Pilot-based Channel Estimation in OFDM System

Download or read book Pilot-based Channel Estimation in OFDM System written by Fei Wang and published by . This book was released on 2011 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) is a multi-carrier transmission technology in wireless environment, and can also be seen as a multi-carrier digital modulation or multi-carrier digital multiplexing technology. A large number of orthogonal sub-carriers are used to transmit information. OFDM system has high utilization of frequency spectrum and satisfactory capability of reducing multi-path inference. So, OFDM has been considered as one of the core technologies of 4th generation (4G) wireless communication system in the future. Channel estimation plays a very important role in OFDM system. As a research hotpot, many related algorithms have been presented these years, which can be generally separated into two methods, pilot-based channel estimation and blind channel estimation. Pilot-based channel estimation estimates the channel information by obtaining the impulse response from all sub-carriers by pilot. Compared with blind channel estimation, which uses statistical information of the received signals, pilot-based channel estimation is a practical and an effective method. This thesis is on the pilot-based channel estimation of OFDM system. Firstly, it introduces the basic principle and realization of OFDM system, and describes the system construction and model with summary of some key technologies, such as fast Fourier transform (FFT) and cyclic prefix (CP). We also analyze OFDM modulation in the frequency domain, and discusses some advantages and disadvantages of OFDM system. Next, a summary of multi-path and time varying statistical properties of general wireless channel of OFDM system are presented. This thesis also investigates principles and performances of the channel estimation methods, block type pilot and comb type pilot. In the arrangement of block type pilot, the performance of channel estimation is analyzed with estimators based on three different algorithms, least square (LS) algorithm, linear minimum mean square error (LMMSE) algorithm and singular value decomposition (SVD) algorithm. To use comb-type pilot arrangement, the thesis introduces three methods of interpolation: linear interpolation, second order interpolation and cubic spline interpolation. Finally, simulation results using Matlab are used to compare bit error rate (BER) performance of different modulation schemes and types of pilot.