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The increasing development and utilisation of optical camera communications offer an excellent opportunity for the implementation of the smartphone‐to‐smartphone‐based visible light communications (S2SVLC) system. In this study, the authors experimentally demonstrate that the S2SVLC system can support high‐quality multimedia transmissions by the investigation of the mean square error estimation, peak signal‐to‐noise (PSNR) degradation, bit error rate (BER), and data rate achieved. The experimental analysis has been carried out for different typical practical background illuminations (i.e., normal illumination and dark condition), distances, tilting, and rotation angles. The PSNR and BER are determined for different frame sizes in the S2SVLC system to provide an insight of system performance. Those results indicate that the data transmission at different conditions significantly impacts the system's performance. [ABSTRACT FROM AUTHOR]

Abstract In this paper, three MAC protocols, EE-MAC, CF-MAC and OD-MAC, are proposed. EE-MAC incorporates emergency communication and allows immediate channel access for emergency traffic. CF-MAC compensates regulatory and open-loop control traffic and introduces a prioritized access for high priority nodes. It also allows nodes with critical data to reserve communication slots using control channel. Whereas OD-MAC presents a deadline based dynamic scheduler which ensures timely delivery of time-critical information. The paper presents mathematical modelling of the proposed protocols. For evaluation purposes, the performance of the proposed protocols is compared to IEEE 802.15.4e LLDN. The results show that the proposed protocols offer up to 92% reduction in delay in emergency communications at the cost of 5% to 15% increase in delay of time-insensitive data. A 60% and 85% reduction was observed in the channel access delay for regulatory and open-loop control traffic respectively along with notable improvements in communications reliability. [ABSTRACT FROM AUTHOR]

This paper studies zero-forcing (ZF) precoding designs for multi-user multiple-input single-output visible light communication (VLC) broadcast channels. In such broadcast systems, the main challenging issue arises from the presence of multi-user interference (MUI) among non-coordinated users. In order to completely suppress the MUI, ZF precoding, which is originally designed for radio frequency (RF) communications, is adopted. Different from RF counterpart, VLC signal is inherently non-negative and has a limited linear range, which leads to an amplitude constraint on the input data signal. Unlike the average power constraint, obtaining the exact capacity for an amplitude-constrained channel is more cumbersome. In this paper, we first investigate lower and upper bounds on the capacity of an amplitude-constrained Gaussian channel, which are especially tight in the high signal-to-noise regime. Based on the derived bounds, optimal beamformer designs for the max-min fairness sum-rate and the maximum sum-rate problems are formulated as convex optimization problems, which then can be efficiently solved by using standard optimization packages. [ABSTRACT FROM AUTHOR]

Indoor positioning or localization based on visible light communications (VLC) is an emerging technology with wide applications. In conventional localization schemes, the trilateration technique is widely used with at least three separate lighting sources to determine the user's location. An indoor VLC positioning scheme based on the optical power distributions of only two light emitting diodes (LEDs) is reported for different environments. We have used two received signal strength indications to determine the user's position based on the LEDs configuration offering less complexity. We propose comprehensive mathematical models for the VLC localization system considering the noise and its impact on the user's location, and numerically evaluated it over a range of signal-to-noise ratios (SNRs). In addition, it is compared to the results with the exiting trilateration technique. The performance of the proposed system is evaluated with a reported accuracy of <20 cm for an SNR of >13 dB. [ABSTRACT FROM AUTHOR]

Underwater Acoustic Communications (UWAC) is an emerging technology in the field of underwater communications, and it is challenging because of the signal attenuation of the sound waves. Multiple Input and Multiple-Output (MIMO) is introduced in UWAC because of its support in enhancing the data throughput even under the conditions of interference, signal fading, and multipath. The paper presents the concept and analysis of 2x2 MIMO UWAC systems that uses a 4-QAM spatial modulation scheme thus minimizing the decoding complexity and overcoming the Inter Channel Interference (IChI). Bit Error Rate (BER) investigation is carried out over different link distances under acoustic Line of Sight (LOS). The utilization of Zero Forcing (ZF) and Vertical-Bell Laboratories Layered Space-Time (VBLAST) equalizers, which estimates the transmitted data proves a success of removing Inter Symbol Interference (ISI). The ISI caused due to multipath effect and scattering in UWAC can be reduced by iterative process considered in VBLAST. A study is made on how the distance between the transmitter and the receiver and the Doppler Effect has its impact on the performance of the system. [ABSTRACT FROM AUTHOR]

Erratum corrects an error in Fig. 8. [ABSTRACT FROM AUTHOR]

