G. Oikonomou, I. Phillips, "Experiences from Porting the Contiki Operating System to a Popular Hardware Platform", in Proc. 2011 International Conference on Distributed Computing in Sensor Systems and Workshops (DCOSS), Barcelona, Spain, pp. 54-59, 2011
In contrast to original belief, recent work has demonstrated the viability of IPv6-based Wireless Sensor Networks (WSNs). This has led to significant research and standardization efforts with outcomes such as the ``IPv6 over Low-Power Wireless Personal Area Networks'' (6LoWPAN) specification. The Contiki embedded operating system is an important open source, multi-platform effort to implement 6LoWPAN functionality for constrained devices. Alongside its RFC-compliant TCP/IP stack (uIP), it provides support for 6LoWPAN and many related standards. As part of our work, we have made considerable fixes and enhancements to one of Contiki's ports. In the process, we made significant optimizations and a thorough evaluation of Contiki's memory and code footprint characteristics, focusing on network-related functionality. In this paper we present our experiences from the porting process, we disclose our optimizations and demonstrate their significance. Lastly, we discuss a method of using Contiki to deploy an embedded Internet-to-6LoWPAN router. Our porting work has been made available to the community under the terms of the Contiki license.
V. Michopoulos, L. Guan, G. Oikonomou, I. Phillips, "A Comparative Study of Congestion Control Algorithms in IPv6 Wireless Sensor Networks", in Proc. 2011 International Conference on Distributed Computing in Sensor Systems and Workshops (DCOSS), Barcelona, Spain, pp. 1-6, 2011
In Wireless Sensor Networks (WSNs), congestion can cause a plethora of malfunctions such as packet loss, lower throughput and energy inefficiency, potentially resulting in reduced deployment lifetime and under-performing applications. This has led to several proposals describing congestion control (CC) mechanisms for sensor networks. Furthermore, the WSN research community has made significant efforts towards power saving MAC protocols with Radio Duty Cycling (RDC). However, careful study of previous work reveals that RDC schemes are often neglected during the design and evaluation of congestion control algorithms. In this paper, we argue that the presence (or lack) of RDC can drastically influence the performance of congestion detection. In addition, most WSN CC mechanisms are evaluated under traditional sensor network topologies and protocols (e.g. trickle data dissemination, tree data collection). The emerging IPv6 over Low power Wireless Personal Area Networks (6LoWPAN) and related standards pose a new requirement: we now need to investigate if previous findings regarding congestion control are still applicable. In this context, this paper contributes a comprehensive evaluation of existing congestion detection mechanisms in a simulated, multi-node 6LoWPAN sensor network. We present results from two sets of experiments, differentiated by the presence or lack of RDC.
G. Oikonomou, I. Phillips, L. Guan, A. Grigg, "ADDER: Probabilistic, Application Layer Service Discovery for MANETs and Hybrid Wired-Wireless Networks", in Proc. 9th Annual Communication Networks and Services Research Conference (CNSR 2011), Ottawa, Canada, pp. 33-40, 2011
Over the past years, Mobile ad-hoc networks (MANETs) have attracted a considerable degree of research attention, with service discovery, selection and invocation being among the topics of interest of previous efforts. In this paper we introduce ADDER, a probabilistic, hybrid, directory-less service discovery mechanism. It has been designed for military IPv6-based MANETs but will work in any hybrid wired-wireless deployment. It achieves very low service acquisition time through the exchange of a very small number of short messages. Propagation of service descriptions is based on a distance vector algorithm, achieving loop and starvation freedom through a feasibility condition, which has been adopted from established and well-tested routing protocols. This paper also presents evaluation results, obtained by actual execution of the ADDER daemon on two different test beds. The experiments aim to demonstrate that the mechanism achieves good scalability with increasing number of services and network size.
A. Jamil, D. Parish, R. Phan, J. Whitley, I. Phillips, G. Oikonomou, "Designing Environmental Aware Routing in Wireless Sensor Networks", London, UK, 2011 (non-refereed)
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