A Group Matching Pursuit Algorithm for Sparse Channel Estimation for OFDM Transmission

Time-domain channel estimation techniques have been proposed for OFDM systems for their ability to yield relatively accurate estimates with only a few pilots. Key information needed in such techniques is the multipath delays of the channel. Prior approaches to estimation of multipath delays require regular pilot structures and may not work in slow fading. We propose a group matching pursuit technique for channel estimation. The technique is an extension of the orthogonal matching pursuit technique. It employs the pilots in several OFDM symbols to estimate the multipath delays in a sequential manner, where the pilots can have an arbitrary structure. Simulation results show that the proposed algorithm has superior performance.

1. INTRODUCTION

Coherent demodulation of orthogonal frequency-division multiplexing (OFDM) signals critically depends on proper channel estimation. Most channel estimation methods are pilot-aided. A common approach is to estimate the channel frequency response at pilot locations first, and then “extend” the estimate to other subcarrier locations. One frequently considered way of “extension” is low-order polynomial interpolation, which can take the form of one-dimensional interpolation in the frequency domain (in the span of one OFDM symbol) or two-dimensional interpolation over frequency and time (across several OFDM symbols) [1], [2]. The performance of these methods is limited by the pilot density and the channel characteristics. For example, if the channel has small coherence bandwidth (i.e., long delay spread) and low coherence time (e.g., due to fast motion) and the pilots are widely spaced in frequency, then they would have difficulty obtaining accurate channel estimates.