Percorrer por autor "Sousa, Paulo Baltarejo"
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- Bit error modelsPublication . Sousa, Paulo Baltarejo; Ferreira, Luís LinoThe use of bit error models in communication simulation has been widely studied. In this technical report we present three models: the Independent Channel Model; the Gilbert-Elliot Model and the Burst-Error Periodic Model.
- Bridge architecture to interconnect hybrid wired/wireless PROFIBUS networksPublication . Sousa, Paulo Baltarejo; Ferreira, Luís LinoThe integration of wired and wireless technologies in modern manufacturing plants is now of paramount importance for the competitiveness of any industry. Being PROFIBUS the most widely used technology in use for industrial communications, several solutions have been proposed to provide PROFIBUS networks with wireless communications. One of them, the bridge-based hybrid wired/wireless PROFIBUS network approach, proposes an architecture in which the Intermediate Systems operate at Data Link Layer level, as bridges. In this paper, we propose an architecture for the implementation of such a bridge and the required protocols to handle communication between stations in different domains and the mobility of wireless stations.
- Development of a mass drug administration monitoring system for a humanitarian NGOPublication . Ribeiro, Rafael; Teixeira, Cláudio; Vicente, Pedro; Sousa, Paulo BaltarejoMass drug administration is the process of distributing medication to people who are in areas with risk of neglected tropical diseases. The monitoring of this process is supported by the application of forms in the communities, which are then sent to the headquarters, where they are manually entered into governmental health information systems. This paper aims at finding a solution for automating the process, making it more efficient, reliable and scalable. The proposed solution involves the usage of Optical Character Recognition (OCR) to extract the data, and is composed of a Backend, an Android Application and a Backoffice. It was evaluated using several metrics, achieving mean values of 0.8% Character Error Rate (CER), 2.5% Word Error Rate (WER), 3.7% Field Error Rate (FER) and 96.2% Precision, Recall and F1 score. Forms filled in English and forms filled using print handwriting style had significantly better results than forms filled in Portuguese and forms filled using cursive style, respectively. The application was used by two testers from the Nongovernmental Organization (NGO), resulting in positive feedback, with some improvements being suggested.
- Enhancing the real-time capabilities of the Linux KernelPublication . Sousa, Paulo Baltarejo; Pereira, Nuno; Tovar, EduardoThe mainline Linux Kernel is not designed forhard real-time systems; it only fits the requirements of soft realtimesystems. In recent years, a kernel developer communityhas been working on the PREEMPT-RT patch. This patch(that aims to get a fully preemptible kernel) adds some realtimecapabilities to the Linux kernel. However, in terms ofscheduling policies, the real-time scheduling class of Linux islimited to the First-In-First-Out (SCHED_FIFO) and Round-Robin (SCHED_RR) scheduling policies. These scheduling policiesare however quite limited in terms of realtime performance.Therefore, in this paper, we report one importantcontribution for adding more advanced real-time capabilitiesto the Linux Kernel. Specifically, we describe modificationsto the (PREEMPT-RT patched) Linux kernel to supportreal-time slot-based task-splitting scheduling algorithms. Ourpreliminary evaluation shows that our implementation exhibitsa real-time performance that is superior to the schedulingpolicies provided by the current version of PREMPT-RT. Thisis a significant add-on to a widely adopted operating system.
- Hybrid wired/wireless PROFIBUS architectures: performance study based on simulation modelsPublication . Sousa, Paulo Baltarejo; Ferreira, Luís LinoThe problem of providing a hybrid wired/wireless communications for factory automation systems is still an open issue, notwithstanding the fact that already there are some solutions. This paper describes the role of simulation tools on the validation and performance analysis of two wireless extensions for the PROFIBUS protocol. In one of them, the Intermediate Systems, which connect wired and wireless network segments, operate as repeaters. In the other one the Intermediate Systems operate as bridge. We also describe how the analytical analysis proposed for these kinds of networks can be used for the setting of some network parameters and for the guaranteeing real-time behaviour of the system. Additionally, we also compare the bridge-based solution simulation results with the analytical results.
- Implementing slot-based task-splitting multiprocessor schedulingPublication . Sousa, Paulo Baltarejo; Andersson, Björn; Tovar, EduardoConsider the problem of scheduling a set of sporadic tasks on a multiprocessor system to meet deadlines using a task-splitting scheduling algorithm. Task-splitting (also called semi-partitioning) scheduling algorithms assign most tasks to just one processor but a few tasks are assigned to two or more processors, and they are dispatched in a way that ensures that a task never executes on two or more processors simultaneously. A particular type of task-splitting algorithms, called slot-based task-splitting dispatching, is of particular interest because of its ability to schedule tasks with high processor utilizations. Unfortunately, no slot-based task-splitting algorithm has been implemented in a real operating system so far. In this paper we discuss and propose some modifications to the slot-based task-splitting algorithm driven by implementation concerns, and we report the first implementation of this family of algorithms in a real operating system running Linux kernel version 2.6.34. We have also conducted an extensive range of experiments on a 4-core multicore desktop PC running task-sets with utilizations of up to 88%. The results show that the behavior of our implementation is in line with the theoretical framework behind it.
- Mobility simulatorPublication . Sousa, Paulo Baltarejo; Ferreira, Luís LinoThis technical report describes the Mobility Simulator that implements a simulation model of the station mobility and the radio wave propagation.
- On the implementation of real-time slotbased task-splitting scheduling algorithms for multiprocessor systemsPublication . Sousa, Paulo Baltarejo; Bletsas, Konstantinos; Tovar, Eduardo; Andersson, BjörnIn this paper we discuss challenges and design principles of an implementation of slot-based tasksplitting algorithms into the Linux 2.6.34 version. We show that this kernel version is provided with the required features for implementing such scheduling algorithms. We show that the real behavior of the scheduling algorithm is very close to the theoretical. We run and discuss experiments on 4-core and 24-core machines.
- Practical aspects of slot-based task- splitting dispatching in its schedulability analysisPublication . Sousa, Paulo Baltarejo; Bletsas, Konstantinos; Andersson, Björn; Tovar, EduardoConsider the problem of scheduling a set of sporadic tasks on a multiprocessor system to meet deadlines using a tasksplitting scheduling algorithm. Task-splitting (also called semipartitioning) scheduling algorithms assign most tasks to just one processor but a few tasks are assigned to two or more processors, and they are dispatched in a way that ensures that a task never executes on two or more processors simultaneously. A certain type of task-splitting algorithms, called slot-based task-splitting, is of particular interest because of its ability to schedule tasks at high processor utilizations. We present a new schedulability analysis for slot-based task-splitting scheduling algorithms that takes the overhead into account and also a new task assignment algorithm.
- Probability distribution functionsPublication . Sousa, Paulo Baltarejo; Ferreira, Luís LinoThis technical report describes the PDFs which have been implemented to model the behaviours of certain parameters of the Repeater-Based Hybrid Wired/Wireless PROFIBUS Network Simulator (RHW2PNetSim) and Bridge-Based Hybrid Wired/Wireless PROFIBUS Network Simulator (BHW2PNetSim).