Rozprawy doktorskie na temat „Node scheduling”

In wireless sensor networks that consist of a large number of low-power, short-lived, unreliable sensors, one of the main design challenges is to obtain long system lifetime without sacrificing sensing quality; i.e. sensing coverage in this context. In this thesis, we first propose a node-scheduling scheme, which can reduce system overall energy consumption, therefore increasing system lifetime, by identifying redundant nodes with respect to sensing coverage and then assigning them an off duty operation mode which has lower energy consumption than the normal on-duty mode. Our scheme aims at completely preserving original sensing coverage. Practically, sensing coverage degradation caused by location error, packet loss and node failure is very limited, not more than 1%, as shown by our experimental results. We implement the proposed scheme in NS-2, as an extension of the LEACH protocol and compare its energy consumption with the original LEACH. Simulation results exhibit noticeably longer system lifetime with our scheme as compared to earlier algorithm. The first scheme we propose aims at completely preserving sensing coverage. This, however, requires each node to get, in some way, the knowledge of its own and its neighbors' location information. Also, in that scheme, each node has to perform some calculations to determine whether to take an off-duty status. To alleviate these restrictions, we propose and study several alternative node-scheduling schemes, which cannot guarantee the complete preservation of the original system coverage, but are nonetheless more light-weighted and flexible than the previous one. The simulation results compare these schemes with the previous one and demonstrate their effectiveness. In a single wireless sensor network, sensors are performing two operations: sensing and communication. Therefore, there might exist two kinds of redundancy in the network. Most of the previous work addressed only one kind of redundancy: sensing or communication alone. Although there have been research efforts trying to combine consideration of coverage and connectivity maintenance in a single activity scheduling, their theoretical basis for safe scheduling integration condition is only applicable in those networks that are initially fully covered by sensors. Random node deployment often makes initial sensing holes inside the deployed area inevitable, even in an extremely high-density network. Therefore, in this thesis, we enhance these works to support general wireless sensor networks by proving another conclusion: "the communication range is twice the sensing range" is the sufficient condition and the tight lower bound to ensure that complete coverage preservation implies connectivity among active nodes, if the original network topology (consisting of all the deployed nodes) is connected. Also, we extend the results to k-degree network connectivity and k-degree coverage preservation.

Node scheduling is one of the most effective techniques to maximize the lifetime of a wireless sensor network. It is the process of selecting a subset of nodes to monitor the sensor field on behalf of redundant nodes. At every round of the scheduling a small group of nodes are active while the rest of the sensor nodes are in sleep mode. In this thesis, we propose a novel node scheduling solution for wireless sensor networks. The main characteristic of our approach is its independence from location information as well as distance information. Moreover, it does not rely on unrealistic circular radio propagation models. In order to have a comprehensive solution, we have considered different relations between sensing range and transmission range. When these ranges are equal in addition to the case that transmission range is higher than sensing range, we devise a node scheduling scheme based on the concept of Minimum Dominating Set. Two heuristics are presented to determine a collection of minimum dominating sets of the graph of the wireless sensor network. At each round of the scheduling only one set is active. Minimum dominating sets are scheduled to be rotated periodically. Moreover, every set is synchronized prior to the end of its active period in order to minimize the effect of clock drift of sensor nodes. Two components are considered to address node failures during the on-duty period of minimum dominating sets. These are probing environment and adaptive sleeping. The former is responsible for probing the working nodes of the active set to detect any node failure. The latter adjusts the frequency of probing for minimizing the overhead of probing while preserving an adequate level of robustness for discovery of node failure. This framework is based on the PEAS protocol that has been developed by Fan Ye et al. [98, 99]. We propose a different node scheduling scheme with a three-tier architecture for the case that sensing range is higher than transmission range. The coverage tier includes a set of nodes to monitor the region of the interest. We propose a heuristic to determine a collection of d-dominating sets of the graph of the wireless sensor network. At every round of the scheduling one d-dominating set forms the coverage tier. Connectivity tier consists of sensor nodes that relay the data collected at the coverage tier back to the base station. Finally, the coverage management tier is responsible for managing different patterns of coverage such as cyclic or uniform coverage.

In this thesis, we consider wireless ad hoc and sensor networks where energy matters. Indeed, sensor nodes are characterized by a small size, a low cost, an advanced communication technology, but also a limited amount of energy. This energy can be very expensive, difficult or even impossible to renew. Energy efficient strategies are required in such networks to maximize network lifetime. We distinguish four categories of strategies: 1. Energy efficient routing, 2. Node activity scheduling, 3. Topology control by tuning node transmission power and 4. Reduction of the volume of information transferred. Our contribution deals with energy efficient routing and node activity scheduling. For energy efficient routing, the idea consists in reducing the energy spent in the transmission of a packet from its source to its destination, while avoiding nodes with low residual energy. The solution we propose, called EOLSR, is based on the link state OLSR routing protocol. We show by simulation that this solution outperforms the solution that selects routes minimizing the end-to-end energy consumption, as well as the solution that builds routes based on node residual energy. We then show how we can improve the benefit of energy efficient routing using cross layering. Informa- tion provided by the MAC layer improves the reactivity of the routing protocol and the robustness of routes. Moreover, taking into account the specificities of some applications like data gathering allows the routing protocol to reduce its overhead by maintaining routes only to the sink nodes. Concerning node activity scheduling, since the sleep state is the least power consuming state, our aim is to schedule node state between sleeping and active to minimize energy consumption while ensuring network and application functionalities. We propose a solution, called SERENA, based on node coloring. The idea is to assign a color to each node, while using a small number of colors and ensuring that two nodes with the same color can transmit without interfering. This color is mapped into a slot in which the node can transmit its messages. Consequently, each node is awake during its slot and the slots granted to its one-hop neighbors. It sleeps the remaining time. We show how this algorithm can adapt to different application requirements: broadcast, immediate acknowledgement of unicast transmissions... The impact of each additional requirement is evaluated by simulation. An originality of this work lies in taking into account real wireless propagation conditions. Color conflicts are then possible. A cross-layering approach with the MAC layer is used to solve these conflicts. We also show how cross-layering with the application layer can improve the coloring per- formance for data gathering applications. This work has been done for the ANR OCARI project whose aim is to design and implement a wireless sensor network for applications in harsh environments such as power plants and war- ships. The network layer including SERENA and EOLSR has been specified and is now under implementation.

