ISEP – CISTER – Comunicações em eventos científicos
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- On the performance of an air-water visible light communication systemPublication . Martínez, Guillermo; Játiva, Pablo Palacios; Gutiérrez Gaitán, Miguel; Azurdia, Cesar; Boettcher, Nicolás; Zabala-Blanco, DavidResearch on wireless communication in water environments is gaining attention due to its relevance in enabling and supporting new applications under the Underwater Internet of Things (UIoT) umbrella. Visible Light Communication (VLC) is one of the emerging communication technologies with the potential to contribute to this domain, especially concerning direct communications from above the surface to underwater nodes. Although more traditional radio frequency (RF) communications are not suitable for air-to-water communications, VLC offers unique opportunities in this area. In this respect, this work presents a simulative study attempting to theoretically understand the performance of VLC systems in both underwater and air-to-water channels. We explore performance metrics including, link gain, time delay, and bit-error rate, while analyzing the optical signal interruption on the sea surface due to water level changes. The investigation offers preliminary results that shed light on the feasibility and challenges of effectively enabling cross-border air-water communication systems using VLC technologies.
- Evaluation of parental control tools functionalities: The Chilean contextPublication . Rojas, Nicolás; Boettcher, Nicolás; Játiva, Pablo Palacios; Gutiérrez Gaitán, MiguelChoosing a reliable parental control tool is essential to supervising minors accessing information and using electronic devices. For this, it is necessary to determine which tools are the most suitable and if their functionalities are effective. To our knowledge, despite the availability of existing tools that evaluate applications and different actors, e.g., parent control applications recommended by Internet Service Providers (ISPs), none of them properly characterize the various functionalities provided by the application while validating their efficacy. In this paper, we propose a new comprehensive metric to effectively identify and evaluate the functionalities provided by tools in the field of parental control. The metric is applied to some of the most downloaded apps from the Play Store, and the results are compared with the applications recommended by ISPs in Chile, which cover more than 93% of the market. The results from our analysis show that none of the parent control applications recommended by Chilean ISPs managed to provide full confidence in the functionalities implemented since at least one of their functions did not pass the test applied. The end goal for the test metric proposed is to allow future developers to assess their applications beforehand while offering a better match with the customer’s expected service.
- Joint spectrum and antenna selection diversity for V2V links with ground reflectionsPublication . Robles, Ramiro; Gutiérrez Gaitán, Miguel; Javanmardi, Gowhar; Kurunathan, HarrisonThis paper addresses the study of a fading-rejection algorithm based on joint spectrum and antenna selection in a vehicle-to-vehicle (V2V) multiple antenna system. The central objective of this selective scheme is to provide resilience against the destructive effects of the superposition of line-of-sight (LOS) and ground-reflected signals. The paper also provides an extension to channels that combine such deterministic superposition of multiple paths and reflections with an uncorrelated double scattering component, which shows how the algorithm is also beneficial under more general channel modelling assumptions. A multiple-ray performance model is used to describe the deterministic signal interactions between multiple antennas across contiguous vehicles. The antenna selection component is shown to reject deterministic fading, particularly at short values of the inter-vehicular distance. By contrast, when the spectrum bands are correctly chosen, the spectrum selection component can exhibit gains for a wider range of inter-vehicular distances than its antenna selection counterpart. This indicates that both components of the proposed solution are, in some cases, complementary, and therefore, they should be considered together in V2V multiple antenna design. Derivation of the statistics of the selective scheme considering an additional double scattering stochastic channel component is here proposed. Simulation results from all expressions show important gains for a given range of inter-vehicular distances.
- 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.
- Memory Contention Analysis for 3-Phase TasksPublication . Arora, Jatin; Rashid, Syed Aftab; Nelissen, Geoffrey; Maia, Cláudio; Tovar, EduardoIn multiprocessor-based real-time systems, the main memory is identified as the main source of shared resource contention. Phased execution models such as the 3-phase task execution model has shown to be a good candidate to tackle the memory contention problem. It divides the execution of tasks into computation and memory phases that enable a fine-grained memory contention analysis. However, the existing work that focuses on the memory contention analysis for 3-phase tasks can overestimate the memory contention that can be suffered by the task under analysis due to the write requests. This overestimation can yield pessimistic bounds on the memory access times and memory contention suffered by tasks which in turn lead to pessimistic worst-case response time (WCRT) bounds. Considering the limitation of the state-of-the-art, this work proposes an improved memory contention analysis for the 3-phase task model. Specifically, we propose a memory contention analysis for the 3-phase task model by tightly bounding the memory contention suffered by the task under analysis due to the write requests. The proposed memory contention analysis integrates memory address mapping of tasks to improve the bounds on the maximum memory contention suffered by tasks.
- Shared Resource Contention Aware Schedulability Analysis for Multiprocessor Real-Time SystemsPublication . Arora, Jatin; Tovar, Eduardo; Maia, CláudioMulticore platforms share the hardware resources such as caches, interconnects, and main memory among all the cores. Due to such sharing, tasks running on different cores compete to access these shared resources which can potentially result in shared resource contention. This shared resource contention can increase the execution times of tasks in a non-deterministic manner. Consequently, the shared resource contention is problematic for hard real-time systems, i.e., systems that run tasks with stringent timing requirements. To address this issue, this PhD dissertation builds novel solutions to model and analyze the shared resource contention that can be suffered by tasks executing on a multicore system. The shared resource contention aware schedulability analysis is then derived by integrating the maximum shared resource contention that can be suffered by the tasks.
