Status Updating under Partial Battery Knowledge in Energy Harvesting IoT Networks

We study status updating under inexact knowledge about the battery levels of the energy harvesting sensors in an IoT network, where users make on-demand requests to a cache-enabled edge node to send updates about various random processes monitored by the sensors. To serve the request(s), the edge node either commands the corresponding sensor to send an update or uses the aged data from the cache. We find a control policy that minimizes the average on-demand AoI subject to per-slot energy harvesting constraints under partial battery knowledge at the edge node. Namely, the edge node is informed about sensors' battery levels only via received status updates, leading to uncertainty about the battery levels for the decision-making. We model the problem as a POMDP which is then reformulated as an equivalent belief-MDP. The belief-MDP in its original form is difficult to solve due to the infinite belief space. However, by exploiting a specific pattern in the evolution of beliefs, we truncate the belief space and develop a dynamic programming algorithm to obtain an optimal policy. Moreover, we address a multi-sensor setup under a transmission limitation for which we develop an asymptotically optimal algorithm. Simulation results assess the performance of the proposed methods.Comment: 32 Pages. arXiv admin note: text overlap with arXiv:2203.10400, arXiv:2212.0597

On the Age-Optimality of Relax-then-Truncate Approach under Partial Battery Knowledge in Energy Harvesting IoT Networks

We consider an energy harvesting (EH) IoT network, where users make on-demand requests to a cache-enabled edge node to send status updates about various random processes, each monitored by an EH sensor. The edge node serves users' requests by either commanding the corresponding sensor to send a fresh status update or retrieving the most recently received measurement from the cache. We aim to find a control policy at the edge node that minimizes the average on-demand AoI over all sensors subject to per-slot transmission and energy constraints under partial battery knowledge at the edge node. Namely, the limited radio resources (e.g., bandwidth) causes that only a limited number of sensors can send status updates at each time slot (i.e., per-slot transmission constraint) and the scarcity of energy for the EH sensors imposes an energy constraint. Besides, the edge node is informed of the sensors' battery levels only via received status update packets, leading to uncertainty about the battery levels for the decision-making.We develop a low-complexity algorithm -- termed relax-then-truncate -- and prove that it is asymptotically optimal as the number of sensors goes to infinity. Numerical results illustrate that the proposed method achieves significant gains over a request-aware greedy policy and show that it has near-optimal performance even for moderate numbers of sensors.Comment: 7 pages. arXiv admin note: substantial text overlap with arXiv:2201.1227

AoI Minimization in Status Update Control with Energy Harvesting Sensors

Information freshness is crucial for time-critical IoT applications, e.g., monitoring and control systems. We consider an IoT status update system with multiple users, multiple energy harvesting sensors, and a wireless edge node. The users receive time-sensitive information about physical quantities, each measured by a sensor. Users send requests to the edge node where a cache contains the most recently received measurements from each sensor. To serve a request, the edge node either commands the sensor to send a status update or retrieves the aged measurement from the cache. We aim at finding the best actions of the edge node to minimize the age of information of the served measurements. We model this problem as a Markov decision process and develop reinforcement learning (RL) algorithms: model-based value iteration and model-free Q-learning methods. 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 analytically 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.Comment: 31 pages, 6 figures, submitted journa

Minimizing the AoI in Resource-Constrained Multi-Source Relaying Systems: Dynamic and Learning-based Scheduling

We consider a multi-source relaying system where the independent sources randomly generate status update packets which are sent to the destination with the aid of a relay through unreliable links. We develop transmission scheduling policies to minimize the sum average age of information (AoI) subject to transmission capacity and long-run average resource constraints. We formulate a stochastic control optimization problem. To solve the problem, a constrained Markov decision process (CMDP) approach and a drift-plus-penalty method are proposed. The CMDP problem is solved by transforming it into an MDP problem using the Lagrangian relaxation method. We theoretically analyze the structure of optimal policies for the MDP problem and subsequently propose a structure-aware algorithm that returns a practical near-optimal policy. By the drift-plus-penalty method, we devise a dynamic near-optimal low-complexity policy. We also develop a model-free deep reinforcement learning policy, which does not require the full knowledge of system statistics. To do so, we employ the Lyapunov optimization theory and a dueling double deep Q-network. Simulation results are provided to assess the performance of our policies and validate the theoretical results. The results show up to 91% performance improvement compared to a baseline policy.Comment: 30 Pages, preliminary results of this paper were presented at IEEE Globecom 2021, https://ieeexplore.ieee.org/document/968594

Multi-Source AoI-Constrained Resource Minimization under HARQ: Heterogeneous Sampling Processes

