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- Cooperative Vehicular Platooning: A Multi- Dimensional Survey Towards Enhanced Safety, Security and ValidationPublication . Vasconcelos Filho, Ênio; Santos, Pedro Miguel; Koubaa, Anis; Tovar, Eduardo; Severino, RicardoCooperative Vehicular Platooning (Co-VP) is a paradigmatic example of a Cooperative Cyber-Physical System (Co-CPS), which holds the potential to vastly improve road safety by partially removing humans from the driving task. However, the challenges are substantial, as the domain involves several topics, such as control theory, communications, vehicle dynamics, security, and traffic engineering, that must be coupled to describe, develop and validate these systems of systems accurately. This work presents a comprehensive survey of significant and recent advances in Co-VP relevant fields. We start by overviewing the work on control strategies and underlying communication infrastructures, focusing on their interplay. We also address a fundamental concern by presenting a cyber-security overview regarding these systems. Furthermore, we present and compare the primary initiatives to test and validate those systems, including simulation tools, hardware-in-the-loop setups, and vehicular testbeds. Finally, we highlight a few open challenges in the Co-VP domain. This work aims to provide a fundamental overview of highly relevant works on Co-VP topics, particularly by exposing their inter-dependencies, facilitating a guide that will support further developments in this challenging field.
- Optimal antenna-height design for improved capacity on over-water radio links affected by tidesPublication . Gutiérrez Gaitán, Miguel; Santos, Pedro M.; Pinto, Luis R.; Almeida, LuisModern observation systems can be composed by heterogeneous entities (e.g., buoys, USVs, UAVs, on-shore sensors, etc.) that rely on dependable communications for coordination and data collection, often provided by over-water radio-frequency (RF) links. In tide-affected water bodies, RF links at a fixed height from the shore can experience the so-called tidal fading, a cyclic time-varying tide-induced interference. To mitigate it, the classical space-diversity reception technique (i.e., the use of two or more receiver antennas positioned at different heights) is often applied, commonly combined with the consideration of having one of the antennas at the largest possible height. Yet, this approach does not always ensure the best performance. In this work, we focus on static over-water links of short-to-medium-range distances that use antennas installed at a few meters above surface. We leverage the geometrical basis of the two-ray propagation model to investigate the optimal single-antenna height design that minimizes overall average path losses over a given tidal range. We then extend this analysis to incorporate a second receiver antenna and identify its optimal antenna height. Analytical results show that our method considerably outperforms the more classical approach, thus enabling superior (average) link capacities.
- Towards Safe Cooperative Autonomous Platoon systems using COTS EquipmentPublication . Kurunathan, John Harrison; Santos, José; Moreira, Duarte; Santos, Pedro MiguelThe domain of Intelligent Transportation Systems (ITS) is becoming a key candidate to enable safer and efficient mobility in IoT enabled smart cities. Several recent research in cooperative autonomous systems are conducted over simulation frameworks as real experiments are still too costly. In this paper, we present a platooning robotic test-bed platform with a 1/10 scale robotic vehicles that functions based on the input front commercially off the shelf technologies (COTS) such as Lidars and cameras. We also present an in-depth analysis of the functionalities and architecture of the proposed system. We also compare the performance of the aforementioned sensors in some real-life emulated scenarios. From our results, we were able to concur that the camera based platooning is able to perform well at partially observable scenarios than its counterpart.
- Waiting Time Analysis for a Network of Signalized IntersectionsPublication . Reddy, Radha; Almeida, Luis; Santos, Pedro M.; Tovar, EduardoVehicle waiting time or stopped delay is one of the major disadvantages of employing signalized intersections (SIs) in road networks. The waiting time delays occur when vehicles stop in the queue, waiting to access the SI, and vary from road lane to road lane with the intersection management (IM) protocol used. In this research line, we propose an analytical expression for estimating the waiting time delays and studying the performance of different IM approaches in a grid network of independent intersections. We consider complex intersections with four legs and two lanes with two left-lane configurations, as well as five state-of-the-art IM approaches: two conventional -- Round-Robin (RR) and Trivial Traffic Light Control (TTLC); two adaptive -- Max-pressure Control Algorithm (MCA) and Websters Traffic Light Control (WTLC); and one reactive -- Synchronous Intersection Management Protocol (SIMP). The waiting time performance of these five IM approaches is compared using two simulation scenarios in the SUMO simulation framework. The simulation results validate the analytical study and show the advantages of employing SIMP, being the IM approach with the lowest waiting time delays.
- CoWiPS: Cooperative wireless positioning to identify position mis-reports in vehicular scenariosPublication . Lam, Luis; Santos, Pedro MiguelAutonomous driving (AD) is advancing rapidly, but enhancing situational awareness beyond the internal sensors (cameras, radar, and Lidar) requires cooperative perception services enabled by Vehicle-to-Everything (V2X) links. However, some vehicles can inject incorrect information, either intentionally or by hardware malfunction. Wireless positioning offers a set of physical-layer mechanisms, such as Angle-of-Arrival (AoA) and RSS-based ranging, that can verify the correctness of shared data, particularly position data. We introduce Cooperative Wireless Positioning System (CoWiPS), an innovative mechanism in which a set of cooperating vehicles cooperate to estimate the position of a Vehicle-of-Interest. Our positioning solution achieves accurate position estimations, with 70.16% accuracy within a 10m error margin under 0dB amplitude noise variance, and 50.01% accuracy under 5dB variance.
