BER analysis of a full-duplex relay-assisted BPSK-SIM based VLC system for indoor applications.

This paper contemplates a relay-assisted visible light communication (VLC) system, where the light source (table lamp) acts as a relay node and cooperates with the main light source. Following the IEEE 802.15.7r1 VLC reference channel model, we assume that there are two different light sources present in an office room. The first one is the source terminal present on the ceiling and another one is the desk lamp that serves as the relay station, which works in a full-duplex method. Because of the loop interference channel, we model the VLC relay terminal using ray tracing simulations. We have analyzed the bit error rate (BER) performance of the relay-assisted VLC system using a binary phase shift keying-subcarrier intensity modulation (BPSK-SIM) technique. The proposed method outperforms existing phase shift keying (PSK) and square M-quadrature amplitude modulation (M-QAM) techniques. The proposed VLC system using the BPSK-SIM technique achieves a BER performance of 10-12 for an SNR of 20 dB. The results of the proposed full-duplex and half-duplex relayed VLC systems are evaluated using equal power allocation (EPA) and optimum power allocation (OPA) techniques over three different modulation schemes, which are 2-PSK, square M-QAM, and BPSK-SIM.

Reconfigurable intelligent surface-assisted free-space optical communication link for the Satellite-Internet of Things.

The Satellite-Internet of Things (S-IoT) is envisaged as one of the promising technological enhancements in this decade due to its outright connectivity, especially in the areas of terrestrial communication and weather forecasting. Invariably, turbulent atmospheric conditions and varied terrain profiles are hindrances for satellite based free-space optical (FSO) communication, and immensely disrupt signal levels. Recently, a new technological invention called a reconfigurable intelligent surface (RIS) empowered radio transmission environments for next generation wireless/optical technology has emerged. Elements of RIS are used to intelligently tune the striking beam towards desired locations. In this paper, we propose an RIS based FSO link to manueuver S-IoT. The challenges of pointing errors and turbulent atmospheric connectivity from a satellite to ground station and vice versa with the cooperation of RIS have been derived and substantiated with closed form solutions. The proposed system's performance has been analyzed using packet and bit error rates, and outage probability over atmospheric turbulence, pointing errors, and signal blockage scenarios. Results are evaluated for different RIS elements as a function of average signal to noise ratio. The proposed system is extremely productive, since this scheme has the capability to provide dependable connectivity in rural, urban, and suburban environments where reliable connectivity is difficult in spite of traditional infrastructures.

Performance analysis of a RIS-assisted RoFSO communication system over Malaga distribution for smart city applications.

Radio over free space optics (RoFSO) is one of the potential technologies that can satisfy the requirements of 5G services in a smart city. However, as RoFSO is line-of-sight (LOS) communication, one of its limitations is the occurrence of a skip zone in the targeted areas. In this work, a reconfigurable intelligent surface (RIS) is proposed as the solution to overcome this connection difficulty, which prevents signal blocking by generating LOS connections. These RIS modules extend the communication channel coverage, making it more intelligent and controllable. The performance analysis based on outage probability, ergodic channel capacity, and bit error rate has been performed using heterodyne detection. Malaga distribution has been used to model atmospheric turbulence. The exact closed-form expressions of the probability density function and cumulative distribution function of the end-to-end signal-to-noise ratio are derived. Exploiting these derived statistics, system performance is investigated through the ergodic channel capacity, outage probability, and average bit error rate for M-ary quadrature amplitude modulation and two binary modulation schemes: non-coherent binary frequency-shift keying and coherent binary phase-shift keying. Numerical results are compared among different turbulence conditions, link lengths, and scattering errors. The results show that the proposed RIS-assisted RoFSO technology has the potential to be effective for 5G smart city applications.

Reconfigurable intelligent surface-assisted free-space optical communication system under the influence of signal blockage for smart-city applications.

Atmospheric turbulence and pointing errors represent substantial hurdles to free-space optical communications (FSOs), impeding their practical design. The reconfigurable intelligent surface (RIS) is an emerging technology that enables reflective radio transmission conditions for next-generation 5G/6G wireless frameworks by intelligently adjusting the beam in the desired direction using low-cost inactive reflecting elements. In this paper, we proposed an RIS-assisted FSO system for mitigating the effects of atmospheric turbulence, pointing errors, and communication system signal blockage. The probability density function and cumulative distribution functions of an FSO system composed of N-RIS elements are evaluated in a free-space environment that contains obstructions. We derived closed-form expressions for the proposed system's bit error rate (BER), outage probability, and channel capacity. The proposed system's performance is analyzed in terms of BER, outage probability, and channel capacity under various weather conditions, pointing errors, and signal blockage. The results are plotted as a function of number of RIS elements and average signal-to-noise ratio. The proposed system will be beneficial in smart-city applications since it will provide reliable connectivity in urban environments with a high population density and high-rise buildings.

Underwater wireless optical communications based reconfigurable UOWSN for monitoring and discovering continental margin ore deposits.

Changes in the environment, such as landslides, tsunamis, rising or falling sea levels in coastal oceans, and neighboring land surfaces, significantly impact the structure of the ocean and human life. These natural climate-change processes have unanticipated and deadly consequences for coastal areas. The continental margin part of the ocean has recently attracted the most attention because of the mineral sources and human activities such as exploration, navigation, recreation, and fishing. The continental margin stretches from the coastal mountains and plains to continental shelf, slope, and rise, where terrestrial and maritime means meet. In this paper, we propose a reconfigurable underwater optical wireless sensor network (UOWSN) based on underwater wireless optical communication (UWOC) to monitor and discover continental margin ore deposits. In this proposed system, a transceiver on the underwater wireless autonomous vehicle moving around the different regions of the continental margin collects information and transmits it to the seashore control station once it reaches the ocean surface. We investigated the outage probability and average bit error rate of the proposed system at the continental margin and used coding techniques to mitigate the effects of high turbulence in the continental shelf region.

Wireless-optical-communication-based cooperative IoT and IoUT system for ocean monitoring applications.

This paper proposes the idea of a new cooperative communication between the Internet of Things (IoT) and the Internet of Underwater Things (IoUT) using wireless optical connectivity for ocean monitoring applications. We considered IoT communication using a hybrid radio frequency (RF)/free space optical (FSO) link and IoUT using a underwater wireless optical communication (UWOC) link. Channel models for RF, FSO, and UWOC links are considered to be Rayleigh, Malaga with pointing errors, and hyperbolic tangent log-normal distributions, respectively. The outage probability and the bit error rate (BER) expressions for the proposed system are derived over the combined channel model, which includes the effects of attenuation, turbulence, and pointing errors. The BER results are plotted for various binary digital modulation schemes such as on-off keying, binary phase-shift keying, binary frequency-shift keying, and differential phase-shift keying over UWOC, hybrid RF/FSO and RF-UWOC, FSO-UWOC with end-to-end systems. BER results are extended for various turbulence regions and pointing errors of the FSO link. Monte Carlo simulation results authenticate the correctness of the results.