The IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences announces a forthcoming Special Section on Networked Control Systems: Theories & Applications to be published in May 2013. In many applications, such as factory automation and smart grid, Networked Control System (NCS) plays an important role, in which the state of environment is monitored and the target is controlled both via the network. Based on conventional control and communication theories, a new unified theory on NCS is needed to realize reliable, robust, delay tolerant, and scalable communication networks for NCS. Under these considerations, Special Section on Networked Control Systems: Theories & Applications is planned to accelerate R&D activities in this area by collecting and publishing the results on up-to-date researches and experimental studies related to NCS.

IEICE transactions on fundamentals of electronics, communications and computer sciences

New high-data-rate multimedia services and applications are evolving continuously and exponentially increasing the demand for wireless capacity of fifth-generation (5G) and beyond. The existing radio frequency (RF) communication spectrum is insufficient to meet the demands of future high-data-rate 5G services. Optical wireless communication (OWC), which uses an ultra-wide range of unregulated spectrum, has emerged as a promising solution to overcome the RF spectrum crisis. It has attracted growing research interest worldwide in the last decade for indoor and outdoor applications. OWC offloads huge data traffic applications from RF networks. A 100 Gb/s data rate has already been demonstrated through OWC. It offers services indoors as well as outdoors, and communication distances range from several nm to more than 10 000 km. This paper provides a technology overview and a review on optical wireless technologies, such as visible light communication, light fidelity, optical camera communication, free space optical communication, and light detection and ranging. We survey the key technologies for understanding OWC and present state-of-the-art criteria in aspects, such as classification, spectrum use, architecture, and applications. The key contribution of this paper is to clarify the differences among different promising optical wireless technologies and between these technologies and their corresponding similar existing RF technologies.

A Comparative Survey of Optical Wireless Technologies: Architectures and Applications

Inter-symbol interference (ISI) is one of the key problems that seriously limit transmission data rate in high-speed VLC systems. To eliminate ISI and further improve the system performance, series of equalization schemes have been widely investigated. As an adaptive algorithm commonly used in wireless communication, RLS is also suitable for visible light communication due to its quick convergence and better performance. In this paper, for the first time we experimentally demonstrate a high-speed RGB-LED based WDM VLC system employing carrier-less amplitude and phase (CAP) modulation and recursive least square (RLS) based adaptive equalization. An aggregate data rate of 4.5Gb/s is successfully achieved over 1.5-m indoor free space transmission with the bit error rate (BER) below the 7% forward error correction (FEC) limit of 3.8x10(-3). To the best of our knowledge, this is the highest data rate ever achieved in RGB-LED based VLC systems.

4.5-Gb/s RGB-LED based WDM visible light communication system employing CAP modulation and RLS based adaptive equalization.

Visible light communication VLC is a newly emerging technology, which integrates communications and lighting purposes, and has become a very active research topic in the areas of wireless communications. It is expected to become an important part of the next generation wireless communications because of its unique features in using unlicensed spectrum, support of high data rate, and its resistance to electromagnetic interferences. In this survey paper, we begin with a review on the basis of photometry, which is used to establish channel models of VLC systems. Then, we will continue to address various issues on the fundamental characteristic features of VLC systems, the impact of indoor environments on system performance, and the analysis and discussions of five different types of typical VLC channel models and other related parameters in VLC channel models. Finally, in terms of the future works, we will show the possible follow-up research focuses and directions as an effort to identify some new research topics on VLCs. Copyright © 2016 John Wiley & Sons, Ltd.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/wcm.2665

Channel modeling for visible light communications-a survey

In this demonstration, we first demonstrate a real-time phosphor-LED visible light communication (VLC) system with 37 Mbit/s total throughput under a 1.5 m free space transmission length. The transmitter and receiver modules are compact size. Utilizing our proposed pre-equalization technology, the ~1 MHz bandwidth of phosphor LED could be extended to ~12 MHz without using blue filter. Thus, the increase in bandwidth would enhance the traffic data rate for VLC transmission. The maximum bit-rate achieved by the VLC system is 37 Mbit/s, and a video transmission at 28.419 Mbit/s is demonstrated using the proposed VLC system. In addition, the relationships of received power and signal performance are discussed and analyzed.

https://ir.nctu.edu.tw:443/bitstream/11536/23273/1/000327007800078.pdf

Real-time white-light phosphor-LED visible light communication (VLC) with compact size.

