Indoor Optical Wireless Communication System Research Articles

Investigation of the baseline wander effect on indoor optical wireless system employing digital pulse interval modulation

In indoor optical wireless communication (OWC) systems, ambient lights in particular fluorescent lamps introduce a periodic interference signal, which has the potential to severely degrade link performance. One of the simplest techniques often used to mitigate the interference from artificial sources of ambient light is electrical high-pass filtering (HPF). However, HPF introduces baseline wander (BLW), which is more severe for modulation techniques that contain a significant amount of power located at DC and low frequencies. In this paper the effects of BLW on systems employing digital pulse interval modulation (DPIM) are extensively investigated. Also investigated are the effects of cut-on frequency of the HPF on the optical power requirement and power penalty for different bit rates, where results are compared with the more established techniques of on-off keying (OOK) with a non-return to zero signalling and pulse position modulation (PPM). The optimum HPF cut-on frequency, which minimises the overall power penalty, is estimated. It is shown that at high data bit rates (100 Mbps), DPIM power requirement is considerably lower (~5 dB) than OOK and similar to that of PPM.

Indoor optical wireless communication systems and networks

International Journal of Communication SystemsVolume 18, Issue 3 p. 191-193 EditorialFree Access Indoor optical wireless communication systems and networks Z. Ghassemlooy, Z. Ghassemlooy Guest Editors fary@ieee.org Search for more papers by this authorA. C. Boucouvalas, A. C. Boucouvalas Guest Editors tboucouv@bournemouth.ac.uk Search for more papers by this author Z. Ghassemlooy, Z. Ghassemlooy Guest Editors fary@ieee.org Search for more papers by this authorA. C. Boucouvalas, A. C. Boucouvalas Guest Editors tboucouv@bournemouth.ac.uk Search for more papers by this author First published: 15 March 2005 https://doi.org/10.1002/dac.698Citations: 13AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume18, Issue3Special Issue: Special Issue on Indoor Optical Wireless Communication Systems and NetworksApril 2005Pages 191-193 RelatedInformation

Optical antenna design for indoor optical wireless communication systems

AbstractIn the present paper, the design of the non‐imaging totally internally reflecting concentrator family denominated optical antennas (OAs) is discussed, and its use for indoor optical wireless communication systems is explained. The lenses presented here can be designed to provide a prescribed angular response in order to limit the central wavelength shift in thin‐film optical filters. They can also be designed for any specific field‐of‐view (FOV), which allows greater rejection of unwanted background radiation and higher gains. The use of a variety of optical filters to achieve a high signal‐to‐noise ratio at the receiver is described. Design methods and properties of different Optical Antennas are explained. Comparisons of size and performance of total internal reflection based concentrators with those based on dielectric hemispheres and compound parabolic concentrators (CPCs) are carried out. Finally different experimental results are presented. Copyright © 2005 John Wiley & Sons, Ltd.

Multiple spot diffusing geometries for indoor optical wireless communication systems

AbstractIn order to improve the performance of indoor optical wireless communication links, two multispot diffusing geometries based on diamond and line strip spot distribution geometries are proposed, analysed and compared to the known uniform spot distribution. Such geometries combine the advantages of the diffuse and the line‐of‐sight systems, giving great robustness and ease of use. The novel line strip multibeam transmitter geometry has resulted in a receiver signal‐to‐noise ratio (SNR) improvement of about 4 dB compared to the conventional diffuse system as well as a significant reduction in the pulse spread. Simulation and comparison results for both the conventional diffuse system and the three multispot diffusing geometries are presented. Further, pulse responses, SNR, and delay spread results at various locations are presented. Copyright © 2003 John Wiley & Sons, Ltd.

