On the capacity of block fading optical wireless channels

This paper investigates the capacity of block fading optical intensity channels with more transmit than receive antennas under different assumptions on the transmitterâ™s channel state information (CSI). Lower and upper bounds on the capacities are derived using the entropy power inequality (EPI) and a dual expression for capacity. Our lower bounds for perfect and partial CSI utilize a transmit-antenna cooperation strategy based on minimum-energy signaling, which we proposed recently. For perfect CSI, this lower bound matches the upper bound asymptotically in the high signal-to-noise ratio (SNR) regime. For imperfect CSI, our lower bound is close to its perfect-CSI counterpart.