An experimental technique is described for observing the effects of switching transients in digital MOS circuits that perturb analog circuits integrated on the same die by means of coupling through the substrate Various approaches to reducing substrate crosstalk (the use of physical separation of analog and digital circuits, guard rings, and a low-inductance substrate bias) are evaluated experimentally for a CMOS technology with a substrate comprising an epitaxial layer grown on a heavily doped bulk wafer Observations indicate that reducing the inductance in the substrate bias is the most effective Device simulations are used to show how crosstalk propagates via the heavily doped bulk and to predict the nature of substrate crosstalk in CMOS technologies integrated in uniform, lightly doped bulk substrates, showing that in such cases the substrate noise is highly dependent on layout geometry A method of including substrate effects in SPICE simulations for circuits fabricated on epitaxial, heavily doped substrates is developed >

Experimental Results and Modeling Techniques for Substrate Noise in Mixed-Signal Integrated Circuits

White light generation by mixing red, green, and blue laser diodes (RGB LDs) was demonstrated with Commission International de l’Eclairage coordinates of (0.2928, 0.2981), a correlated color temperature of 8382 K, and a color rendering index of 54.4 to provide a maximal illuminance of 7540 lux. All the white lights generated using RGB LDs were set within the risk group-1 criterion to avoid the blue-light hazard to human eyes. In addition, the RGB-LD mixed white light was diffused using a frosted glass to avoid optical aberration and to improve the performance of the lighting source. In addition, visible light communication (VLC) by using RGB-LD mixed white-light carriers and a point-to-point scheme over 1 m was performed in the directly modulated 16-QAM OFDM data format. In back-to-back transmission, the maximal allowable data rate at 10.8, 10.4, and 8 Gbps was determined for R, G, and B LDs, respectively. Moreover, the RGB-LD mixed white light-based indoor wavelength-division multiplexing (WDM)-VLC system yielded a total allowable transmission data rate of 8.8 Gbps over 0.5 m in free space. Such a high-speed RGB-LD mixed WDM-VLC system without any channel interference can be used to simultaneously provide data transmission and white lighting in an indoor environment.

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Tricolor R/G/B Laser Diode Based Eye-Safe White Lighting Communication Beyond 8 Gbit/s.

Optical wireless communication (OWC) is an excellent complementary solution to its radio frequency (RF) counterpart. OWC technologies have been demonstrated to be able to support high traffic generated by massive connectivity of the Internet of Things (IoT) and upcoming 5th generation (5G) wireless communication systems. As the characteristics of OWC and RF are complementary, a combined application is regarded as a promising approach to support 5G and beyond communication systems. Hybrid RF/optical and optical/optical wireless systems offer an excellent solution for recovering the limitations of individual systems as well as for providing positive features of each of the technologies. An RF/optical wireless hybrid system consists both RF and optical-based wireless technologies, whereas an optical/optical wireless hybrid system consists two or more types of OWC technologies. The co-deployment of wireless systems can improve system performance in terms of throughput, reliability, and energy efficiency of individual networks. This study surveys the state of the art and key research directions regarding optical wireless hybrid networks, being the first extensive survey dedicated to this topic. We provide a technology overview of existing literature on optical wireless hybrid networks, such as RF/optical and optical/optical systems. We consider the RF-based macrocell, small cell, wireless fidelity, and Bluetooth, as well as optical-based visible light communication, light fidelity, optical camera communication, and free-space optical communication technologies for different combinations of hybrid systems. Moreover, we consider underwater acoustic communication for hybrid acoustic/optical systems. The opportunities brought by hybrid systems are presented in detail. We outline important challenges that need to be addressed for successful deployment of optical wireless hybrid network systems for 5G and IoT paradigms.

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Optical Wireless Hybrid Networks: Trends, Opportunities, Challenges, and Research Directions

The upcoming fifth- and sixth-generation (5G and 6G, respectively) communication systems are expected to deal with enormous advances compared to the existing fourth-generation communication system. The few important and common issues related to the service quality of 5G and 6G communication systems are high capacity, massive connectivity, low latency, high security, low-energy consumption, high quality of experience, and reliable connectivity. Of course, 6G communication will provide several-fold improved performances compared to the 5G communication regarding these issues. The Internet of Things (IoT) based on the tactile internet will also be an essential part of 5G-and-beyond (5GB) (e.g., 5G and 6G) communication systems. Accordingly, 5GB wireless networks will face numerous challenges in supporting the extensive verities of heterogeneous traffic and in satisfying the mentioned service-quality-related parameters. Optical wireless communication (OWC), along with many other wireless technologies, is a promising candidate for serving the demands of 5GB communication systems. This review paper clearly presents how OWC technologies, such as visible light communication, light fidelity, optical camera communication, and free space optics communication, will be an effective solution for successful deployment of 5G/6G and IoT systems.