Nowadays most communication networks like GSM, WLan or WiMAX are based on pre-existing infrastructure. These infrastructures are complicated, costly and difficult to deploy in very short time. Whereas Wireless Ad Hoc Networks are infrastructure-free self organizing networks which consist of co-operating nodes. These networks are highly desirable for various emerging applications for military and to extend the range and capacity of infrastructure based wireless networks. One critical issue that we face in Ad Hoc Network is the problem of scheduling. Scheduling algorithms in an Ad Hoc Network allows the nodes to share the wireless channel efficiently. But on the other hand, the scheduling algorithm needs to be easily implementable in a distributed fashion with little, if any, coordination between nodes in the network. Spread spectrum technologies allow interference averaging and therefore are employed in Ad Hoc networks. There are two major types of spread spectrum physical layer, which are frequency hopping (FH) spread spectrum and direct sequence (DS) spread spectrum. FH-CDMA divides the bandwidth into M sub channels, the receiver only sees the interference from the transmitter side which is on the same sub channel whereas in DS-CDMA we increase the spreading code M to decrease the signal to interference plus noise ratio (SINR) requirement. The purpose of research is to study a hybrid spread spectrum based on physical layer, in which the direct sequence signal is also frequency hoped. The DS will reduce the region of dominating interferes, while frequency hopping will be used within this region intelligently and allow the dominating interferes to transmit on different frequencies. First the system bounds on the transmission capacity of the proposed scheme is evaluated, and than a comparative analysis of different multiple access schemes is done with our proposed model with respect to their transmission capacity to evaluate its performance.

Thesis (M. S.)--Industrial and Systems Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Reveliotis, Spyros; Committee Member: Ayhan, Hayriye; Committee Member: Goldsman, Dave; Committee Member: Shamma, Jeff; Committee Member: Zwart, Bert.

Les protocoles de routage dans les réseaux peuvent être amenés à changer pour de nombreuses raisons : la détection d'un événement particulier, un changement de topologie planifié ou non, la mobilité des nœuds, l'obsolescence de version, etc. Ces changements ne pouvant être simultanément détectés ou pris en compte par tous les nœuds du réseau, il est nécessaire de considérer le cas où certains nœuds utilisent le protocole de routage initial, tandis que d'autres ont migré vers le nouveau protocole de routage. Les travaux de cette thèse portent sur le problème de boucles de routage susceptibles d'apparaître dans ce contexte, et qui dégradent considérablement les performances du réseau. Nous proposons des solutions d'ordonnancement des nœuds, dans le but de contrôler la migration afin d'éviter ces boucles. Premièrement, nous considérons le contexte des réseaux statiques et des protocoles centralisés avec pour cas particulier le changement de métriques dans le réseau. Nous proposons deux solutions d'évitement des boucles centralisées : SCH-m (amélioration mineure d'un protocole existant), et ACH (nouvelle contribution), basées sur l'identification des boucles de routage dans les composantes connexes que contient l'union des deux protocoles de routage. Nous accélérons la migration du réseau par une opération de fusion étape par étape des différentes transitions produites. Deuxièmement, nous évoluons vers les protocoles distribués en conservant le contexte statique du réseau, et considérons le cas particulier du retrait ou de la panne d'un nœud. Nous proposons également deux solutions : RTH-d (amélioration mineure d'un protocole existant) et DLF (nouvelle contribution traitant les boucles de taille 2) basées sur un échange de messages entre les nœuds tant pour la détection de la panne que pour la notification de la migration. Troisièmement, nous considérons le contexte de mobilité des nœuds, et étudions les performances de DLF-k (version améliorée de DLF qui prend en compte les boucles de taille inférieures ou égales à k, avec k >= 2) sur deux types d'applications : les applications avec un unique nœud mobile qui est la destination, et les applications avec un groupe de nœuds mobiles
Routing protocols in networks may change for many reasons: detection of a particular event, planned or unplanned change of topology, mobility of nodes, version obsolescence, etc. As these changes can not be simultaneously detected or taken into account by all nodes of the network, it is necessary to consider the case where some nodes use the initial routing protocol, while others have migrated to the new routing protocol. The work of this thesis deals with the problem of routing loops that may appear in this context, and which considerably degrade the performance of the network. We propose node scheduling solutions to control migration to avoid these loops. First, we consider the context of static networks and centralized protocols with the particular case of changing metrics. We propose two centralized avoidance solutions: SCH-m (minor improvement of an existing heuristic), and ACH (new contribution), based on the identification of the routing loops in the strongly connected components contained in the union of the two routing protocols. We accelerate the migration of the network by a step-by-step merge operation of the different transitions produced. Second, we evolve towards the distributed protocols while preserving the static context of the network, and consider the particular case of the withdrawal or breakdown of a node. We also propose two solutions: RTH-d (minor improvement of an existing heuristic) and DLF (new contribution for loops of size 2) based on message exchange of nodes for both failure detection and for migration notification. Thirdly, we consider the context of nodes mobility, and study the performance of DLF- k (improved version of DLF which takes into account loops of size less than or equal to k, with k >= 2) on two types of applications: applications with a single mobile node that is the destination, and applications with a group of mobile nodes

