Reducing power consumption in LEO satellite network

Current low earth orbit (LEO) satellite network display poor power efficiency, running network devices at full capacity all the time regardless of the traffic matrix and the distribution of the population over the Globe. Most of the research on energy efficiency of LEO satellites has focused on component level or link level. Therefore, this kind of research is not holistic to try to look at the satellite system as a single node. To enhance the energy efficiency. The solution should exploits multipath routing and load balancing. LEO network is overprovisioned, and hence selectively shutting down some satellite nodes and links during off-peaks hours seems like a good way to reduce energy consumption. In this paper, we exploit the fact that due to geographical and climatic conditions, some satellite links are expected to be loaded with data while others remain unused. Our approach is to power down satellite nodes and links during period of low traffic, while guaranteeing the connectivity and QoS. Finding the optimal solution is NP-problem and therefore, we explore in this work two heuristic algorithms. We evaluate our heuristics on a realistic LEO topology and real traffic matrices. Simulation results show that the power saving can be significant

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Effizientes Datenmanagement in drahtlosen Sensornetzen durch Peer-to-Peer Methoden

The data-centric nature of Wireless Sensor Networks (WSNs) and the severe resource constraints of the sensor nodes distinguish sensor data management from other communication networks. Both the client-server approach as well as the end-to-end communication principle that have been proposed in the for Mobile Ad Hoc Networks (MANETs) do not suit the characteristics of WSNs. Efficient lookup and routing of sensor data are of great significance for WSNs, especially as the size of these networks continues to grow. On an abstract level, structured peer-to-peer protocols, which rely on Distributed Hash Tables (DHTs) provide O(1) complexity for storing and retrieving data in the network, seem overcome these restrictions. However, the fact that they rely on underlayer routing techniques leads to inefficient resource usage in the context of sensor networks. The combination of DHTs and underlayer routing led to the establishment of so called virtual coordinate routing techniques. Most of these algorithms are quite complicated and do not guarantee packet delivery on the shortest path. Additionally, only few of them are implemented in real sensor nodes. In this dissertation, we present the Virtual Cord Protocol (VCP), a virtual position based routing protocol that also provides means for data management such as identifying, storing, and retrieving data items. The key contributions of this protocol are independence of real location information by relying on virtual relative positions of neighboring nodes, the simplicity of obtaining the virtual positions, near optimal routing paths, and high scalability because only information about direct neighbors is needed for routing. Furthermore, VCP provides a unique position for each node and inherently prevents dead-ends. We extensively evaluated VCP in a number of simulation experiments. The simulation results show that VCP consistently provides high throughput and low overhead for a wide range of application scenarios. We compared VCP with Dynamic MANET on Demand (DYMO), a typical MANET protocol, and with Virtual Ring Routing (VRR), another virtual coordinate based approach. In static networks, both VCP and VRR clearly outperform DYMO. In the case of frequent node failures, however, VCP benefits from its light-weight design. Our protocol is more failure tolerant compared to VRR. We finally integrated data replication techniques that support high success rates even in very unreliable sensor networks. A prototype implementation on real sensor nodes outlines the feasibility of our approach in a proof-of-concept study.Die datenzentrische Arbeitsweise von drahtlosen Sensornetzen sowie die kritischen Ressourcenbeschränkungen von Sensorknoten unterscheiden die Datenverarbeitung in diesem Bereich von klassischen Kommunikationsnetzen. Sowohl der Client-Server- Ansatz als auch die Ende-zu-Ende Kommunikationsparadigmen, welche u.a. auch für mobile ad-hoc Netze erfolgreich eingesetzt werden, sind nur bedingt für Sensornetze nutzbar. Von besonderer Bedeutung in Sensornetzen sind effiziente Identifikations und Routingmethoden. Dies betrifft vor allem die Skalierbarkeit für größer werdende Netze. Auf einer abstrakten Ebene scheinen strukturierte Peer-to-Peer-Ansätze eine Alternative darzustellen, da durch den Einsatz verteilter Hash-Tabellen eine O(1) Komplexität für die Identifikation von Daten erreicht werden kann. Allerdings bedürfen diese Verfahren einer stabilen Routing-Infrastruktur auf den unteren Schichten. Die Kombination von verteilten Hash-Tabellen und Routingverfahren führte zur Entwicklung sogenannter Virtuelle-Coordinaten-Algorithmen. Viele dieser Methoden sind allerdings sehr kompliziert und geben keine Garantie für den Datenversand auf einem kürzesten Weg. Weiterhin sind nur wenige in einer realen Sensorumgebung implementiert. In dieser Dissertation wird das Virtual Cord Protocol (VCP) vorgestellt, welches virtuelle Knotenpositionen für das Datenmanagement und den Datentransport einsetzt. Die wesentlichen Beiträge können wie folgt zusammengefasst werden: Unabhängigkeit des Protokolls von realen Knotenpositionen, einfache Definition und Verwaltung der virtuellen Koordinaten, kurze Routingpfade nahe dem kürzesten Weg, hohe Skalierbarkeit durch die Beschränkung auf lokal verfügbare Nachbarschaftsinformationen. Weiterhin verwaltet VCP eindeutige Knotenadressen und vermeidet konzeptuell mögliche Sackgassen. VCP wurde im Rahmen der Arbeit in umfangreichen Simulationsexperimenten bewertet. Die Ergebnisse zeigen, dass VCP hohen Durchsatz und geringe Kosten für einen breiten Einsatzbereich ermöglicht. In einem direkten Vergleich mit Dynamic MANET on Demand (DYMO), einem typischen ad-hoc Routing Protokoll, sowie Virtual Ring Routing (VRR), einem kompetitiven Ansatz basierend auf virtuellen Koordinaten, zeigte sich, dass VCP und VRR in statischen klassischen ad-hoc Verfahren überlegen sind. Für dynamische Netze mit häufig ausfallenden Knoten dominiert allerdings VCP durch sein leichtgewichtiges Design. Das Protokoll ist stärker fehlertolerant als VRR. Weiterhin wurden Replikationsmethoden integriert, die hervorragende Erfolgsraten auch in sehr unzuverlässigen Sensornetzen ermöglichen. Ein implementierter Prototyp zeigt die Fähigkeiten des neuen Ansatzes in einer Proof-of-Concept Studie