The Role of Optical Wireless Communication Technologies in 5G/6G and IoT Solutions: Prospects, Directions, and Challenges

In this investigation, we experimentally demonstrated a high-speed Gbps long-distance real-time visible light communication system based on non-return-to-zero on-off keying modulation by using a high-bandwidth Gallium nitride-based micro-LED with a modulation bandwidth of ∼230 MHz and a size of 40 μ m $ \times $ 40 μ m. The maximum real-time data rate obtained is up to 1.3 Gbps at a 3 m free-space transmission distance with a bit-error rate (BER) of 3.4 $ \times $ 10 –3 and 1 Gbps at a 10 m distance with a BER of 3.2 $ \times $ 10–3, both of which are underneath the forward error correction threshold of 3.8 $ \times $ 10–3 required for free-error operation. In addition, when the transmission distance is increased to 16 m in free space through reflecting the emission light beam by blue reflectors mounted on the wall, a data rate of 0.87 Gbps with a BER of 3.5 $ \times $ 10–3 is achieved successfully.

Gbps Long-Distance Real-Time Visible Light Communications Using a High-Bandwidth GaN-Based Micro-LED

Red, green, and blue (RGB) light-emitting diodes (LEDs) are widely used in everyday illumination, particularly where color-changing lighting is required. On the other hand, digital cameras with color filter arrays over image sensors have been also extensively integrated in smart devices. Therefore, optical camera communications (OCC) using RGB LEDs and color cameras is a promising candidate for cost-effective parallel visible light communications (VLC). In this paper, a single RGB LED-based OCC system utilizing a combination of undersampled phase-shift on–off keying (UPSOOK), wavelength-division multiplexing (WDM), and multiple-input–multiple-output (MIMO) techniques is designed, which offers higher space efficiency (3 bits/Hz/LED), long-distance, and nonflickering VLC data transmission. A proof-of-concept test bed is developed to assess the bit-error-rate performance of the proposed OCC system. The experimental results show that the proposed system using a single commercially available RGB LED and a standard 50-frame/s camera is able to achieve a data rate of 150 bits/s over a range of up to 60 m.

https://northumbria-test.eprints-hosting.org/id/document/263698

Experimental Demonstration of RGB LED-Based Optical Camera Communications

A versatile outdoor and indoor position detection mobile prototype has been successfully constructed and tested. The receiver consists of a GPS module, a GSM shield, a visible-light data receiver, and two ultrasonic sensors, all controlled by an Arduino Mega and an Arduino Uno microcontroller. Each ultrasonic sensor detects distance in the X and Y axis respectively. The transmitter system consists of four LED shields each attached to an Arduino Uno which is programmed to transmit the global position relevant to the indoor position of the LED lamp. When a person is outdoors, the GPS module receives global position from the satellite. When a person goes indoors, his or her global position will be given by the LEDs and ultrasound sensors. The location data can be transmitted via GSM to a monitoring system or to an individual smartphone. This system is extremely useful in elderly care service. It ensures specific accuracy in locating senior citizens during cases of emergency.

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An Arduino-based indoor positioning system (IPS) using visible light communication and ultrasound

Today, the Bluetooth transceiver is integrated into almost all modern mobile devices. Although it can transmit audio signals, it is unable to transmit video signals. But VLC can. With advances in visible light communication (VLC) research, it is likely that one day mobile equipments would include the visible-light transceiver for wireless optical access to the Internet and visual and audio information. An audio/video (A/V) transceiver and a data transceiver that can connect to Android platforms are presented here. Real-time video and pulse-position modulated stereo audio signals are transmitted by a white LED over free space. For file exchanges, a USB Android host IC FT311D is used to bridge smartphones to any external VLC UART peripheral.

A fully integrated audio, video, and data VLC transceiver system for smartphones and tablets

In this work, we propose two decision techniques that interchange between MIMO and diversity schemes for improving shadowing and alignment problems. In a visible-light communication (VLC) system, the transmission nature can be of two types: (1) all LEDs transmit the same signal stream simultaneously; or (2) each LED transmits different parts of a signal stream independently. The MIMO-diversity technique detects and computes the transmitted signal power during reception and conditionally informs the transmitter to switch between Type (1) and Type (2) transmission. Two experimental models have been tested to show the feasibility of such a technique. In the first model, we constructed a full transceiver and uses a switch IC to switch between MIMO and diversity. The second model uses a microcontroller and software decision to switch between two COM ports, each of them dedicated to MIMO and diversity output respectively. Results suggest that shadowing and alignment problems commonly encountered in visible-light communication systems can be readily solved using these methods. A focusing equation has also been formulated to predict signal intensity more accurately. The focusing gap between the concentrator and the photodiode is taken into consideration during channel computation.

MIMO-diversity switching techniques for digital transmission in visible light communication

Based on visible light communication (VLC) technology, three designs of audio transmitters and receivers have been built and tested successfully. The simplicity of these circuits and the very few components that are used enable them to be mass manufactured for use on passenger aircrafts. The receiver circuits can be implemented on headphones. The transmitter circuits can be integrated with LED reading lights above passengers' seats. The circuits presented here have different performance characteristics and sound qualities, depending on the type of audio ICs that are used.

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Lih Chieh Png

Papers

Experimental Demonstration of RGB LED-Based Optical Camera Communications

An Arduino-based indoor positioning system (IPS) using visible light communication and ultrasound

A fully integrated audio, video, and data VLC transceiver system for smartphones and tablets

MIMO-diversity switching techniques for digital transmission in visible light communication

Designs of VLC transceiver circuits for reading light transmission of high-quality audio signals on commercial airliners