Mathematical programming has not been used extensively for the solution of scheduling problems. Moreover, the study of bicriteria problems on single and parallel machines is an open field for research. This thesis is aimed at developing algorithms to solve bicriteria problems more efficiently and in reasonable amount of time and with little compromise on the optimality of the solutions obtained. Two classes of problems are considered. The first class consists of scheduling unit duration tasks on parallel machines. Various combinations of primary and secondary criteria are considered and optimal seeking algorithms of polynomial time complexity are developed. The second class of problems assume general processing time tasks. An algorithm is developed for the primary criterion of total tardiness and the secondary criterion of total flow time. This algorithm is based on the solution of the underlying mathematical program and makes use of dominance relationship among the jobs and fixing of variables. Experimental results are presented regarding its performance.
Master of Science

Le reti ottiche, grazie alla loro elevata capacità, hanno acquisito sempre maggiore importanza negli ultimi anni, sia per via del crescente volume di dati scambiati, legato soprattutto alla larga diffusione di Internet, sia per la necessità di comunicazioni in tempo reale. Dati i (relativamente) lunghi tempi di adattamento, questa tecnologia nativamente non è quella ottimale per il trasporto di un traffico a burst, tipico delle telecomunicazioni odierne. Le reti ibride cercano, quindi, di coniugare al meglio le potenzialità della commutazione ottica di circuito e della commutazione ottica a pacchetto. In questo lavoro, in particolare, ci si è concentrati su un'architettura di rete ibrida denominata 3LIHON (3-Level Integrated Hybrid Optical Network). Essa prevede tre distinti livelli di qualità di servizio (QoS) per soddisfare differenti necessità: - Guaranteed Service Type (GST): simile ad un servizio a commutazione di circuito, non ammette perdita di dati. - Statistically Multiplexed Real Time (SM/RT): simile ad un servizio a commutazione di pacchetto, garantisce ritardo nullo o molto basso all'interno della rete, permette un piccolo tasso di perdita di dati e ammette la contesa della banda. - Statistically Multiplexed Best Effort (SM/BE): simile ad un servizio a commutazione di pacchetto, non garantisce alcun ritardo tra i nodi ed ammette un basso tasso di perdita dei dati. In un nodo 3LIHON, il traffico SM/BE impossibile da servire, a causa ad es. dell'interruzione da parte di pacchetti aventi un livello di QoS più prioritario, viene irrimediabilmente perso. Questo implica anche lo spreco del tempo e delle risorse impiegati per trasmettere un pacchetto SM/BE fino alla sua interruzione. Nel presente lavoro si è cercato di limitare, per quanto possibile, questo comportamento sconveniente, adottando e comparando tre strategie, che hanno portato alla modifica del nodo 3LIHON standard ed alla nascita di tre sue varianti.

The objective of this dissertation is to develop task scheduling guidelines and algorithms for wireless sensor nodes that harvest energy from ambient environment and use supercapacitor based storage systems to buffer the harvested energy. This dissertation makes five contributions. First, a physics based equivalent circuit model for supercapacitors is developed. The variable leakage resistance (VLR) model takes into account three mechanisms of supercapacitors: voltage dependency of capacitance, charge redistribution, and self-discharge. Second, the effects of time and supercapacitor initial state on supercapacitor voltage change and energy loss during charge redistribution are investigated. Third, the task scheduling problem in supercapacitor based environmentally powered wireless sensor nodes is studied qualitatively. The impacts of supercapacitor state and energy harvesting on task scheduling are examined. Task scheduling rules are developed. Fourth, the task scheduling problem in supercapacitor based environmentally powered wireless sensor nodes is studied quantitatively. The modified earliest deadline first (MEDF) algorithm is developed to schedule nonpreemptable tasks without precedence constraints. Finally, the modified first in first out (MFIFO) algorithm is proposed to schedule nonpreemptable tasks with precedence constraints. The MEDF and MFIFO algorithms take into account energy constraints of tasks in addition to timing constraints. The MEDF and MFIFO algorithms improve the energy performance and maintain the timing performance of the earliest deadline first (EDF) and first in first out (FIFO) algorithms, respectively.

In [9], Maniezzo and Mingozzi study a project scheduling problem with irregular starting time costs. Starting from the assumption that its computational complexity status is open, they develop a branch-and-bound procedure, and identify special cases that are solvable in polynomial time. In this note, we review three previously established, related results which show that the general problem is solvable in polynomial time.

Optical networks became very important in the latest years, thanks totheir high trac capacity, because of the continuous growth of totalexchanged data and the request of real-time communication.Since they have (relatively) long adaptation times, this technology isnot inherently the most suitable to carry bursty traffic like the currentone. Hybrid networks try to get the best from optical circuit switchingand optical packet switching.This work is focused on an hybrid network architecture called 3LIHON (3-Level Integrated Hybrid Optical Network). It has three different quality of service (QoS) levels, in order to meet different requirements:- Guaranteed Service Type (GST): resembling an optical circuitswitched service, it does not allow data loss.- Statistically Multiplexed Real Time (SM/RT): resembling anoptical packet switched service, it ensures none or very smalldelay inside the network, it allows a low data loss ratio andbandwidth contention.- Statistically Multiplexed Best Effort (SM/BE): resembling anoptical packet switched service with very small overall packetloss but no guaranteed delay inside the nodes.In a 3LIHON node, SM/BE traffic interrupted by packets with higherpriority is dropped. This means that time and resources spent sendingthe SM/BE packet until the interruption are wasted.In this work we try to avoid this behaviour, by implementing andcomparing three new output scheduling algorithms. They are differentversions of the standard 3LIHON node:- 3LIHON-RS: SM/BE interrupted packets are resumed oncehigher priority trac has been sent.- 3LIHON-RT: SM/BE interrupted packets are retransmitted.- 3LIHON-2R: since GST packets are usually much longer thanSM/RT ones, resuming an interruption caused by GST trafficleads to a long wait. This architecture resumes SM/BE packetsinterrupted by SM/RT traffic and retransmits them if they havebeen interrupted by GST traffic.A proper (Fragment End) Optical Code can be used to implement andsignal packets interruption and resuming, Every 3LIHON version hasbeen tested with increasing traffic loads, but never so high to overloadthe node. Three different simulators have been written in order tostudy the behaviour of the different architectures, by using the Simula programming language and its context class DEMOS, specificallyintended for discrete event modelling. The node input part has justbeen modelled, since it does not directly influences results.As a function of system load, performances of these new architectureshave been analysed, paying attention especially to SM/BE packetsmean delay, SM/BE queues, delay distribution of SM/BE traffic,wavelengths utilization, GST and SM/RT interruptions over SM/BEtraffic, standard deviation of SM/BE delay and SM/RT packet loss.It has been observed that 3LIHON-2R does not have the best absoluteperformances, but is the best trade off among all the systemsand is very well balanced when system load increases. It is the architectureshowing the lowest mean SM/BE packet delay. 3LIHON-RS proved to have the lowest SM/BE queue values and less interruptions of SM/BE traffic. Furthermore, it has the best wavelengths utilization performances. 3LIHON-RT achieved the worst results and is the first architecture overloading.

