Otto W. Visser

Murphy loves potatoes: experiences from a pilot sensor network deployment in precision agriculture

We report on preliminary experiences with deploying a large-scale sensor network (about 100 nodes) for a pilot in precision agriculture. The pilot did not answer the initial research questions, but instead revealed many engineering problems typically overlooked by (computer) scientists evaluating their work by means of simulation. The deployment prompted us to rethink our development process and includes important lessons for the WSN research community as a whole

Simulating wireless and mobile networks in OMNeT++ the MiXiM vision

Wireless communication has attracted considerable interest in the research community, and many wireless networks are evaluated using discrete event simulators like OMNeT++. Although OMNeT++ provides a powerful and clear simulation framework, it lacks of direct support and a concise modeling chain for wireless communication. Both is provided by MiXiM. MiXiM joins and extends several existing simulation frameworks developed for wireless and mobile simulations in OMNeT++. It provides detailed models of the wireless channel (fading, etc.), wireless connectivity, mobility models, models for obstacles and many communication protocols especially at the Medium Access Control (MAC) level. Further, it provides a user-friendly graphical representation of wireless and mobile networks in OMNeT++, supporting debugging and defining even complex wireless scenarios. Though still in development, MiXiM already is a powerful tool for performance analysis of wireless networks. Its extensive functionality and clear concept may motivate researches to contribute to this open-source project [4].

An analysis of online match-based games

Online match-based games, such as the online versions of the board game of chess, have already captured a global audience of tens of millions of players. Through a unique combination of characteristics, a relatively short duration-often “coffee-break” minutes instead of hours of continuous gameplay-, weak correlation between matches, and clear emphasis on winning, match-based games may serve a unique segment of the global player population. Although this segment of the gaming population may later become consumers of more sophisticated Massively Multiuser Virtual Environment (MMVE) systems, few previous studies have focused on the characteristics of online match-based games. Complementing them, in this work we collect and analyze information corresponding to 5 online match-based game datasets, totaling over 170 million matches played by a population of 1.3 million unique gamers over 14 years. Our analysis focuses on workload characteristics, win ratio, and player evolution. Studies such as ours may guide the multi-disciplinary field of MMVE design by providing new understanding of player lifetime and behavior. For example, we find a correlation between the interactivity of match-based games and the retention of players over both long and short term, that friendship does not always help to perform better in games, and that in match-based games each player explores tens of different play strategies over time.

Towards comparable simulations of cooperating objects and wireless sensor networks

Simulators are indispensable tools to support the development and testing of cooperating objects such as wireless sensor networks (WSN). However, it is often not possible to compare the results of different simulation tools. Thus, the goal of this paper is the specification of a generic simulation platform for cooperating objects. We propose a platform that consists of a set of simulators that together fulfill desired simulator properties. We show that to achieve comparable results the use of a common specification language for the software-under-test is not feasible. Instead, we argue that using common input formats for the simulated environment and common output formats for the results is useful. This again motivates that a simulation tool consisting of a set of existing simulators that are able to use common scenario-input and can produce common output which will bring us a step closer to the vision of achieving comparable simulation results.

RTSenv: An experimental environment for real-time strategy games

Today, Real-Time Strategy (RTS) games entertain tens of millions of players world-wide. This growing population expects new game designs and more scalable games every year. However, few tools and environments exist for game designers and implementers; of these, even fewer are available to researchers and game communities. In this work, we introduce RTSenv, an environment and associated set of tools for RTS games. Our environment can configure and manage the main aspects of RTS games, such as maps, computer-controlled units, and game scenarios. RTSenv leverages multi-cluster systems and reactive fault tolerance mechanisms to perform robust, multi-machine, and multi-instance game experiments. Using our reference implementation of RTSenv in DAS-4, a real multi-cluster system, and Amazon EC2, a commercial cloud, we show that our approach can be used in a variety of scenarios. Our results give evidence that several common assumptions made by researchers about game workloads do not hold in general for RTS games and thus warrant a more detailed investigation.

A mirroring architecture for sophisticated mobile games using computation-offloading: A Mirroring Architecture for Sophisticated Mobile Games using Computation-Offloading

Mobile gaming is already a popular and lucrative market. However, the low performance and reduced power capacity of mobile devices severely limit the complexity of mobile games and the duration of their game sessions. To mitigate these issues, in this article, we explore using computation‐offloading, that is, allowing the compute‐intensive parts of mobile games to execute on remote infrastructure. Computation‐offloading raises the combined challenge of addressing the trade‐offs between performance and power‐consumption while also keeping the game playable. We propose Mirror, a system for computation‐offloading that supports the demanding performance requirements of sophisticated mobile games. Mirror proposes several conceptual contributions: support for fine‐grained partitioning, both offline (set by developers) and dynamic (policy‐based), and real‐time asynchronous offloading and user‐input synchronization protocols that enable Mirror‐based systems to bound the delays introduced by offloading and thus to achieve adequate performance. Mirror is compatible with all games that are tick‐based and user‐input deterministic. We implement a real‐world prototype of Mirror and apply it to the real‐world, complex, popular game OpenTTD. The experimental results show that, in comparison with the non‐offloaded OpenTTD, Mirror‐ed OpenTTD can significantly improve performance and power consumption while also delivering smooth gameplay. As a trade‐off, Mirror introduces acceptable delay on user inputs.

Mirror: A computation-offloading framework for sophisticated mobile games

The low performance and power limitations of mobile devices severely limit the complexity and the duration of playing sessions of mobile games. This article examines the possibility of using computation-offloading to mitigate these problems while keeping the game playable. We design Mirror, a framework for offloading computation targeted at the demanding performance requirements of sophisticated mobile games. The key conceptual contributions of Mirror are design decisions that allow for dynamic fine-grained client-side offloading decisions, and a protocol for real-time asynchronous offloading for bounding network delays. We implement a prototype of Mirror and test it by performing offloading for the game OpenTTD. The results are promising, showing that Mirror can increase the performance and decrease the power consumption of games while keeping the gameplay fairly smooth.