Optimization And Implementation Of 5G Cell Search And Downlink Synchronization Technology

The 5th generation mobile communication(5G)is the latest generation of mobile communication technology with advantages of high transmission rate,low delay,low power consumption and high reliability.At present,5G basic version standard has been released.With the commercial promotion of 5G globalization,research on 5G key technologies and applications has become a hot topic in the field of information technology.Similar to the Long Term Evolution(LTE)system,the terminal of 5G system also accesses the base station and realizes communication through the cell search process.Compared with LTE system,the 5G system has changed in frequency band,frame structure and synchronization signal etc,which puts forward higher requirements for 5G cell search capability.Therefore,it is of great significance to study 5G cell search and downlink synchronization technology.Firstly,the thesis analyzes the general process of 5G cell search and optimizes the algorithm of 5G timing synchronization process.The traditional 5G coarse timing synchronization algorithm has weak anti-frequency offset performance and high complexity,which cannot meet the hardware requirements of terminal chip.Therefore,after a thorough study of the traditional segmented timing synchronization algorithm,this thesis proposes an improved algorithm combining Fast Fourier Transform(FFT)and overlapping block.The improved algorithm presets the normalized frequency offset to the local primary synchronization sequence,and executes the adaptive threshold decision according to the chi-square distribution characteristics of the related operation results,which reduces the overall operation amount by about 77%.The simulation results show that the improved algorithm has good robustness to noise and frequency offset.Secondly,the thesis studies the Secondary Synchronization S ignal(SSS)detection algorithm of 5G system.In view of the high complexity of traditional SSS detection algorithm based on frequency domain coherence,an improved algorithm based on Fast Hadamard Transform(FHT)is proposed by using the generation characteristics of SSS.The improved SSS detection algorithm replaces the traditional traversal correlation with FHT fast correlation,which effectively reduces the computational complexity on the premise that the detection performance is equivalent.Finally,the 5G cell search scheme is designed,and the key modules of 5G cell search and downlink synchronization are implemented at fixed points based on the Maotu Digital Signal Processing(DSP)developed by the Chinese Academy of Sciences.The processing efficiency of the fixed-point DSP model is further improved by optimizing the time complexity using the structure characteristics and instruction set of DSP.Through the performance comparison and analysis of 5G cell search floating-point model and fixed-point model,the performance gap between fixed-point model and floating-point model is only 0.1d B,which proves the feasibility and correctness of 5G cell search DSP.