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.
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.
Due to the dramatic increase in high data rate services and in order to meet the demands of the fifth-generation (5G) networks, researchers from both academia and industry are exploring advanced transmission techniques, new network architectures and new frequency spectrum such as the visible light and the millimeter wave (mmWave) spectra. Visible light communication (VLC) particularly is an emerging technology that has been introduced as a promising solution for 5G and beyond, owing to the large unexploited spectrum, which translates to significantly high data rates. Although VLC systems are more immune against interference and less susceptible to security vulnerabilities since light does not penetrate through walls, security issues arise naturally in VLC channels due to their open and broadcasting nature, compared to fiber-optic systems. In addition, since VLC is considered to be an enabling technology for 5G, and security is one of the 5G fundamental requirements, security issues should be carefully addressed and resolved in the VLC context. On the other hand, due to the success of physical layer security (PLS) in improving the security of radio-frequency (RF) wireless networks, extending such PLS techniques to VLC systems has been of great interest. Only two survey papers on security in VLC have been published in the literature. However, a comparative and unified survey on PLS for VLC from information theoretic and signal processing point of views is still missing. This paper covers almost all aspects of PLS for VLC, including different channel models, input distributions, network configurations, precoding/signaling strategies, and secrecy capacity and information rates. Furthermore, we propose a number of timely and open research directions for PLS-VLC systems, including the application of measurement-based indoor and outdoor channel models, incorporating user mobility and device orientation into the channel model, and combining VLC and RF systems to realize the potential of such technologies.
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.
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.
Visible light communication (VLC) is a new enabling communication technology that exploits illumination devices, mostly high-brightness light-emitting diodes (LEDs), to establish high-speed short-range wireless communication links. VLC is a promising technology that has gained significant interest in the last decade due to its high data rates and low cost of deployment. Although VLC systems are less susceptible to eavesdropping than RF systems since light does not penetrate through walls, they become as vulnerable as their radio-frequency (RF) counterparts when their nodes are deployed in public areas and/or when there are large windows. Thus, security for VLC systems is as important as it is for RF systems. Security in wireless communication systems may be enhanced by introducing physical layer security (PLS) techniques. In fact, PLS has been applied to a wide range of RF applications in an effort to improve the overall security by complementing existing cryptography-based security techniques. The potential of PLS stems from its ability of leveraging features of the surrounding environments via sophisticated encoding techniques at the physical layer. Indeed, PLS schemes can be applied in the same spirit to VLC systems. \n \nThere exist many specificities that characterize VLC systems, leading to major differences compared to RF systems. Specifically, VLC channels are quasi-static and real valued channels, which seemingly simplify the application of PLS techniques. However, due to the limited dynamic range of the LEDs, VLC systems impose an amplitude constraint on the channel input, which makes unbounded inputs not admissible. As a result, the performance of PLS schemes must be revised in the VLC context due to its different operating constraints. \n \nWe propose in this thesis enhancing the secrecy performance of VLC systems through PLS techniques. Firstly, we consider the degraded single-input single-output (SISO) VLC system. We derive achievable secrecy rates using continuous and discrete input distributions and we demonstrate the substantial improvement in the secrecy performance by using discrete distributions. Secondly, we consider the multiple-input single-output (MISO) VLC systems. We consider at first the case of randomly located eavesdroppers, in which we develop an associated achievable secrecy rate and we develop a beamforming-based precoding scheme that enhances the secrecy performance of this class of systems. In the second part, we consider the multi-user (MU) MISO broadcast system with confidential messages and we develop linear precoding schemes that enhance typical secrecy performance measures, including the max-min fairness and the weighted fairness. Finally, we consider the multiple-input multiple-output (MIMO) VLC system. We derive achievable secrecy rates using continuous and discrete distributions and we develop linear precoding schemes that improve its secrecy performance.
Optical wireless communications (OWC) and its potential to solve physical layer security (PLS) issues are becoming important research areas in 6G communications systems. In this paper, an overview of PLS in visible light communications (VLC), is presented. Then, two new PLS techniques based on generalized space shift keying (GSSK) modulation with spatial constellation design (SCD) and non-orthogonal multiple access (NOMA) cooperative relaying are introduced. In the first technique, the PLS of the system is enhanced by the appropriate selection of a precoding matrix for randomly activated light emitting diodes (LEDs). With the aid of a legitimate user's (Bob's) channel state information (CSI) at the transmitter (CSIT), the bit error ratio (BER) of Bob is minimized while the BER performance of the potential eavesdroppers (Eves) is significantly degraded. In the second technique, superposition coding with uniform signaling is used at the transmitter and relays. The design of secure beamforming vectors at the relay nodes along with NOMA techniques is used to enhance PLS in a VLC system. Insights gained from the improved security levels of the proposed techniques are used to discuss how PLS can be further improved in future generation communication systems by using VLC.
Since the development of remote applications and benefit, the request for a secure and quick information exchange association requires unused innovation arrangements competent to guarantee the finest countermeasure against security assaults, it is one of the foremost promising unused remote communication innovation, due to the plausibility of utilizing natural counterfeit lights as information exchange channel in free- space. The broadcast nature of VLC makes it fundamental to consider the security of fundamental transmissions. Physical layer information communication and security beneath the channel has ended up a raising concern for communication analysts and due to the victory of physical layer security (PLS) in making strides the security of radio-frequency (RF) remote systems, expanding such PLS techniques to VLC frameworks has been of incredible intrigued. By analysing some cases of the conceivable busybody dangers that can happen in these frameworks, this offers novel bits of knowledge into the vulnerabilities of state-of-the-art PLS plans for VLC frameworks, counting distinctive channel models, input disseminations, arrange arrangements, precoding/signalling techniques, and mystery capacity and data rates and beneath VLC the tall level security and security overhauling arrangements are educated and moderated a period. Key Words: Visible Light, Physical layer security, Multi User, Spread-spectrum, security performance.