P2P-based Routing and Data Management using the Virtual Cord Protocol (VCP)

We present Virtual Cord Protocol (VCP), a virtual relative position based routing protocol for sensor networks that also provides methods for data management as known from standard DHT services. Self-organizing and cooperative algorithms are thought to be the optimal solution to overcome the inherent resource limitations in sensor networks. On an abstract level, DHT techniques offer O(1) complexity data lookup. Unfortunately, they usually rely on underlayer routing techniques. The key contributions of VCP are the independence of real location information by relying on relative positions of neighboring nodes, successors and predecessors in the cord are always in their vicinity, and the high scalability because only information about direct neighbors are needed for routing. Furthermore, VCP inherently prevents dead-ends and it is easy to be implemented

Sensor/Actuator Networks in Smart Homes for Supporting Elderly and Handicapped People

Abstract—Smart Home, this term comprises various approaches, engaged in living and working now and in the future. The objectives of the various approaches range from enhancing comfort in daily life to enabling a more independent life for elderly and handicapped people. The term Ubiquitous Computing, coined by Mark Weiser describes the ubiquity of computer and information technology. The task of Smart Objects, implanted into everyday items, is to sense the immediate environment using various types of sensors, and to process these information. This functionality assigns a kind of artificial intelligence to common, well known objects and enables comprehensive information-processing and interconnection of almost any kind of everyday object. The (preferably) transparent and hidden technology ranges from Wearable Computers and Smart Clothes to ”intelligent ” artificial replacements. It supports the user in almost every part of his life by extending his cognition and information processing capacity and tries to compensate for certain handicaps. The challenge regarding smart homes, especially for supporting the elderly and handicapped, is to compensate for handicaps and support the individual in order to give them a more independent life for as long as possible. In this paper, a common architecture for smart home environments is developed, mapped to an experimental setup, and finally evaluated. I

Inter-Domain Routing and Data Replication in Virtual Coordinate Based Networks

In recent work it has been shown that the use of virtual coordinates or identifiers for efficient routing and data management has several advantages compared to the use of predefined addresses or geographical coordinates. However, these advantages only hold for single domain networks with limited mobility. In this paper, we discuss the challenges arising from using virtual coordinates for routing (to a particular sensor ID or to indexed data or resources) in ad hoc and sensor networks in multi-domain network scenarios. We show the feasibility of inter-domain routing by exploiting a concept that is central to most virtual coordinate approaches: the availability of data management operation using a DHT like mechanism. Based on the Virtual Cord Protocol (VCP), we show how inter-domain routing can be realized using appropriate indirections. Furthermore, we investigate the possibility of replicating data among different networks, or DHTs, to provide seamless data access in multidomain environments. Our simulation results clearly show that both functions can be realized with only marginal overhead