- Empirical Evaluation of Short-Range WiFi Vessel-to-Shore Overwater CommunicationsPublication . d'Orey, Pedro; Gutiérrez Gaitán, Miguel; Santos, Pedro M.; Ribeiro, Manuel; Sousa, J. Borges de; Almeida, LuísUnmanned vehicles used in ocean science, defense operations and commercial activities collect large amounts of data that is further processed onshore. For real-time information exchange, the wireless link between the unmanned vehicle and onshore devices must be reliable. In this work, we empirically evaluate a WiFi link between an autonomous underwater vehicle on the surface and an onshore device under real-world conditions. This work allowed i) collecting a large-scale realistic dataset and ii) identifying major factors impairing communication in such scenarios. The TX-RX antenna alignment, the operation mode (manual vs automatic) and varying reflecting surface induced by AUV mobility lead to sudden changes (e.g. nulls) in the received signal strength that can be larger than 20 dB. This study provides useful insights to the design of robust vessel-to-shore short-range communications.
- Minimal-Overlap Centrality-Driven Gateway Designation for Real-Time TSCH NetworksPublication . Gutiérrez Gaitán, Miguel; D'Orey, Pedro; Santos, Pedro M.; Almeida, LuisThis research proposes a novel minimal-overlap centrality-driven gateway designation method for real-time wireless sensor networks (WSNs). The goal is to enhance network schedulability by design, particularly, by exploiting the relationship between path node-overlaps and gateway designation. To this aim, we define a new metric termed minimal-overlap network centrality which characterizes the overall overlapping degree between all the active flows in the network when a given node is selected as gateway. The metric is then used to designate as gateway the node which produces the least overall number of path overlaps. For the purposes of evaluation, we assume a time-synchronized channel-hopping (TSCH) WSN under centralized earliest-deadline-first (EDF) scheduling and shortest-path routing. The assessment of the WSN traffic schedulability suggests our approach is dominant over classical network centrality metrics, namely, eigenvector, closeness, betweenness, and degree. Notably, it achieves up to 50% better schedulability than a degree centrality benchmark.
- Demonstrating RA-TDMAs+ for robust communication in WiFi mesh networksPublication . Almeida, Diogo; Gutiérrez Gaitán, Miguel; D'Orey, Pedro; Santos, Pedro M.; Pinto, Luís; Almeida, LuisThis work will demonstrate a new flavor of the RA-TDMA set of protocols, namely RA-TDMAs+, which uses IEEE-802.11 (WiFi) COTS hardware in ad-hoc mode to set up a dynamic mesh network of mobile nodes with highbandwidth. The protocol uses topology tracking to configure the TDMA frame and robust relative synchronization to define the TDMA slots without resorting to a global clock and in the presence of interfering traffic. The demo will set up a small-scale testbed using COTS hardware, thus evidencing the feasibility of the approach, and it will show 1clive plots 1d of the temporal (synchronization) and topological views of the network.
- Complex Intersections with a Dedicated Road Lane per Crossing DirectionPublication . Reddy, Radha; Almeida, Luis; Santos, Pedro M.; Tovar, EduardoComplex intersections are often busier with a separate road lane per crossing direction, i.e., left, straight, and right. These intersections eliminate the diverging and merging conflicts; thus, vehicles only fall under crossing conflicts within intersections. However, the traditional way of serving vehicles from one road at a time increases traffic congestion and hinders performance. To address this issue, we extended the synchronous framework for complex intersections with a separate road lane per crossing direction, which was initially presented for single-lane and two-lane intersections in which roads are shared among vehicles with different crossing directions. We compare the performance of our synchronous framework against the traditional Round-Robin (RR) intersection management approach.
- Synchronous Management of Mixed Traffic at Signalized Intersections towards Sustainable Road TransportationPublication . Reddy, Radha; Almeida, Luis; Gutiérrez Gaitán, Miguel; M. Santos, Pedro; Tovar, EduardoIn urban road transportation, intersections are traffic bottlenecks with increased waiting delays and associated adverse effects. A recently proposed intelligent intersection management (IIM) approach, the Synchronous Intersection Management Protocol (SIMP), synchronizes the vehicles access to simple single-lane isolated intersections, outperforming competing approaches in various performance metrics. In this paper, we apply SIMP to multi-lane intersections, increasing significantly the applicability of the protocol while dealing with the additional complexity emerging from the multiple crossing conflicts. Using the SUMO simulator, we compare the performance of SIMP with two conventional (Round-Robin - RR and Trivial Traffic Light Control - TTLC) and two IIM approaches (Intelligent Traffic Light Control - ITLC and Q-learning based Traffic Light Control - QTLC) under continuous and interrupted upstream traffic flows scenarios in urban settings. The results using a maximum speed of 30km/h confirm the superiority of SIMP, improving traffic throughput (~14.4%) and reducing travel delays (~64.4%) and associated fuel consumption (~25.5%) when compared to the best of the other approaches.