An overview of outdoor visible light communications

Abstract: In visible light communications (VLC) technology, the outdoor applications are less explored when compared to those indoors. This is due to the fact that: (i) the dual use of light emitting diodes (LEDs) is not always practicable in the outdoor VLC environment; (ii) the level of interference and noise is considerably higher in outdoor VLC; (iii) many other communication technologies are available to be used which, due to their specific characteristics, adapt better to the outdoor environment when compared to VLC technology. Nevertheless, several outdoor VLC applications have been identified. They include and are not limited to building-to-building (B2B), vehicle-to-vehicle (V2V) and road-to-vehicle (R2V) communications. Deploying light fidelity (Li-Fi) using street and park lights is also feasible. Finally, some applications exploit the ability of solar panels to simultaneously harvest the electrical energy and serve as a VLC receiving antenna. The implementation of these communication systems faces lots of challenges. Most of them are related to environmental factors such as fog, rain, sunlight, haze, snow, dust, and atmospheric disturbances. Some challenges are based on parameters such as the geometrical aspect of the light diffusion, which is Lambertian in most cases. These challenges contribute to lower interest in outdoor VLC to date. However, the environment presents several opportunities. In this article, we explore the outdoor VLC environment, review and present some promising applications selected from the literature. Furthermore, we underline likely research opportunities based on the actual state-of-the-art and our outdoor VLC characterisation experiments

Inter-building PLC-VLC integration based on PSK and CSK techniques

Abstract: This paper presents the implementation of an integration technique used to combine power line commu- nications (PLC) and visible light communications (VLC) channels in inter-building scenarios. It considers the narrow band PLC (NBPLC). Phase-shift keying (PSK) is used to convey the information over the PLC link and colour shift keying (CSK) technique is used on the VLC link. The colour wheel method is exploited to map PSK symbols to colours.We define a parameter x, which represents different magnitudes of the PSK complex symbol observed over the PLC channel. x is adjusted to an optimal value to meet the requirement of the CSK design. The bit error rate (BER) is analysed and the performance of the system is presented for multiple values of the modulus of the detected PSK symbol. A practical implementation is performed to verify the PSK-CSK mapping method. The impact of the sun’s rays on the red-green-blue (RGB) symbols is analysed and the interference source is highlighted

Segmental analysis of the transmission in CSK systems based on the Euclidean distance

Abstract: This article presents a segmental analysis of the transmission in colour shift keying (CSK). The Euclidean distance is fractionally studied to find the distance limits between the observed and the expected points. Practical segmental characterisation of the CSK receiver is presented to verify the Voronoi segmentation over the CSK channel and confirm crosstalk and correlation between the red, green and blue channels based on the threshold selection

Review of power line communications standards in Africa

The standards in power line communications (PLC) calibrate parameters such as frequencies allocation, signal level, security, topology of the network and many others parameters. The leap forward of power line communications technology is motivated by the willingness of the standardization organizations (SDO)s such as ITU, IEC, ISO, IEEE, CENELEC to define how the technologies are going to be deployed. This paper presents the different SDOs, Alliances and groups regulating the PLC sector. The interoperability and coexistence for some technologies are underlined. The process of developing PLC standards by ITU, IEEE 1901, CENELEC is described. The advantages and disadvantages of using PLC technology in Africa are discussed

A review of Bluetooth and NFC for financial applications

Abstract: Bluetooth and near field communications (NFC) are two of the most recently emerging wireless technologies [1] [2], largely because of the integral role they play in the Internet of everything (IoE). In this paper, the security aspect is evaluated for these two wireless technologies for potential applications in financial systems. Their frame size is also analyzed. This is done by reviewing their characteristics based on the state of the art and on the standards governing their deployment. It is found that Bluetooth has good security mechanisms when compared to NFC, which requires developers to implement their own security features at application level; however, NFC’s short range and its requirement for intentional communication between devices makes it inherently secure. It is also found that NFC has a larger message size, however, the classic Bluetooth message size is not that far below that of NFC data exchange format (NDEF) short records (SR) message size

Low-complexity SOCPBFSK-OOK interface between PLC and VLC channels for low data rate transmission applications

This paper studies and proposes a low cost low complexity interface between power line communications (PLC) and visible light communications (VLC) for low data rate transmission applications. The discussion presents the performance of a spread orthogonal continuous phase binary frequency shift keying (SOCPBFSK) receiver combined with an on-off keying (OOK) modulator to relay low data transmission between PLC and VLC channels. The characteristics of the interface are presented. The results of an experimental test using the proposed interface over the European Committee for Electrotechnical Standardization (CENELEC) bands C and D are presented. The eye diagrams of the combined error are presented as well

AF cooperative VLC communication systems : cascaded channel analysis

Abstract: Visible light communications (VLC) technology is a relatively new emerging telecommunication paradigm. It offers the opportunity to design cost-effective communication systems due to the dual use of the light sources, which are exploited as illumination devices and as communication antennas. However, this technology is mostly deployed in short-range communication applications because of the light diffusion range, which is short by nature. One good response to this dilemma is the imple- mentation of relay-assisted cooperative communication systems. Cooperative VLC systems provide three advantages, which are an increase in the transmission range, an improvement of the detection, hence of the bit error rate (BER), and an improved lighting system. In this paper, we analyze the channel response of a single-relay indoor VLC system based on an amplify-and- forward (AF) strategy. The system takes into account the fact that the relay also receives a reflected message. Results show the influence of the room’s reflection index, Lambertian index, the number of scattered rays on the overall channel response and confirms the importance of relay-assisted strategies in improving systems’ reliability

Evaluation of the SFSK-OOK integrated PLC-VLC system under the influence of sunlight

Abstract: With the widespread of light emitting diodes (LEDs) as a primary source of illumination, visible light communication (VLC) offers a lot of potentials by providing both resources and energy saving advantages. This paper presents a practical implementation of an integration of Power Line Communication (PLC) and VLC. The system uses spread frequency shift keying (S-FSK) and on-off keying (OOK) in the PLC and VLC channel respectively. The system is of low complexity, low cost and dedicated to enhance low data rate application of PLC technology. The practical design is compatible with the European Committee for Electrotechnical Standardization (CENELEC) band A and the test are done on a Chinese home environment where the Electric Power Research Institute (EPRI) specifies a 3 kHz to 500 kHz band. Results illustrating the effect of sunlight on this system are presented

Detecting the zero-crossing message to achieve low bit transmission over H-bridge inverter

Home automation and smart grid development is motivated by many advantageous situations that include the demands on renewable energy and the advantages provided by power line communications technology (PLC). The integration of solar energy into conventional grid implies the control of different modules included in the system. Remote control seems to be the control mode by excellence, in which communication is the main point to focus on. The pulse width modulation (PWM) scheme used to control the inverter is also used to modulate the zero-crossing point of the output sine wave of the inverter, to transfer data. The zero-crossing modulation technique is proposed and basic elements to construct the model are proposed. Simulated constellations of the received signal are presented

Constellation design for cascaded MPSK-CSK systems

Abstract: This paper proposes a constellation design for color shift keying (CSK) based on phase shift keying (PSK) conversion, to be used in cascaded power line communications (PLC) and visible light communications (VLC) systems integration. We optimize the design of MPSK-CSK constellations and analyze the performance of MPSK-CSK systems based on the optimized Euclidean distance calculated on the red-green-blue (RGB) color space