We consider a multi-source hybrid automatic repeat request (HARQ) based system, where a transmitter sends status update packets of random arrival (i.e., uncontrollable sampling) and generate-atwill (i.e., controllable sampling) sources to a destination through an error-prone channel. We develop transmission scheduling policies to minimize the average number of transmissions subject to an average age of information (AoI) constraint. First, we consider known environment (i.e., known system statistics) and develop a near-optimal deterministic transmission policy and a low-complexity dynamic transmission (LC-DT) policy. The former policy is derived by casting the main problem into a constrained Markov decision process (CMDP) problem, which is then solved using the Lagrangian relaxation, relative value iteration algorithm, and bisection. The LC-DT policy is developed via the drift-plus-penalty (DPP) method by transforming the main problem into a sequence of per-slot problems. Finally, we consider unknown environment and devise a learning-based transmission policy by relaxing the CMDP problem into an MDP problem using the DPP method and then adopting the deep Q-learning algorithm. Numerical results show that the proposed policies achieve near-optimal performance and illustrate the benefits of HARQ in status updating

Analysis of anabolic steroids in urine by gas chromatography-microchip atmospheric pressure photoionization-mass spectrometry with chlorobenzene as dopant

Corrigendum to J. Chromatogr. A 1312 (2013), p. 111-117: Support by one project was inadvertently not mentioned in the Acknowledgements. The Acknowledgement should read:Funding from the Academy of Finland (projects 251575 and 257316) and the Finnish Funding Agency for Technology and Innovation(project 1291/31/084) is acknowledged. L. Hintikka is grateful to the CHEMSEM graduate school for financial support. Dr. Ville Saarela isthanked for the design and fabrication of the microchips. J. Chromatogr. A 1448 (2016) p. 128.Peer reviewe

Imatran kaupunkipuron suunnittelu, toteutus ja seuranta

Rakennettu luonnonmukainen elinympäristö voi edistää vaelluskalojen poikastuotantoa vesivoimalaitoksen tai muun patorakenteen yhteydessä. Elinympäristö toimii samalla kokonaisen ekosysteemin perustana. Tyypillisesti vesivoiman rakentamisessa on menetetty huomattavasti virtavesien eliöstölle soveltuvaa elinympäristöä, jota luonnonmukaiset ratkaisut voivat korvata osana ekologista kompensaatiota. Toimenpiteellä voidaan siis parantaa rakennetun vesistön ekologista arvoa ja tilaa. Tässä raportissa kuvataan Imatran kaupunkipuron suunnittelu- ja rakennusvaiheet sekä raportoidaan seurannan tulokset rakennusvaiheen jälkeen. Imatran kaupunkipuron suunnittelussa korostettiin puron soveltuvuutta taimenelle sopivana elinympäristönä. Vaikka kaupunkipuroa ei ole suunniteltu vaellusreitiksi, käytettyjä suunnitteluperiaatteita voi soveltaa suoraan myös luonnonmukaisiin ohitusuomiin. Imatran kaupunkipuro valmistui vuonna 2014 puistomaiselle alueelle ja joutomaalle Imatrankosken voimalaitoksen läheisyyteen. Puro on noin yhden kilometrin mittainen ja sen leveys vaihtelee 2–10 metrin välillä. Uoman suunnittelussa huomioitiin erilaisten elinympäristöjen ja taimenen kutu- ja poikasalueiden lisäksi myös maisemalliset tekijät ja soveltuvuus virkistyskäyttöön. Imatrankosken padon putouskorkeus, 24 m, ja käytettävissä oleva alue pyrittiin hyödyntämään mahdollisimman hyvin. Lisäksi mutkittelemalla uomaa sen pituus voitiin maksimoida. Uoman materiaalina käytettiin (vaihtelevan kokoista) soraa, isompia kiviä sekä puumateriaalia. Kaupunkipuron virtaama on kesäaikaan noin 250 l/s ja talvella noin 100 l/s. Tavoite purosta taimenen lisääntymisympäristönä näyttää toteutuneen, sillä taimen ja muutkin kala- ja eliölajit ovat ottaneet puron käyttöönsä. Imatran kaupunkipurossa taimenen lisääntyminen on onnistunut jopa odotuksia paremmin ja poikastiheys on korkeampi kuin vastaavissa luonnonpuroissa. Kaupunkipuron pinta-ala on huomattavan vähäinen verrattuna valtavaan määrään patoamisen seurauksena menetettyä koskipinta-alaa. Rakennettu luonnonmukainen elinympäristö kuitenkin tarjoaa uhanalaiselle taimenelle soveltuvaa elinympäristöä. Jokaista luonnossa syntynyttä yksilöä voidaan pitää lajin kannalta tärkeänä. Pohjaeläimistö on runsastunut lajirikkaudeltaan joka vuosi. Samalla pohjaeläinten lukumäärä on moninkertaistunut neljän tarkkailuvuoden aikana. Luonnolle, lajistolle ja ekosysteemeille aiheutettujen haittojen vähentäminen on tulossa myös olemassa olevan vesivoiman vastuulle. Pelkät kalataloudelliset kompensaatiot tai pelkkä kalatie eivät riitä ratkaisemaan ongelmia, jotka vesirakentaminen ja vesivoima ovat aiheuttaneet erityisesti soveltuvien elinympäristöjen määrälle ja laadulle. Imatran kaupunkipurolta saadut tulokset rohkaisevat jatkossa nostamaan erilaiset rakennetut luonnonmukaiset elinympäristöt ja kompensaatiohabitaatit toimivaksi vaihtoehdoksi virtavesien tilan parantamisessa.Abstract Nature-like habitat as ecological compensation in streams Built nature-like habitat can promote the juvenile production of migratory fish in vicinity of a hydropower plant or a distinct dam structure. At the same time, the habitat serves as the basis for the entire ecosystem. Typically, the construction of hydropower has resulted in a significant loss of habitat suitable for aquatic life, which can be replaced by nature-like solutions as part of ecological compensation. The measure can therefore improve the ecological value and status of the human-modified water body. This report describes the design and construction phases of the Imatra City Brook and reports the results of monitoring after the construction phase. The design of the Imatra City Brook emphasized that the brook will become suitable habitat for trout. However, brook is not designed as a bypass, albeit the design principles used can be applied directly to natural bypasses. The Imatra City Brook was completed in 2014 in a park-like area in the vicinity of the Imatrankoski power plant. The brook is about one kilometer long and varies in width from 2 to 10 meters. In addition to different habitats and spawning and juvenile areas for trout, landscape design and suitability for recreational use were also taken into account in the design of the area. The height of the Imatrankoski dam, 24 m, and the available area were utilized to make the best possible use, and by meandering the brook, its length could be maximized. Gravel of varying sizes, larger stones and wood were used as the base material for the structures. The flow of the brook is about 250 l/s in summer and about 100 l/s during winter. The goal of the stream being a spawning and rearing ground for trout seems to have been achieved, as trout and other species of fish and organisms have taken over the stream. In the Imatra City Brook, trout reproduction has been even better than expected and the density of juvenile fish is higher than in the compared natural streams. The total area of the brook is remarkably small compared to the huge amount of rapids and riverine habitats lost for hydropower production and construction of dams. However, the built natural-like habitat provides a suitable habitat for trout as an endangered species and any individual born in the wild can be considered important for the population of the species. The species richness of benthic macroinvertebrates increases every year. At the same time, the number of macroinvertebrate individuals has multiplied during the four years of observation. Reducing damage to nature, species and ecosystems is becoming the responsibility of existing hydropower. Fisheries compensation alone (stockings) or the technical fishways alone are not enough to solve the problems that hydropower and damming have caused, especially for the quantity and quality of suitable habitats. In the future, the results from the Imatra City Brook will encourage the upgrading of various built natural-like habitats or compensatory habitats as one viable option for improving the status of the water bodies

