Efficient ICI matrix estimation using hadamard sequences for wireless OFDM systems

Document Type

Conference Proceeding

Publication Date

1-1-2005

Abstract

The intercarrier interference (ICI) matrix for the orthogonal frequency division multiplexing (OFDM) systems in the frequency-domain, usually involves a fairly large dimension. The traditional least-square solution based on the pseudo-inverse operation therefore has its limitation. In addition, the provision of a sufficiently long training sequence to estimate the complete ICI matrix is not feasible since it will result in the severe throughput reduction. In this paper, we derive a lower bound for the mean-square estimation error among the least-square ICI matrix estimators using different training sequences and prove that the minimum mean-square error (MMSE) optimality is attained when the training sequences in different OFDM blocks are orthogonal to each other, regardless of the sequence length. Then we propose to employ the training sequences based on the Hadamard matrix so as to achieve a highly efficient and optimal ICI matrix estimator with the minimum mean-square estimation error among all least-square ICI matrix estimators. Besides, our new scheme involves only linear complexity while other existing least-square methods always require the complexity proportional to the cube of the ICI matrix size. Both analytical and experimental comparisons between our new scheme using Hadamard sequences and the existing method using m-sequences show the significant advantages of our new ICI matrix estimator.

Publication Source (Journal or Book title)

IEEE Vehicular Technology Conference

First Page

1782

Last Page

1786

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