Pilot-symbol aided channel estimation and signal detection for MIMO-OFDM system

Abstract

OFDM is one of the attractive schemes for high data rate wireless networks because of its various advantages in lessening the severe effects of frequency-selective fading. The basic principle of OFDM is to split a high-rate datastream into a number of lower rate streams that are transmitted simultaneously over a number of subcarriers. The relative amount of dispersion in time caused by multipath delay spread is decreased because the symbol duration increases for lower rate parallel subcarriers. Since the radio channel is frequency selective and time-varying for wideband mobile communication systems, a dynamic estimation of channel is necessary before the demodulation of OFDM signals. Pilot-aided channel estimation algorithm for OFDM has received considerable attention for many years. In the estimation, the obtained channel response at pilot locations are used to estimate the channel response at data locations by interpolation schemes. We propose a channel estimation algorithm for MIMO-OFDM system. In the proposed algorithm, we introduce an EM type channel estimation for the low computational complexity. The EM-type algorithms provide an iterative and more easily implementable solution. Moreover, we proposed estimation scheme based on nonlinear 2-D regression model. This estimation algorithm has an advantage of reducing unknown parameters. Additionally, for the regression model based estimation, we introduce the guideline for designing pilot value. In these algorithms, the channel can be assumed to be approximately constant over an OFDM block. However, the assumption on the time-invariance may not be valid with the high Doppler or the disturbance such as synchronization errors. Then, time variation of the channel will introduce ICI that is a convolution of the transmitted sequence. There-fore, we propose channel estimation algorithms for OFDM with time-varying channels. The proposed channel estimation is able to robust to fast-fading channel using iterative ICI ...