Research On Channel Estimation And Synchronization Of LTE Downlink

Mobile communications has experienced three generations of development. LTE (LongTerm Evolution) is proposed by3GPP (3rdGeneration Partnership Project), for meeting theincreasing demand of higher business rate, higher spectral efficiency and lower constructioncosts. With the increasingly wide global development of LTE, it is very necessary to researchthe key technology.OFDM and MIMO are two of the key technologies in the LTE downlink transmissionsystem and enable the system have high spectral efficiency and resistance to the multipathfading features. For the LTE adopting OFDM to have the performance and OFDM systemsare more sensitive to synchronization, it is important to analyze the channel estimationalgorithms and synchronization algorithms. The work of this thesis is to determine thechannel estimation and synchronization scheme for LTE downlink systems on the basis of theanalysis of the classical channel estimation algorithms and synchronization algorithms.Firstly, the thesis describes the basic concept on the type of the radio channel, the framestructure of the LTE physical layer, the physical resource allocation, the basic principle ofOFDM and MIMO.Secondly, the article describes the channel estimation criterias and algorithms, includingthe LS, MMSE, LMMSE, SVD and several interpolation algorithms. The article design thesimulation platform based on LTE protocols Channel estimation based on RS for downlinkwas simulated, comparing the LS、MMSE、LMMSE and interpolation algorithms. Thenthrough the time-frequency two-dimensional interpolation algorithms, the channel function ofthe data subcarriers is estimated. In frequency domain, LMMSE interpolation is used, and intime domain, liner interpolation is used. Simulation results are given in the paper.Finally, several classical OFDM synchronization algorithms are introduced, includingmaximum likelihood algorithms based on the cyclic prefix (CP) and algorithms based ontraining sequence. The article proposes improved algorithms for the lack of these algorithms.Then the synchronization algorithms for LTE are studied. The article researched the coarsetiming synchronization and coarse frequency offset based on PSS. The the fine timingsynchronization and residual frequency offset based on RS also is studied. Simulation resultsare given in the thesis.