We propose an adaptive localization and channel state information (CSI) estimation model using the distance vector for indoor multiple-input multiple-output (MIMO) visible light communication (VLC). Under normal conditions, receivers (Rxs) require the CSI of all channels [formed by multiple transmitters (Txs) and multiple Rxs] to recover the original data, and the received signal strength (RSS) obtained from Txs, i.e., light-emitting diodes (LEDs) to predict the Rx's location. A beacon [or pilot signal (PS)] with CSI is periodically broadcasted from each LED to MIMO Rxs for constructing the CSI matrix and measuring the RSS. However, in an abnormal condition, PSs from one or multiple Txs might not reach Rxs due to shadowing, thus resulting in a failure in positioning and data recovery. To combat this, the proposed model enables the Rx to predict its location without the need for all PSs based on the construction of the distance vectors at Rx. Simulations conducted for two scenarios of user's mobility, i.e., lattice and random direction mobility, show a low positioning error of ∼0.1 and 0.2 m, respectively. Based on predicted positions, MIMO VLC is capable of fulfilling the CSI matrix and assists the Rx in recovering transmitted data with a very low bit error rate. [ABSTRACT FROM AUTHOR]

This paper comparatively investigates the transmission performance of absolute added correlative coding (AACC) using non-return-to-zero (NRZ) and return-to-zero (RZ) pulse shapes with a binary intensity modulation direct detection receiver in 40 Gb/s optical metro-access networks operating at 1550 nm. It is shown that, for AACC transmission, the NRZ impulse shaping is superior in comparison to RZ in spectral efficiency, dispersion tolerance, residual dispersion and self-phase modulation (SPM) tolerance. However, RZ-AACC experiences a ~1–2 dB advantage in receiver sensitivity over NRZ-AACC for back-to-back configuration as well as after 300-km single-mode fiber delivery. [ABSTRACT FROM AUTHOR]

This paper proposes a simple and effective model applied for image-based malware classification using machine learning in which malware images (converted from malware binary files) are directly fed into the classifiers, i.e. k nearest neighbour (k -NN), support vector machine (SVM) and convolution neural networks (CNN). The proposed model does not use the normalized fixed-size square images (e.g. 64 × 64 pixels) or features extracted by image descriptor (e.g. GIST) for training classifiers as existing models do in the literature. Instead, the input images are normalized and horizontally sized down (the width of the image) to a lower dimension of 32 × 64, 16 × 64 or even 8 × 64 than square ones (e.g. 64 × 64 pixels) to reduce the complexity and training time of the model. It is based on the fact that the texture of the malware image is mainly vertically distributed as analysed in this paper. This finding is significant for training those devices which have limited computational resources such as IoT devices. The experiment was conducted on the Malimg, Malheur datasets which contains 9339 (25 malware families) and 3133 variant samples (24 malware families) using k -NN, SVM and CNN classifiers. The achieved results show that it is possible to reduce the dimension of the input images (i.e. 32 × 64, 16 × 64 or even 8 × 64) while still retaining the accuracy of classification as the same as the accuracy obtained by classifier feeding by the fixed-size square image (i.e. 64 × 64 pixels). As a result, training time of the propose model reduces by a half, a quarter, and one-eighth compared to training time taken by the same machine learning-based classifier (i.e. k -NN, SVM and CNN) feeding by fixed-sized square images, i.e. 64 × 64, respectively. [ABSTRACT FROM AUTHOR]

The demand for access to broadband data services in high‐speed trains is increasing as more people are travelling to and from work, which is not met by the existing radio frequency technology. Therefore an alternative technology known as free space optics (FSO) could be readily adopted that could overcome the bandwidth bottleneck problem. The study presents a mathematical model of an FSO link for ground‐to‐train communications link and analyses the system performance in terms of the signal‐to‐noise ratio and the bit error rate (BER). The authors show that the simulated BER is in good agreement with the predicted results for bit rates up to 50 Mbps. The link budget analysis for the proposed system is also presented showing a link margin of 17.75 dB. [ABSTRACT FROM AUTHOR]

The paper presents a bidirectional high-speed, power-compensated, 3×3 reconfigurable and multiwavelength optical cross-connect (RMB-OXC) for all-optical networks. RMB-OXC characteristics and its performance are experimentally verified in a bidirectional 8-channel×10 Gb/s capacity system. The optical signal to noise ratio (OSNR) is achieved of 18.4 dB corresponds to a BER of 5×10 −10 . The channel cross-connect function was demonstrated by incorporating RMB-OXC in an 50 km lightwave system. We have observed only ~0.5 dB power penalty in the bidirectional transmission in comparison to the unidirectional transmission. The proposed RMB-OXC has vast potential and it can be utilized in many applications in high-speed wavelength division multiplexed (WDM) networks. [ABSTRACT FROM AUTHOR]

In this paper, we propose and validate an artificial neural network-based equalizer for the constant power 4-level pulse amplitude modulation in an optical camera communications system. We introduce new terminology to measure the quality of the communications link in terms of the number of row pixels per symbol N pps , which allows a fair comparison considering the progress made in the development of the current image sensors in terms of the frame rates and the resolutions of each frame. Using the proposed equalizer, we experimentally demonstrate a non-flickering system using a single light-emitting diode (LED) with N pps of 20 and 30 pixels/symbol for the unequalized and equalized systems, respectively. Potential transmission rates of up to 18.6 and 24.4 kbps are achieved with and without the equalization, respectively. The quality of the received signal is assessed using the eye-diagram opening and its linearity and the bit error rate performance. An acceptable bit error rate (below the forward error correction limit) and an improvement of ~66% in the eye linearity are achieved using a single LED and a typical commercial camera with equalization. [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]