Aspect] is a simple and practical aspect-oriented extension to Java With just a few new constructs, AspectJ provides support for modular implementation of a range of crosscutting concerns. In AspectJ's dynamic join point model, join points are well-defined points in the execution of the program; pointcuts are collections of join points; advice are special method-like constructs that can be attached to pointcuts; and aspects are modular units of crosscutting implementation, comprising pointcuts, advice, and ordinary Java member declarations. AspectJ code is compiled into standard Java bytecode. Simple extensions to existing Java development environments make it possible to browse the crosscutting structure of aspects in the same kind of way as one browses the inheritance structure of classes. Several examples show that AspectJ is powerful, and that programs written using it are easy to understand.

An overview of AspectJ

This study examines the random waypoint model widely used in the simulation studies of mobile ad hoc networks. Our findings show that this model fails to provide a steady state in that the average nodal speed consistently decreases over time, and therefore should not be directly used for simulation. We show how unreliable results can be obtained by using this model. In particular, certain ad hoc routing metrics can drop by as much as 40% over the course of a 900-second simulation using the random waypoint model. We give both an intuitive and a formal explanation for this phenomenon. We also propose a simple fix of the problem and discuss a few alternatives. Our modified random waypoint model is able to reach a steady state and simulation results are presented.

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Random waypoint considered harmful

Originating from basic research conducted in the 1970's and 1980's, the parallel and distributed simulation field has matured over the last few decades. Today, operational systems have been fielded for applications such as military training, analysis of communication networks, and air traffic control systems, to mention a few. The article gives an overview of technologies to distribute the execution of simulation programs over multiple computer systems. Particular emphasis is placed on synchronization (also called time management) algorithms as well as data distribution techniques.

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Parallel and Distributed Simulation Systems

The random waypoint model is a commonly used mobility model for simulations of wireless communication networks. By giving a formal description of this model in terms of a discrete-time stochastic process, we investigate some of its fundamental stochastic properties with respect to: (a) the transition length and time of a mobile node between two waypoints, (b) the spatial distribution of nodes, (c) the direction angle at the beginning of a movement transition, and (d) the cell change rate if the model is used in a cellular-structured system area.

The results of this paper are of practical value for performance analysis of mobile networks and give a deeper understanding of the behavior of this mobility model. Such understanding is necessary to avoid misinterpretation of simulation results. The movement duration and the cell change rate enable us to make a statement about the "degree of mobility" of a certain simulation scenario. Knowledge of the spatial node distribution is essential for all investigations in which the relative location of the mobile nodes is important. Finally, the direction distribution explains in an analytical manner the effect that nodes tend to move back to the middle of the system area.

Stochastic properties of the random waypoint mobility model

Objects. The ~ b s t rac t ~ b j ect forms the fundamental base class for the entire design and all other classes are derived from this base class. The Abstract Object class defines and characterizes all the essential properties every class in this 404 OBJECT-ORIENTED SIMULATION

Handbook of Simulation

Smart homes and home health monitoring technologies for older adults: a systematic review

We present a beacon-based clustering algorithm aimed at prolonging the cluster lifetime in VANETs. We use a new aggregate local mobility criterion to decide upon cluster re-organisation. The scheme incorporates a contention method to avoid triggering frequent re-organisations when two clusterheads encounter each other for a short period of time. Simulation results show a significant improvement of cluster lifetime and reduced node state/role changes compared to previous popular clustering algorithms.

A New Aggregate Local Mobility (ALM) Clustering Algorithm for VANETs

We consider the problem of scheduling in wireless sensor networks for the purposes of aggregation convergecast. We observe that existing schemes adopt essentially a two phase approach, consisting of, first, a tree construction and, second, a scheduling phase. Following a similar approach, we propose two new improvements, one to each of the two phases. Starting with a new lower bound on the schedule length, we make use of it in the tree construction phase. The tree construction phase consists of solutions to instances of bipartite graph semi-matchings. The scheduling phase is a weight-based priority scheme that obeys dependency (tree) and interference constraints. Our extensive experiments show that, overall, our proposed solution not only outperforms all previously proposed solutions in terms of schedule length, but it also significantly extends the network's lifetime.

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Aggregation convergecast scheduling in wireless sensor networks

Monitoring building energy consumption, thermal performance, and indoor air quality in a cold climate region

The Smart-Condo is a hardware/software platform that aims to support and assist an individual in performing a variety of everyday tasks within his/her living space. The key to achieving this goal is being able to recognize the individual's general activities in real-time, without impeding these activities or compromising privacy. Since location and movement constitute meaningful evidence for many everyday tasks (e.g., presence in the bathroom correlates with personal hygiene activities), we are motivated to develop an efficient, accurate, and noninvasive occupant-localization method. To this end, we propose a methodology for planning the deployment of an array of privacy-respecting binary motion sensors. In particular, given the geometric constraints of the deployment space, we generate a model of indoor mobility patterns typical for a single occupant. We then use this model as the basis for a specific optimization problem: maximizing a measure of how well the frequently-visited areas of the living space are covered by a number of sensors, subject to a cardinality constraint on this number. We argue this optimization objective is a good surrogate for maximizing localization accuracy, and prove that it bears exploitable properties that make it receptive to a simple optimization routine. As a result, we obtain sensor configurations with localization accuracy superior to that achievable with the same number of sensors placed manually or randomly in the same environment.

Ioanis Nikolaidis

Papers

Smart homes and home health monitoring technologies for older adults: a systematic review

A New Aggregate Local Mobility (ALM) Clustering Algorithm for VANETs

Aggregation convergecast scheduling in wireless sensor networks

Monitoring building energy consumption, thermal performance, and indoor air quality in a cold climate region

The Smart-Condo: Optimizing Sensor Placement for Indoor Localization