Singular Value Decomposition Channel Estimation in STBC MIMO-OFDM System

Abstract

The multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) technology is the combination of the OFDM and MIMO technologies, which could improve the system capacity and make efficient utilization of the frequency spectrum. This paper utilizes space-time block coding (STBC) to achieve diversity gains and combat the channel fading. However, channel estimation is an essential block for space-time block decoding (STBD). Many channel estimation methods are utilized for the single antenna OFDM system, but they cannot be directly applied to the multiple antennas system due to the interference from other antennas. In this paper, orthogonal pilot sequences are designed to suppress the interference of pilot symbols from other transmit antennas. This paper also derives a minimum mean square error (MMSE) channel estimation method in MIMO-OFDM systems. The MMSE method involves the inverse operation of the channel autocorrelation matrix, which has a large calculation complexity. To further reduce the complexity of the MMSE method, the singular value decomposition (SVD) is used to decompose the channel autocorrelation matrix, which avoids the inverse operation. Simulation results verify that the SVD channel estimation method with comb-type pilots and STBC can be effectively adapted to multipath propagation conditions. Keywords: channel estimation; multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM); space-time block coding (STBC); singular value decomposition (SVD); bit error rate (BER)

Time-Varying Sparse Channel Estimation Based on Adaptive Average and MSE Optimal Threshold in STBC MIMO-OFDM Systems

“…In practice, the orthogonality is usually realized by using orthogonal training sequences in code domain or silent pilot approach in frequency domain [16], [17]. Specially, for STBC MIMO-OFDM systems where the channel is assumed to be quasit-static over two or more sequential OFDM symbols, a space-time orthogonal pilot pattern is proposed in [18], which can be used for channel estimation without the reduction of frequency-domain sampling density. This pilot pattern can work well when the channel is constant over several sequential OFDM symbols, which is coincide with the assumption of STBC MIMO-OFDM systems.…”

“…This pilot pattern can work well when the channel is constant over several sequential OFDM symbols, which is coincide with the assumption of STBC MIMO-OFDM systems. Therefore, the pilot pattern in [18] is also used in this paper.…”

“…A 2 × 2 STBC MIMO-OFDM system with N subcarriers and utilizing the proposed channel estimation method, is presented in Fig. 1, where a space-time orthogonal pilot pattern [18] is used to avoid interference from other transmit antennas. This paper assumes that the system is perfectly synchronized and that the CP length CP N is longer than the maximum channel delay spread M .…”

“…For the 2 × 2 STBC MIMO-OFDM system, it is assumed that the channel responses are constant during two sequential OFDM symbols. Therefore, STBD can be implemented only by using CFR estimated for a specific OFDM symbol, and the received signals corresponding to the kth subcarrier after STBD can be represented as [18]:…”

“…The LS estimator can be directly applied to STBC MIMO-OFDM systems by using space-time orthogonal pilot pattern [18]. In space-time orthogonal pilot pattern, the pilot symbols from different transmit antennas are orthogonal in time domain instead of in frequency domain.…”