scholarly journals Network Calculus-Based Latency for Time-Triggered Traffic under Flexible Window-Overlapping Scheduling (FWOS) in a Time-Sensitive Network (TSN)

2021 ◽  
Vol 11 (9) ◽  
pp. 3896
Author(s):  
Khaled M. Shalghum ◽  
Nor Kamariah Noordin ◽  
Aduwati Sali ◽  
Fazirulhisyam Hashim
Keyword(s):  
Real Time ◽  
Connected Vehicles ◽  
Network Calculus ◽  
Timing Constraints ◽  
Traffic Scheduling ◽  
Worst Case ◽  
Continuous Increase ◽  
Scheduled Traffic ◽  
Support Time ◽  
New Framework

Deterministic latency is an urgent demand to pursue the continuous increase in intelligence in several real-time applications, such as connected vehicles and automation industries. A time-sensitive network (TSN) is a new framework introduced to serve these applications. Several functions are defined in the TSN standard to support time-triggered (TT) requirements, such as IEEE 802.1Qbv and IEEE 802.1Qbu for traffic scheduling and preemption mechanisms, respectively. However, implementing strict timing constraints to support scheduled traffic can miss the needs of unscheduled real-time flows. Accordingly, more relaxed scheduling algorithms are required. In this paper, we introduce the flexible window-overlapping scheduling (FWOS) algorithm that optimizes the overlapping among TT windows by three different metrics: the priority of overlapping, the position of overlapping, and the overlapping ratio (OR). An analytical model for the worst-case end-to-end delay (WCD) is derived using the network calculus (NC) approach considering the relative relationships between window offsets for consecutive nodes and evaluated under a realistic vehicle use case. While guaranteeing latency deadline for TT traffic, the FWOS algorithm defines the maximum allowable OR that maximizes the bandwidth available for unscheduled transmission. Even under a non-overlapping scenario, less pessimistic latency bounds have been obtained using FWOS than the latest related works.

scholarly journals Comparison of Scheduling Algorithms in The Design of Fault Tolerant Real Time Systems

2018 ◽  
Vol 7 (2.7) ◽  
pp. 618
Author(s):  
Mary Swarna Latha Gade ◽  
K Sreenivasa Ravi
Keyword(s):  
Real Time ◽  
Fault Tolerant ◽  
Scheduling Algorithms ◽  
Timing Constraints ◽  
Real Time Systems ◽  
Worst Case ◽  
Real Time System ◽  
Utilization Factor ◽  
Functional Correctness ◽  
Time Systems

Most of the real time systems have the timing constraints. The main important timing constraints of any real time systems are to meet the deadlines of its application tasks. Not only satisfying the timing constraints of any real-time system, but also the functional correctness of application needs to be guaranteed. Meeting the dead line of application is no use if it deviates from its precise output. Timing constraints of the system can be satisfied by choosing proper task scheduling algorithms and the reliability of the system can be reached by providing fault-tolerance. In this paper, various fault scheduling algorithms like fixed priority, EDF(Earliest dead line first), LLF (Least Laxity First),Rate monotonic etc have been studied and compare the parameters like Worst-case execution times, response time, task missed deadlines, Number of preemption, number of context switches, Deadlock  and processor utilization factor. 

scholarly journals Real-Time Safety Optimization of Connected Vehicle Trajectories Using Reinforcement Learning

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3864
Author(s):  
Tarek Ghoul ◽  
Tarek Sayed
Keyword(s):  
Reinforcement Learning ◽  
Real Time ◽  
Low Cost ◽  
Safety Evaluation ◽  
Traffic Volume ◽  
Connected Vehicles ◽  
Connected Vehicle ◽  
Real World Data ◽  
Physical Constraints ◽  
Traffic Conflicts

Speed advisories are used on highways to inform vehicles of upcoming changes in traffic conditions and apply a variable speed limit to reduce traffic conflicts and delays. This study applies a similar concept to intersections with respect to connected vehicles to provide dynamic speed advisories in real-time that guide vehicles towards an optimum speed. Real-time safety evaluation models for signalized intersections that depend on dynamic traffic parameters such as traffic volume and shock wave characteristics were used for this purpose. The proposed algorithm incorporates a rule-based approach alongside a Deep Deterministic Policy Gradient reinforcement learning technique (DDPG) to assign ideal speeds for connected vehicles at intersections and improve safety. The system was tested on two intersections using real-world data and yielded an average reduction in traffic conflicts ranging from 9% to 23%. Further analysis was performed to show that the algorithm yields tangible results even at lower market penetration rates (MPR). The algorithm was tested on the same intersection with different traffic volume conditions as well as on another intersection with different physical constraints and characteristics. The proposed algorithm provides a low-cost approach that is not computationally intensive and works towards optimizing for safety by reducing rear-end traffic conflicts.

