The Internet of Things (IoT) is a transformative technology marking the beginning of a new era where physical and digital worlds are integrated by connecting a plethora of uniquely identifiable smart objects. Although the Internet of terrestrial things (IoTT) has been at the center of our IoT perception, it has been recently extended to different environments, such as the Internet of underWater things (IoWT), the Internet of Biomedical things (IoBT), and Internet of underGround things (IoGT). Even though radio frequency (RF) based wireless networks are regarded as the default means of connectivity, they are not always the best option due to the limited spectrum, interference limitations caused by the ever-increasing number of devices, and severe propagation loss in transmission mediums other than air. As a remedy, optical wireless communication (OWC) technologies can complement, replace, or co-exist with audio and radio wave-based wireless systems to improve overall network performance. To this aim, this paper reveals the full potential of OWC-based IoT networks by providing a top-down survey of four main IoT domains: IoTT, IoWT, IoBT, and IoGT. Each domain is covered by a dedicated and self-contained section that starts with a comparative analysis, explains how OWC can be hybridized with existing wireless technologies, points out potential OWC applications fitting best the related IoT domain, and discusses open communication and networking research problems. More importantly, instead of presenting a visionary OWC-IoT framework, the survey discloses that OWC-IoT has become a reality by emphasizing ongoing proof-of-concept prototyping efforts and available commercial off-the-shelf (COTS) OWC-IoT products.
We demonstrate a fifth generation (5G) new radio (NR) signal transmitted by an analog optical and seamless antenna wireless connection at the frequency band of 60 GHz to exploit a high-frequency unlicensed frequency range. An optical frequency doubling technique, using two Mach-Zehnder modulators operating in a carrier suppressed and linear regime, respectively , was adopted to obtain the desired millimeter wave frequency at the photodetector's output. The proposed system was tested with the 5G NR signals with a maximum bandwidth of 200 MHz and 64 quadrature amplitude modulation format. It was shown that the signal transmitted through the optical fiber and free space optical link with 1 m long seamless antenna transmission at 62 GHz was capable of meeting the signal quality requirements in terms of error vector magnitude. Moreover, the system phase noise performance showed an almost negligible difference between the various system configurations.
Microwave photonics presents an advanced technology of optical devices and techniques for signal processing and transport of radio frequency (RF) signals for 5G and beyond networks. Optical fibers and optical wireless communication (OWC) links, used in microwave photonic systems as transmission mediums, have already shown their vast possibilities and significant advantages, especially at frequencies over 6 GHz compared with coaxial cables. The PhD research will be focused on the optical generation of the millimeter-wave signals (60 GHz and higher) for 5G and beyond networks and the signal transmission over joint fiber and OWC networks. The research will include data signal generation and processing (advanced modulation formats, signal evaluation, noise optimization), optical network simulation, the design and development of specialized components, and finally, the optimization of the whole microwave photonics system. The successful candidate will join our research group and will work on a fully international level in cooperation with one of the world-leading institutes in microwave photonics, OWC, and optical fibers, for example - Northumbria University (UK), Valencia University (ESP), University of Southampton (UK), etc.
In this Letter, we propose and demonstrate a novel wireless communications link using an illuminating optical fiber as a transmitter (Tx) in optical camera communications. We demonstrate an indoor proof-of-concept system using an illuminating plastic optical fiber (POF) coupled with a light emitting diode and a commercial camera as the Tx and the receiver, respectively. For the first time, to the best of our knowledge, we experimentally demonstrate flicker-free wireless transmission within the off-axis camera rotation angle range of 0-45˚ and the modulation frequencies of 300 and 500 Hz. We also show that, a reception success rate of 100 % is achieved for the camera exposure and gain of 200 µs and 25 dB, respectively.
Intelligent transport systems (ITS) rely upon the connectivity, cooperation and automation of vehicles aimed at the improvement of safety and efficiency of the transport system. Connectivity, which is a key component for the practical implementation of vehicular light communications (VeLC) systems in ITS, must be carefully studied prior to design and implementation. In this paper, we carry out a performance evaluation study on the use of different vehicle taillights (TLs) as the transmitters in a VeLC system. We show that, the transmission coverage field of view and the link span depend on TLs illumination patterns and the transmit power levels, respectively, which fail to meet the typical communication distances in vehicular environments. This paper proposes an infrared-based VeLC system to meet the transmission range in daytimes under Sunlight noise. We show that, at the forward error correction bit error rate limit of 3.8 10^-3, the communication distances of the proposed link are 63, 72, and > 89 m compared with 4.5, 5.4 and 6.3 m for BMWs vehicle TL at data rates of 10, 6, and 2 Mbps, respectively.
This paper experimentally investigates, for the first time, a new wavelength-division multiplexing-based visible light communications link based on a defocused non-imaging multiple-input multiple-output (MIMO), which removes the need for tuned optical bandpass filters paired with each receiver. The proposed system is based on using the natural diversity of the individual light emitting diodes (LEDs) within a single light source to generate an H-matrix, which is independent of spatial diversity. We show that, by transmitting K-independent sets of non-return to zero on-and-off keying signals on separate wavelengths, the received superposed symbols can be demultiplexed. The non-imaging MIMO diversity is achieved by considering the power-current characteristics of the light emitting diode, the responsivity of the photodetector array, and the defocused beam spot. The system is empirically verified for K = 3 using red, green, and blue LEDs with Q-factors of 7.66, 7.69, and 4.75 dB, respectively.
Optical wireless communications in outdoor scenarios are challenged by uncontrollable atmospheric conditions that impair the channel quality. In this paper, different optical camera communications (OCC) equipment are experimentally studied in the laboratory and the field, and a sub-pixel architecture is raised as a potential solution for outdoor wireless sensor networks (WSN) applications, considering its achievable data throughput, the spatial division of sources, and the ability of cameras to overcome the attenuation caused by different atmospheric conditions such as rain, turbulence and the presence of aerosols. Sub-pixel OCC shows particularly adequate capabilities for some of the WSN applications presented, also in terms of cost-effectiveness and scalability. The novel topology of sub-pixel projection of multiple transmitters over the receiver using small optical devices is presented as a solution using OCC that re-uses camera equipment for communication purposes on top of video-monitoring.