The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this review, we summarise methods towards achieving 10 Mb/s connectivity for visible light communications links utilising organic polymer based light-emitting diodes as the transmitter. We present two different methods; on-off keying supported by least mean squares equalisation and orthogonal frequency division multiplexing without equalisation.
This paper proposes a novel detection technique for the Android-based smartphone to smartphone visible light communications system. In this system, data is encoded into images and displayed on the flashing transmitter's screen. The receiver captures the flashing images from the transmitter and performs a frame subtraction to detect the transmitted data. A Canny edge detector is then applied and the...
This paper experimentally investigates the performance of an FSO communications system by increasing the link length under an indoor laboratory controlled turbulence condition. A plane mirror is used to increase the link length by means of optical beam reflection. The experimental results show that the turbulence strength is highly dependent on the link length. The measured scintillation index (SI)...
Physical layer network coding (PNC) is a promising technique used to improve the network throughput in a wireless two-way relay (TWR) channel. In this paper, the PNC technique is embraced for a TWR-free space optical (FSO) communication link for the full utilization of network resources. Such a scheme is particularly useful in situations where multiple nodes wish to exchange their information but...
The paper presents a hybrid orthogonal frequency division multiplexing (OFDM) — wavelength division multiplexing (WDM) visible light communication (VLC). Direct detection is adopted in place of complex digital signal processing such as channel estimation and channel equalization, or even forward error corrections. Generic red, green and blue light emitting diodes (LED) are used for high-speed WDM...
Physical layer network coding (PNC) technique has been adopted in recent works for increasing the system throughput in a two way relay channel (TWRC) where two users exchange their information via an intermediate node. In this paper, we investigate the effectiveness of increasing numbers of users for PNC technique where multiple pairs of users swap their information simultaneously through a single...
In this paper we experimentally demonstrate a 10 Mb/s error free visible light communications (VLC) system using polymer light-emitting diodes (PLEDs) for the first time. The PLED under test is a blue emitter with ∼600 kHz bandwidth. Having such a low bandwidth means the introduction of an intersymbol interference (ISI) induced penalty at higher transmission speeds and thus the requirement for an...
We demonstrate a practical 2×80 Gbit/s dense wavelength division multiplexing (DWDM) bidirectional short-range optical wireless link. The measured power penalty for the bidirectional transmission is less than 0.8 dB compared to the back-to-back link and is only 0.2 dB compared to the unidirectional transmission system. This technology may find potential applications for building-to-building and/or...
In this paper, we present the experimental results forfree 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...
In this paper, the attenuation of free space optical (FSO) communication systems operating at selected wavelengths of 0.83 μm, 1.31 μm and 1.55 μm in the controlled laboratory based fog and smoke environments are compared. The fog and smoke are generated and controlled homogeneously along the indoor atmospheric chamber of length 6 m. The experimental results from the selected wavelengths are compared...
This paper investigates the requirements for uniform illumination using white LEDs, showing the balance between lighting and visible light communications. The communications system performance of the is also investigated for mobility with a varying field of view at the receiver, showing that there is a limit that beyond which there are no longer gains to be made in mobility.
This paper studies the optimised Lambertian order (OLO) of light-emitting diodes (LEDs) for an indoor non-directed line of sight optical wireless communication (NLOS-OWC) systems. We firstly derive an expression of the OLO from a conventional Lambertian LED model, Then, we analyse the indoor multi-cell NLOS-OWC channel characteristics including optical power distribution and multipath time dispersion...
The paper presents the concept, design and analysis for a visible light communications receiver which has a full 180° perception angle thus offering the guard against blocking and enhancing the system mobility. The proposed receiver includes seven sub-receivers with the proposed geometrical shape investigated and analyzed in MATLAB® for evaluating the received power, RMS delay spread and corresponding...
This paper presents the concept, design and analysis for a visible light communications receiver to guard against blocking and enhance mobility. Different geometrical shapes have been investigated, with two being chosen and analyzed in MATLAB for the received power and the root-mean-square (RMS) delay spread. The results show that the receiver is fully mobile within the test area and can handle data...
There is a increasing demand for high speed data services while travelling on trains and other means of public transportation. Hence, an alternative technology to radio frequency (RF) communications called free space optics (FSO) could be used to provide truly high-speed broadband services in trains. This paper presents a Lambertian source modelling of FSO ground-to-train communication link along...
In this paper, we compare the fog attenuation of free space optical (FSO) communication systems operating at infrared wavelengths of 830 and 1550 nm in the controlled laboratory based fog environment. The fog is generated and controlled homogeneously along the atmospheric chamber of length 5.5 m. The visibility (V) is measured to characterize the fog within the chamber using Koschmieder relationship...
In this paper, we propose a novel cellular optical wireless communications (COWC) system with four diffused cells. A dynamic handover scheme is proposed to make the link more flexible by the way of adaptive channel allocation in different environments. The simulation results show that the proposed algorithm offers almost five times of the maximum dynamic transmission bandwidth and energy efficiency...
This paper presents the development of a Visible Light Communications (VLC) system for a local area network (LAN). The link is analyzed for all development stages and compared with a typical Ethernet system. The VLC system uses a Philips Luxeon Rebel as the transmitter and a Centronic OSD15-5T as the receiver coupled with a blue filter to achieve the required 10 Mb/s bit rates. The distance in which...
In this letter the performance of a free space optical (FSO) communication link in the presence of fog is experimentally investigated in an indoor environment. A dedicated indoor atmospheric chamber, replicating the outdoor environment, is being used to evaluate the FSO link performance under the fog condition. Theoretical analysis supported by the experimental evaluation has been carried out for...
In this paper, two models for diffuse indoor cellular optical wireless communication (OWC) systems with and without a holographic light shaping diffuser (LSD) are presented. For both models, the power distribution, the impulse response of the channels and root mean square (RMS) delay are described and analyzed. We perform a computer simulation to compare the channel characteristics of the typical...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.