PILOT BASED CHANNEL ESTIMATION USING DIFFERENT INTERPOLATION TECHNIQUES IN OFDM SYSTEM

Abstract

In this thesis, we investigate and compare various efficient pilot sequence based channel estimation schemes for OFDM systems. The channel estimation can be performed by either inserting pilot tones into all sub-carriers of OFDM symbols with a specific period or inserting pilot tones into each OFDM symbol. In the present study, two major types of pilot arrangement such as block-type and comb-type pilot have been performed employing Least Square Error (LSE) and Minimum Mean Square Error (MMSE) channel estimators. Block type pilot sub-carriers is especially suitable for slow-fading radio channels whereas comb type pilot provides better resistance to fast fading channels. Also comb type pilot arrangement is sensitive to frequency selectivity when comparing to block type pilot arrangement. The channel estimation algorithm based on comb type pilots is divided into pilot signal estimation and channel interpolation. In slow fading environment, block type pilot-based channel estimation in OFDM system shows better performance. LS estimator shows the worst performance but with simplest complexity. Based on LS algorithm, LMMSE is analysed and it shows better performance compared with LS and MMSE but with more computation complexity. In fast fading environment, comb type pilot-based channel estimation in OFDM system has better performance. FFT, Linear interpolation, second order interpolation and spline interpolation techniques are discussed in this thesis. The simulation results show that the performance becomes better as the increasing order of polynomial for interpolation. But the complexity also increases.The bit error rate (BER) performances of OFDM system comb type pilot subcarriers are presented in the thesis.