Dans cette thèse, les techniques de coopération ont été étudiées pour un canal multi-accès multi-relais composé d'au moins deux sources qui communiquent avec une seule destination à l'aide d'au moins deux nœuds de relayage en mode semi-duplex. Le multiplexage par répartition dans le temps est supposé. Tout d'abord, l’algorithme d’adaptation de lien est exécuté par l'ordonnanceur centralisé. Durant la première phase de transmission, les sources transmettent chacune à leur tour leur message respectif pendant des intervalles de temps consécutifs. Dans chaque intervalle de temps dans la deuxième phase, la destination planifie un nœud pour transmettre les redondances, mettant en œuvre un protocole coopératif d'Hybrid Automatic Repeat reQuest (HARQ), où les canaux de contrôle limités bidirectionnels sont disponibles depuis les sources et les relais vers la destination. Dans la première partie de la thèse, les stratégies de sélection des nœuds centralisé sont proposées pour la deuxième phase de transmission. Les décisions d’ordonnancement sont prises en fonction de la connaissance des ensembles de sources correctement décodées par chaque noeud et ayant comme objectif de maximiser l’efficacité spectrale moyenne. L'analyse de la probabilité de coupure de l'information ainsi que les simulations Monte-Carlo (MC) sont effectués afin de valider ces stratégies. Dans la seconde partie, un algorithme d’adaptation de lien lent est proposé afin de maximiser l’efficacité spectrale moyenne sous contrainte de vérification d'une qualité de service individuelle cible pour une famille donnée de schémas de modulation et de codage, réposant sur l'information sur la distribution des canaux signalée. Les débits des sources discrets sont déterminés en utilisant l’approche "Genie-Aided" suivie d’un algorithme itératif de correction de débit. Les simulations MC montrent que l’algorithme d’adaptation de lien proposé offre des performances proches de celles de la recherche exhaustive. Dans la troisième partie, les performances de protocole HARQ à redondance incrémentale (IR) avec codage mono et multi-utilisateur, ainsi que l'HARQ de type Chase Combining avec codage mono-utilisateur sont comparées. Les simulations MC montrent que l'IR-HARQ avec codage mono-utilisateur offre le meilleur compromis entre performance et complexité pour le scénario de petit nombre de sources. Un schéma de codage pratique est proposé et validé à l'aide de simulations MC
In this thesis, cooperation techniques have been studied for Multiple Access Multiple Relay Channel, consisted of at least two sources which communicate with a single destination with the help of at least two half-duplex relaying nodes. Time Division Multiplexing is assumed. First, the link adaptation algorithm is performed at the centralised scheduler. Sources transmit in turns in consecutive time slots during the first transmission phase. In each time slot of the second phase, the destination schedules a node to transmit redundancies, implementing a cooperative Hybrid Automatic Repeat reQuest (HARQ) protocol, where bidirectional limited control channels are available from sources and relays towards the destination. In the first part of the thesis, centralized node selection strategies are proposed for the second phase. The scheduling decisions are made based on the knowledge of the correctly decoded source sets of each node, with the goal to maximize the average spectral efficiency. An information outage analysis is conducted and Monte-Carlo (MC) simulations are performed to evaluate their performance. In the second part, a slow-link adaptation algorithm is proposed which aims at maximizing the average spectral efficiency under individual QoS targets for a given modulation and coding scheme family relying on the reported Channel Distribution Information of all channels. Discrete source rates are first determined using the "Genie-Aided" assumption, which is followed by an iterative rate correction algorithm. The resulting link adaptation algorithm yields performance close to the exhaustive search approach as demonstrated by MC simulations. In the third part, performances of Incremental Redundancy (IR) HARQ with Single and Multi User encoding, as well as the Chase Combining HARQ with Single User encoding are compared. MC simulations demonstrate that IR-HARQ with Single User encoding offers the best trade-off between performance and complexity for a small number of sources in our setting. Practical coding scheme is proposed and validated using MC simulations