scholarly journals Constructing Test Suites for Real-Time Embedded Systems Under Input Timing Constraints

IEEE Access ◽  
2019 ◽  
Vol 7 ◽  
pp. 20920-20937
Author(s):  
Yunlong Sheng ◽  
Shouda Jiang ◽  
Changan Wei
Keyword(s):  
Embedded Systems ◽  
Real Time ◽  
Timing Constraints ◽  
Test Suites

scholarly journals A RED modified weighted moving average for soft real-time application

2014 ◽  
Vol 24 (3) ◽  
pp. 697-707 ◽  
Author(s):  
Joanna Domanśka ◽  
Adam Domański ◽  
Dariusz R. Augustyn ◽  
Jerzy Klamka
Keyword(s):  
Real Time ◽  
Optimization Problem ◽  
Optimality Criterion ◽  
Task Force ◽  
Moving Average ◽  
Timing Constraints ◽  
Real Time Traffic ◽  
Real Time Application ◽  
Weighted Moving Average

Abstract The popularity of TCP/IP has resulted in an increase in usage of best-effort networks for real-time communication. Much effort has been spent to ensure quality of service for soft real-time traffic over IP networks. The Internet Engineering Task Force has proposed some architecture components, such as Active Queue Management (AQM). The paper investigates the influence of the weighted moving average on packet waiting time reduction for an AQM mechanism: the RED algorithm. The proposed method for computing the average queue length is based on a difference equation (a recursive equation). Depending on a particular optimality criterion, proper parameters of the modified weighted moving average function can be chosen. This change will allow reducing the number of violations of timing constraints and better use of this mechanism for soft real-time transmissions. The optimization problem is solved through simulations performed in OMNeT++ and later verified experimentally on a Linux implementation

The Ach Library: A New Framework for Real-Time Communication

2015 ◽  
Vol 22 (1) ◽  
pp. 76-85 ◽  
Author(s):  
Neil T. Dantam ◽  
Daniel M. Lofaro ◽  
Ayonga Hereid ◽  
Paul Y. Oh ◽  
Aaron D. Ames ◽  
...  
Keyword(s):  
Real Time ◽  
New Framework

Telecommunications- and Information Technology–Inspired Analyses: Review of an Intelligent Transportation Systems Experience

2017 ◽  
Vol 2658 (1) ◽  
pp. 44-55 ◽  
Author(s):  
Yupo Chan
Keyword(s):  
Information Technology ◽  
Big Data ◽  
Real Time ◽  
Traffic Management ◽  
Transportation Systems ◽  
Lessons Learned ◽  
Connected Vehicles ◽  
Ongoing Research ◽  
Real Time Information ◽  
Time Information

This paper reviews both the author’s experience with managing highway network traffic on a real-time basis and the ongoing research into harnessing the potential of telecommunications and information technology (IT). On the basis of the lessons learned, this paper speculates about how telecommunications and IT capabilities can respond to current and future developments in traffic management. Issues arising from disruptive telecommunications technologies include the ready availability of real-time information, the crowdsourcing of information, the challenges of big data, and the need for information quality. Issues arising from transportation technologies include autonomous vehicles and connected vehicles and new taxi-like car- and bikesharing. Illustrations are drawn from the following core functions of a traffic management center: ( a) detecting and resolving an incident (possibly through crowdsourcing), ( b) monitoring and forecasting traffic (possibly through connected vehicles serving as sensors), ( c) advising motorists about routing alternatives (possibly through real-time information), and ( d) configuring traffic control strategies and tactics (possibly though big data). The conclusion drawn is that agility is the key to success in an ever-evolving technological scene. The solid guiding principle remains innovative and rigorous analytical procedures that build on the state of the art in the field, including both hard and soft technologies. The biggest modeling and simulation challenge remains the unknown, including such rapidly emerging trends as the Internet of things and the smart city.

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