Abstract
A novel hybrid channel estimator is proposed for multiple-input multiple-output orthogonal frequency- divi- sion multiplexing (MIMO-OFDM) system with per-subcar- rier transmit antenna selection having optimal power allo- cation among subcarriers. In practice, antenna selection information is transmitted through a binary symmetric control channel with a crossover probability. Linear mini- mum mean-square error (LMMSE) technique is optimal technique for channel estimation in MIMO-OFDM system. Though LMMSE estimator performs well at low signal to noise ratio (SNR), in the presence of antenna-to-subcar- rier-assignment error (ATSA), it introduces irreducible error at high SNR. We have proved that relaxed MMSE (RMMSE) estimator overcomes the performance degrada- tion at high SNR. The proposed hybrid estimator combines the benefits of LMMSE at low SNR and RMMSE estimator at high SNR. The vector mean square error (MSE) expres- sion is modified as scalar expression so that an optimal power allocation can be performed. The convex optimiza- tion problem is formulated and solved to allocate optimal power to subcarriers minimizing the MSE, subject to transmit sum power constraint. Further, an analytical expression for SNR threshold at which the hybrid estimator is to be switched from LMMSE to RMMSE is derived. The simulation results show that the proposed hybrid estimator gives robust performance, irrespective of ATSA error.
Highlights
Orthogonal frequency division multiplexing (OFDM) is a popular method for high data rate wireless transmission [1]
The performance of Linear minimum mean-square error (LMMSE) based channel estimator in multiple-input multiple-output (MIMO)-OFDM system is improved by combining with optimal power allocation [15,16,17,18]
When LMMSE channel estimator is used in the system employing per tone selection with antenna to subcarrier assignment (ATSA) error, it results in intolerable performance at high signal to noise ratio (SNR)
Summary
Orthogonal frequency division multiplexing (OFDM) is a popular method for high data rate wireless transmission [1]. The performance of LMMSE based channel estimator in MIMO-OFDM system is improved by combining with optimal power allocation [15,16,17,18]. Extending this to per tone antenna selection scheme is not simple as the autocorrelation matrix is noninvertible due to fluctuations in its rank. Poses a LMMSE based channel estimation along with optimal power allocation scheme for MIMO-OFDM with per tone antenna selection system. When LMMSE channel estimator is used in the system employing per tone selection with ATSA error, it results in intolerable performance at high SNR This is due to error introduced in channel frequency correlation [12]. Superscript H denotes Hermitian operations, denotes the Kronecker product and E[ ] denotes the expectation operation. vec(C) transforms a matrix C c1, c2 , , cn into a column vector c1T , cT2 , , cTn , where ci is the ith column vector of C
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