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In this paper, we investigate the modulation order selection and power allocation for energy efficient (EE) orthogonal frequency division multiplexing (OFDM) visible light communication (VLC) systems. Unlike the widely studied Gaussian inputs, we consider that each subcarrier has discrete modulation scheme inputs. Under the constraints of the maximum total transmission power and the minimum spectral...
In this paper, we propose a systematic design approach of polar codes for multicolor visible light communication (VLC). Owing to the mixed ratio of multicolor light intensities and the interference between different colors, the channel polarization over a multicolor VLC system is markedly different from that over a uniform channel. Our scheme quantifies these different color channels and constructs...
This paper proposes a neural network (NN) approach for demodulating output signals of a nonlinear channel with memory. The feed-forward neural network is trained to learn the appropriate mapping between nonlinear input patterns and source bits. The simulation results provide some evidence that neural networks can learn the effect of nonlinear channels with memory and demodulate the output signal of...
In a visible light communication (VLC) system, the nonlinearity of LED is one of the challenges that prevents reliable communication. In order to mitigate the nonlinearity of LED, in this paper, the concept of spatial summing pulse amplitude modulation (PAM) is developed where PAM signals are separated into several on#x002F;off keying (OOK) signals transmitted by different LED groups. The signal streams...
Multi-level per cell (MLC) /Triple-Level per cell (TLC) technique significantly improves storage density with low cost increases, which stores more than one bit per cell, but also drastically decreases reliability in NAND flash memory. As the bit number per cell increases, correspondingly cell-to-cell interference (CCI) becomes the major challenge for NAND flash memory technology scaling. Recently,...
In this paper, we propose a construction method of quasi-cyclic low-density parity-check (QC-LDPC) codes with multi-weight circulants (MQC-LDPC codes) which is suitable for high-rate LDPC codes with moderate length. MQC-LDPC codes can achieve better degree distributions, Hamming weight distributions, and stopping set weight distributions than conventional QC-LDPC codes with single-weight circulants...
Challenges in bit-pattered magnetic recording (BPMR) include two-dimensional (2D) inter-symbol interference (ISI) constituted by both one-dimensional ISI and inter-track interference (ITI), and media noise arising from island position jitter (PJ) and island size fluctuations (SF) in both the down-track and cross-track directions. A LDPC code optimization approach is proposed for BPMR channel with...
White light-emitting diode (LED) consisting of red, green, blue, and amber chips (RGBA-LED) has recently been adopted as transmitter in visible light communication (VLC) systems. This paper proposed a reshaped orthogonal frequency division multiplexing (R- OFDM) scheme for RGBA-LED-based VLC systems. In the R- OFDM, the signal is adjusted by separation and biasing after clipping (BAC) operations for...
This paper investigates performance of a mixed radio frequency (RF)/free space optical (FSO) two-way relaying system. A half-duplex two-way relay is adopted to establish the communication between both RF and FSO links. Under this scenario, the associated end-to-end statistical features of the system are derived. They are then used for calculating outage and average symbol error rate (ASER) of M-ary...
In this paper, we advocate a novel constellation design methodology for multi-color visible light communication (VLC) systems deploying protograph-based low-density parity-check (P-LDPC) codes. We utilize the protograph-based extrinsic information transfer (PEXIT) analysis to evaluate the coded system performance accurately and employ the differential evolution algorithm for the optimal constellation...
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 dependent noise channel, traditional log likely-hood...
Short range free-space optical (FSO) communication is vulnerable to atmospheric turbulence (AT). In urban environment, weak turbulence is popularly existed in light windy clear weather condition during both daytime and night, which deteriorates the performance of such an FSO communication system. However, impacts of the weak AT on the performance of adaptive FSO transmissions are rarely reported....
This paper presents a four-dimensional (4-D) modulation scheme combined pulse position modulation (PPM) with four-color (RGBA) light-emitting diode (LED) in a visible light communication (VLC) system. In the proposed scheme, multi-LED selection is used within a symbol interval in order to decrease the cross-talk between each LED and make sure that each LED works in its linear area. Based on the maximal...
In this paper, we study a hybrid free-space optical/radio-frequency (FSO/RF) communication system deploying protograph-based low-density parity-check (P-LDPC) codes. We use the protograph-based extrinsic information transfer (PEXIT) algorithm to accurately evaluate the system performance and employ the hybrid FSO/RF symbol mapping technique and the generalized variable degree matched mapping (G-VDMM)...
In this paper, we investigate the system performance from the physical layer security provision under imperfect channel state information (CSI). In a classical transmitter (Alice)-legitimate receiver (Bob)- eavesdropper (Eve) model, we introduce artificial noise (AN) to disturb Eve's reception, as Eve's CSI is unknown to Alice. For designing the transmit beamforming vector of the information signal...
This paper considers a visible light system that serves the dual purpose of illumination and communication. We maximize the joint offset and power optimization in direct-current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) for visible light communications (VLC). We take both the optical and electrical power constraints into account. We analytically characterize the optimal...
Device-to-device (D2D) communication is a promising technique for improving the spectral efficiency of cellular networks. In this paper, we consider joint optimization of pair assignment and power control for D2D pairs reusing downlink cellular resources, and aim to maximize the aggregate rate of D2D communications while guaranteeing the quality of service (QoS) of the cellular users. By transforming...
This paper studies adaptive coordinated control of device-to-device (D2D) communications underlaying a cellular network with a multi-antenna base station (BS). We analyze the performance of cellular and D2D users under the channel imperfections including both quantization error and feedback delay. More specifically, we derive the received signal-to-interference-and-noise ratio (SINR) distributions...
In systems that allow device-to-device (D2D) communications, user pairs in close proximity communicate directly without using an access point (AP) as an intermediary. D2D communications leads to improved throughput, reduced power consumption and interference, and more flexible resource allocation. We show that the D2D paradigm also provides significantly improved security at the physical layer, by...
In this paper, we proposed an efficient shuffled-turbo receiver for the downlink transmission in the long term evolution (LTE) systems. Different with the conventional ones, all modules in the shuffled-turbo receiver work simultaneously. Improved hardware utilization and processing efficiency are achieved owing to this workflow. Besides, our receiver can adaptively support various scenarios with flexible...
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