Visible light communication (VLC) applied in an intelligent transportation system (ITS) has attracted growing attentions, but it also faces challenges, for example deep path loss and optical multi-path dispersion. In this work, we modelled an actual outdoor optical channel as a Rician channel and further proposed space-time block coding (STBC) orthogonal frequency-division multiplexing (OFDM) technology to reduce the influence of severe optical multi-path dispersion associated with such a mock channel for achieving the effective BER of 10−6 even at a low signal-to-noise ratio (SNR). In this case, the optical signals transmission distance can be extended as long as possible. Through the simulation results of STBC-OFDM and single-input-single-output (SISO) counterparts in bit error rate (BER) performance comparison, we can distinctly observe that the VLC–ITS system using STBC-OFDM technique can obtain a strongly improved BER performance due to multi-path dispersion alleviation.

Performance analysis of visible light communication using the STBC-OFDM technique for intelligent transportation systems

In an indoor visible light communication (VLC) system, diffuse channels are very easily caused by numerous reflections of the optical signals from the obstacle surface, resulting in optical multipath dispersion which can further reduce the bit error rate (BER) performance of wireless communication system. In this paper, we investigated non-directed LOS links and optimized the design of this short-range communication model using white light-emitting diodes illumination. In our VLC system, we proposed spreading scheme to combat the severe effects of multipath dispersion. We compared the BER performances of four spread codes on the diffuse channel: pseudo random code, Walsh code, m-sequence code, and gold code. Through the analysis and comparison of simulation results, we obtained the optimum spread code, namely Walsh code, which can alleviate the serious effects of multipath dispersion.

Optimum Spread Code Applied in Indoor Visible Light Data Transmission for Optical Multipath Dispersion Reduction

Multipath dispersion results from optical signals passing through more than one path. In this paper, we investigate a non-directed line of sight (LOS) model using white light emitting diode illumination. Typically in such a link, the optical signals are modeled as a reflection component and a directed LOS component over optical wireless (OW) channels. However, inter-symbol interference (ISI) induced by multipath dispersion critically influences the performance of OW communications. In this paper, we propose the adaptive minimum mean squared error (MMSE) equalizer scheme to suppress the multipath ISI, since this scheme can minimize the mean square error (MSE) between the desired equalizer output and the actual equalizer output. We compared the following two algorithms: Least mean square and recursive least square. Our computer simulations demonstrated that visible light communication using an adaptive MMSE equalizer can alleviate the serious effects of optical multipath dispersion.

Adaptive MMSE Equalizer for Optical Multipath Dispersion in Indoor Visible Light Communication

This paper studies the performance degradation caused by optical Doppler shift in light-emitting diode-based visible light communication systems, which integrate orthogonal frequency division multiplexing (OFDM). Through theoretical analysis and computer simulations, we can observe that frequency offset plays a significant role in the OFDM performance deterioration due to inter-carrier interference (ICI) and common phase error (CPE). Therefore, a scheme to correct the frequency offset by using wavelength division-adaptive interference cancellation (WD-AIC) was proposed. The main approach is to assign an estimated sub-carrier after every two adjacent sub-carriers to reduce the negative effects of both ICI and CPE. Finally, the simulation results declare that our proposed WD-AIC is indeed effective against the high degree of frequency offset.

Wavelength Division-adaptive Interference Cancellation Applied in OFDM Visible Light Communication Systems

In an outdoor environment light emitting diodes-identification (LED-ID) systems, the provision of real-time location information to mobile users has become an active area of research. Visible light communication (VLC) in a LED-ID system offers the promise of a safe, efficient, reliable, and environmentally friendly ID technique. However, there are still several problems associated with such a combination, especially optical multipath dispersion, which has a severe impact on the communication performance. In this paper, we simulated a realistic optical channel in outdoor environment and modeled it as a Rician channel. Based on such a channel model, we further proposed an effective scheme of STBC-OFDM to solve the severe optical multipath dispersion problem and to obtain a target BER of 10−6 at a low SNR, where the received optical signals suffer from deep optical path loss over a long propagation distance. By comparing the BER performances of STBC-OFDM and SISO, our simulation results demonstrated that the STBC-OFDM technique used in a LED-ID system can alleviate the serious effects of multipath dispersion and can tolerate a low SNR for a target BER of 10−6.

Outdoor environment LED-identification systems integrate STBC-OFDM

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