Research On Key Technologies Of Downlink Synchronization In 5G System

With the gradual popularization and application of the 5th generation mobile communication(5G),5G network users experience faster download speed and more reliable network connection.Compared with the previous generation 4G system,the5 G system has not made great changes in realizing the communication purpose.The establishment of the connection between the terminal and the base station also depends on the downlink synchronization process.However,the settings of the synchronization signal,carrier interval and application frequency band have greatly changed.Therefore,it is necessary to further study the 5G system downlink synchronization algorithm.Its performance not only determines whether the 5G terminal downlink signal parameters can be accurately obtained,but also determines whether the 5G uplink random access initial parameters can be accurately obtained.First,5G downlink physical signals are analyzed.In order to solve the problems of 5G end-users’ frequent switching of base stations and the difficulty of signal timing synchronization in the process of signal transmission,a joint detection algorithm of segmentation and difference is designed in this paper.On the basis of improving the segmented correlation algorithm,the algorithm superimposes the local synchronous signals,reduces the computational complexity,and effectively resists the frequency offset while reducing the impact of noise accumulation.Through the test and Simulation in different channels,it is verified that the algorithm can effectively improve the success rate of timing synchronization detection.Secondly,when the terminal equipment obtains the received signal,in order to obtain better signal quality,it needs to eliminate the impact of carrier frequency offset.In order to solve this problem,this paper proposes an improved frequency offset estimation detection algorithm,which is better than the frequency offset estimation under cyclic prefix detection and the frequency offset estimation under segmented main synchronous signal detection,and can better adapt to the channel environment in 5G.Finally,the downlink synchronous search simulation link is built,and the beam measurement scheme of the synchronous signal block is formulated.Combined with the improved synchronous search and frequency offset estimation methods,after obtaining the cell number,the beam power of each synchronous block is measured to identify the strongest transceiver beam pair.