Research And Implementation Of Timing And Frequency Synchronization For OFDM System

The current 4G network can meet people's communication needs at this stage.However,with the advent of the Internet of Everything,people requires higher information exchange rate,as result,5G technology with high-speed,low-latency,and high-capacity has received widespread attention from the society,and has gradually moved from theoretical research to formal commercial use.Nowadays,the OFDM technology,it is considered to be the most effective communication method to achieve efficient data transmission,and synchronization technology is an actual problem that needs to be solved in any communication system,so the synchronization in OFDM system attracts extensive attention from researchers in related fields all over the world.Firstly,this paper studies synchronization algorithm in OFDM system and summarizes the previous research thoroughly,introduce different kinds of time and frequency algorithms and analyze their performance.Secondly,to solve the problem that timing is sensitive to frequency offset,a new conjugate repeating preamble structure is designed,and a timing and frequency synchronization algorithm based on Zadoff-Chu(ZC)sequence based on ZC sequence is proposed.The new algorithm uses the shift relationship between the front and back training sequences to estimate the integer frequency offset while timing synchronization is completed,so that the timing is not affected by the frequency offset,thereby not only greatly simplifying the synchronization process,but also significantly improving synchronization performance.Thirdly,Aiming at the problem of high computational complexity,this paper proposes a time-domain synchronization method based on the piecewise CAZAC(Constant Envelope Zero Auto Correlation)sequence.The algorithm designed a conjugate symmetric preamble with only a symbol length to complete the entire synchronization process,effectively reducing the computational complexity,and taking into account the algorithm performance.Fourthly,the paper designs a complete OFDM system synchronization scheme for based on the IEEE802.11a protocol,and gives the system parameters,sub-module division,and new preamble structure.The scheme includes four modules:frame synchronization,symbol synchronization,carrier synchronization and OFDM demodulation.This paper introduces function,design principle and logical structure of each module in detail.Finally,this paper simulates the functions of each module design scheme using Modelsim,and the RTL-level circuit diagram and simulation data synthesized proves the rationality and correctness of the design.