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In many sensor network applications the major traffic pattern consists of data collected from many source nodes to a sink through a tree. In this paper, we propose S-Non Bcn based on nonbeacon-enabled (Non Bcn) mode of IEEE 802.15.4, an energy-efficient and low-collision MAC that is designed and optimized for such data gathering trees in wireless sensor networks. S-Non Bcn uses staggered sleep mechanism...
Wireless sensor networks, WSNs, are an efficient way to deal with low-rate communications in confined environments such as mines or nuclear power plants because of their simplicity of deployment and low cost. In these application domains, WSNs are used to gather data from sensor nodes towards a sink in a multi-hop convergecast structure. In this paper, we focus on a traffic-aware time slot assignment...
Timeliness and accuracy are two major concerns in many real-time embedded systems working in dynamic environments. It has been emphasized in the literature that in various real-time applications such as control systems and Kalman filters, delay is one main source of inaccuracy in the system. In this paper, we present a solution based on scheduling algorithms for the problem of inaccuracy in such systems...
The lacking of a thorough understanding on the capacity in mobile ad hoc networks (MANETs) has been stunting their applications in the last decade. Available capacity studies focus on exploring either the order sense capacity scaling laws, the closed-form capacity under some specific routing protocols, or the exact capacity without careful consideration of wireless interference issue in MANETs. In...
Systems with tightly interacting computational (cyber) units and physical systems are generally referred to as cyber-physical systems. They involve an interplay between embedded systems, control theory, real-time systems and software engineering. A very good example of cyber-physical systems design arises in the context of automotive architectures and software. Modern high-end cars have 50–100 processors...
Real-time systems are often modeled as a collection of tasks, describing the structure of the processor's workload. In the literature, task-models of different expressiveness have been developed, ranging from the traditional periodic task model to highly expressive graph-based models. For dynamic priority schedulers, it has been shown that the schedulability problem can be solved efficiently, even...
We examine the problem of computing the worst-case first-to-first information propagation delay through a sequence of fixed-priority periodic tasks with different periods. This propagation delay is the span of time from the moment information becomes available until the first time the final task in the sequence produces an output that uses this (or more recent) input. We consider task systems in which...
Systems engineering is often ineffective in development environments where large, complex, brownfield systems of systems are evolved through parallel development of new capabilities in response to external, time-sensitive requirements. This paper defines a conceptual framework to improve that effectiveness and better integrate the systems engineering and software engineering processes. The framework...
Data centers are nowadays ubiquitous, in a worldwide scale, and often geographically dispersed. In such environments, data reliability and availability are enhanced via data redundancy throughout the distributed storage. Because user performance is important in data centers, data updates in such distributed environments are done such that eventual consistency is achieved. In this paper we utilize...
In this paper we develop a novel bottleneck model which assumes that the capacity of the bottleneck is stochastic and follows uniform distribution. Commuters form a heterogeneous population with distinctive requirements on the probability of punctual arrival and the commuters' trip scheduling follows user equilibrium (UE) principle in terms of the mean travel cost. The analytical solution of the proposed...
A large part of power dissipation in a system is generated by I/O devices. Increasingly these devices provide power saving mechanisms, inter alia to enhance battery life. While I/O device scheduling has been studied in the past for real-time systems, the use of energy resources by these scheduling algorithms may be improved. These approaches are crafted considering a very large overhead of device...
Wireless Sensor Networks have been used in many mobile applications such as wildlife tracking and participatory urban sensing. Because of the combination of high mobility and low-duty-cycle operations, it is a challenging issue to reduce discovery delay among mobile nodes, so that mobile nodes can establish connection quickly once they are within each other's vicinity. Existing discovery designs are...
In this paper, we present an approach to bounded optimal planning and flexible execution for a robot team performing a set of spatially distributed tasks related by temporal ordering constraints such as precedence or synchronization. Furthermore, the manner in which the temporal constraints are satisfied impacts the overall utility of the team, due to the existence of both routing and delay costs...
In social swarming applications, participants equipped with 3G and WiFi-capable smart phones are tasked to provide reports (possibly voluminous ones that include full-motion video) about their immediate environment to a central coordinator. In this paper, we consider the problem of timely delivery of these reports: each report has an associated deadline and the goal of the system is to retrieve as...
This paper is focused on the research of instruction scheduling technology for clustered VLIW architecture. A novel scheduling technology is presented in this work, which exploits the tradeoff between the balancing of distribution of instructions amongst clusters and reduction of the amount of inter-cluster data communications, and guides the cluster assign and cycle schedule of instructions by estimating...
When airport arrival slots are scheduled in excess of the available capacity, the scheduled flights are assigned slots by a rationing scheme. The traditional approach is to ration slots by schedule (RBS) on a first-scheduled/first-assigned basis. This approach, although meeting equity criteria, can result in inefficient use of the arrival slots in terms of passenger throughput and fuel burn; however,...
In this work, we consider a passive optical network (PON) with reduced buffer capacity at the Optical Network Unit (ONU). The objective is to reduce the ONU power consumption by having smaller buffers. This requires that some of the end-nodes packets be buffered at the end-node itself (EN) and some buffered at the ONU. These packets will be used to fill the upstream transmission time slot allotted...
This paper draws an overview of rail passenger service disruptions which lead to service delays. Some findings on the train service delays in some parts of Asia and Western Europe are presented. The types and causes of service disruptions are analyzed across some rail network operators. The equivalent cost measures of delays done by past studies are also discussed. These costs are expressed in terms...
Energy consumption of wireless data transmission heavily depends on the shape of the outgoing traffic of the mobile device. In this paper, we propose a traffic scheduler that shapes the packets into consistent bursts based on per-packet performance constraints in order to reduce the overall transmission cost. Our scheduler takes into account the scenarios where multiple network applications run concurrently...
This paper presents an exact method and a heuristic method for static rate-optimal multiprocessor scheduling of real-time multi rate DSP algorithms represented by synchronous data flow graphs (SDFGs). Through exploring the state-space generated by a self-timed execution (STE) of an SDFG, a static rate-optimal schedule via explicit retiming and implicit unfolding can be found by our exact method. By...
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