Low Complexity Transmitter Architectures for SFBC MIMO-OFDM Systems

Multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with space-frequency block coding (SFBC) have a high computational complexity since the number of inverse fast Fourier transforms (IFFTs) required scales in direct proportion to the number of antennas at the transmitter. This paper proposes to generate the SFBC encoded signals of the various antennas in time domain by exploiting the time-domain signal properties and signal correlations among the various transmitter antennas, achieving a significant reduction in computational complexity. In particular, it is demonstrated that the time domain SFBC encoded signals of the various antennas can be obtained from the time domain signal of the first antenna. Therefore, the proposed scheme requires only one IFFT irrespective of the number of transmission antennas. In addition, a low-complexity peak-to-average power ratio (PAPR) reduction scheme is presented based on the proposed transmitter architectures.

I. Introduction

Multiple-Input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with space-frequency block coding (SFBC) [1]–[7] have attracted substantial attention due to their robust performance in time selective fading channels. However, the transmitters in SFBC MIMO-OFDM systems have a relatively high computational complexity since they are required to perform one inverse fast Fourier transform (IFFT) operation for each transmission antenna. To reduce the system complexity, time domain encoding approach has been proposed in [6] and [7]. However, the proposed methods are only applicable to a fraction of known SFBC encoding schemes and still have a high computational complexity.