Recent Advances in Fully Dynamic Graph Algorithms

In recent years, significant advances have been made in the design and analysis of fully dynamic algorithms. However, these theoretical results have received very little attention from the practical perspective. Few of the algorithms are implemented and tested on real datasets, and their practical potential is far from understood. Here, we present a quick reference guide to recent engineering and theory results in the area of fully dynamic graph algorithms

Design Space Exploration and Resource Management of Multi/Many-Core Systems

The increasing demand of processing a higher number of applications and related data on computing platforms has resulted in reliance on multi-/many-core chips as they facilitate parallel processing. However, there is a desire for these platforms to be energy-efficient and reliable, and they need to perform secure computations for the interest of the whole community. This book provides perspectives on the aforementioned aspects from leading researchers in terms of state-of-the-art contributions and upcoming trends

Power System Simulation, Control and Optimization

This Special Issue “Power System Simulation, Control and Optimization” offers valuable insights into the most recent research developments in these topics. The analysis, operation, and control of power systems are increasingly complex tasks that require advanced simulation models to analyze and control the effects of transformations concerning electricity grids today: Massive integration of renewable energies, progressive implementation of electric vehicles, development of intelligent networks, and progressive evolution of the applications of artificial intelligence

Robust and cheating-resilient power auctioning on Resource Constrained Smart Micro-Grids

The principle of Continuous Double Auctioning (CDA) is known to provide an efficient way of matching supply and demand among distributed selfish participants with limited information. However, the literature indicates that the classic CDA algorithms developed for grid-like applications are centralised and insensitive to the processing resources capacity, which poses a hindrance for their application on resource constrained, smart micro-grids (RCSMG). A RCSMG loosely describes a micro-grid with distributed generators and demand controlled by selfish participants with limited information, power storage capacity and low literacy, communicate over an unreliable infrastructure burdened by limited bandwidth and low computational power of devices. In this thesis, we design and evaluate a CDA algorithm for power allocation in a RCSMG. Specifically, we offer the following contributions towards power auctioning on RCSMGs. First, we extend the original CDA scheme to enable decentralised auctioning. We do this by integrating a token-based, mutual-exclusion (MUTEX) distributive primitive, that ensures the CDA operates at a reasonably efficient time and message complexity of O(N) and O(logN) respectively, per critical section invocation (auction market execution). Our CDA algorithm scales better and avoids the single point of failure problem associated with centralised CDAs (which could be used to adversarially provoke a break-down of the grid marketing mechanism). In addition, the decentralised approach in our algorithm can help eliminate privacy and security concerns associated with centralised CDAs. Second, to handle CDA performance issues due to malfunctioning devices on an unreliable network (such as a lossy network), we extend our proposed CDA scheme to ensure robustness to failure. Using node redundancy, we modify the MUTEX protocol supporting our CDA algorithm to handle fail-stop and some Byzantine type faults of sites. This yields a time complexity of O(N), where N is number of cluster-head nodes; and message complexity of O((logN)+W) time, where W is the number of check-pointing messages. These results indicate that it is possible to add fault tolerance to a decentralised CDA, which guarantees continued participation in the auction while retaining reasonable performance overheads. In addition, we propose a decentralised consumption scheduling scheme that complements the auctioning scheme in guaranteeing successful power allocation within the RCSMG. Third, since grid participants are self-interested we must consider the issue of power theft that is provoked when participants cheat. We propose threat models centred on cheating attacks aimed at foiling the extended CDA scheme. More specifically, we focus on the Victim Strategy Downgrade; Collusion by Dynamic Strategy Change, Profiling with Market Prediction; and Strategy Manipulation cheating attacks, which are carried out by internal adversaries (auction participants). Internal adversaries are participants who want to get more benefits but have no interest in provoking a breakdown of the grid. However, their behaviour is dangerous because it could result in a breakdown of the grid. Fourth, to mitigate these cheating attacks, we propose an exception handling (EH) scheme, where sentinel agents use allocative efficiency and message overheads to detect and mitigate cheating forms. Sentinel agents are tasked to monitor trading agents to detect cheating and reprimand the misbehaving participant. Overall, message complexity expected in light demand is O(nLogN). The detection and resolution algorithm is expected to run in linear time complexity O(M). Overall, the main aim of our study is achieved by designing a resilient and cheating-free CDA algorithm that is scalable and performs well on resource constrained micro-grids. With the growing popularity of the CDA and its resource allocation applications, specifically to low resourced micro-grids, this thesis highlights further avenues for future research. First, we intend to extend the decentralised CDA algorithm to allow for participants’ mobile phones to connect (reconnect) at different shared smart meters. Such mobility should guarantee the desired CDA properties, the reliability and adequate security. Secondly, we seek to develop a simulation of the decentralised CDA based on the formal proofs presented in this thesis. Such a simulation platform can be used for future studies that involve decentralised CDAs. Third, we seek to find an optimal and efficient way in which the decentralised CDA and the scheduling algorithm can be integrated and deployed in a low resourced, smart micro-grid. Such an integration is important for system developers interested in exploiting the benefits of the two schemes while maintaining system efficiency. Forth, we aim to improve on the cheating detection and mitigation mechanism by developing an intrusion tolerance protocol. Such a scheme will allow continued auctioning in the presence of cheating attacks while incurring low performance overheads for applicability in a RCSMG

