In this paper, two techniques including uplink positioning and multiple-input multiple output (MIMO) singular value decomposition (SVD) beamforming are proposed and utilized to provide a novel physical layer security (PLS) scheme for visible light communication (VLC) systems, which much enhance the integrated location-sensing and data security strength. The paper first develops a closed-form mathematical model for ubiquitous uplink positioning using a single light-emitting diode with the trilateration algorithm, considering the field-of-view constraints due to the user’s optical transmitter and access point receivers. SVD in MIMO VLC is subsequently introduced to exploit the acquired user’s location to form a pair of public and private keys for secure data transfer over the physical medium. The proposed system performance is evaluated in terms of the root mean square positioning error$\varepsilon _{\mathbb {X}}$and the achieved bit error rate (BER) for the uplink positioning and the downlink data transmission, respectively. Results show that the effective area of the photodiode significantly impacts$\varepsilon _{\mathbb {X}}$, with smaller areas resulting in higher$\varepsilon _{\mathbb {X}}$. It is also observed that the$\varepsilon _{\mathbb {X}}$directly relates to the strength of ambient light inducing noise in the system. However, the proposed uplink positioning is less prone to natural ambient light as compared to the traditional downlink visible light positioning. The BER analysis of the downlink data transmission shows that the proposed SVD-based PLS enhances the system’s confidentiality by significantly narrowing the communication zone area by over 90% in comparison to the zero-forcing beamforming scheme and achieves reasonable secrecy capacity.

This study proposes a chaos‐based security model applied to the physical (PHY) layer of visible light communication (VLC) systems in accordance with the IEEE 802.15.7 standard. The proposed model employs a chaotic signal generated by a Colpitts oscillator to encrypt the header of IEEE 802.15.7 VLC frames in the PHY layer to prevent eavesdropping, traffic analysis and error function attacks. The encryption method employed here is chaotic inclusion or embedding, which is known as one of the most secure chaos‐based approaches. Thus, the essential information pertaining to the employed chaotic oscillator, i.e. its structure, parameter set, the utilised modulation and synchronisation methods is not visible or traceable to the eavesdropper. Moreover, the unencrypted payload is extended by an additional number of random padding bits which can only be determined by decrypting the header of the VLC frame hence the payload is unrecognisable to eavesdroppers though it has not been encrypted. At the legitimate receiver side, the received IEEE 802.15.7 frames are successfully recovered by removing the chaotic wave using chaotic synchronisation techniques. The simulation results show that the encrypted header and the unencrypted payload of the IEEE 802.15.7 frames are well protected and successfully recovered by legitimate receivers.

Active Constellation Extension (ACE) is widely used to reduce Peak-to-Average Power Ratio (PAPR) in Offset Quadrature Amplitude Modulation based Orthogonal Frequency Division Multiplexing (OFDM/OQAM). To improve overall performance and energy efficiency in OFDM/OQAM systems, this paper proposes Adaptive Scaling (AS) for effective ACE (AS-ACE). The proposed scheme exploits the overlapping structure of the OFDM/OQAM signals and jointly considers adjacent data blocks to obtain the clipping noise. The proposed scheme adaptively extends the constellation points to effectively eliminate peaks in OFDM/OQAM signals. This is achieved by using peak samples of clipping noise, used to generate the peak correcting signal. Least square approximation algorithm is used to fit the waveform of peak correcting signal to the waveform of clipping noise without any decrease in the constellation distance. Simulation results show that the AS-ACE reduces PAPR and Bit Error Rate (BER) and improves convergence speed compared to OSGP technique without requiring increased processing or additional information at the receiver end.

Accurate orientation information is the key in many applications, ranging from map reconstruction with crowdsourcing data, location data analytics, to accurate indoor localization. Many existing solutions rely on noisy magnetic and inertial sensor data, leading to limited accuracy, while others leverage multiple, dense anchor points to improve the accuracy, requiring significant deployment efforts. This paper presents LiCompass, the first system that enables a commodity camera to accurately estimate the object orientation using just a single optical anchor. Our key idea is to allow a camera to observe varying intensity level of polarized light when it is in different orientations and, hence, perform estimation directly from image pixel intensity. As the estimation relies only on pixel intensity, instead of the location of the anchor in an image, the system performs reliably at long distance, with low resolution images, and with large perspective distortion. LiCompass' core designs include an elaborate optical anchor design and a series of signal processing techniques based on trigonometric properties, which extend the range of orientation estimation to full 360 degrees. Our prototype evaluation shows that LiCompass produces very accurate estimates with median errors of merely 2.5 degrees at 5 meters and 7.4 degrees at 2.5 meters with an irradiance angle of 55 degrees.

