Low-Complexity Heuristic Optimization of RIS Orientation for V2V Visible Light Communication at Urban Intersections

The research on reconfigurable intelligent surface (RIS)-aided visible light communication (VLC) has been widely investigated in recent years. However, traditional research on this area only concentrates on one kind of VLC RIS (such as a mirror-based RIS or a liquid crystal (LC)-based RIS), however, dismissing the combination of different kinds of VLC RISs. Consequently, in consideration of the huge potential of the combination for VLC RIS, this paper proposes a trial combing a mirror array-based RIS with a liquid crystal-based RIS in an indoor visible light communication system. The optimization problem is formulated with achievable data rate maximization as the objective function, and meanwhile, the parameters of the two types of RIS is regarded as the independent variables. As for the non-convexity of the proposed optimization problem, in order to determine the optimal configuration of parameters for the two types of RIS, the particle swarm optimization (PSO) algorithm is adopted. Finally, the PSO algorithm is demonstrated to be an effective method to solve the optimization problem in the simulation results, and meanwhile, the combination of a mirror array-based RIS and a liquid crystal-based RIS is able to enhance communication performance to a greater degree compared with the RIS-aided VLC system which employs only one type of VLC RIS.

This paper investigates a reconfigurable intelligent surface (RIS)-aided integrated visible light communication and positioning (VLCP) system, which aims to reduce sensitivity to line-of-sight (LoS) blockage in visible light and simultaneously achieve capabilities for both visible light communication (VLC) and visible light positioning (VLP). The framework of this system is divided into three parts: positioning, channel state information (CSI) estimation, and data transmission. When the LoS links are present, due to the potential adverse positioning effects RIS caused in this scenario, the RIS only plays a role in assisting the communication. Meanwhile, the positioning process is based on the received signal strength (RSS) information from the LoS transmission. If the LoS links are blocked, the RIS provides added non-line-of-sight (NLoS) positioning signals and achieves subsidiary communications accordingly. The Cramer-Rao lower bound (CRLB) on the positioning result is derived and the CSI estimation is conducted based on the results provided by the positioning schemes to reduce the pilot overhead. The achievable rate is evaluated based on the estimated CSI. The configurations of RIS parameters and the power allocated to positioning and communication are jointly optimized to minimize the CRLB while satisfying constraints on the maximum tolerable outage probability, RIS parameter acquisition, and total transmit power. To address this non-convex optimization problem, we proposed an alternative optimization (AO) algorithm to optimize the RIS assignment matrix and the power coefficient alternatively. We employ the worst-case distribution of the Conditional Value-at-Risk (CVaR) along with successive convex approximation (SCA) techniques to derive feasible solutions of the power coefficient optimization subproblem. Meanwhile, we optimize the RIS assignment matrix based on the principle of maximum received power chosen (MRPC). Simulation results demonstrate the influence of RIS in the positioning process in our proposed VLCP system with or without the presence of LoS links, and meanwhile, the relationship between communication performance and positioning performance is validated through the simulations. From the simulation results, the RIS-aided VLCP system can be verified as a viable option for the upcoming era of sixth-generation (6G) technology.

This study investigated the feasibility of utilizing the ITS deployment analysis system (IDAS) program version 2.2 as a tool for evaluating intelligent transport systems (ITS) deployment plans. First, an online survey was conducted among MPO staffs in the US to understand the usage and the issues of the IDAS program for the ITS deployment plan evaluation. Second, case studies were carried out to examine the benefits of deploying several popular ITS options. The case studies of Hampton Roads area and a simple network with six selected ITS options identified three issues: (i) overestimation of ITS option benefits when the benefits are estimated from travel time savings, (ii) incorrect interpolation on travel time reliability rates for non-integer V/C ratios, and (iii) insensitive cost savings for combined ITS options.

The Intelligent Transportation Systems (ITS) Deployment Analysis System (IDAS) is a sketch planning analysis tool that can be used to estimate the impacts and costs resulting from the deployment of ITS components. The program includes default values for the parameters required to calculate ITS deployment costs and benefits. IDAS allows users to override the default values of ITS device cost and benefit parameters, including unit cost estimates, cost assumptions, benefit module parameters, ITS impacts, and impact dollar values. On one hand, the use of cost and benefit parameter values that better represent the region under consideration is expected to produce better assessments of ITS deployment alternatives. On the other hand, collection of regional ITS cost and benefit parameters could be expensive, and some required parameters might not be available for the region under consideration. For this reason, IDAS users tend to use many of the program's default values in their analyses. This paper reports on the results of a project that was initiated by the Florida Department of Transportation to identify Florida-specific cost and benefit parameters for use as inputs to IDAS ITS alternative assessments in Florida. The paper also compares the results obtained by using these derived parameters with the results obtained by using the national defaults when a real world ITS deployment project is being evaluated. The produced cost estimate for this deployment project is also compared with the actual cost of the project.

