Digital Baseband Compensation for Mobile SFBC-OFDM Systems with Receiver I/Q Imbalance

In-phase and quadrature-phase (I/Q) imbalance is a major performance-limiting impairment for direct- conversion orthogonal frequency division multiplexing (OFDM) transceivers. I/Q imbalance degrades the signal-to-noise-ratio in an OFDM system by causing inter-channel-interference (ICI) between image subcarriers. Doppler spread due to mobility also causes ICI but mainly between adjacent subcarriers. In this work, we investigate the combined effects of mobility and I/Q imbalance in a multiple-input-multiple-output-OFDM system with the alamouti space-frequency block-coding scheme and design an effective compensation technique. Furthermore, we propose a novel pilot allocation and channel estimation scheme, and exploit the problem structure to reduce complexity.