Research And Implementation Of Downlink Synchronization Tracking Algorithms In LTE-A Air Interface Monitoring Analyzer

With the development of LTE-A network construction,and users' increasing demand for network performance.It is of great significance to develop a new type of LTE-A air interface monitoring analyzer.The key technology of data demodulation is OFDM in the downlink baseband physical layer of LTE-A air interface monitoring analyzer,while the orthoganality between OFDM symbol carrier waves is very sensitive to time-frequency synchronization variance,the accurate time-frequency synchronization is of great significance to improve the performance of LTE-A air interface monitoring analyzer.Due to the environment in the receiver is complexity and changeable,resulting in the synchronization changing with time.In order to maintain the correctness of the synchronization,real-time synchronous tracking is necessary.This thesis mainly focuses on the research of frequency synchronization and OFDM symbol timing synchronization algorithm in LTE-A.According to the characteristics and requirements of LTE-A downlink synchronous tracking,a downlink synchronous tracking scheme for LTE-A air interface monitoring analyzer is designed and implemented.The main contributions of this dissertation are summarized as follows.Firstly,based on the related research of LTE-A network,the functional requirements of LTE-A air interface monitoring analyzer are specified.Combined with the overall design architecture of LTE-A air interface monitoring analyzer,the downlink baseband physical layer design architecture and data processing flow are given.Secondly,quantitatively analyze the influence of frequency offset to LTE-A system.Based on the CRS-based frequency offset estimation algorithm,a frequency offset estimation algorithm based on CRS interpolation is proposed by interpolation,which limits the frequency offset estimation error under 0.001 subcarriers.In order to further extend the range of frequency offset estimation,a joint frequency offset estimation method based on CP and CRS is proposed,which not only expands the range of frequency offset estimation to [-3500 Hz,3500Hz],but also guaranties the accuracy of frequency offset estimation.Thirdly,analyze the influence of timing synchronization offset to LTE-A system in multipath channel.Study and modify the time synchronization algorithm based on CRS which is suitable for multipath to meet the requirements of high timing synchronization accuracy in harsh environments,thus achieving the purpose of accurate demodulation.Finally,design and implement the joint frequency offset estimation algorithm based on CP and CRS and the timing synchronization algorithms based on CRS by using modular method based on FPGA.The correctness of the two algorithms was verified by function simulation software.The rationality of the two algorithms was proved by analyzing the resource consumption,and the performance of the synchronous tracking algorithm in LTE-A air interface monitoring analyzer was verified by the whole machine testing.