Polytechnic Institute of Porto
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Symphony: routing aware scheduling for DSME networks
No full textDeterministic Synchronous Multichannel Extension (DSME) is a
prominent MAC behavior first introduced in IEEE 802.15.4e. It can
avail deterministic and best effort Service using its multisuperframe
structure. RPL is a routing protocol for wireless networks with low
power consumption and generally susceptible to packet loss. These
two standards were designed independently but with the common
objective to satisfy the requirements of IoT devices in terms of
limited energy, reliability and determinism. A combination of these
two protocols can integrate real-time QoS demanding and largescale IoT networks. In this paper, we propose a new multi-channel,
multi-timeslot scheduling algorithm called Symphony that provides
QoS efficient schedules in DSME networks. In this paper we provide
analytical and simulation based delay analysis for our approach
against some state of the art algorithms. In this work, we show that
integrating routing with DSME can improve reliability by 40 % and
by using Symphony, we can reduce the network delay by 10-20%
against the state of the art algorithms.info:eu-repo/semantics/publishedVersio
Design and Implementation of Secret Key Agreement for Platoon-based Vehicular Cyber-physical Systems
No full textIn a platoon-based vehicular cyber-physical system (PVCPS), a lead vehicle that is responsible for managing the platoon’s moving directions and velocity periodically disseminates control messages to the vehicles
that follow. Securing wireless transmissions of the messages between the vehicles is critical for privacy and
confidentiality of the platoon’s driving pattern. However, due to the broadcast nature of radio channels, the
transmissions are vulnerable to eavesdropping. In this article, we propose a cooperative secret key agreement
(CoopKey) scheme for encrypting/decrypting the control messages, where the vehicles in PVCPS generate
a unified secret key based on the quantized fading channel randomness. Channel quantization intervals are
optimized by dynamic programming to minimize the mismatch of keys. A platooning testbed is built with
autonomous robotic vehicles, where a TelosB wireless node is used for onboard data processing and multihop dissemination. Extensive real-world experiments demonstrate that CoopKey achieves significantly low
secret bit mismatch rate in a variety of settings. Moreover, the standard NIST test suite is employed to verify
randomness of the generated keys, where the p-values of our CoopKey pass all the randomness tests. We also
evaluate CoopKey with an extended platoon size via simulations to investigate the effect of system scalability
on performance.info:eu-repo/semantics/publishedVersio
AI-based Pilgrim Detection using Convolutional Neural Networks
No full textPilgrimage represents the most important Islamic religious gathering in the world where millions of pilgrims visit the holy places of Makkah and Madinah to perform their rituals. The safety and security of pilgrims is the highest priority for the authorities. In Makkah, 5000 cameras are spread around the holy mosques for monitoring pilgrims, but it is almost impossible to track all events by humans considering the huge number of images collected every second. To address this issue, we propose to use an artificial intelligence technique based on deep learning and convolutional neural networks to detect and identify Pilgrims and their features. For this purpose, we built a comprehensive dataset for the detection of pilgrims and their genders. Then, we develop two convolutional neural networks based on YOLOv3 and Faster-RCNN for the detection of Pilgrims. Experiment results show that Faster RCNN with Inception v2 feature extractor provides the best mean average precision over all classes (51%). A video demonstration that illustrates a real-time pilgrim detection using our proposed model is available at [1].info:eu-repo/semantics/publishedVersio
Unmanned Aerial Systems: Theoretical Foundation and Applications
No full textUnmanned Aerial Systems: Theoretical Foundation and Applications presents some of the latest innovative approaches to drones from the point-of-view of dynamic modeling, system analysis, optimization, control, communications, 3D-mapping, search and rescue, surveillance, farmland and construction monitoring, and more. With the emergence of low-cost UAS, a vast array of research works in academia and products in the industrial sectors have evolved. The book covers the safe operation of UAS, including, but not limited to, fundamental design, mission and path planning, control theory, computer vision, artificial intelligence, applications requirements, and more.
