| 1. |
- Ahmed, Saad, et al.
(author)
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Demystifying Energy Consumption Dynamics in Transiently Powered Computers
- 2020
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In: ACM Transactions on Embedded Computing Systems. - : Association for Computing Machinery. - 1539-9087 .- 1558-3465. ; 19:6
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Journal article (peer-reviewed)abstract
- Transiently powered computers (TPCs) form the foundation of the battery-less Internet of Things, using energy harvesting and small capacitors to power their operation. This kind of power supply is characterized by extreme variations in supply voltage, as capacitors charge when harvesting energy and discharge when computing. We experimentally find that these variations cause marked fluctuations in clock speed and power consumption. Such a deceptively minor observation is overlooked in existing literature. Systems are thus designed and parameterized in overly conservative ways, missing on a number of optimizations.We rather demonstrate that it is possible to accurately model and concretely capitalize on these fluctuations. We derive an energy model as a function of supply voltage and prove its use in two settings. First, we develop EPIC, a compile-time energy analysis tool. We use it to substitute for the constant power assumption in existing analysis techniques, giving programmers accurate information on worst-case energy consumption of programs. When using EPIC with existing TPC system support, run-time energy efficiency drastically improves, eventually leading up to a 350% speedup in the time to complete a fixed workload. Further, when using EPIC with existing debugging tools, it avoids unnecessary program changes that hurt energy efficiency. Next, we extend the MSPsim emulator and explore its use in parameterizing a different TPC system support. The improvements in energy efficiency yield up to more than 1000% time speedup to complete a fixed workload.
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| 2. |
- Ahmed, Saad, et al.
(author)
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Intermittent Computing with Dynamic Voltage and Frequency Scaling
- 2020
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In: EWSN '20. ; , s. 97-107
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Conference paper (peer-reviewed)abstract
- We present D2VFS, a run-time technique to intelligently regulate supply voltage and accordingly reconfigure clock frequency of intermittently-computing devices. These devices rely on energy harvesting to power their operation and on small capacitors as energy buffer. Statically setting their clock frequency fails to achieve energy efficiency, as the setting remains oblivious of fluctuations in capacitor voltage and of their impact on a microcontroller operating range. In contrast, D2VFS captures these dynamics and places the microcontroller in the most efficient configuration by regulating the microcontroller supply voltage and changing its clock frequency. Our evaluation shows that D2VFS markedly increases energy efficiency; for example, ultimately enabling a 30-300% reduction of workload completion times.
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| 3. |
- Alizai, Muhammad Hamad, et al.
(author)
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Exploiting the Burstiness of Intermediate-Quality Wireless Links
- 2012
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In: International Journal of Distributed Sensor Networks. - : SAGE Publications. - 1550-1329 .- 1550-1477. ; , s. 826702-
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Journal article (peer-reviewed)abstract
- We address the challenge of link estimation and routing over highly dynamic links, thats is, bursty links that rapidly shift between reliable and unreliable periods of transmissions. Based on significant empirical evidence of over 100,000 transmissions over each link in 802.15.4 and 802.11 testbeds, we propose two metrics, expected future transmissions (EFT) and MAC(3), for runtime estimation of bursty wireless links. We introduce a bursty link estimator (BLE) that based on these two metrics, accurately estimates bursty links in the network rendering them available for data transmissions. Finally, we present bursty routing extensions (BRE): an adaptive routing strategy that uses BLE for forwarding packets over bursty links if they offer better routing progress than long-term stable links. Our evaluation, comprising experimental data from widely used IEEE 802.15.4-based testbeds, reveals an average of 19% and a maximum of 42% reduction in the number of transmissions when routing over long-range bursty links typically ignored by routing protocols. Additionally, we show that both BLE and BRE are not tied to any specific routing protocol and integrate seamlessly with existing routing protocols and link estimators.
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| 4. |
- Iqbal, Hassan, et al.
(author)
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Poster Abstract: Taming Link-layer Heterogeneity in IoT through Interleaving Multiple Link-Layers over a Single Radio
- 2017
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In: SenSys 2017 - Proceedings of the 15th ACM Conference on Embedded Networked Sensor Systems. - New York, NY, USA : ACM. - 9781450354592 ; 2017-January
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Conference paper (peer-reviewed)abstract
- We propose dynamic reconfiguration of the radio interface in IoT platforms to support multiple link layers simultaneously. This allows us to tackle the increasing link layer heterogeneity in IoT devices, thus bringing a multitude of benefits: extensible and vender agnostic multihop deployments, rapid integration of the new “things” into an existing network, as well as seamless integration of the IoT with the traditional wireless Internet.
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| 5. |
- Maioli, Andrea, et al.
(author)
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Discovering the Hidden Anomalies of Intermittent Computing
- 2021
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In: Proceedings of the 18th ACM International Conference on Embedded Wireless Systems and Networks (EWSN), Delft (The Netherlands), February 2021..
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Conference paper (other academic/artistic)abstract
- Energy harvesting battery-less embedded devices compute intermittently, as energy is available. Intermittent executions may differ from continuous ones due to repeated executions of non-idempotent code. This anomaly is normally recognized as a “bug” and solutions exist to retain equivalence between intermittent and continuous executions. We argue that our current understanding of these “bugs” is limited. We address this issue by devising techniques to comprehensively identify where and how intermittent and continuous executions possibly differ and by implementing them in SCEPTIC: a code analysis tool for intermittent programs. Thereby, we find execution anomalies and their manifested impact on program behavior in ways previously not considered. This analysis is enabled by SCEPTIC design, implementation, and performance. SCEPTIC runs up to ten orders of magnitude faster than the baselines we consider, enabling many types of analyses that would be otherwise impractical.
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| 6. |
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| 7. |
- Munawar, Waqaas, et al.
(author)
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Modular Remote Reprogramming of Sensor Nodes
- 2015
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In: International Journal of Sensor Networks. - 1748-1279 .- 1748-1287. ; 19:3, s. 251-265
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Journal article (peer-reviewed)abstract
- Wireless sensor networks are envisioned to be deployed in the absence of permanent network infrastructure and in environments with limited or no human accessibility. Hence, such deployments demand mechanisms to remotely (i.e., over the air) reconfigure and update the software on the nodes. In this paper we introduce DyTOS, a TinyOS based remote reprogramming approach that enables the dynamic exchange of software components and thus incrementally update the operating system and its applications. The core idea is to preserve the modularity of TinyOS, i.e., its componentisation, which is lost during the normal compilation process, and enable runtime composition of TinyOS components on the sensor node. The proposed solution integrates seamlessly into the system architecture of TinyOS: It does not require any changes to the programming model of TinyOS and all existing components can be reused transparently. Our evaluation shows that DyTOS incurs a low performance overhead while keeping a smaller – up to one third – memory footprint than other comparable solutions.
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