Underwater wireless optical communications are a developing alternative to meet the increasing need for high-speed connections in oceans and seas. Optical wireless communications (OWCs) are more secure and less susceptible to eavesdropping compared to acoustic communications or radio frequency (RF) communications due to their narrow optical beam coverage and reliance on line-of-sight components. Nevertheless, the existence of a hostile eavesdropper can compromise the level of confidentiality achieved by OWC networks. This article provides a concise overview of the latest research conducted on physical layer security (PLS) in underwater optical wireless communication (UOWC). Furthermore, this work presents the relevant unresolved matters, approaches for enhancing secrecy performance, and potential areas for further research.
Underwater wireless optical communications are a developing alternative to meet the increasing need for high-speed connections in oceans and seas. Optical wireless communications (OWCs) are more secure and less susceptible to eavesdropping compared to acoustic communications or radio frequency (RF) communications due to their narrow optical beam coverage and reliance on line-of-sight components. Nevertheless, the existence of a hostile eavesdropper can compromise the level of confidentiality achieved by OWC networks. This article provides a concise overview of the latest research conducted on physical layer security (PLS) in underwater optical wireless communication (UOWC). Furthermore, this work presents the relevant unresolved matters, approaches for enhancing secrecy performance, and potential areas for further research.
As the existing radio-frequency (RF) networks cannot meet the ever-increasing data rate demand, the optical wireless communication (OWC), which uses a wide untapped unregulated spectrum, has been proposed as a promising technology to overcome the RF spectrum limitations. On the other hand, with the increasing demand for high data rate and the prevalence of the broadcast-nature networks, researchers have recently come up with new mechanisms to improve secure communication using physical layer techniques. Compared to RF networks, the OWC networks are more secure and less susceptible to the interception because of the small coverage provided by LEDs, and because they work properly only in the presence of the line-of-sight (LoS) components. However, the security in OWC networks is still an issue, especially in visible light communication (VLC) when the transmitted information can be accessed by multiple users as in public areas, meeting rooms, laboratories, and libraries. That means potential eavesdroppers may be existing to gather confidential messages. This paper reviews all the conducted work on physical layer security (PLS) in two types of OWC networks, which are the VLC and free space optical (FSO) networks. Furthermore, the paper proposes several open problems in these networks to optimize and enhance the security performance.
With the demand for economical and high-speed wireless services, Optical Wireless Communication (OWC) has attracted increasing attention in both research and the market. In the past decades, numerous optical-related techniques (e.g., LEDs, displays, cameras) and systems (e.g., VLC, LiFi, LiDAR) have been invented. OWC techniques, which are considered as a competitive mechanics in next-generation networks as an alternative to RF approaches, offer 10,000 times more bandwidth than conventional radio frequency (RF)-based wireless techniques (e.g., WiFi, LoRa, Bluetooth, LTE), as well as tremendous spatial reuse potential with even less interference. Because optical communications have a limited wavelength and travel in the line of sight (LoS) manner, the OWC is commonly thought as a secure wireless approach to confine light transmissions within physical bounds. However, in the real world, it is completely untrue. The privacy leakages and security risks broadly exist in the optical-related wireless applications including OWC networks. These threats and weaknesses have recently been the subject of several initial studies. However, they lack systematic analysis and are isolated. This survey first presents a general workflow of OWC systems, which consists of three stages: before signal emission (BSE), during signal propagation (DSP), and after signal receiving (ASV). For each stage, related risks are reviewed. Then, we summarize existing attacks in optical-related wireless applications and corresponding counter-attack solutions. Finally, we outline the future trends for improving OWC security.
The advantages of physical layer security (PLS) have led researchers to apply this in various communication scenarios, such as radio frequency (RF) communication, free space optical (FSO) communication, and underwater optical wireless communication (UOWC). This paper analyzes the PLS, specifically the effective secrecy throughput (EST) over the mixture exponential generalized gamma (mEGG) UOWC channel link in the presence of a passive eavesdropper. To achieve this goal, firstly the closed-form expression of the secure outage probability (SOP) of the system is derived, and using that SOP expression, the final EST expression is found considering the underwater turbulence (air bubble and temperature gradient) as well as two different detection scenarios (heterodyne detection (HDD) & intensity modulation/direct detection(IM/DD)) in terms of Meijer-G functions. Moreover, the average secrecy capacity (ASC) of such a scenario is also exploited in this work. Finally, the expressions are verified through Monte-Carlo simulation.
In this study, physical layer security (PLS) in a dual-hop underwater optical wireless communication (UOWC)-radio frequency (RF) network under the intruding attempts of multiple eavesdroppers via RF links is considered. An intermediate decode-and-forward (DF) relay node between an underwater source and a destination transforms the optical signal into an electrical form and forwards it to the destination node with the help of harvested energy by the relay from an integrated power beacon within the system. The source-to-relay link, i.e., a UOWC link, is assumed to follow a mixture of exponential generalized Gamma turbulence with pointing error impairments whereas all the remaining links, i.e., RF links, are assumed to undergo κ-μ shadowed fading. Here, two eavesdropping scenarios are considered depending on the types of intruders, i.e., colluding (Scenario-I) and non-colluding (Scenario-II) eavesdropping operations. The analytical expressions of secrecy outage probability (SOP), probability of strictly positive secrecy capacity (SPSC), and effective secrecy throughput (EST) are derived for each scenario. Furthermore, the impacts of UOWC and RF channel parameters as well as detection techniques on secrecy capacity are demonstrated. A comparative study between two scenarios demonstrates that the collusion between the eavesdroppers imposes the most harmful threat on secrecy throughput but a better secrecy level can be attained by adopting diversity at the destination and power beacon nodes along with heterodyne detection rather than intensity modulation and direct detection technique. Finally, all the derived expressions are verified with the numerical results.
In response to the dearth of radio frequency (RF) equivalents, there has been a recent surge in interest in optical wireless communication in underwater environments. To ensure a strong line-of-sight (LOS) connection, the intelligent reflecting surface (IRS) is installed to create a virtual LOS. Then, the first part of this study looks into the security of underwater optical wireless communication (UOWC) in relation to a number of real-world phenomena, including oceanic propagation loss, oceanic turbulence, and IRS-induced geometric loss. Then, a wiretap channel with three authorized users - a reputable broadcaster named Alice (the submarine), a law-abiding user named Bob, and an eavesdropper named Eve - is examined over turbulent channels that exhibit the Log-normal distribution. Furthermore, our study derives the closed-form formulas for the secrecy performance measures, secrecy outage probability, and secrecy throughput. Finally, the numerical results show how the impact of oceanic turbulence-induced fading and distance between Bob’s and Eve’s positions on the secrecy system performance.
Optical wireless communication (OWC) has emerged as one promising candidate to mitigate the frequency spectrum crisis. Due to the broadcast nature of OWC channel, physical layer security (PLS) techniques have been considered and explored to improve the transmission confidentiality of OWC links. However, almost all current schemes focus on scenarios including multiple transmitters and fail to match the scenarios with limited transmitters, even single transmitter. For addressing this issue, in this work, the dynamic optical beam based PLS enhancement scheme is proposed. Unlike conventional Lambertian beam based technique paradigm, the above scheme tentatively utilize the commercially available non-Lambertian beam to configure the secure OWC links. Numerical results show that, compared with about 1.10 bps/Hz average secrecy capacity (SC) of the conventional configuration, up to 1.93 bps/Hz average SC gain could be provided by the proposed dynamic beam scheme. Moreover, this potential gain will be increased to about 2.39 bps/Hz when the diversity combing is available for the legitimate user receiver.