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Single-bit closed-loop quasi-orthogonal space-time codes for MIMO systems

This paper proposes a closed-loop beamforming algorithm for MIMO systems employing quasi-orthogonal space-time block codes (QOSTCB) and low rate feedback channels over slowly fading channels. A recursion is formulated using a stochastic signed gradient approximation, where the receiver employs a single feedback bit to command the transmit antenna weights adaptation, at a frequency much lower than that of the data rate. The algorithm tracks the weight vector that optimizes a link performance measure, which takes into account both the self-interference properties of the space-time code and the channel conditions. Simulations show that the proposed algorithm can effectively exploit the channel temporal correlation, and outperform existing single-bit feedback schemes in low mobility scenarios.