This work was in the center of Ricardo Gomes's work towards the achievement of his MSc degree in Electronics and Computers Engineering, at the Engineering School of the Polytechnic Institute of Porto (ISEP-IPP).
The WiFLEX project was the starting point for his MSc thesis entitled "Efficient Implementation of a Dominance Protocol for Wireless Medium Access", which the main goal was "the development of radio communication modules for Wireless Sensor Networks (WSN) to enable efficient implementations of bit dominance-based Medium Access Control (MAC) Protocols." The supervision and scientific orientation was played with the common effort of Dr. Björn Andersson and Prof. Nuno Pereira at CISTER / IPP-Hurray! R&D group.
The project intents to solve some of the problems that are limiting the acceptance of WiDOM bit dominance-based wireless MAC protocol, acting as a proof of feasibility and/or hardware state of the art requirement for the implementation of such protocol.
Thesis Abstract:
"Embedded computing systems went through extraordinary evolutions during the past two decades, representing nowadays one of the most promising technologies for improving a wide range of application areas such as energy/resource management, safety, health or entertainment. New sensors and actuators are leading to an unprecedented level of interaction between computing systems and their surrounding physical environment. These embedded computers tend to be networked, often wirelessly, and they are becoming denser, of larger scale and more pervasively deployed.
Since the wireless channel is a "natural resource" which must be shared between this large number of embedded computers, the medium access control (MAC) protocol significantly influences the performance of the entire system. In particular, satisfying real-time requirements — something that is needed for a computer to tightly interact with its physical environment — plays an important role. One solution was recently proposed by Pereira, Andersson and Tovar. It was a prioritized and collision-free MAC protocol belonging to a family of protocols called dominance/binary countdown protocols. This solution was implemented in commercial-off-the-shelf (COTS) wireless sensor networks (WSN) platforms and the implementation was demonstrated to be working. Unfortunately, those platforms had (for the MAC protocol) unfavourable characteristics which lead to limited efficiency and excessive overhead of the MAC protocol.
This work presents a new hardware platform, in the form of a network adapter for common WSN platforms, that allows an efficient implementation of dominance protocols for wireless medium access, allowing the medium access to be performed in less than 5 ms for 216 priority levels, which represents an overhead reduction of more than ten times as compared to the protocol implementation in COTS WSN platforms. Additionally, the overall energy consumption was reduced by approximately 45 % when compared to the theoretical best-case performance of the protocol implementation in COTS WSN platforms.
This work also allowed, for the first time ever, an aggregate computation scheme for WSN to work exploiting the new efficient implementation of a binary/dominance countdown protocol."
This work served as basis for the paper “Efficient Aggregate Computations in Large-Scale Dense WSN”, which has been accepted at the conference IEEE RTAS’09 Cyber Physical Systems (CPS) track. [DOI: 10.1109/RTAS.2009.22 | also available here]
Paper Abstract:
"We focus on large-scale and dense deeply embedded systems where, due to the large amount of information generated by all nodes, even simple aggregate computations such as the minimum value (MIN) of the sensor readings become notoriously expensive to obtain. Recent research has exploited a dominance-based medium access control(MAC) protocol, the CAN bus, for computing aggregated quantities in wired systems. For example, MIN can be computed efficiently and an interpolation function which approximates sensor data in an area can be obtained efficiently as well. Dominance-based MAC protocols have recently been proposed for wireless channels and these protocols can be expected to be used for achieving highly scalable aggregate computations in wireless systems. But no experimental demonstration is currently available in the research literature. In this paper, we demonstrate that highly scalable aggregate computations in wireless networks are possible. We do so by (i) building a new wireless hardware platform with appropriate characteristics for making dominance-based MAC protocols efficient, (ii) implementing dominance-based MAC protocols on this platform, (iii) implementing distributed algorithms for aggregate computations (MIN, MAX, Interpolation) using the new implementation of the dominance-based MAC protocol and (iv) performing experiments to prove that such highly scalable aggregate computations in wireless networks are possible."
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