Vehicle-to-vehicle (V2V) visible light communication (VLC) systems are increasingly being deployed for real-time data exchange in intelligent transportation systems (ITS). However, these systems are highly vulnerable to eavesdropping, especially in scenarios such as road intersections where signals may be exposed to unauthorized receivers. To address these security challenges, we propose a novel reconfigurable intelligent surface (RIS)-assisted security enhancement scheme for V2V VLC networks. The proposed scheme leverages RIS to improve the reception of legitimate signals at the destination vehicle while simultaneously introducing artificial noise (AN) to interfere with potential eavesdroppers. Optimization problems are formulated to maximize the SINR of the destination vehicle and simultaneously minimize the worst-case SINR of eavesdroppers. The simulation results demonstrate that the proposed scheme achieves a notable improvement in the system’s secrecy rate by 1.64 bit/s/Hz and enhances the overall security performance, offering a robust solution to the security challenges in V2V VLC systems.

Integrating visible light communication (VLC) with the reconfigurable intelligent surface (RIS) significantly enhances physical layer security by enabling precise directional signal control and dynamic adaptation to the communication environment. These capabilities strengthen the confidentiality and security of VLC systems. This paper presents a comprehensive study on the joint optimization of VLC access point (AP) power allocation, RIS association, and RIS elements orientation angles for secure VLC systems, while considering rate-splitting multiple access (RSMA) and power-domain non-orthogonal multiple access (NOMA) schemes. Specifically, two frameworks are proposed to maximize both the minimum secrecy rate (SR) and the minimum secrecy energy efficiency (SEE) by jointly optimizing power allocation, RIS association, and RIS elements orientation angles for both power-domain NOMA and RSMA-based VLC systems. The proposed frameworks consider random device orientation and guarantee the minimum user-rate requirement. The proposed optimization frameworks belong to the class of mixed integer nonlinear programming, which has no known feasible solution methodology to guarantee the optimal solution. Moreover, the increased degree of freedom and flexibility from the joint consideration of power control, RIS association and element orientation results in a large set of decision variables and constraints, which further complicates the optimization problem. To that end, we utilize a genetic algorithm-based solution method, which through its exploration and exploitation capabilities can obtain a good quality solution. Additionally, comprehensive simulations show that the RSMA scheme outperforms the power-domain NOMA scheme across both the SR and SEE metrics over various network parameters. Furthermore, useful insights on the impact of minimum user rate requirement, number of RIS elements, and maximum VLC AP transmit power on the minimum SR and SEE performances are provided.

Intelligent transportation systems (ITS) are a powerful technology, not only for gaining traffic and transport benefits, such as less congestion and shorter travel times, but also for economic growth. The European Union (EU) has already published a directive (2010/40/EU) to regulate the coordinated and coherent deployment of ITS in all EU-member states. However, ITS deployment in some EU member states has yet to be integrated. According to the European Commission, South East Europe (SEE) is an area in which ITS deployment is “fragmented and uncoordinated and cannot provide geographical continuity of ITS services throughout the region.” An overview is provided of the current deployment and implementation status of ITS in nine countries of the SEE area. The results highlight the strengths and weaknesses for further ITS deployment in these countries and the level of harmonization of their national laws with the European directive, a prerequisite that could alleviate the fragmentation of the ITS provision along different regions within the nations and also at cross-border areas. Afterward, the methodology for creating national roadmaps for ITS deployment is presented as well as the final roadmaps for each of the nine countries. The findings of these roadmaps are crucial for future ITS deployment in SEE countries; the level of maturity of ITS deployment in each country has been taken into account.

