Abstract
Channel estimation is a challenging problem for space time block coding (STBC) multiple-input and multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems in dynamic environments. To handle this problem and improve the system performance, this paper proposes a Kalman filter (KF) based channel estimation method applied to $2\times2$ and $4\times4$ STBC MIMO-OFDM systems. The proposed method based on the dynamic tracking property of KF is well adopted for dynamic channel estimation. First, a new orthogonal space-time codeword is adopted, and the orthogonal pilot sequences are designed to suppress the interference among transmit antennas. Then, the prediction and update characteristics of KF are researched, and the state space model is established for STBC MIMO-OFDM system. Subsequently, the channel state information (CSI) is estimated iteratively according to the KF estimation equation. At last, to further improve the accuracy of KF channel estimation, the threshold is utilized to suppress the noise in the channel impulse response (CIR) estimated by KF method. Simulation results verify that the proposed KF channel estimation method with orthogonal pilots and STBC provides better bit error rate (BER) and normalized mean square error (NMSE) performance compared with other conventional channel estimation methods, and it can be effectively adapted to dynamic multipath propagation conditions with different low and high order modulations.
Highlights
Multiple-input multiple-output (MIMO) [1], [2] and orthogonal frequency division multiplexing (OFDM) [3]–[5] are the core technologies of 4G, and the key technologies of 5G
The proposed Kalman filter (KF) channel estimation method is applied in 2 × 2 and 4 × 4 space time block coding (STBC) MIMO-OFDM systems
The prediction and update characteristics of KF are researched, and the state space model is established for STBC MIMO-OFDM system
Summary
Multiple-input multiple-output (MIMO) [1], [2] and orthogonal frequency division multiplexing (OFDM) [3]–[5] are the core technologies of 4G, and the key technologies of 5G. It uses KF and data detection to jointly estimate the time varying channel and has fast convergence speed This method only considers a MIMO-OFDM system with one transmit antenna and two receive antennas. An enhanced EKF based channel estimation method was proposed in [23] It could jointly estimate carrier frequency offset and CFR. For the 4 × 4 STBC MIMO-OFDM system with higher diversity gains and channel fading resistance ability, a new orthogonal space-time codeword is adopted, and the orthogonal pilot sequences are designed to suppress the interference among antennas. The designed orthogonal pilot sequences can be utilized to linearize the STBC MIMO-OFDM system, and KF can be applied to estimate the CFR directly, which has low calculation complexity.
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