| 1. |
- Boano, Carlo Alberto, et al.
(författare)
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Mitigating the Adverse Effects of Temperature on Low-Power Wireless Protocols
- 2014. - 7
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Konferensbidrag (refereegranskat)abstract
- Research and industrial installations have shown that the on-board temperature of wireless sensor nodes deployed outdoors can experience high fluctuations over time with a large variability across the network. These variations can have a strong impact on the efficiency of low-power radios and can significantly affect the operation of communication protocols, often compromising network connectivity. In this paper, we show the adverse effects of temperature on communication protocols and propose techniques to increase their resilience. First, we experimentally show that fluctuations of the on-board temperature of sensor nodes reduce the efficiency of data link layer protocols, leading to a substantial decrease in packet reception rate and to a considerable increase in energy consumption. Second, we investigate the reasons for such performance degradation, and show that high on-board temperatures reduce the effectiveness of clear channel assessment, compromising the ability of a node to avoid collisions and to successfully wake-up from low-power mode. After modelling the behaviour of radio transceivers as a function of temperature, we propose two mechanisms to dynamically adapt the clear channel assessment threshold to temperature changes, thus making data link layer protocols temperature-aware. An extensive experimental evaluation shows that our approaches considerably increase the performance of a network in the presence of temperature variations commonly found in real-world outdoor deployments, with up to 42% lower radio duty-cycle and 87% higher packet reception rate.
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| 2. |
- Boario, Carlo Alberto, et al.
(författare)
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TempLab : A testbed infrastructure to study the impact of temperature on wireless sensor networks
- 2014
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Ingår i: IPSN 2014 - Proceedings of the 13th International Symposium on Information Processing in Sensor Networks (Part of CPS Week). - : IEEE Computer Society. - 9781479931460 ; , s. 95-106
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Konferensbidrag (refereegranskat)abstract
- Temperature has a strong impact on the operations of all electrical and electronic components. In wireless sensor nodes, temperature variations can lead to loss of synchronization, degradation of the link quality, or early battery depletion, and can therefore affect key network metrics such as throughput, delay, and lifetime. Considering that most outdoor deployments are exposed to strong temperature variations across time and space, a deep understanding of how temperature affects network protocols is fundamental to comprehend flaws in their design and to improve their performance. Existing testbed infrastructures, however, do not allow to systematically study the impact of temperature on wireless sensor networks. In this paper we present TempLab, an extension for wireless sensor network testbeds that allows to control the on-board temperature of sensor nodes and to study the effects of temperature variations on the network performance in a precise and repeatable fashion. TempLab can accurately reproduce traces recorded in outdoor environments with fine granularity, while minimizing the hardware costs and configuration overhead. We use TempLab to analyse the detrimental effects of temperature variations (i) on processing performance, (ii) on a tree routing protocol, and (iii) on CSMA-based MAC protocols, deriving insights that would have not been revealed using existing testbed installations.
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| 3. |
- Oppermann, Felix Jonathan, et al.
(författare)
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Design and compilation of an object-oriented macroprogramming language for wireless sensor networks
- 2014
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Ingår i: Proceedings - Conference on Local Computer Networks, LCN. - : IEEE Computer Society. ; , s. 574-582
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Konferensbidrag (refereegranskat)abstract
- Wireless sensor network (WSN) programming is still largely performed by experts in a node-centric way using low-level languages such as C. Although numerous higher-level abstractions exist, each simplifying a specific aspect of distributed programming, real applications often require to combine multiple abstractions into a single program. Using current programming frameworks, this represents a difficult task. In previous work, we therefore defined a conceptual framework that facilitates abstraction composition by defining sound compositional rules among few fundamental abstraction categories. The framework is extensible: programmers can add new abstractions within the boundaries determined by the compositional rules. In this paper we describe the design of a language - called MPL - that instantiates this conceptual framework. To support the extensible nature of the framework, the language is object-oriented, which allows programmers to add new abstractions by inheriting from existing classes that implement predefined interfaces. We modeled the syntax after Java, to make it more palatable to inexperienced embedded programmers. Compared to Java, we modified the language to enable efficient execution on WSN devices. We designed and implemented a compiler that translates MPL language into executable C code, which spares the overhead of a virtual machine. By comparing MPL implementations against functionally-equivalent Contiki/C implementations of several benchmark applications, we determined that the performance overhead of MPL is limited, and yet the programming task is simplified.
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