Familial idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a late-onset surgically alleviated, progressive disease. We characterize a potential familial subgroup of iNPH in a nation-wide Finnish cohort of 375 shunt-operated iNPH-patients. The patients were questionnaired and phone-interviewed, whether they have relatives with either diagnosed iNPH or disease-related symptomatology. Then pedigrees of all families with more than one iNPH-case were drawn. Eighteen patients (4.8%) from 12 separate pedigrees had at least one shunt-operated relative whereas 42 patients (11%) had relatives with two or more triad symptoms. According to multivariate logistic regression analysis, familial iNPH-patients had up to 3-fold risk of clinical dementia compared to sporadic iNPH patients. This risk was independent from diagnosed Alzheimer's disease and APOE epsilon 4 genotype. This study describes a familial entity of iNPH offering a novel approach to discover the potential genetic characteristics of iNPH. Discovered pedigrees offer an intriguing opportunity to conduct longitudinal studies targeting potential preclinical signs of iNPH. (C) 2016 Elsevier B.V. All rights reserved.Peer reviewe

Diabetes is associated with familial idiopathic normal pressure hydrocephalus : a case-control comparison with family members

Background The pathophysiological basis of idiopathic normal pressure hydrocephalus (iNPH) is still unclear. Previous studies have shown a familial aggregation and a potential heritability when it comes to iNPH. Our aim was to conduct a novel case-controlled comparison between familial iNPH (fNPH) patients and their elderly relatives, involving multiple different families. Methods Questionnaires and phone interviews were used for collecting the data and categorising the iNPH patients into the familial (fNPH) and the sporadic groups. Identical questionnaires were sent to the relatives of the potential fNPH patients. Venous blood samples were collected for genetic studies. The disease histories of the probable fNPH patients (n = 60) were compared with their >= 60-year-old relatives with no iNPH (n = 49). A modified Charlson Comorbidity Index (CCI) was used to measure the overall disease burden. Fisher's exact test (two-tailed), the Mann-Whitney U test (two-tailed) and a multivariate binary logistic regression analysis were used to perform the statistical analyses. Results Diabetes (32% vs. 14%, p = 0.043), arterial hypertension (65.0% vs. 43%, p = 0.033), cardiac insufficiency (16% vs. 2%, p = 0.020) and depressive symptoms (32% vs. 8%, p = 0.004) were overrepresented among the probable fNPH patients compared to their non-iNPH relatives. In the age-adjusted multivariate logistic regression analysis, diabetes remained independently associated with fNPH (OR = 3.8, 95% CI 1.1-12.9, p = 0.030). Conclusions Diabetes is associated with fNPH and a possible risk factor for fNPH. Diabetes could contribute to the pathogenesis of iNPH/fNPH, which motivates to further prospective and gene-environmental studies to decipher the disease modelling of iNPH/fNPH.Peer reviewe