Med-Hoc-Net 2007

Session 6: Modelling and Performance Evaluation

Performance Analysis of Wireless Controller Area Networks with Priority Scheme  

• Bechir Ben Gouissem (National School of Engineering of Tunisia (ENIT) – Tunisia)
• Sofiene Dridi (National School of Engineering of Tunis (ENIT) – Tunisia)
• Salem Hasnaoui, (National School of Engineering of Tunis (ENIT) – TUNISIA)

Abstract: For large-scale distributed systems, Data centric communication based on the publish/subscribe paradigm plays a key role on traffic volume control. More data filtering efficient and adaptive to different traffic conditions bring some solutions at the high layers of the communication model. Data Distribution Service (DDS) and OLE for Process Control Data Exchange (OPC-DX) are the most adopted solutions, in real-time data centric sensor networks. Some Real-time transport and Medium access control (MAC) protocols are proposed in the literature to support these types of networks.
Existing MAC protocols, scheduling based, collision free, contention based or hybrid schemes focus more on optimizing system throughput and do not adequately consider the requirements of sensor networks. The key challenge remains to provide predictable delay and/or prioritization guarantees while minimizing overhead packets and energy consumption. It is widely known that Control Area Networks (CAN) protocol is used in real-time, distributed and parallel processing. In this paper, we introduced a novel approach based on WCAN protocol in data centric communications model to manage concurrency and we use a Markov chain model for this protocol in order to evaluate his performances.

Pages: 153-158

Improving system clock precision with NTP offline skew correction

• Wolfgang Kiess (Heinrich-Heine Univ. Dusseldorf, Germany)
• Stephan Zalewski (Heinrich-Heine Univ. Dusseldorf, Germany)
• Martin Mauve (Heinrich-Heine Univ. Dusseldorf, Germany)

Abstract: The precision of computer clocks in personal digital assistant (PDA) class devices is typically quite low, they can easily drift more than 5 seconds per day. This is problematic when such devices are used for mobile ad-hoc network experiments, in which it is often necessary that devices distributed over a large area perform a certain action like sending packets simultaneously. We present in this paper a simple method that improves clock precision with standard Linux software components. This method is experimentally evaluated and it is shown that the clock precision in the devices used (HP iPAQ5550 and Sharp Zaurus SL-6000) improves by two orders of magnitude.

Pages: 159-164

Time Synchronization for Predictable and Secure Data Collection in Wireless Sensor Networks

• Shujuan Chen (Swedish Institute of Computer Science, Sweden)
• Adam Dunkels (Swedish Institute of Computer Science, Sweden)
• Fredrik Osterlind (Swedish Institute of Computer Science, Sweden)
• Thiemo Voigt (Swedish Institute of Computer Science, Sweden)
• Mikael Johansson (KTH Stockholm, Sweden)

Abstract: Wireless sensor networks are trying to find their way from relatively undemanding applications such as environmental monitoring to applications such as industrial control, which have stronger requirements in terms of security and predictability. Predictability cannot be achieved without coordination and the coordination of distributed entities and events requires time synchronization. Towards this end, we present a secure time synchronization service, that as our experimental results show does not degrade time synchronization accuracy. Based on the time synchronization service we implement time slotted data collection and present results that show that this way we can provide a predictable data collection service.

Pages: 165-172

Sensor Networks

• Markos Avlonitis (Ionian University, Greece)
• Panagiotis Vlamos (Ionian University, Greece)
• Konstantinos Oikonomou (Ionian University, Greece)

Abstract: Sensor network lifetime suffers from increased energy consumption especially for those nodes in close proximity to the sink node that undertake rather the role of forwarding other nodes’ data packets than their own. In this paper, a space-time analytical model is proposed to characterize the energy consumed in a sensor network under a rather simple medium access control policy. The proposed analytical model is studied and analyzed in this work revealing a phase transition phenomenon as the offered traffic load increases. Simulation results presented here are in compliance with the aforementioned analytical results.

Pages: 173-179

A Space-Time Analytical Model for Energy Consumption in Wireless
Energy-optimized Data Serialization For Heterogeneous WSNs Using Middleware Synthesis

• D. Pfisterer (University of Lubeck, Germany)
• M. Wegner (University of Lubeck, Germany)
• H. Hellbruck (University of Lubeck, Germany)
• C. Werner (University of Lubeck, Germany)
• S. Fischer (University of Lubeck, Germany)

Abstract: Developing applications for resource constrained devices is an intricate task in itself and additionally requires in-depth domain expertise to optimize aspects such as communication overhead, resource usage and energy consumption. Frequently, these refinements are omitted because they are time-consuming, laborious and error-prone. Hence, automating these aspects lets developers and applications intrinsically benefit from the wisdom of experts. In this paper we propose a combined approach to WSN development that is comprised of our novel data type serialization scheme microFibre and our previously published work FABRIC to generate custom tailored, lean code for heterogeneous devices. We present measurements showing that microFibre clearly outperforms existing well-known solutions in encoding quality while only moderately increasing the application’s footprint.

Pages: 180-187