Abstract
The rapid time-variation of a fading multipath environment can impair the performance of multiple-input multiple-output orthogonal frequency division multiplexing (MIMO OFDM). This paper proposes a pilot placement method for MIMO OFDM systems under time-varying channels with the guard band. The time-varying channel is described by complex exponential basis expansion model (BEM). We discuss the least square (LS) channel estimation to obtain the minimum mean square error (MSE) and derive the pilot allocation that can satisfy the minimum MSE with regard to guard band in time-varying channels. It is shown that optimal pilot clusters can distribute non-uniformly in frequency domain and minimize the MSE. We generalize our scheme over G OFDM symbols and compare it with comb pilots. It is demonstrated that the proposed approach is more effective than previous work. Simulation results validate our theoretical analysis.
Highlights
Orthogonal frequency division multiplexing (OFDM) gives an effective technique for high data rate transmission
We suggest an optimal pilot allocation that does not rest in the guard band based on the minimum mean square error (MSE) under time-varying channel
We described pilot sequences that can minimize the MSE for time-varying channel with virtual subcarriers
Summary
Orthogonal frequency division multiplexing (OFDM) gives an effective technique for high data rate transmission. In [10], a pilot design scheme for the LS channel estimation is described in MIMO OFDM systems. General groups of pilot sequences are addressed in [11] for frequency-selective channel estimation in MIMO OFDM systems. A pilot design approach is proposed in [12], where the data sequences transmit over frequency-selective channels This low complexity scheme is based on the maximum a lower bound of the average capacity. We suggest an optimal pilot allocation that does not rest in the guard band based on the minimum MSE under time-varying channel. The remainder of the paper is organized as follows: Section 2 expresses the basis expansion model for timevarying channels and describes the MSE of the LS channel estimation. Bold letters is presented for matrices (column vectors) and variables are displayed in italic
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