LTE Downlink Channel Estimation Algorithm

LTE(Long Term Evolution)is proposed by 3GPP(3rd Generation Partnership Project) which have produced Technical Specification and Technical Reports for 3G Mobile System, for meeting the increasing demand of high data rate for multimedia services. The LTE mobile communication system is forward to improve the spectral efficiency, data rate and the propagation delay. It is very necessary to research the key technology. So the centralization of this dissertation is the channel estimation technology of LTE downlink channel.For LTE adopting MIMO and OFDM to improve its performance in physical layer, it is very important to analyze the principle for researching the channel estimation algorithms. Especially, orthogonal frequency division multiplexing (OFDM) technology is widely used for its good anti-multipath fading characteristics and high spectrum efficiency in high-speed data transmission. In order to overcome the frequency selective fading caused by multi-path channel, in the OFDM communication system, the signal is transmitted on the orthogonal sub-carrier with a bandwidth of less than the correlated channel bandwidth. In order to compensate the multi-path fading of each subcarrier, a channel estimation algorithm with good performance is needed.Thus the LTE downlink pilot-aided channel estimation algorithm is studied. Firstly, the principle of OFDM and its key techniques were briefly introduced, then the basic knowledge of physical layer in LTE system was introduced, such as frame structure, downlink slot structure, physical resource distribution, etc., also the CP selection criterion was analyzed. Secondly, pilot-based channel estimation for LTE downlink was studied, including the LS, MMSE, and several interpolation algorithms. The third part is mainly about the design of simulation platform based on LTE protocols of 3GPP. Pilot-based channel estimation for LTE downlink was simulated, comparing the LS, MMSE. The channel function of the pilot subcarriers is estimated with LS algorithm, and then through the time-frequency two-dimensional interpolation method, the channel function of the data subcarriers is estimated. In frequency domain, LMMSE interpolation is used, and in time domain, Lagrange interpolation is used. Simulation results are finally given in this paper. The analysis and simulation results show that the performance of the improved algorithm is better.At the end, a summary of the paper is made, and the prospects of further study in the future are also put forward.