AoI Minimization in Status Update Control With Energy Harvesting Sensors

Information freshness is crucial for time-critical IoT applications, e.g., monitoring and control. We consider an IoT status update system with users, energy harvesting sensors, and a cache-enabled edge node. The users receive time-sensitive information about physical quantities, each measured by a...

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Vydané v:	IEEE transactions on communications Ročník 69; číslo 12; s. 8335 - 8351
Hlavní autori:	Hatami, Mohammad, Leinonen, Markus, Codreanu, Marian
Médium:	Journal Article
Jazyk:	English
Vydavateľské údaje:	New York IEEE 01.12.2021 The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Predmet:	age of information (AoI) Algorithms Batteries dynamic programming Energy harvesting Internet of Things (IoT) Iterative methods Machine learning Markov processes Minimization Monitoring Nodes Optimization Q-learning reinforcement learning (RL) Sensor systems Sensors value iteration algorithm (VIA) Wireless sensor networks Internet of Things (IoT) Q-learning dynamic programming Minimization value iteration algorithm (VIA) Sensor systems Batteries Energy harvesting reinforcement learning (RL) Wireless sensor networks age of information (AoI) Sensors Monitoring
ISSN:	0090-6778, 1558-0857, 1558-0857
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Abstract	Information freshness is crucial for time-critical IoT applications, e.g., monitoring and control. We consider an IoT status update system with users, energy harvesting sensors, and a cache-enabled edge node. The users receive time-sensitive information about physical quantities, each measured by a sensor. Users demand for the information from the edge node whose cache stores the most recently received measurements from each sensor. To serve a request, the edge node either commands the sensor to send an update or retrieves the aged measurement from the cache. We aim at finding the best actions of the edge node to minimize the average AoI of the served measurements at the users, termed on-demand AoI. We model this problem as a Markov decision process and develop reinforcement learning (RL) algorithms: model-based value iteration and model-free Q-learning. We also propose a Q-learning method for the realistic case where the edge node is informed about the sensors' battery levels only via the status updates. The case under transmission limitations is also addressed. Furthermore, properties of an optimal policy are characterized. Simulation results show that an optimal policy is a threshold-based policy and that the proposed RL methods significantly reduce the average cost compared to several baselines.
AbstractList	Information freshness is crucial for time-critical IoT applications, e.g., monitoring and control. We consider an IoT status update system with users, energy harvesting sensors, and a cache-enabled edge node. The users receive time-sensitive information about physical quantities, each measured by a sensor. Users demand for the information from the edge node whose cache stores the most recently received measurements from each sensor. To serve a request, the edge node either commands the sensor to send an update or retrieves the aged measurement from the cache. We aim at finding the best actions of the edge node to minimize the average AoI of the served measurements at the users, termed on-demand AoI. We model this problem as a Markov decision process and develop reinforcement learning (RL) algorithms: model-based value iteration and model-free Q-learning. We also propose a Q-learning method for the realistic case where the edge node is informed about the sensors battery levels only via the status updates. The case under transmission limitations is also addressed. Furthermore, properties of an optimal policy are characterized. Simulation results show that an optimal policy is a threshold-based policy and that the proposed RL methods significantly reduce the average cost compared to several baselines.
Author	Hatami, Mohammad Leinonen, Markus Codreanu, Marian
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Cites_doi	10.1109/TIT.2018.2871079 10.1109/SURV.2011.060710.00094 10.1109/TII.2014.2300753 10.1109/LWC.2018.2890605 10.1109/TMC.2019.2936199 10.1109/PIMRC48278.2020.9217302 10.1109/JPROC.2014.2357031 10.1109/TWC.2019.2920351 10.1109/TNET.2020.3041654 10.1002/9780470980033 10.1109/INFOCOMWKSHPS50562.2020.9162973 10.1109/INFCOM.2012.6195689 10.1109/ISIT.2017.8006506 10.1109/TCOMM.2020.2991992 10.1109/ICC.2016.7511440 10.1109/GCWkshps45667.2019.9024463 10.1287/moor.24.2.293 10.1561/1300000060 10.1109/ISIT.2019.8849636 10.1109/TCOMM.2019.2931538 10.2200/S00954ED2V01Y201909CNT023 10.1109/TIT.2016.2533395 10.1109/LSP.2017.2686377 10.1109/JIOT.2018.2882583 10.1109/INFCOMW.2019.8845182 10.1109/PIMRC.2019.8904358 10.1109/INFOCOM.2019.8737508 10.1109/ISIT.2015.7283009 10.1109/TIT.2019.2938969 10.1109/ITA.2015.7308962 10.1109/TCOMM.2013.052013.120565 10.1109/IEEECONF44664.2019.9048659 10.1109/TCCN.2019.2916097 10.1109/ACCESS.2019.2899001 10.1109/COMST.2020.2988367 10.1109/CISS48834.2020.1570629110 10.1109/GLOBECOM38437.2019.9013454 10.1109/TGCN.2017.2778501
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References	ref35 ref34 ref12 bastopcu (ref18) 2020 ref37 ref15 ref36 ref14 ref31 ref30 ref33 ref11 ref32 ref10 ref2 ref39 ref17 ref16 ref19 mankar (ref13) 2020 da xu (ref1) 2014; 10 ref24 ref23 ref26 ref25 ref20 ref41 ref22 ref21 ref28 ref27 ref29 ref8 ref7 sutton (ref38) 2018 ref9 ref4 ref3 ref6 ref5 ref40
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SubjectTerms	age of information (AoI) Algorithms Batteries dynamic programming Energy harvesting Internet of Things (IoT) Iterative methods Machine learning Markov processes Minimization Monitoring Nodes Optimization Q-learning reinforcement learning (RL) Sensor systems Sensors value iteration algorithm (VIA) Wireless sensor networks
Title	AoI Minimization in Status Update Control With Energy Harvesting Sensors
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