This study introduces a weighted k ‐nearest neighbour model for user positioning in a visible light communications (VLC) system. The new model offers a higher degree of accuracy compared with conventionally existing techniques in VLC, such as trilateration. In the proposed model, the current position of the receiver is estimated based on the positions of the k ‐NN (known as reference points) pre‐defined and recorded in a lookup table. The Euclidean distances from the actual receiver to the reference points are weighted in order to improve accuracy. Simulation results show that the proposed model outperforms the trilateration method by 36 and 50% accuracy with and without ambient light interference, respectively.

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.

We present recent progress on visible light communication systems using polymer light-emitting diodes as the transmitters and a commercial silicon photodetector as the receiver. In this paper, we use transmitters at red, green, and blue wavelengths to investigate the maximum on-off keying link performance of each device type as the first steps toward a wavelength-division multiplexed link. We show that a total transmission speed of 13 Mb/s is achievable when considering the raw bandwidth of each of the RGB PLEDs. Such a rate represents a 30% gain over previously demonstrated systems. Further capacity improvement can be achieved using high performance artificial neural network equalizer offering a realistic prospect for transmission speeds up to 54.9 Mb/s.

In this paper, we experimentally demonstrate a multiband carrierless amplitude and phase modulation format for the first time in VLC. We split a conventional carrierless amplitude and phase modulated signal into m subcarriers in order to protect from the attenuation experienced at high frequencies in low-pass VLC systems. We investigate the relationship between throughput/spectral efficiency and m, where m = {10, 8, 6, 4, 2, 1} subcarriers over a fixed total signal bandwidth of 6.5 MHz. We show that transmission speeds (spectral efficiencies) of 31.53 (4.85), 30.88 (4.75), 25.40 (3.90), 23.65 (3.60), 15.78 (2.40), and 9.04 (1.40) Mb/s (b/s/Hz) can be achieved for the listed values of m, respectively.

In this paper, we present the experimental results free space optics (FSO) communication systems operating at visible and near infrared wavelengths (from 0.6 μm to 1.6 μm) under fog conditions. Different empirical fog models are typically used to characterize the fog attenuation of optical beam in FSO systems. A number of empirical fog models are evaluated in order to verify them experimentally and to fill several unmeasured gaps within the entire spectrum from the visible - near infrared (NIR) range for light to dense fog conditions. The experimental results in the controlled laboratory fog environment are compared with the selected empirical fog models in order to practically validate their performance over wide range of wavelengths. The results indicate wavelength dependency of the fog attenuation for visibilities higher than 15 m, whereas the cases with shorter visibilities contradict the Kim model.

This paper introduces a Bayesian model to predict and classify the mobility of a node in Mobile Ad-hoc Networks (MANETs). The proposed model does not use the additional information from Global Positioning System (GPS) for its prediction as some existing models did. Instead, it relies on the “average encounter rate” and “node degree” calculated at each node. However, the outcome is still recorded at high accuracy, i.e. prediction error is fewer than 10% at high speed level (above 15m/s). The aim of this model is to help a routing protocol in MANETs avoid broadcasting request messages from a high mobility node/region relied on the outcome of the prediction. Through simulation experiments, route error rate observed reduced significantly compared to normal broadcast scheme of the Ad-hoc On-demand Distance Vector (AODV) protocol. The packet delivery ratio improved up to 46.32% at the maximum velocity of 30m/s (equal to 108km/h) in the density of 200nodes/km2.

The design, simulation and practical implementation for a bidirectional 1.25 Gbit/s indoor optical wireless communications system has been presented. It is a part of the European community funded hOME Gigabit Access project (OMEGA). The line-of-sight (LOS) system uses angle-diversity transceivers enabling discrete beam steering. Each transceiver uses three transmitting and receiving elements giving an overall field of view of ∼25×8° and a transmission range of 3 m. Measurement shows that the system can operate at a bit error rate below 10−9 without channel coding and the handover between cells is <400 ns. Detail of a demonstrator of high-definition (HD) video embedded in gigabit ethernet stream using this system is also reported.

Future Home Access Networks (HANs) should operate at Gbit/s and provide data services that are as straightforward to use as an electrical outlet or any other utility. This is an extremely challenging goal, and an EU funded project 'Home Gigabit Access Networks' (OMEGA) aims to achieve this. In this project a significant part is to realize bi-directional Gigabit infrared (IR) optical wireless communications. In this paper we introduce the overall approach to the HAN, and outline the challenges and approaches required to implement these IR Gigabit links. Results from a proof-of-concept 1.25Gbit/s light-of-sight (LOS) IR link are shown, as well as designs for the first IR link demonstration.

In future high-speed photonic packet switching networks, it is highly desirable to carry out robust all-optical header recognition to provide high-throughput routing. The authors present a pulse-position modulation header processing (PPM-HP) scheme, offering significantly reduced routing table size and employing a single bit-wise AND operation to carry out correlation of the packet header with the entire routing table entries. The downsized routing table also offers multiple transmission modes (unicast, multicast and broadcast) in the optical layer and improves core network scalability where the number of core/edge nodes could be altered without the need for changing the number of routing table entries. The authors present modelling and simulation of the packet switching router based on PPM-HP. Noise propagation and crosstalk incurred in a multiple-hop routing scenario are investigated. The simulation results are presented and compared with the theoretical calculations.

