Research On Scheme Design And Synchronization Algorithm Of Frequency Hopping System Based On OFDM Framework

The traditional frequency hopping system has the disadvantages of frequency hopping limitation,frequency hopper design complexity,low spectrum utilization and long hopping frequency residence time.These restrict the development of frequency hopping system,and also cannot adapt to the communication demand of modern large data high-speed and secure transmission.In this research background,this paper puts forward the idea of combining the traditional frequency hopping technology with the mature Orthogonal Frequency Division Multiplexing technology.This idea abandoned the traditional design of frequency hopping frequency hopping system and realized the design of FH system based on OFDM framework.This idea makes the system structure more simple and flexible,it is easy to implement on software radio hardware platform and provide a way of thinking for the further development of frequency hopping system.The content of this paper is divided into two major parts,which are as follows:Firstly,it describes the design of the frequency hopping system based on OFDM framework,which involves soft spread spectrum technology,frequency hopping technology and OFDM technology.As for soft spread spectrum technology,this paper focuses on the generation and selection of spread spectrum code in soft spread spectrum coding mapping,and based on that,we analyze the factors that influence the performance of soft spread spectrum and the relationship between them.For frequency hopping module,this paper focuses on the design of FH sequence generator and design principle of frequency hopping pattern,through the analysis of the deficiencies of the FH system,which leads to the idea of combining OFDM technology,combined with the specific method of frequency hopping and OFDM are described in detail.Frequency hopping module generates frequency hopping frequency control instruction to control the selection of OFDM symbol neutron carrier,and based on IFFT/FFT algorithm,it is very easy to get modulated signal with OFDM property.The combination mode is divided into single frequency hopping mode and multi frequency hopping mode to compare and analyze their advantages and disadvantages and the applicable environment.The overall performance of the design system is demonstrated through simulation,and the improvement of the bit error rate of the soft spread spectrum technology is discussed,as well as the improvement of the system's anti-interference and interception capability by frequency hopping.Secondly,several synchronization algorithms based on the training sequence are studied,and the estimation ability of their respective timing synchronization and carrier synchronization is compared and analyzed.The timing synchronization focuses on the Schmidl algorithm,Minn algorithm and Park algorithm,the platform phenomenon in the Schmidl algorithm,analyzes the structure characteristics of the training sequence,the cyclic prefix is the cause of this phenomenon,and then compared with the Minn algorithm and Park algorithm,prove the excellent performance of Park algorithm of conjugate the symmetry in the timing estimation.Comparing the performance of Moose algorithm,Schmidl algorithm and Kim algorithm on carrier synchronization,it is found that the repeatability of training sequence structure has a direct impact on the acquisition range of frequency offset.Further research is conducted on the relationship between training sequence repeatability and conjugate symmetry.The improvement of algorithm structure shows that we can improve the algorithm's frequency offset estimation ability by sacrificing a certain timing estimation ability.