White LED offers advantageous properties such as high brightness, reliability, lower power consumption and long lifetime. White LEDs are expected to serve in the next generation of lamps. An indoor visible-light communication system utilizing white LED lights has been proposed from our laboratory. In the proposed system, these devices are used not only for illuminating rooms but also for an optical wireless communication system. Generally, plural lights are installed in our room. So, their optical path difference must be considered. In this paper, we discuss about the influence of interference and reflection. Based on numerical analyses, we show that the system is expected to be the indoor communication of the next generation.

Fundamental analysis for visible-light communication system using LED lights

Optical wireless communication (OWC) refers to transmission in unguided propagation media through the use of optical carriers, i.e., visible, infrared (IR), and ultraviolet (UV) bands. In this survey, we focus on outdoor terrestrial OWC links which operate in near IR band. These are widely referred to as free space optical (FSO) communication in the literature. FSO systems are used for high rate communication between two fixed points over distances up to several kilometers. In comparison to radio-frequency (RF) counterparts, FSO links have a very high optical bandwidth available, allowing much higher data rates. They are appealing for a wide range of applications such as metropolitan area network (MAN) extension, local area network (LAN)-to-LAN connectivity, fiber back-up, backhaul for wireless cellular networks, disaster recovery, high definition TV and medical image/video transmission, wireless video surveillance/monitoring, and quantum key distribution among others. Despite the major advantages of FSO technology and variety of its application areas, its widespread use has been hampered by its rather disappointing link reliability particularly in long ranges due to atmospheric turbulence-induced fading and sensitivity to weather conditions. In the last five years or so, there has been a surge of interest in FSO research to address these major technical challenges. Several innovative physical layer concepts, originally introduced in the context of RF systems, such as multiple-input multiple-output communication, cooperative diversity, and adaptive transmission have been recently explored for the design of next generation FSO systems. In this paper, we present an up-to-date survey on FSO communication systems. The first part describes FSO channel models and transmitter/receiver structures. In the second part, we provide details on information theoretical limits of FSO channels and algorithmic-level system design research activities to approach these limits. Specific topics include advances in modulation, channel coding, spatial/cooperative diversity techniques, adaptive transmission, and hybrid RF/FSO systems.

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Survey on Free Space Optical Communication: A Communication Theory Perspective

The solid-state lighting is revolutionizing the indoor illumination. Current incandescent and fluorescent lamps are being replaced by the LEDs at a rapid pace. Apart from extremely high energy efficiency, the LEDs have other advantages such as longer lifespan, lower heat generation, and improved color rendering without using harmful chemicals. One additional benefit of LEDs is that they are capable of switching to different light intensity at a very fast rate. This functionality has given rise to a novel communication technology (known as visible light communication—VLC) where LED luminaires can be used for high speed data transfer. This survey provides a technology overview and review of existing literature of visible light communication and sensing. This paper provides a detailed survey of 1) visible light communication system and characteristics of its various components such as transmitter and receiver; 2) physical layer properties of visible light communication channel, modulation methods, and MIMO techniques; 3) medium access techniques; 4) system design and programmable platforms; and 5) visible light sensing and application such as indoor localization, gesture recognition, screen-camera communication, and vehicular networking. We also outline important challenges that need to be addressed in order to design high-speed mobile networks using visible light communication.

Visible Light Communication, Networking, and Sensing: A Survey, Potential and Challenges

Driven by the rapid escalation of the wireless capacity requirements imposed by advanced multimedia applications (e.g., ultrahigh-definition video, virtual reality, etc.), as well as the dramatically increasing demand for user access required for the Internet of Things (IoT), the fifth-generation (5G) networks face challenges in terms of supporting large-scale heterogeneous data traffic. Nonorthogonal multiple access (NOMA), which has been recently proposed for the third-generation partnership projects long-term evolution advanced (3GPP-LTE-A), constitutes a promising technology of addressing the aforementioned challenges in 5G networks by accommodating several users within the same orthogonal resource block. By doing so, significant bandwidth efficiency enhancement can be attained over conventional orthogonal multiple-access (OMA) techniques. This motivated numerous researchers to dedicate substantial research contributions to this field. In this context, we provide a comprehensive overview of the state of the art in power-domain multiplexing-aided NOMA, with a focus on the theoretical NOMA principles, multiple-antenna-aided NOMA design, on the interplay between NOMA and cooperative transmission, on the resource control of NOMA, on the coexistence of NOMA with other emerging potential 5G techniques and on the comparison with other NOMA variants. We highlight the main advantages of power-domain multiplexing NOMA compared to other existing NOMA techniques. We summarize the challenges of existing research contributions of NOMA and provide potential solutions. Finally, we offer some design guidelines for NOMA systems and identify promising research opportunities for the future.

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Nonorthogonal Multiple Access for 5G and Beyond

In this paper, the problem of designing linear precoders for fixed multiple-input-multiple-output (MIMO) receivers is considered. Two different design criteria are considered. In the first, the transmitted power is minimized subject to signal-to-interference-plus-noise-ratio (SINR) constraints. In the second, the worst case SINR is maximized subject to a power constraint. It is shown that both problems can be solved using standard conic optimization packages. In addition, conditions are developed for the optimal precoder for both of these problems, and two simple fixed-point iterations are proposed to find the solutions that satisfy these conditions. The relation to the well-known uplink-downlink duality in the context of joint transmit beamforming and power control is also explored. The proposed precoder design is general, and as a special case, it solves the transmit rank-one beamforming problem. Simulation results in a multiuser system show that the resulting precoders can significantly outperform existing linear precoders.

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Linear precoding via conic optimization for fixed MIMO receivers

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.

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

The illuminating end communication device is equipped with an illuminating light source An electric power fed to the light source is modulated with a modulating unit responding to transmission data, and the modulated light is sent out as illuminating light The illumination light is received by the light receiving unit of a terminal end communication device to maintain a downlink Light emitted from the light emitting unit of the terminal end communication device is received by the light receiving unit of the illuminating end communication device to keep an uplink Or, illuminating light is modulated on the basis of data when it is reflected, whereby data can be transmitted to the illuminating end communication device It is preferable that illuminating light is reflected by CCR A high-quality communication is realized using illuminating light of high power

Illuminative light communication device

The present invention has been developed considering the above-described problems and aims to provide various structures and applications for illuminative light communication. According to the first aspect of the prevent invention, a broadcast system includes an LED light source 115 for lighting, a power line 103 that supplies electric power to the LED light source 115, a data modulator 102 that modulates and multiplexes a plurality of pieces of data, superimposes the resulting signal on an electric power waveform, and then transmits the resulting superimposed signal waveform to the power line 103, and a filter 112 that selectively separates one or more of a plurality of pieces of modulated data on the power line so as to control light intensity or blinking of the LED light source. Data is transmitted through changes in light intensity or blinking of the LED light source.

Illumination light communication device

White LEDs offer advantageous properties such as high brightness, reliability, lower power consumption and long lifetime. The biggest potential application for white LEDs is general illumination and lighting. Indoor wireless optical communication systems employing white LED lighting have been proposed. This system is able to offer high QoS due to the high power from this lighting equipment. However, it is difficult for existing offices and households to install the communication cable to the ceiling. An easy wiring system for optical communication using existing power-lines 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 lighting easily like exchanging electric bulbs. This integrated system can have a big impact as a new signal transmission system and its economical effect can be great. The basic performance of this system is analyzed. The actual system is built and its feasibility is shown through experiments.

Masao Nakagawa

Papers

Fundamental analysis for visible-light communication system using LED lights

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

Illuminative light communication device

Illumination light communication device

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