A new space-time signaling scheme for MIMO-OFDM systems with limited feedback

Multiple antenna wireless technology and orthogonal frequency division multiplexing (OFDM) have the potential to enable high data rate wireless applications. While the multiple-input multiple-output (MIMO) wireless techniques exploit spatial domain for improving the quantity and reliability of the data transmitted, OFDM converts the frequency-selective broadband channel into a bank of narrow band frequency-flat channels, allowing low complexity equalization at the receiver. To realize the spatial diversity offered by the multiple antennas in a MIMO-OFDM system, either the receiver has to perform complex signal processing (such as ML decoding) or the transmitter has to preprocess the signals which requires channel knowledge at the transmitter, often through a feedback link. In this paper, we propose a new space-time signaling scheme that requires limited amount of feedback and exploits the spatial diversity. We focus on 2 times 2 MIMO-OFDM systems and, through error analysis, show that the proposed method achieves full spatial diversity of 4. We also present simulation results that confirm our analytical results and show the superior performance of our method in comparison with existing methods.