Research And Implement In Time-frequency Synchronization Techniques In Future Mobile Communication Systems

The OFDM system has the advantages of high spectrum utilization and strong anti-multipath interference capability,and has been applied in technical standards such as 4G and 5G.On the basis of inheriting the advantages of the OFDM system,the F-OFDM system is flexible.A single system can meet the needs of a variety of differentiated services.It is one of the popular solutions for the new generation of mobile communication systems.This article focuses on the synchronization algorithm in the OFDM/F-OFDM system and the implementation of the synchronization algorithm based on FPGA.In terms of synchronization algorithm research,this paper studies the classic algorithms in non-data-assisted and data-assisted synchronization algorithms and improves one of them.The maximum likelihood algorithm based on the cyclic prefix does not require additional data overhead and the algorithm complexity is low,but the synchronization performance is poor under complex channel conditions.Although the traditional data-assisted synchronization algorithm has a large working signal-to-noise ratio range,it cannot take into account the symbol timing accuracy,algorithm complexity,frequency offset estimation accuracy,and frequency offset estimation range.This paper designs an improved training sequence and corresponding synchronization algorithm based on the Schmidl&Cox algorithm.This algorithm synchronizes in the time domain.Compared with the original algorithm,it has a significant improvement in timing synchronization performance and guarantees the frequency under the condition of low algorithm complexity.Synchronization accuracy,while having a large frequency offset estimation range.In the aspect of FPGA-based synchronization algorithm implementation,this paper divides the improved synchronization algorithm into modularization,and completes the modular design and implementation of the symbol timing algorithm and frequency offset estimation algorithm in the algorithm.The symbol timing module is divided into a coarse timing module,a fine timing module and a timing position judgment module,which respectively complete the output of the coarse timing flag bit,the fine timing flag bit and the timing position address.The frequency synchronization module is divided into a frequency offset estimation module,a correction waveform generation module and a carrier recovery module,which respectively complete the output of the frequency offset estimation value,the correction data stream and the recovered data.The entire synchronization algorithm function can be realized by connecting the symbol timing module and the frequency synchronization module.Aiming at the related calculations and energy calculations in the algorithm,this article adopts a recursive method in the design to reduce hardware resource consumption.Software simulation and board-level test results show that the hardware design meets the system requirements.