-noise performance.Then,aiming at the defect of excessively high calculation amount of the secondary synchronization signal detection,a fast detection scheme based on Walsh-Hadamard matrix is proposed.Since the secondary synchronization signal detection needs to traverse the local 336 sets of SSS sequences,the amount of calculation is too large.In order to reduce the time for users to connect to the network,the equivalence between the m-sequence matrix and the Walsh-Hadamard matrix is used to construct the transformation matrix.Using the fast butterfly algorithm of the Walsh-Hadamard matrix,the frequency-domain related calculations are reduced by 95.95%,which greatly improves the detection speed of the algorithm.Finally,the 5G NR downlink synchronization software platform was built using VC6.0,and the program flow of several key modules such as PSS coarse synchronization,PSS fine synchronization,frequency offset estimation and compensation,SSS decoding,etc.were designed,and the user demodulated synchronization signal was successfully realized.The basic function of acquiring symbol starting point and physical cell ID.The detection result is consistent with the preset data of the base station,which verifies the feasibility of the downlink synchronization software design scheme and the correctness of the logic function.