Search

With an emphasis on the real-time implementation of a practical carrier-less amplitude and phase (CAP) receiver for visible light communication (VLC), this paper proposes a full-digital architecture for the $M$ -CAP receiver with synchronisation and adaptive blind equalisation. The architecture is mainly based on the observation that a CAP signal can be demodulated using a quadrature and amplitude (QAM) receiver with an added counterclockwise rotation operation. The proposed CAP receiver employs two digital phase-locked loops (DPLL) to realise the symbol timing and carrier synchronisation, which are the most critical issues in practical systems. With the constant-modulus algorithm (CMA) offering the benefit of decoupling carrier and symbol timing synchronisation, the receiver can blindly equalise the distorted signal at the output of symbol timing synchronisation. Finally, the performance of 4/16/64-CAP receivers, which are designed using this architecture and operates at 80/160/240 Mbit/s through a low-pass light-emitting diode (LED) with a 3-dB bandwidth of 7 MHz cascaded with three measured optical wireless channels, is evaluated by Monte Carlo simulations. Results show that the receiver architecture can successfully solve the symbol timing and carrier synchronisation problems and mitigate inter-symbol interference caused by LED and/or wireless channels. The design framework for a full-digital CAP receiver has been laid out in this paper. [ABSTRACT FROM AUTHOR]

In this letter, we investigate the performance of vehicular visible light communications based on the radiation patterns of different commercial taillights (TLs) using non-sequential ray tracing simulations. Our simulation results indicate a significant variation in the path loss compared with Lambertian model. Based on the ray tracing results, we propose a new path loss model as a function of the propagation distance considering the asymmetrical radiation pattern of TLs. We use this model to derive the attainable transmission distance. We further present the delay spread for various vehicular communication scenarios to demonstrate the effect of neighboring vehicles. [ABSTRACT FROM AUTHOR]

This letter investigates a vehicle-to-vehicle relay-assisted visible light communications link with amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes and analyze the effect of the relay vehicle’s orientation with respect to the source vehicle. Results show up to 150 % increase in the link span under emulated sunlight for the DF relay link compared with AF at the end of the second hop using the same system parameters at the forward error correction bit error rate limit of $3.8\times 10^{-3}$. A method to mitigate the effect of system performance degradation due to misalignment between communicating vehicles is also proposed. [ABSTRACT FROM AUTHOR]

In this article, we experimentally demonstrate a novel expanded nonorthogonal multiband super-Nyquist carrier-less amplitude and phase (m-ESCAP) modulation for bandlimited organic visible light communication (VLC) systems. The proposed scheme has the same bandwidth requirement as the conventional m-CAP while breaking the orthogonality between subcarriers by purposely overlapping them. We compare m-ESCAP with the conventional m-CAP and a compressed nonorthogonal version of m-CAP (m-SCAP) in terms of measured bit error rate (BER) performance, bit rates, and spectral efficiencies. We show that the m-ESCAP system offers improvement in the bit rate of $\sim$ 10% and 20% compared to the m-CAP and m-SCAP, respectively, and in the spectral efficiency of $\sim$ 20% compared to m-CAP. These gains are achieved at the cost of increased BER, which, however, remains below the 7% forward error correction limit. [ABSTRACT FROM AUTHOR]

This paper proposes and experimentally demonstrates, for the first time, two new candidate pulse shapes for carrierless amplitude and phase modulation in the context of visible light communications. It is commonly accepted that the pulse shape at the heart of the Hilbert pair used to generate the required orthogonal signal spaces should be the square-root raised cosine. In this paper, we introduce two additional candidate pulse shapes, namely the first csv pulse and the so-called better-than-Nyquist pulse. We demonstrate experimentally that the better-than-Nyquist pulse offers superior bit-error rate performance compared to the square-root raised cosine and Xia pulses under additive white Gaussian noise channel conditions, while offering lower computational complexity. [ABSTRACT FROM AUTHOR]

This paper focuses on the performance analysis of a camera-based vehicle-to-vehicle visible light communication system employing undersampled phase shift on-off keying modulation under interference scenario. Two Nissan Qashqaifront lights with daylight running light emitting diodes based lamps are used for communications. The bit error rate (BER) performance of the proposed system is experimentally measured for a transmission span up to 24 m focusing mostly on the side interference due to reflections. Based on experimental data we demonstrate reduction o f the system performance due to the side reflection and illumination of the detector by other light sources which have to be taken into account during further data processing. We provide with further statistics for particular shutter speed and transmitter power setting and discuss BER improvement especially to meet FEC via the method of the adaptive region of interest. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the performance of a vehicular visible light communications (VVLC) link with a non-collimated and incoherent light source (a light-emitting diode) as the transmitter (Tx), and two different optical receiver (Rx) types (a camera and photodiode (PD)) under atmospheric turbulence (AT) conditions with aperture averaging (AA). First, we present simulation results indicating performance improvements in the signal-to-noise ratio (SNR) under AT with AA with increasing size of the optical concentrator. Experimental investigations demonstrate the potency of AA in mitigating the induced signal fading due to the weak to moderate AT regimes in a VVLC system. The experimental results obtained with AA show that the link's performance was stable in terms of the average SNR and the peak SNR for the PD and camera-based Rx links, respectively with <1 dB SNR penalty for both Rxs, as the strength of AT increases compared with the link with no AT. [ABSTRACT FROM AUTHOR]

The accuracy of the received signal strength-based visible light positioning (VLP) system in indoor applications is constrained by the tilt angles of transmitters (Txs) and receivers as well as multipath reflections. In this paper, for the first time, we show that tilting the Tx can be beneficial in VLP systems considering both line of sight (LoS) and non-line of sight transmission paths. With the Txs oriented towards the center of the receiving plane (i.e., the pointing center F), the received power level is maximized due to the LoS components on F. We also show that the proposed scheme offers a significant accuracy improvement of up to ~66% compared with a typical non-tilted Tx VLP at a dedicated location within a room using a low complex linear least square algorithm with polynomial regression. The effect of tilting the Tx on the lighting uniformity is also investigated and results proved that the uniformity achieved complies with the European Standard EN 12464-1. Furthermore, we show that the accuracy of VLP can be further enhanced with a minimum positioning error of 8 mm by changing the height of F. [ABSTRACT FROM AUTHOR]

This paper proposes a comprehensive study of indoor intruder tracking using visible light communication (VLC). A realistic indoor VLC channel was developed, taking into consideration reflections, shadowing, and ambient noise. The intruder was considered smart and aiming to escape tracking. This was modelled by adding noise and disturbance to the intruder's trajectory. We propose to extend the application of minimax filtering from state estimation in the radio frequency (RF) domain to intruder tracking using VLC. The performance of the proposed method was examined and compared with Kalman filter for both VLC and RF. The simulation results showed that the minimax filter provided marginally better tracking and was more robust to the adversary behavior of the intruder than Kalman filter, with less than 0.5 cm estimation error. In addition, minimax was significantly better than Kalman filter for RF tracking applications. [ABSTRACT FROM AUTHOR]