Experimental characterization of rate-adaptive transmission and angle diversity reception techniques

Ambient light is the main impairment in indoor wireless optical communication systems for data rates up to several megabits per second. Its wide dynamic range, associated with the strong directivity of wireless optical signals, produce large variations on the received signal-to-noise ratio. This article discusses experimental results obtained from a testbed developed to compare different techniques for SNR improvement. The two techniques analyzed are rate-adaptive transmission, which introduces adaptive levels of redundancy in the transmitted signal to improve connectivity, and angle diversity reception, which exploits the inherent directionality of both signal and noise to improve the SNR at the receiver. Furthermore, systems employing both techniques simultaneously were also considered. The testbed replicated a typical indoor environment with both natural and artificial light, containing incandescent and fluorescent light sources. Both the SNR and the associated coverage areas were determined for all considered techniques. Our results show that the combined use of angle diversity based on maximal ratio combining and rate adaptation through the use of repetition coding achieves very good performance with only moderate complexity, allowing connectivity at all locations with data rates close to the maximum possible. In particular, with incandescent illumination and without angle diversity, the data rate had to be decreased down to 2 and 1 Mb/s in 25.9 and 7.7 percent of the room, area, respectively, whereas with maximal ratio combining a decrease to 2 Mb/s was only needed in 0.7 percent of the room area.

Angle diversity and rate-adaptive transmission for indoor wireless optical communications

The main degrading factor in indoor wireless optical communication systems for bit rates up to several megabits per second is the shot noise induced by ambient light (sunlight and artificial light produced by incandescent and fluorescent lamps). Due to the directional nature of both signal and ambient light noise, the spatial distribution of the signal-to-noise ratio in indoor environments can show large variations. This article compares techniques that are able to mitigate the effect of such SNR variations: rate-adaptive transmission and angle diversity. In the first technique, the effective data rate is adjusted to the local SNR conditions by introducing different levels of redundancy. The second technique explicitly explores the directionality of the SNR by combining signals collected from different observation angles. We address the performance of rate-adaptive transmission and angle diversity techniques, and compare them based on experimental results obtained in a typical indoor environment.

Optimization of a pyramidal fly‐eye diversity receiver for optical wireless systems under the influence of multipath dispersion and background noise

AbstractA performance analysis of an indoor optical wireless communication system has been carried out for both a conventional hybrid system and a pyramidal fly‐eye diversity receiver with different fields of view. Novel results are presented for a hybrid system that employs a diversity technique, based on a triangular pyramidal receiver under various FOVs and in the presence of directive noise sources and multipath dispersion. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 401–406, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10776

Integrated system of white LED visible-light communication and power-line communication

White LED offers advantageous properties such as high brightness, reliability, lower power consumption and long lifetime. Indoor optical wireless communication systems employing white LED lighting have been proposed. This system will enable high quality of service by the high radiation power from this lighting equipment. And, this system does not cause or suffer from radio or electromagnetic interference. But, it is difficult for existing offices and households to install the communication cable to the ceiling. In this paper, an easy wiring system for optical communication using the existing power-line is proposed. This system is emitted as visible-light from LED lighting according to the transmitted signal waveform without demodulating the signal from the power-line. This system is expected to be applicable from the existing illuminant easily like exchanging electric bulbs. This integrated system will surely have a big impact as a new signal transmission system and its economical effect will be great. The basic performance of this system is analyzed. The actual system is built and its feasibility is shown through experiments.

Angle Diversity to Combat the Ambient Noise in Indoor Optical Wireless Communication Systems

We propose and study the use of angle diversityto combat the ambient noise in indoor optical wirelesscommunication systems. Models for the radiation patternof spot lamps and for the spatial distribution of the ambient light based on an isotropic anda directional noise component are derived. Performanceevaluation of receivers using angle diversity is carriedout and significant optical power gains are demonstrated. The optical gains are seen toincrease with the relative weight of the directionalnoise within the cell, with the sharpness of thedirectional noise source beam width, and in environments where there are noise sources positionedoutside the cell. Also, the signal-to-noise ratio (SNR)of a sectored receiver is seen to be much less sensitiveto the position and beam width of the noise sources than the SNR of a nonsectored receiver,allowing for more universal transceiverdesigns.

Indoor infrared wireless communications using spot diffusing and fly-eye receivers

A new configuration is proposed for indoor optical wireless communication systems. The main features are the use of spot diffusing, multiple lines of sight and fly-eye receivers. Design issues such as the power budget, ambient-light interference and farsighted-eye designs for the receivers are discussed using simple models. An experimental set-up demonstrating the feasibility of the spot-diffusing concept is also described.