Pengfei Luo

Undersampled Phase Shift ON-OFF Keying for Camera Communication

In this paper, an optical camera communication system utilizing the under-sampled phase shift ON-OFF keying modulation is proposed to support non-flickering visible light communication. This system sends three types of light symbols through light emitting diode (LED) lamps, which are recorded by a camera. By employing a dual LED lamp with a designated mapping and framing method, the data rate can reach up to 3 times of the cameras frame rate. The experiment results show that the proposed camera communication system can achieve 150 bps error-free communications for a range up to 12 m.

Experimental Demonstration of RGB LED-Based Optical Camera Communications

Red, green, and blue (RGB) light-emitting diodes (LEDs) are widely used in everyday illumination, particularly where color-changing lighting is required. On the other hand, digital cameras with color filter arrays over image sensors have been also extensively integrated in smart devices. Therefore, optical camera communications (OCC) using RGB LEDs and color cameras is a promising candidate for cost-effective parallel visible light communications (VLC). In this paper, a single RGB LED-based OCC system utilizing a combination of undersampled phase-shift on-off keying (UPSOOK), wavelength-division multiplexing (WDM), and multiple-input-multiple-output (MIMO) techniques is designed, which offers higher space efficiency (3 bits/Hz/LED), long-distance, and nonflickering VLC data transmission. A proof-of-concept test bed is developed to assess the bit-error-rate performance of the proposed OCC system. The experimental results show that the proposed system using a single commercially available RGB LED and a standard 50-frame/s camera is able to achieve a data rate of 150 bits/s over a range of up to 60 m.

Multi-band carrier-less amplitude and phase modulation for bandlimited visible light communications systems

Visible light communications is a technology with enormous potential for a wide range of applications within next generation transmission and broadcasting technologies. VLC offers simultaneous illumination and data communications by intensity modulating the optical power emitted by LEDs operating in the visible range of the electromagnetic spectrum (~370-780 nm). The major challenge in VLC systems to date has been in improving transmission speeds, considering the low bandwidths available with commercial LED devices. Thus, to improve the spectral usage, the research community has increasingly turned to advanced modulation formats such as orthogonal frequency-division multiplexing. In this article we introduce a new modulation scheme into the VLC domain; multiband carrier-less amplitude and phase modulation (m-CAP) and describe in detail its performance within the context of bandlimited systems.

Fundamental analysis of a car to car visible light communication system

This paper presents a mathematical model for car-to-car (C2C) visible light communications (VLC) that aims to predict the system performance under different communication geometries. A market-weighted headlamp beam pattern model is employed. We consider both the line-of-sight (LOS) and non-line-of-sight (NLOS) links, and outline the relationship between the communication distance, the system bit error rate (BER) performance and the BER distribution on a vertical plane. Results show that by placing a photodetector (PD) at a height of 0.2-0.4 m above road surface in the car, the communications coverage range can be extended up to 20 m at a data rate of 2Mbps.

Experimental Demonstration of a 1024-QAM Optical Camera Communication System

In this letter, we experimentally demonstrate a 1024-quadrature-amplitude-modulation (QAM) optical camera communications (OCC) system using a dual light-emitting diode (LED) and a commercial digital single-lens reflex camera. An undersampled QAM subcarrier modulation (UQAMSM) is proposed to support a high-efficiency and non-flickering OCC system. Owing to the built-in gamma correction function of the camera, pre- and post-compensation techniques are successfully applied to compensate for the non-linear impairment. A dedicated framing structure is also designed to support the proposed UQAMSM and compensation techniques. The experimental results show that this system is able to achieve a data rate of 500 b/s using a dual LED and a 50 ft/s commercial camera over a transmission span of 1.5 m, which is suitable for the transmission and reception of location-based information.

Optical Camera Communications

Visible light communications (VLC) has been evolving at a much faster rate because of the development of high energy efficient white light emitting diodes (LED). For the first time, we see a unique device which offers triple functionalities of illumination, data communications and indoor localization, thus opening up the opportunities for applications at homes, offices, planes, trains, etc. In modern vehicles with LED-based head and tail lights, VLC can be used for car-to-car communications to convey regular traffic information to other vehicles as well as the road side infrastructure. Cameras are also being widely used in vehicles for monitoring speed, collision detection avoidance, traffic sign and object recognition. The VLC technology employing the camera as a receiver opens up new possibilities offering multiple functionalities including data communications. This chapter gives an overview of the optical camera communications and outlines the technological concept behind it.

1.2 Gbps non-imaging MIMO-OFDM scheme based VLC over indoor lighting LED arrangments

We propose a non-imaging MIMO-OFDM based VLC, and analyzed its bit-error-rate (BER) performance for different LED arrangements. Rectangular LED arrangement offers improved BER compared to the linear arrangement for a range of higher-order modulation schemes.

Undersampled-PAM with subcarrier modulation for camera communications

In this paper, a novel undersampled pulse amplitude modulation with subcarrier modulation (UPAMSM) is proposed to supporting high efficiency non-flickering visible light camera communication (CamCom). A post-compensation technique is employed to reduce nonlinear effects caused by camera gamma correction. In order to eliminate phase uncertainty between transmitter and camera, and obtain the built-in gamma correction function of a camera, a dedicated framing structure is designed and applied. A test-bed with a light emitting diode (LED) and a commercial digital single-lens reflex (DSLR) camera is built to evaluate the performance of the proposed UPAMSM CamCom system. Experiment results show that this system can achieve a data rate of 250 bps (5 (bit/s)/Hz/LED) with a 50 fps camera at a distance of 1.5 m.

SVM detection for superposed pulse amplitude modulation in visible light communications

A support vector machine (SVM)-based data detection for 8-superposed pulse amplitude modulation in visible light communication is proposed and experimentally demonstrated. In this work, the SVM detector contains three binary classifiers with different classification strategies. And the separating hyperplane of each SVM is constructed by training data. The experiment results show that the SVM detection offers 35% higher data rates when compared with the traditional direct decision method.

Performance analysis of a DSSS-based UV communication with inter-symbol interference

Inter-symbol interference (ISI) may become detrimental when the data rate rises in the atmospheric scattering UV channel. In this paper, we model the ISI effect due to delay spread in the UV channel and evaluate the approach of direct sequence spread spectrum (DSSS) in eliminating ISI and improve the system performance. Both the measured noise and newly reported experimental results of impulse response are introduced and incorporated. Numerical simulations are conducted to analyze the relations between bit-error-rate (BER) and spread factor, sample number, data rate. The results indicate that the DSSS reduces the ISI effect evidently.