The reconfigurable intelligent surface (RIS) technology has gained increased attention for improving the performance and efficiency of the fifth-generation (5G) millimeter-wave (mmWave) wireless communication by obviating the propagation and blockage issues. On the other hand, the great flexibility of unmanned aerial vehicles (UAVs) has made them effective gadgets to enhance the coverage of wireless communication networks. Combining these two emerging technologies, the RIS-outfitted UAV (RISoUAV) is a promising solution for providing line-of-sight (LoS) wireless links for mobile targets (MTs) in obstructed high-dense urban areas. In this light, high-speed real-time communication is essential for some vital municipal services like ambulances, fire engines, security guards, police, etc. This important goal is achievable thanks to the RISoUAV-assisted 5G/quasi-optic wireless communication. This paper develops a framework for optimal navigation of a team of RISoUAVs for maintaining LoS links with a team of ground vehicles in a dense urban area. The trajectories of the RISoUAVs are optimized considering the energy efficiency, communication channel gains, and constraints associated with RISoUAVs motion and LoS service. A consensus-based coordinating approach is adopted to coordinate the RISoUAVs navigation to cover all MTs under a good quality of service. Simulation results show the effectiveness of the method. Note to Practitioners—In this paper, we consider a scenario where vehicles need to have high-speed, uninterrupted data links in obstructed, highly dense urban environments. Due to spectrum crunch, the data links are increasingly likely to rely on a high-frequency spectrum, including mmWave with quasi-optic nature, visible light communications, or even laser. However, the obstructed LoS and propagation are critical issues with the 5G and beyond as they rely on the availability of an unobstructed path (e.g., the LoS or a quality reflective path). On the other hand, the RIS performs as a passive reflective element that provides an indirect LoS link, a one-bounce channel, to improve the performance and efficiency of mmWave, and beyond, wireless communication networks. UAVs equipped with RISs are suggested in this paper to be adopted as aerial transponders to reflect signals and facilitate communication in high-density environments. Therefore, the problem of UAV navigation and 3D trajectory planning should be addressed regarding the application, particularly, for providing LoS service for mobile vehicles with arbitrary directions. Autonomous navigation of RISoUAVs for LoS wireless communication is a natural multi-dimensional extension of autonomous navigation with obstacle avoidance where regions in which LoS communication is lost are viewed as obstacles to avoid. However, the environment and valid LoS links can change dynamically due to moving vehicles in the obstructed environment. This makes the navigation design an NP-hard problem that is tackled in this paper by developing an effective navigation program.

The Intelligent Transportation Systems (ITS) Deployment Analysis System (IDAS) is a sketch planning analysis tool that can be used to estimate the impacts and costs resulting from the deployment of ITS components. The program includes default values for the parameters required to calculate ITS deployment costs and benefits. IDAS allows users to override the default values of ITS device cost and benefit parameters, including unit cost estimates, cost assumptions, benefit module parameters, ITS impacts, and impact dollar values. On one hand, the use of cost and benefit parameter values that better represent the region under consideration is expected to produce better assessments of ITS deployment alternatives. On the other hand, collection of regional ITS cost and benefit parameters could be expensive, and some required parameters might not be available for the region under consideration. For this reason, IDAS users tend to use many of the program's default values in their analyses. This paper reports on the results of a project that was initiated by the Florida Department of Transportation to identify Florida-specific cost and benefit parameters for use as inputs to IDAS ITS alternative assessments in Florida. The paper also compares the results obtained by using these derived parameters with the results obtained by using the national defaults when a real world ITS deployment project is being evaluated. The produced cost estimate for this deployment project is also compared with the actual cost of the project.

To help transportation planners, the Federal Highway Administration (FHWA) has recently sponsored the development of a sketch planning analysis tool for estimating the benefits and costs of intelligence transportation system (ITS) deployment. Called the ITS Deployment Analysis System (IDAS), the tool was developed by Cambridge Systematics for FHWA and operates as a postprocessor to traditional planning models that are based on the four-step planning process. IDAS was used to predict the likely benefits of deploying ITS in Chittenden County, Vermont, a medium-sized region in northwestern Vermont, to gain insight into IDAS’ applicability in evaluating ITS benefits. A sensitivity analysis was also conducted to assess the sensitivity of IDAS’ results to the choice of values of some of the model’s parameters. The sensitivity analysis demonstrates that some of the model’s parameters tend to have a more significant impact on the results than others. Finally, the results indicate that, for medium-sized areas similar to Chittenden County, coordination of signals along major arterials and transit projects for automatic vehicle location and scheduling appear to be more cost-effective than freeway and incident management systems.

The upcoming fifth generation (5G) and beyond communications introduce numerous immerging technological systems. With the rising number of users, meeting the data rate demand utilizing radio frequency (RF) spectrum is becoming extremely difficult, even for 5G communications. For this reason, researchers have shifted to visible spectrum as an alternative to the RF spectrum. Visible spectrum can provide huge channel capacity as a result the network traffic jam can be solved for future communication networks. Visible light communication (VLC) system is done by this visible spectrum. VLC is mainly an indoor communication system. VLC has a high channel capacity over RF communication. The major concern of this VLC system is when the users are far from light source or remote areas, the signal strength becomes poor and data rate received by users is comparatively low. Reconfigurable intelligent surface (RIS) is a brand new technology for 5G and beyond communications. It allows to maintain high signal strength, better network security, and helps to provide seamless connectivity with high data rate. RIS creates a great impact on VLC system. RIS uses its intelligent beamforming to allow it to get better signal strength and seamless connection to users in remote areas or far from the source. This article combines the RIS technology with VLC and performance analysis between RIS-assisted VLC over traditional VLC. Research finding clearly shows that the overall performance of RIS-assisted VLC is much higher than the current VLC system.

