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—Interference alignment can help achieve high capacity in multiuser and multi-channel wireless interference environments. Because the degree of freedom (DOF) metric is defined under asymptotic signal to noise ratio (SNR), it has practical limitations under finite SNR. In addition, perfect interference alignment requires conditions on the number of antennas(More)
—Our investigation centers on the issue of linear precoding for hybrid-ARQ retransmissions in linear multi-input-multi-output (MIMO) channels driven by non-Gaussian inputs. Leveraging recent works on single transmission MIMO precoding [1], we derive the gradient of input-output mutual information with respect to precoder matrix for optimization. We further(More)
Direct-current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) is used in visible light communications (VLC) for high rate transmission. Due to the unipolarity of optical signals, a direct current (DC) offset along with proper clipping is adopted in DCO-OFDM. A high DC-offset causes a waste of power and a low DC-offset causes a severe(More)
Accurate channel estimation is a necessary condition for data demodulation in wireless communication systems. Compared to traditional channel estimation method, compressed sensing theory can take full use of the sparse characteristics of the channel. The contradiction between channel estimation error and message rate can be effectively solved. Based on a(More)
Avalanche photo-diodes (APD) are widely employed in visible light communication (VLC) systems. Experiments show that under official illuminance APD shot noise can not be ignored due to the multiplication process. Under VLC dual-purpose illumination, symbols on different constellation points inevitably experience different levels of noise. In such a signal(More)
A hemispherical lens is often used in Visible Light Communication (VLC) systems to provide a wide field of view (FOV) and spatial multiplexing gain. Depending on the way of placing the lens, in practice there are generally two kinds of receivers, namely the flat-surface and curved-surface receivers, where the former one uses the flat surface of lens to(More)