- Outage Probability of V2V Multiple-Antenna Rice Fading Links with Explicit Ground ReflectionPublication . Gutiérrez Gaitán, Miguel; Samano-Robles, Ramiro; Rodriguez, JonathanThis paper investigates the improvement in terms of outage probability of a vehicle-to-vehicle (V2V) communication link with respect to the density of antennas used at each vehicle end. The objective is to find a trade-off between system complexity and communication performance considering that the deterministic component of the link is affected explicitly by multiple ground reflections (self-interference). The antennas are assumed to be located at regularly distributed positions across the surface of contiguous vehicles. Part of the work assumes symbol repetition at the transmitter side, and different signal combining mechanisms at the receiver side, namely, maximum-ratio and equal-gain combining (MRC and EGC, respectively). The objective is to minimize outage probability of the link with deterministic and stochastic channel components (Rice-distributed), where the line-of-sight (LOS) is affected by multi-ray ground reflections as an extension of the well-known two-ray model. This scenario is considered more realistic for V2V scenarios due to the potential proximity of ground to the antenna elements. The outage probability is calculated over a range of inter-vehicle distances with respect to the free-space loss solution. The results show that performance is improved even for a relatively small number of antennas and that a critical point is reached beyond which improvement is only differential. This suggests that an optimum trade-off can be obtained to ensure a value of outage probability with a complexity constraint over a range of inter-vehicle distances.
- Wireless Channel Prediction Using Artificial Intelligence with Constrained Data SetsPublication . Javanmardi, Gowhar; Samano-Robles, RamiroThis work deals with the study of artificial intelligence (AI) tools for purposes of vehicular wireless channel prediction. The objective is to test the ability of different types of AI and machine learning (ML) algorithms under different types of implementation constraints. We focus particularly in highly changing scenarios where the channel state information changes relatively fast and therefore the relevant measurements or long-term statistical models are therefore scarce. This means that the training of our models can be potentially inaccurate or incomplete and we need to investigate which AI algorithm behaves better in this challenging condition. In future work we aim to investigate also computation complexity constraints, real-time deadlines, and outdated/distorted or noisy data set samples. We also aim to correlate the main properties of the well-known Jakes' channel model with the effectiveness of the type of prediction and the parameters of the different algorithms being tested. The objective of channel prediction in vehicular networks is to reduce allocation and transmission errors, thereby reducing latency and improving message transmission reliability, which is crucial for future applications such as autonomous vehicles. Results show that even in situations with incomplete data sets, AI can provide good approximate predictions on the channel outcome.
- IPDeN: Real-Time deflection-based NoC with in-order flits deliveryPublication . Ribot González, Yilian; Nelissen, Geoffrey; Tovar, EduardoIn deflection-based Network-on-Chips (NoC), when several flits entering a router contend for the same output port, one of the flits is routed to the desired output and the others are deflected to alternatives outputs. The approach reduces power consumption and silicon footprint in comparison to virtual channels (VCs) based solutions. However, due to the nondeterministic number of deflections that flits may suffer while traversing the network, flits may be received in an out-of-order fashion at their destinations. In this work, we present IPDeN, a novel deflectionbased NoC that ensures in-order flit delivery. To avoid the use of costly reordering mechanisms at the destination of each communication flow, we propose a solution based on a single small buffer added to each router to prevents flits from over taking other flits belonging to the same communication flow. We also develop a worst-case traversal time (WCTT) analysis for packets transmitted over IPDeN. We implemented IPDeN in Verilog and synthesized it for an FPGA platform. We show that a router of IPDeN requires "483-times less hardware resources than routers that use VCs. Experimental results shown that the worst-case and average packets communication time is reduced in comparison to the state-of-the-art
- nDimNoC: Real-Time D-dimensional NoCPublication . Ribot, Yilian; Nelissen, Geoffrey; Tovar, EduardoThe growing demand of powerful embedded systems to perform advanced functionalities led to a large increase in the number of computation nodes integrated in Systems-on-chip (SoC). In this context, network-on-chips (NoCs) emerged as a new standard communication infrastructure for multi-processor SoCs (MPSoCs). In this work, we present nDimNoC, a new D-dimensional NoC that provides real-time guarantees for systems implemented upon MPSoCs. Specifically, (1) we propose a new router architecture and a new deflection-based routing policy that use the properties of circulant topologies to ensure bounded worst-case communication delays, and (2) we develop a generic worst-case communication time (WCCT) analysis for packets transmitted over nDimNoC. In our experiments, we show that the WCCT of packets decreases when we increase the dimensionality of the NoC using nDimNoC 19s topolgy and routing policy. By implementing nDimNoC in Verilog and synthesizing it for an FPGA platform, we show that a 3D-nDimNoC requires "485-times less silicon than routers that use virtual channels (VC). We computed the maximum operating frequency of a 3D-nDimNoC with Xilinx Vivado. Increasing the number dimensions in the NoC improves WCCT at the cost of a more complex routing logic that may result in a reduced operating clock frequency.