Virtual Cluster Management for Analysis of Geographically Distributed and Immovable Data

Thesis (Ph.D.) - Indiana University, Informatics and Computing, 2015Scenarios exist in the era of Big Data where computational analysis needs to utilize widely distributed and remote compute clusters, especially when the data sources are sensitive or extremely large, and thus unable to move. A large dataset in Malaysia could be ecologically sensitive, for instance, and unable to be moved outside the country boundaries. Controlling an analysis experiment in this virtual cluster setting can be difficult on multiple levels: with setup and control, with managing behavior of the virtual cluster, and with interoperability issues across the compute clusters. Further, datasets can be distributed among clusters, or even across data centers, so that it becomes critical to utilize data locality information to optimize the performance of data-intensive jobs. Finally, datasets are increasingly sensitive and tied to certain administrative boundaries, though once the data has been processed, the aggregated or statistical result can be shared across the boundaries. This dissertation addresses management and control of a widely distributed virtual cluster having sensitive or otherwise immovable data sets through a controller. The Virtual Cluster Controller (VCC) gives control back to the researcher. It creates virtual clusters across multiple cloud platforms. In recognition of sensitive data, it can establish a single network overlay over widely distributed clusters. We define a novel class of data, notably immovable data that we call "pinned data", where the data is treated as a first-class citizen instead of being moved to where needed. We draw from our earlier work with a hierarchical data processing model, Hierarchical MapReduce (HMR), to process geographically distributed data, some of which are pinned data. The applications implemented in HMR use extended MapReduce model where computations are expressed as three functions: Map, Reduce, and GlobalReduce. Further, by facilitating information sharing among resources, applications, and data, the overall performance is improved. Experimental results show that the overhead of VCC is minimum. The HMR outperforms traditional MapReduce model while processing a particular class of applications. The evaluations also show that information sharing between resources and application through the VCC shortens the hierarchical data processing time, as well satisfying the constraints on the pinned data