Avec les avancées récentes en microélectronique, en traitement numérique et en technologie de communication, les noeuds de réseau de capteurs sans fil (noeud RCSF) deviennent de moins en moins encombrants et coûteux. De ce fait la technologie de RCSF est utilisée dans de larges domaines d’application. Comme les noeuds RCSF sont limités en taille et en coût, ils sont en général équipés d’un petit microcontrôleur de faible puissance de calcul et de mémoire etc. De plus ils sont alimentés par une batterie donc son énergie disponible est limitée. A cause de ces contraintes, la plateforme logicielle d’un RCSF doit consommer peu de mémoire, d’énergie, et doit être efficace en calcul. Toutes ces contraintes rendent les développements de logiciels dédiés au RCSF très compliqués. Aujourd’hui le développement d’un système d’exploitation dédié à la technologie RCSF est un sujet important. En effet avec un système d’exploitation efficient, les ressources matérielles d’une plateforme RCSF peuvent être utilisées efficacement. De plus, un ensemble de services système disponibles permet de simplifier le développement d’une application. Actuellement beaucoup de travaux de recherche ont été menés pour développer des systèmes d’exploitation pour le RCSF tels que TinyOS, Contiki, SOS, openWSN, mantisOS et simpleRTJ. Cependant plusieurs défis restent à relever dans le domaine de système d’exploitation pour le RCSF. Le premier des défis est le développement d’un système d’exploitation temps réel à faible empreinte mémoire dédié au RCSF. Le second défi est de développer un mécanisme permettant d’utiliser efficacement la mémoire et l’énergie disponible d’un RCSF. De plus, comment fournir un développement d’application pour le RCSF reste une question ouverte. Dans cette thèse, un nouveau système d’exploitation hybride, temps réel à énergie efficiente et à faible empreinte mémoire nommé MIROS dédié au RCSF a été développé. Dans MIROS, un ordonnanceur hybride a été adopté ; les deux ordonnanceurs évènementiel et multithread ont été implémentés. Avec cet ordonnanceur hybride, le nombre de threads de MIROS peut être diminué d’une façon importante. En conséquence, les avantages d’un système d’exploitation évènementiel qui consomme peu de ressource mémoire et la performance temps réel d’un système d’exploitation multithread ont été obtenues. De plus, l’allocation dynamique de la mémoire a été aussi réalisée dans MIROS. La technique d’allocation mémoire de MIROS permet l’augmentation de la zone mémoire allouée et le réassemblage des fragments de mémoire. De ce fait, l’allocation de mémoire de MIROS devient plus flexible et la ressource mémoire d’un noeud RCSF peut être utilisée efficacement. Comme l’énergie d’un noeud RCSF est une ressource à forte contrainte, le mécanisme de conservation d’énergie a été implanté dans MIROS. Contrairement aux autres systèmes d’exploitation pour RCSF où la conservation d’énergie a été prise en compte seulement en logiciel, dans MIROS la conservation d’énergie a été prise en compte à la fois en logiciel et en matériel. Enfin, pour fournir un environnement de développement convivial aux utilisateurs, un nouveau intergiciel nommé EMIDE a été développé et intégré dans MIROS. EMIDE permet le découplage d’une application de système. Donc le programme d’application est plus simple et la reprogrammation à distance est plus performante, car seulement les codes de l’application seront reprogrammés. Les évaluations de performance de MIROS montrent que MIROS est un système temps réel à faible empreinte mémoire et efficace pour son exécution. De ce fait, MIROS peut être utilisé dans plusieurs plateformes telles que BTnode, IMote, SenseNode, TelosB et T-Mote Sky. Enfin, MIROS peut être utilisé pour les plateformes RCSF à fortes contraintes de ressources
With the recent advances in microelectronic, computing and communication technologies, wireless sensor network (WSN) nodes have become physically smaller and more inexpensive. As a result, WSN technology has become increasingly popular in widespread application domains. Since WSN nodes are minimized in physical size and cost, they are mostly restricted to platform resources such as processor computation ability, memory resources and energy supply. The constrained platform resources and diverse application requirements make software development on the WSN platform complicated. On the one hand, the software running on the WSN platform should be small in the memory footprint, low in energy consumption and high in execution efficiency. On the other hand, the diverse application development requirements, such as the real-time guarantee and the high reprogramming performance, should be met by the WSN software. The operating system (OS) technology is significant for the WSN proliferation. An outstanding WSN OS can not only utilize the constrained WSN platform resources efficiently, but also serve the WSN applications soundly. Currently, a set of WSN OSes have been developed, such as the TinyOS, the Contiki, the SOS, the openWSN and the mantisOS. However, many OS development challenges still exist, such as the development of a WSN OS which is high in real-time performance yet low in memory footprint; the improvement of the utilization efficiency to the memory and energy resources on the WSN platforms, and the providing of a user-friendly application development environment to the WSN users. In this thesis, a new hybrid, real-time, energy-efficient, memory-efficient, fault-tolerant and user-friendly WSN OS MIROS is developed. MIROS uses the hybrid scheduling to combine the advantages of the event-driven system's low memory consumption and the multithreaded system's high real-time performance. By so doing, the real-time scheduling can be achieved on the severely resource-constrained WSN platforms. In addition to the hybrid scheduling, the dynamic memory allocators are also realized in MIROS. Differing from the other dynamic allocation approaches, the memory heap in MIROS can be extended and the memory fragments in the MIROS can be defragmented. As a result, MIROS allocators become flexible and the memory resources can be utilized more efficiently. Besides the above mechanisms, the energy conservation mechanism is also implemented in MIROS. Different from most other WSN OSes in which the energy resource is conserved only from the software aspect, the energy conservation in MIROS is achieved from both the software aspect and the multi-core hardware aspect. With this conservation mechanism, the energy cost reduced significantly, and the lifetime of the WSN nodes prolonged. Furthermore, MIROS implements the new middleware software EMIDE in order to provide a user-friendly application development environment to the WSN users. With EMIDE, the WSN application space can be decoupled from the low-level system space. Consequently, the application programming can be simplified as the users only need to focus on the application space. Moreover, the application reprogramming performance can be improved as only the application image other than the monolithic image needs to be updated during the reprogramming process. The performance evaluation works to the MIROS prove that MIROS is a real-time OS which has small memory footprint, low energy cost and high execution efficiency. Thus, it is suitable to be used on many WSN platforms including the BTnode, IMote, SenseNode, TelosB, T-Mote Sky, etc. The performance evaluation to EMIDE proves that EMIDE has less memory cost and low energy consumption. Moreover, it supports small-size application code. Therefore, it can be used on the high resource-constrained WSN platforms to provide a user-friendly development environment to the WSN users

