Abstract
In communication systems, efficient use of the spectrum is an indispensable concern. Recently the use of compressed sensing for the purpose of estimating orthogonal frequency division multiplexing (OFDM) sparse multipath channels has been proposed to decrease the transmitted overhead in form of the pilot subcarriers which are essential for channel estimation. In this article, we investigate the problem of deterministic pilot allocation in OFDM systems. The method is based on minimizing the coherence of the submatrix of the unitary discrete fourier transform (DFT) matrix associated with the pilot subcarriers. Unlike the usual case of equidistant pilot subcarriers, we show that non-uniform patterns based on cyclic difference sets are optimal. In cases where there are no difference sets, we perform a greedy method for finding a suboptimal solution. We also investigate the performance of the recovery methods such as orthogonal matching pursuit (OMP) and iterative method with adaptive thresholding (IMAT) for estimation of the channel taps.
Highlights
In wireless communications, orthogonal frequency division multiplexing (OFDM) is a well-known solution for overcoming the problem of multipath fading channels [1,2]
3 Iterative thresholding method for sparse channel estimation we propose an iterative method with adaptive thresholding (IMAT) [10] for the purpose of estimating the sparse channel impulse response (CIR)
6 Conclusion In this article, we investigated the problem of OFDM pilot allocation in sparsity-based channel estimation methods
Summary
Orthogonal frequency division multiplexing (OFDM) is a well-known solution for overcoming the problem of multipath fading channels [1,2]. The other approach which is considered in this article, is to use fast greedy methods such as OMP which iteratively detect and estimate the location and value of the channel taps These methods are usually faster than l1 minimization techniques by orders of magnitude while they may fall short of performance. The reconstruction performance is independent of the location and value of the taps; i.e., unlike the interpolationbased methods, the number of required pilot subcarriers does not depend on the delay spread and degree of frequency selectivity of the channel. We choose Np pilot indices in the following Np stages: since rather than the exact value of the indices, their cyclic difference are important, we initialize the index set by P(1) = {1} (1 is arbitrary).
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