Doubly-selective channel estimation for OFDM systems

Abstract

Orthogonal frequency division multiplexing (OFDM) is considered an effective technique for frequency selective channels. It has very good spectral efficiency and robustness against multipath propagation environments and capability of combatting inter-symbol interference (ISI). Many conventional channel estimators assume a time-invariant model for the channel during one OFDM symbol, and do not account for interchannel interference (ICI), losing subchannel orthogonality. On the other hand, in the next generation wireless systems, high speed of the mobile terminals make the channel time-selective, causing considerable variations of the channel within one multicarrier symbol. In this paper, we propose a two-dimensional (2D) pilot-symbol assisted channel estimation for wireless OFDM systems by using low-pass interpolation which is applied in both time and frequency domains. We also investigate the performance of proposed channel estimation for different detection approaches. The proposed method has the advantage of minimizing the system complexity and processing delay, providing a good approximation to the real mobile channel.