Cette thèse a pour objectif de proposer de nouvelles approches d'ordonnancement, de coopération et de gestion de la mobilité dans les réseaux sans fil de type IEEE 802.11. Le maintien de la qualité de service (QoS), au niveau MAC, représente la caractéristique fondamentale de ces approches. L'analyse des mécanismes existants nous a conduits à retenir le protocole EDCF, supportant la QoS, comme une base de travail pour l'ensemble de nos propositions. Dans le but de pallier certaines faiblesses du standard 802.11, une nouvelle architecture à base de multi-ordonnanceurs HCF-T, est proposée. Les performances obtenues sont exprimées en termes de gestion du trafic, de maintien du débit, d'élimination de collisions et de réduction de la charge du réseau. Ensuite, un schéma coopératif est présenté et analysé. Il comporte une étude de deux protocoles de relayage AAF et DAF ainsi qu'une évaluation d'un ensemble de techniques de combinaison au niveau du récepteur. Concernant la problématique de la mobilité, nous avons retenu et analysé un scénario prenant en considération les différentes situations rencontrées dans un modèle réel. Un algorithme de résolution multi-couvertures est proposé afin de traiter l'accès dans les zones de recouvrement. Cette étude a mené à distinguer trois régimes de mobilité : faible, moyen et fort. Les performances sont évaluées en fonction des métriques MAC et pour chaque mode de mobilité, un schéma de synthèse est établi
This thesis proposes a new approach relating to the packets scheduling algorithm, the cooperation scheme and the nodes' mobility for IEEE 802.11 wireless network family. Considering the QoS delivery process at the MAC level consists the main feature of the proposal research study. The analysis of the current mechanisms leads to keep the protocol EDCF as the basic model for our work platform. In order to overcome the weakness of the earlier 802.11 standard, a new model based on multi-scheduler algorithm, called HCF-T, is proposed. The achieved performances are summarized following several criteria: traffic control, throughput improving, collisions avoidance, and network load decreasing. Furthermore, in the way of getting better results according to the PHY layer, we presented and analyzed a model of cooperative diversity scheme. It included a couple of relaying protocols AAF and DAF supported by a set of combining techniques to backup the signal at the receiver. To support node's mobility within EDCF, we built-up a model of WLAN which able to track node motion and control the access as in real condition. In the case of overlapping APs ranges, we developed a Multi-coverage algorithm aiming to carry out the session associations. As a result, three levels (Low, Medium, and High) of node's speed are discerned. Finally, EDCF has been implemented on various static and dynamic scenarios. The performances, based on the main MAC-layer metrics, such as throughput, End-2-End delay, and jitter, have been classified and comprehensively evaluated

This report describes Processor Coupling, a mechanism for controlling multiple ALUs on a single integrated circuit to exploit both instruction-level and inter-thread parallelism. A compiler statically schedules individual threads to discover available intra-thread instruction-level parallelism. The runtime scheduling mechanism interleaves threads, exploiting inter-thread parallelism to maintain high ALU utilization. ALUs are assigned to threads on a cycle byscycle basis, and several threads can be active concurrently. Simulation results show that Processor Coupling performs well both on single threaded and multi-threaded applications. The experiments address the effects of memory latencies, function unit latencies, and communication bandwidth between function units.

碩士
義守大學
資訊工程學系碩士班
98
Wireless sensor networks are applied in many areas, which require long-term supervising, such as medical, military, catastrophe sensor, and environment monitor. In general, these areas are not easy to supervise and are not suitable for people to operate. Therefore, wireless sensor networks can take the place to conduct and monitor theses areas. WSN consists of low power and unreliable sensor nodes. As a result, WSN encounters a lot of problems. One major problem is to avoid sacrificing sensing coverage and sensing reliability whereas extending the lifetime of the sensor network. Since we need to save the energy of sensor nodes, we thereby don’t turn on all the sensor nodes, and have some of them in sleep. Therefore we propose our algorithm of sleeping schedule for the sensor network in this thesis. We undertake experiments to prove that our algorithm helps select more sleeping nodes than traditional algorithms. In the way, hopefully each sensor node can be effectively utilized in order to extend the lifetime of sensor network.

碩士
元智大學
資訊工程學系
97
In wireless sensor networks (WSNs), due to that sensor nodes have limited energy and it''s difficult to recharge or replace the batteries. So scheduling play an important role in WSNs. In this paper, we proposed a grid-based node scheduling algorithm which can reduce the overall system energy consumption thus extending the system lifetime. First, we investigate the relationship of the intersection points between the sensor node and the sides of the grid. Via the investigation of the intersection points, we proposed mono-grid algorithm to separate the nodes into subsets while each subset guarantee the grid area is full cover. We further present multi-grid algorithm to turn off the redundant node through estimating the coverage degree of the nodes. Using extensive simulation in ns2, we demonstrate that the grid-based scheduling can reduce energy consumption and the active node density decrease up to 83% while maintaining the coverage.

碩士
中國文化大學
資訊管理學系
99
A collaborated framework of grid computing was well defined, every grid node would be able to share resources and collaborate with each other. In grid environment, every dynamically used resources should be monitored and analyzed. How should we monitor and allocate dynamic resources in grid is an important issue all the time. In this thesis, there are two different types of process scheduling model, one is non-grouped grid node process scheduling model and the other one is grouped grid node process scheduling model. With non-grouped grid node process scheduling model, users could assign jobs at any node in the grid, and this node would dispatch those jobs based on collected information of resources and job scheduling algorithm. That is to say the overall performance of grid environment would be improved because non-grouped grid node process scheduling model could monitor and allocate dynamic resources. However, there is a CPU consumption caused by monitoring dynamic resources in grid. The non-grouped grid node process scheduling model is not suitable when there are more than fifty nodes in the grid environment. With grouped grid node process scheduling model, nodes would be classified into five classifications by the CPU specification scores. Within each classification, every node in the same classification would be assigned to a group which is no more than ten nodes in that group. By separating nodes into groups, the CPU consumption caused by monitoring the resources of nodes in a group would be effectively reduced. While the group-agents node deal with all the resource allocation between groups, the utility ratio of the grid resource would be increase. Grouped process scheduling grid node model could be implemented in the grid with more than fifty nodes. By implementing these two types of process scheduling model, the overall performance of grid would be improved.

