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In this text, we consider the problem of fair scheduling in the downlink of Orthogonal Frequency Division (OFDM) systems. Based on be proportional fair scheduling algorithm proposed in the CDMAfHDR, we present three schemes to manage the parallel subcarriers in the OFDM system to utilize the time selectivity and frequency selectivity. Subcarriers in a slot(More)
—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)
Visible light communication (VLC) has drawn much attention in the field of high-rate indoor wireless communication. While most existing works focused on point-to-point VLC technologies, few studies have concerned multiuser VLC, where multiple optical access points (APs) transmit data to multiple user receivers. In such scenarios, inter-user interference(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)
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)
We consider the problem of precoding optimization for wireless MIMO nodes that are assigned both to serve its own destination and to relay another data transmission with a different destination. Unlike the traditional MIMO relay broadcast model, our cooperative node not only amplifies and relays another source signal to its destination but also sends its(More)