Recent intensive and extensive development of the fifth-generation (5G) of cellular networks has led to their deployment throughout much of the world. As part of this implementation, one of the challenges that must be addressed is the skip-zone problem, which occurs when objects such as trees, people, animals, and vehicles obstruct the transmission of signals. In free-space optical (FSO) and radio frequency (RF) systems, dead zones are most often caused by buildings and trees, while in visible light communications (VLC), obstructions are caused by individuals moving around a room or objects placed in the room. A signal obstruction can significantly reduce the signal-to-noise ratio in RF and indoor VLC systems, whereas in FSO systems, where the transmitted signals are directional, the obstruction can completely disrupt data transmission. Therefore, the skip-zone dilemma must be resolved to ensure the smooth and efficient operation of 5G and beyond networks. By placing a relay between a transmitter and a receiver, the effects of obstacles can be mitigated. As a result, the signal from the transmitter will reach the receiver. In recent years, reconfigurable intelligent surfaces (RISs) that are more efficient than relays have become widely accepted as a method of mitigating skip-zones and providing reconfigurable radio environments. However, there have been limited studies of RISs for optical wireless communication (OWC) systems. Through the RIS technology, OWC and RF communication channels can be reconfigured. This paper aims to provide a comprehensive tutorial on indoor VLC systems utilizing RIS technology. The article discusses the basics of VLC and RISs and reintroduces RISs for OWC systems, focusing on RIS-assisted indoor VLC systems. We also provide a comprehensive overview of optical RISs and examine the differences between optical RISs, RF-RISs, and optical relays. Furthermore, we discuss in detail how RISs can be used to overcome line-of-sight blockages and the device orientation issue in VLC systems while revealing key challenges such as RIS element orientation design, RIS elements to access point/user assignment design, and RIS array positioning design problems that need to be studied. Moreover, we discuss and propose several research problems on integrating optical RISs with other emerging technologies, including non-orthogonal multiple access, multiple-input multiple-output systems, physical layer security, and simultaneous lightwave and power transfer in VLC systems. Finally, we highlight other important research directions that can further improve the performance of RIS-assisted VLC systems.

With low-cost energy consumption, the reconfigurable intelligent surface (RIS) technique is a potential solution to the real-time data processing for intelligent transportation systems (ITSs). In this paper, an intelligent transmissive surface is introduced into the vehicular communications, enabling vehicle-to-infrastructure (V2I) signals to penetrate the intelligent RIS to access the base station (BS) on the opposite side of the vehicle. Considering that the vehicle-to-vehicle (V2V) communication reuses the spectrum spanned for V2I link, we investigate the ergodic capacity optimization problem for the vehicle performing V2I communications with the assistance of RIS, while meeting the low-latency and high-reliability requirements of the V2V link. The RIS transmission coefficients and power allocation of vehicles are jointly optimized, for the management of the desired and undesired vehicular communication links. Moreover, the expression of optimal phase shifts is derived in a closed-form, which reveals that the performance gain brought by RIS is proportional to the number of intelligent elements, while inversely proportional to the distance from vehicle-to-BS, in a quadratic form. Moreover, in the case of discrete phase shifts, an intelligent algorithm is proposed for the beamforming design at RIS. Afterwards, with the objective to maximize the ergodic capacity of the V2I link, the optimal power allocation is also proposed. Simulation results confirm the accuracy of the proposed resource allocation strategy, and that the system performance in terms of the ergodic V2I capacity can be significantly improved by the RIS.

Optimizing resource allocation for enhanced urban connectivity in LEO-UAV-RIS networks

Traffic safety at road intersections can be enhanced by improving opportunistic exchange of safety messages between vehicles. In urban intersection scenario, obstacles such as buildings and road side installations/signboards block the line-of-sight communication between vehicles. In order to enhance the reliability of communication link, the existing vehicular solution utilizes relay placement at road intersection. However, as the vehicular density increases, the existing vehicular-radio frequency (V-RF) communication with relaying tends to suffer from higher interference, lower packet reception rate, and longer communication delays due to channel congestion. In contrast to the existing solutions, we propose to use practical deployment strategies namely hybrid vehicular-visible light communication (V-VLC)/V-RF with relaying and reconfigurable intelligent surface (RIS) aided V-RF solutions to improve the communication range for urban vehicle-to-vehicle (V2V) communication. We present stochastic geometry based analytical framework to analyze the performance of proposed solutions in terms of outage probability, throughput and delay outage rate (DOR). Numerical results illustrate that the proposed solutions can achieve considerable performance improvement in outage, throughput while ensuring low latency as compared to conventional V-RF with relaying. These deployment strategies may also serve as a preferred alternative for Intelligent Transportation System (ITS) to meet ultra-high reliable and ultra-low latency communication for beyond 5 G (B5G) vehicular networks.