碩士
國立高雄大學
資訊工程學系碩士班
99
The coverage problems in wireless sensor network are always been concerned. In Q-coverage, every object should be monitored by specific sensors. In the study, we try to arrange sensors in Q-coverage restriction and maximize their lifetimes. Most assumptions in other approaches are discussed in homogeneous sensor network, but this approaches in heterogeneity. Therefore, this problem can be discussed in different consumptions and radius. In this approach, we offer an algorithm to choose the set of sensors in greedy method. By this algorithm, the experiment will present the performance of sensors’ life and approach to the theory (upper- bound). Q-coverage was proved as NPC problem, and there are no polynomial solutions to optimize. But In this study, we offer a heuristic to trace network and monitor time, and we try to find the best solutions in restriction.

碩士
國立臺灣科技大學
電機工程系
100
With advances in the flash memory process technology and reduction of manufacturing costs, flash memory has been used in many popular products recently. The controller IC technology is the critical one making flash memory function well. Error control coding is one of the key components in the controller IC. BCH code has been adopted for the error control on the NAND flash memory for many years. However, due to high error characteristic of the new-generation NAND flash memory system, the industry must find more powerful and efficient error correction codes to perform error correction. Low-density parity-check codes (LDPC codes) are good candidates, especially, when soft information is used to decode. LDPC codes usually result in good bit error performance. 　　This thesis is mainly focus on implementing the hardware architecture of decoding algorithm for LDPC codes. After investigating several well-known decoding algorithms, the variable-node-centric sequential scheduling algorithm is adopted to reduce the hardware complexity of the decoder. This algorithm is one kind of group shuffled scheduling algorithms, which combine the parallel and serial decoding features to reduce the hardware complexity. By using this algorithm one can reduce the connection number of the hardware architecture to make routing easier. Moreover, the check node units and variable node units in the decoder can be simplified efficiently. The proposed LDPC decoder circuit is synthesized with UMC 0.11 μm standard process and the size of gate count is provided.

碩士
國立中山大學
資訊工程學系研究所
103
Nowadays, with the rapid growth of handheld devices, people rely on wireless network more than anytime before. Since wireless network are more and more important, 3GPP proposed a new 4G wireless communication standard called “Long Term Evolution Advance” (LTE-A). In Release 9, 3GPP set a standard of “Relay” architecture to improve locations with bad connection, such as Hot Spot, Dead Spot, and Cell-edge. RN (Relay Node) can connect with DeNB (Donor eNodeB) by wireless Backhaul Link, therefore makes it a better choice for a large outdoor event held in a short duration compared to the wired Backhaul connection. CoMP (Coordinated multipoint transmission/reception) is a new architecture widely discussed and researched in LTE-A. CoMP can improve Cell-edge connection, and improve bitrate while decreasing interference. In this paper, we proposed a new scheduling mechanism combined of Relay and CoMP to improve the efficiency of wireless RN. The proposed scheduling can identify different UE (User Equipment) under a eNB (eNodeB). UE will report how many users served and the CSI (Channel State Information) to eNB. After gathering the information, our mechanism calculate a new weight. Then the weight and CSI exchange between eNBs, so RN can get more resources and allow RN combined with CoMP JT (Joint Transmission) mechanism to get higher priority. That is, four different priorities from high to low for JT RN, RN, JT UE, and UE are arranged. In the end of paper, we use a network simulator ns3 to simulate our method. Experiment results show the scheduling mechanism can improve the average throughput, and let the Relay Node has higher throughput by keeping benefit of CoMP.

碩士
國立交通大學
電信工程研究所
106
Low-density parity-check (LDPC) codes provide the powerful capability of error correction. Therefore, they have been widely adopted for data protection in many communication standards. LDPC Codes are often decoded by the sum-product algorithm with flooding scheduling which is based on updating all of the edges in the Tanner graph simultaneously. In the previous researches, dynamic scheduling schemes which update only part of the edges in the Tanner graph at the same time have been shown to result in faster convergence speed or better error rate performance. For some traditional dynamic scheduling schemes, some variable nodes are observed to change their signs repeatedly in a single iteration of decoding. We think that the decoding messages associated with the edges in the Tanner graph connected to those variable nodes are unstable. Keeping on updating those nodes according to the unstable messages might not lead to a better convergence of decoding and it may be more effective to update other variable nodes preferentially. In this study, we propose to control the numbers of updated variable nodes in order to limit the numbers of changed signs based on the above discovery. Simulation results also show that our method can obtain better a decoding performance than other traditional schemes.

碩士
國立成功大學
電腦與通信工程研究所
98
In this thesis, we study for minimizing frame length of group communications in node scheduling, which is based on wireless multi-hop networks given source-specific tree and collision-free, called “In-Order Collision-Free Multiple Group Communications Scheduling (OCF-MGCS)”problem. We prove that OCF-MGCS problem is NP-complete and can be represented as an integer-linear programming (ILP) problem. The solution of the ILP is an optimal solution in OCF-MGCS. Here we develop a novel algorithm in polynomial time to attain an approximate solution efficiently in OCF-MGCS, called “ Broadcasting Level-by-Level ” (B-LBL) algorithm. The complexity of B-LBL is O(N2). Unlike link scheduling, the performance of B-LBL is much better because of the characteristic of “Broadcast”. Moreover, the effect of “Spatial reuse” and stream scheduling scheme make the result that the performance of B-LBL is better than Tree-based scheduling algorithm and pure color scheduling algorithm separately. Furthermore, for conquering the exposed terminal problem in wireless networks, we propose a new node scheduling algorithm, which has the characteristic of “Spatial reuse” and “Broadcast”, called “Collision Allowed Level-by-Level” (CA-LBL) algorithm. Under the condition that guaranteeing group communications form fail, CA-LBL allows partial and lesser collisions to increase the utilization of channel. Even though CA-LBL is against the collision-free in OCF-MGCS, the performance of CA-LBL is much better than B-LBL. By the way, for guaranteeing group communications form fail and avoiding the determining color problem in general color algorithms, CA-LBL filters constraints directly rather than general color algorithms. In the simulations, the performance of CA-LBL is better than other node scheduling algorithm certainly. Finally, we find that the frame length of CA-LBL varies little as the number of maximal degree increases in a specific number of nodes.