This book provides a unique reference of the state-of-the-art research and development of unmanned aerial systems, making it an essential resource for researchers, instructors and practitioners.info:eu-repo/semantics/publishedVersio
Decoupling of Optical and Electrical Properties of Rear Contact CIGS Solar Cells
No full textA novel architecture that comprises rear interface passivation and increased rear optical reflection is presented with the following advantages: i) enhanced optical reflection is achieved by the deposition of a metallic layer over the Mo rear contact; ii) improved interface quality with CIGS by adding a sputtered Al 2 O 3 layer over the metallic layer; and, iii) optimal ohmic electrical contact ensured by rear-openings refilling with a second layer of Mo as generally observed from the growth of CIGS on Mo. Hence, a decoupling between the electrical function and the optical purpose of the rear substrate is achieved. We present in detail the manufacturing procedure of such type of architecture together with its benefits and caveats. A preliminary analysis showing an architecture proof-of-concept is presented and discussed.info:eu-repo/semantics/publishedVersio
An Integrated Lateral and Longitudinal Look Ahead Controller for Cooperative Vehicular Platooning
No full textCooperative Vehicular Platooning (CoVP), has been emerging as a challenging Intelligent Traffic Systems application, promising to bring-about several safety and societal benefits. Relying on V2V communications to control such cooperative and automated actions brings several advantages. In this work, we present a Look Ahead PID controller for CoVP that solely relies upon V2V communications, together with a method to reduce the disturbance propagation in the platoon. The platooning controller also implements a solution to solve the cutting corner problem, keeping the platooning alignment. We evaluate its performance and limitations in realistic simulation scenarios, analyzing the stability and lateral errors of the CoVP, proving that such V2V enabled solutions can be effectively implemented.This work was partially supported by National Funds through FCT/MCTES (Portuguese Foundation for Science and Technology), within the CISTER Research Unit (UIDB/04234/2020).info:eu-repo/semantics/publishedVersio
Cache Persistence-Aware Memory Bus Contention Analysis for Multicore Systems
No full textMemory bus contention strongly relates to the number of main memory requests generated by tasks running on different cores of a multicore platform, which, in turn, depends on the content of the cache memories during the execution of those tasks. Recent works have shown that due to cache persistence the memory access demand of multiple jobs of a task may not always be equal to its worst-case memory access demand in isolation. Analysis of the variable memory access demand of tasks due to cache persistence leads to significantly tighter worst-case response time (WCRT) of tasks.In this work, we show how the notion of cache persistence can be extended from single-core to multicore systems. In particular, we focus on analyzing the impact of cache persistence on the memory bus contention suffered by tasks executing on a multi-core platform considering both work conserving and non-work conserving bus arbitration policies. Experimental evaluation shows that cache persistence-aware analyses of bus arbitration policies increase the number of task sets deemed schedulable by up to 70 percentage points in comparison to their respective counterparts that do not account for cache persistence.info:eu-repo/semantics/publishedVersio
Towards a Cooperative Robotic Platooning Testbed
No full textHighly Commended Paper AwardThe deployment of information and communication technologies in vehicles and into the transportation infrastructure in general, holds the promise of significant improvements to traffic safety and efficiency. The ETSI ITS-G5 standard presents itself as a viable and already available solution, to enable such intelligent social and mobility scenarios in the near future, including cooperative and autonomous vehicle platooning. However, the usage of wireless communications in safety-critical scenarios poses several challenges, and their reliability and safety must be adequately tested and validated. To do this, the safety concerns and cost of relying on real vehicles is prohibitive for early deployments. A solution lies in the use of robotic platforms, since these are relatively cheaper and allow to partially test real platforms and components, as well as different control mechanisms. This work presents the development of a 1/10 scale Cooperative Platooning Robotic Testbed with such aim. Real ITS-G5 On Board Units (OBU) were integrated in the vehicles for communications support and a cooperative control algorithm that solely relies on communications was successfully implemented.info:eu-repo/semantics/publishedVersio
Memory Bandwidth Regulation for Multiframe Task Sets
No full textTiming analysis of safety-critical real-time embedded systems should be free of both optimistic and pessimistic
aspects. The multiframe model was devised to eliminate the
pessimism in the schedulability analysis of systems with tasks
whose worst-case execution times vary from job to job, according
to known patterns. However, this model is optimistic and unsafe
for multicores with shared memory controllers, since it ignores
memory contention, and existing approaches to stall analysis
based on memory regulation are very pessimistic if straightforwardly applied. This paper remedies this by adapting existing
stall analyses for memory-regulated systems of conventional
Liu-and-Layland tasks to the multiframe model. Experimental
evaluations with synthetic task sets (and different task and
memory budget assignment heuristics) show up to 85% higher
scheduling success ratio for our analysis, compared to the frameagnostic analysis, enabling higher platform utilisation without
compromising safety. We also explore implementation aspects,
such as how to speed up the analysis and how to trade off
accuracy with tractability.info:eu-repo/semantics/publishedVersio
Techniques and Analysis for Mixed-criticality Scheduling with Mode-dependent Server Execution Budgets
No full textThis article appears as part of the ESWEEK-TECS special issue and was presented at the International Conference on Embedded Software (EMSOFT) 2019.In mixed-criticality systems, tasks of different criticality share system resources, mainly to reduce cost. Cost is
further reduced by using adaptive mode-based scheduling arrangements, such as Vestal’s model, to improve
resource efficiency, while guaranteeing schedulability of critical functionality. To simplify safety certification, servers are often used to provide temporal isolation between tasks. In its simplest form, a server is a
periodically recurring time window, in which some tasks are scheduled. A server’s computational requirements may greatly vary in different modes, although state-of-the-art techniques and schedulability tests do
not allow different budgets to be used by a server in different modes. This results in a single conservative
execution budget for all modes, increasing system cost.
The goal of this paper is to reduce the cost of mixed-criticality systems through three main contributions:
(i) a scheduling arrangement for uniprocessor systems employing fixed-priority scheduling within periodic
servers, whose budgets are dynamically adjusted at run-time in the event of a mode change, (ii) a new schedulability analysis for such systems, and (iii) heuristic algorithms for assigning budgets to servers in different
modes and ordering the execution of the servers. Experiments with synthetic task sets demonstrate considerable improvements (up to 52.8%) ininfo:eu-repo/semantics/publishedVersio