Resource management in cable access networks

Een kabelnetwerk is tegenwoordig niet meer alleen een medium waarover analoge TV-signalen vanuit een centraal punt, kopstation genaamd, naar de aangesloten huizen worden gestuurd. Sinds enkele jaren is het mogelijk om thuis data digitaal te versturen en te ontvangen. Deze data gaat via een kabelmodem thuis en het kopstation, dat in verbinding staat met andere netwerken. Op deze wijze zijn kabelnetwerken onderdeel geworden van het wereldwijde Internet en kunnen computers thuis hier mee verbonden worden. Door aan zo’n kopstation een digitaal videosysteem met duizenden films te koppelen, ontstaat er de mogelijkheid een video-op-verzoek dienst aan te bieden: Via de computer of zelfs de TV thuis kunnen films worden besteld en direct bekeken, of worden opgeslagen in de computer. Om dit te bewerkstelligen is meer nodig dan alleen een netwerk: Voor de transmissie van video data dient er zorg voor te worden gedragen dat deze zonder hinderende interrupties kan geschieden, omdat dergelijke gebeurtenissen door de gebruiker direct te zien zijn in de vorm van een stilstaand of zwart beeld. Verder is ook de reactiesnelheid van het systeem van belang voor het ondersteunen van operaties door de gebruiker, zoals het bestellen van een film, maar ook het vooruit- of terugspoelen, pauzeren, enzovoorts. Binnen deze context beschrijven en analyseren we in dit proefschrift zes problemen. Vier daarvan houden verband met de transmissie van data over het kabelnetwerk en de overige twee houden verband met het opslaan van video data op een harde schijf. In twee van de vier problemen uit de eerste categorie analyseren we de vertraging die data ondervindt wanneer die vanuit een modem wordt gestuurd naar het kopstation. Deze vertraging bepaalt met name de reactiesnelheid van het systeem. Karakteristiek voor dataverkeer in deze richting is dat pakketten van verschillende modems tegelijkertijd mogen worden verstuurd en daardoor verloren gaan. Met name de vereiste hertransmissies zorgen voor vertraging. Meer concreet beschouwen we een variant op het bekende ALOHA protocol, waarbij we uitgaan van een kanaalmodel dat afwijkt van het conventionele model. Het afwijkende model is van toepassing wanneer een modem een eerste contact probeert te leggen met het kopstation na te zijn opgestart. Met name na een stroomuitval, wanneer een groot aantal modems tegelijkertijd opnieuw opstart, kunnen de vertragingen aanzienlijk zijn. Daarnaast beschouwen we modems tijdens normale operatie en analyseren wij de verbetering in vertraging wanneer pakketten die vanuit ´e´en modem moeten worden verstuurd, worden verpakt in een groter pakket. In beide studies worden wiskundige resultaten vergeleken met simulaties die re¨ele situaties nabootsen. In de andere twee van de vier problemen richten wij ons op de transmissie van video data in de andere richting, namelijk van het kopstation naar de modems. Hierbij spelen stringente tijdsrestricties een voorname rol, zoals hierboven reeds is beschreven. Meer specifiek presenteren we een planningsalgoritme dat pakketten voor een aantal gebruikers op een kanaal zodanig na elkaar verstuurt dat de variatie in de vertraging die de verschillende pakketten ondervinden, minimaal is. Op deze wijze wordt zo goed mogelijk een continue stroom van data gerealiseerd die van belang is voor het probleemloos kunnen bekijken van een film. Daarnaast analyseren we een bestaand algoritme om een film via een aantal kanalen periodiek naar de aangesloten huizen te versturen. In dit geval ligt de nadruk op de wachttijd die een gebruiker ondervindt na het bestellen van een film. In deze analyse onderbouwen we een in het algoritme gebruikte heuristiek en brengen hierin verdere verbeteringen aan. Daarnaast bewijzen we dat het algoritme asymptotisch optimaal is, iets dat reeds langer werd aangenomen, maar nooit rigoreus bewezen was. Bij de laatste twee problemen, die verband houden met het opslaan van video data op een harde schijf, analyseren we hoe deze data zodanig kan worden opgeslagen dat die er nadien efficient van kan worden teruggelezen. In het ene probleem beschouwen we een bestaand planningsalgoritme om pakketten van verschillende videostromen naar een harde schijf te schrijven en passen dit aan om ervoor te zorgen dat het teruglezen van de stroom met bijvoorbeeld een andere pakketgrootte mogelijk wordt zonder daarbij de schijf onnodig te belasten. In het andere probleem analyseren we hoe we effectief gebruik kunnen maken van het gegeven dat data aan de buitenkant van de schijf sneller gelezen kan worden dan aan de binnenkant. We bewijzen dat het probleem van het zo efficient mogelijk opslaan van een gegeven aantal video files NPlastig is en presenteren een eenvoudige heuristiek die, hoewel voor bijzondere instanties een bewijsbaar slechte prestatie levert, in de praktijk in het algemeen goede prestaties levert. Hierbij maken we met name gebruik van het verschil in populariteit van de verschillende films

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

Unmanned Aerial Vehicle (UAV)-Enabled Wireless Communications and Networking

The emerging massive density of human-held and machine-type nodes implies larger traffic deviatiolns in the future than we are facing today. In the future, the network will be characterized by a high degree of flexibility, allowing it to adapt smoothly, autonomously, and efficiently to the quickly changing traffic demands both in time and space. This flexibility cannot be achieved when the network’s infrastructure remains static. To this end, the topic of UAVs (unmanned aerial vehicles) have enabled wireless communications, and networking has received increased attention. As mentioned above, the network must serve a massive density of nodes that can be either human-held (user devices) or machine-type nodes (sensors). If we wish to properly serve these nodes and optimize their data, a proper wireless connection is fundamental. This can be achieved by using UAV-enabled communication and networks. This Special Issue addresses the many existing issues that still exist to allow UAV-enabled wireless communications and networking to be properly rolled out

An Annotated Bibliography of Mobile Agents in Networks

The purpose of this thesis is to present a comprehensive colligation of applications of mobile agents in networks, and provide a baseline association of these systems. This work has been motivated by the fact that mobile agent systems have been deemed proficuous alternatives in system applications. Several mobile agent systems have been developed to provide scalable and cogent solutions in network-centric applications. This thesis examines some existing mobile agent systems in core networking areas, in particular, those of network and resource management, routing, and the provision of fault tolerance and security. The inherent features of these systems are discussed with respect to their specific functionalities. The applicability and efficacy of mobile agents are further considered in the specific areas mentioned above. Although an initial foray into a collation of this nature, the goal of this annotated bibliography is to provide a generic referential view of mobile agent systems in network applications