Solid-state lighting is a rapidly growing area of research and applications, due to the reliability and predicted high efficiency of these devices. The white LED sources that are typically used for general illumination can also be used for data transmission, and Visible Light Communications (VLC) is a rapidly growing area of research. One of the key challenges is the limited modulation bandwidth of sources, typically several MHz. However, as a room or coverage space would typically be illuminated by an array of LEDs there is the potential for parallel data transmission, and using optical MIMO techniques is potentially attractive for achieving high data rates. In this paper we investigate non-imaging and imaging MIMO approaches: a non-imaging optical MIMO system does not perform properly at all receiver positions due to symmetry, but an imaging based system can operate under all foreseeable circumstances. Simulations show such systems can operate at several hundred Mbit/s, and up to Gbit/s in many circumstances.

In this paper we present the modeling and simulation of multiple-hop routing in ultrafast all-optical packet switching based routers employing multiple pulse position modulation (PPM) formatted routing table. In multiple PPM routing tables (PPRTs) with reduced entry length, only a subset of the header address is converted into a PPM format in order to reduce the packet header recognition time. Packet header address correlation is carried out using only a single optical AND gate to improve the processing time. We show that the proposed scheme offers unicast/multi-cast/broadcast transmitting capabilities. The simulation results for the optical signal-to-noise ratio (OSNR) at each hop are presented and compared with the theoretical calculations.

Fibre to the home and other ‘last-mile’ transmission technologies provide end-user data rates of at least 100 of Mbit/s. These technologies are currently deployed around the world, and in the short term gigabit-class home access networks will be required if this capacity is to be fully used, and new services are to be developed. In order to meet this goal, the Home Gigabit Access project (OMEGA, EU FP 7-1) aims at a range of transmission techniques and intelligent control. A significant part of this effort is devoted to two areas of optical wireless communications.

Solid-state lighting is a rapidly developing field. White-light and other visible LEDs are becoming more efficient, have high reliability and can be incorporated into many lighting applications. Recent examples include car head-lights based on white LEDs, and LED illumination as an architectural feature. The prediction that general illumination will use white LEDs in the future has been made, due to the increased energy efficiency that such an approach may have. Such sources can also be modulated at high-speed, offering the possibility of using sources for simultaneous illumination and data communications. Such visible light communications (VLC) was pioneered in Japan, and there is now growing interest worldwide, including within bodies such as the Visible Light Communications Consortium (VLCC) and the Wireless World Research Forum (WWRF). In this paper we outline the basic components in these systems, review the state of the art and discuss some of the challenges and possibilities for this new wireless transmission technique.

This paper presents a high-speed multiple-channel optical time division multiplexed (OTDM) demultiplexer based on a chained symmetric Mach-Zehnder (CSMZ) switch. In CSMZ switch semiconductor optical amplifier (SOA) are shared between two chained arms in contrast to the MZ based multiple-channel demultiplexers where there is an SOA in each arm. The analysis for bit error rate (BER) and the average received power penalty is presented and the results are compared with the simulated data. It is shown that the power penalty incurred is highly dependent on the value of coupling ratio and the channel number.

This paper introduces a novel 1×2 all-optical switch based on Tri-arm Mach-Zehnder (TaMZ) that uses an all-optical flip-flop (AOFF). The proposed switch is analytically modeled and simulation shows a marked improvement in signal on/off contrast ratio (CR) between two outputs over a larger range of control signal power compared to the existing symmetric Mach- Zehnder (SMZ) switches. In addition, TaMZ switch offers both broadcasting and complete switch-off capability, which further enhances the flexibility of the optical switching applications. The paper presents the principle of TaMZ-based switch and investigates theCRperformance. It is shown that theCRimprovement is more than 10 dB compared to conventional SMZ switch in a control signal power range of 20 dB.

In this paper we present modeling and simulation of multiple-hop all-optical packet routing based on the pulse- position modulation header processing (PPM-HP) scheme in ultrafast optical packet switching network. Optical core node employing PPM-HP requires a dedicated routing table based on PPM scheme that will result in significantly reduced number of routing table entries. In this scheme, the header address correlation, using optical AND gates, is carried out by employing only a single bit-wise for each entry rather than a multiple-bit stream as in the existing systems thus resulting in reduced header processing time and avoiding the slow gain-recovery of AND gates. The reduced routing table also offers embedding multiple transmitting modes (unicast, multicast, broadcast) in optical layer and improves core network scalability where the number of core/edge nodes could be altered without the need for changing the number of routing table entries. The simulation results for the optical signal-to-noise ratio (OSNR) of packets at each hop are presented and compared with the theoretical calculations.