碩士
淡江大學
資訊工程學系碩士班
93
Wireless sensor networks (WSNs) comprise a sink node and a large number of sensor nodes. In the application of environmental monitoring, sensor nodes that are deployed far away from the sink node transmit the gathered information to the sink node in a multi-hop manner. Therefore, sensor nodes nearby the sink node tend to exhaust their energy earlier than other nodes due to their heavy traffic for packet forwarding. The unbalanced power consumption among sensor nodes may cause network partitioned. This paper proposes efficient node placement, topology control, and MAC scheduling protocols to prolong the sensor network lifetime, reduce the packet transmission delay, and avoid collision. Firstly, a virtual tree topology is constructed based on mesh-based WSNs. Then two node-placement techniques, namely distance-based and density-based deployments are proposed to balance the power consumption of sensor nodes. Finally, a collision-free MAC scheduling protocol is proposed to prevent the packet transmissions from collision. In addition, extension of the proposed protocols are made from the mesh-based WSN to the random deployed WSN, making the mechanisms developed for Mesh-based WSNs can be applied to random deployed WSNs. Simulation results reveal that the developed protocols can efficiently balance each sensor node’s power consumption and prolong the network lifetime in both mesh-based and random deployed WSNs.

Wireless technology has become an increasingly popular way to gain network access. Wireless networks are expected to provide efficient and reliable service and support a broad range of emerging applications, such as multimedia streaming and video conferencing. However, limited wireless spectrum together with interference and fading pose signi cant challenges for network designers. The novel technique of network coding has a significant potential for improving the throughput and reliability of wireless networks by taking advantage of the broadcast nature of wireless medium. Reverse carpooling is one of the main techniques used to realize the benefits of network coding in wireless networks. With reverse carpooling, two flows are traveling in opposite directions, sharing a common path. The network coding is performed in the intermediate (relay) nodes, which saves up to 50% of transmissions. In this thesis, we focus on the scheduling at the relay nodes in wireless networks with reverse carpooling. When two packets traveling in opposite directions are available at the relay node, the relay node combines them and broadcasts the resulting packet. This event is referred to as a coding opportunity. When only one packet is available, the relay node needs to decide whether to wait for future coding opportunities, or to transmit them without coding. Though the choice of holding packets exploits the positive aspects of network coding, without a proper policy in place that controls how long the packets should wait, it will have an adverse impact on delays and thus the overall network performance. Accordingly, our goal is to find an optimal control strategy that delicately balances the tradeoff between the number of transmissions and delays incurred by the packets. We also address the fundamental question of what local information we should keep track of and use in making the decision of of whether to transmit uncoded packet or wait for the next coding opportunity. The available information consists of queue length and time stamps indicating the arrival time of packets in the queue. We could also store history of all previous states and actions. However, using all this information makes the control very complex and so we try to find if the overhead in collecting waiting times and historical information is worth it. A major contribution of this thesis is a stochastic control framework that uses state information based on what can be observed and prescribes an optimal action. For that, we formulate and solve a stochastic dynamic program with the objective of minimizing the long run average cost per unit time incurred due to transmissions and delays. Subsequently, we show that a stationary policy based on queue lengths is optimal, and the optimal policy is of threshold-type. Then, we describe a non-linear optimization procedure to obtain the optimal thresholds. Further, we substantiate our analytical ndings by performing numerical experiments under varied settings. We compare systems that use only queue length with those where more information is available, and we show that optimal control that uses only the queue length is as good as any optimal control that relies on knowing the entire history.

Στην εργασία αυτή μελετήθηκαν αρχιτεκτονικές χρονοπρογραμματισμού διεργασιών σε κόμβο ασύρματου δικτύου αισθητήρων, ο οποίος έχει πηγή περιορισμένης και μεταβλητής ισχύος. Τα ασύρματα δίκτυα αισθητήρων αποτελούνται από κόμβους που επικοινωνούν και ανταλλάσουν δεδομένα μεταξύ τους. Κάθε κόμβος πρέπει να έχει μεγάλη αυτονομία λειτουργίας και μικρή κατανάλωση ενέργειας. Στην εργασία αυτή προσομοιώθηκε ένα μοντέλο ενός κόμβου με πηγή ενέργειας την ηλιακή ισχύ, καθώς και ένα σύνολο διεργασιών με συγκεκριμένα χαρακτηριστικά και προθεσμίες εκτέλεσης. Εξετάστηκε η βέλτιστη διαχείριση της ενέργειας για την επιτυχή εκτέλεση των διεργασιών. Αρχικά μελετήθηκαν διάφοροι αλγόριθμοι χρονοπρογραμματισμού των διεργασιών του κόμβου (task scheduling), προσομοιώθηκε ένας βέλτιστος αλγόριθμος πραγματικού χρόνου (Lazy Scheduling Algorithm), μελετήθηκε και συγκρίθηκε η συμπεριφορά του. Στο επόμενο στάδιο, σχεδιάσθηκε μία αρχιτεκτονική για τον αλγόριθμο αυτό και υλοποιήθηκε με τη γλώσσα VHDL. Το υλικό, που προέκυψε με διαδικασία σύνθεσης της περιγραφής VHDL, προσομοιώθηκε και διαπιστώθηκε η αποτελεσματικότητα και η χαμηλή κατανάλωση ενέργειας του. Στο τελικό στάδιο βελτιώθηκε η αρχιτεκτονική του υλικού και μειώθηκε ακόμη περισσότερο η κατανάλωση ενέργειας.
-

碩士
中國文化大學
資訊管理學系
99
This article explains the whole grid environment, how can the best system perfor-mance. The whole point of the grid points to monitor, backup, monitoring points and enforcement points. Each point in the grid environment has its own particular portfolio. Each implementation of the point of its current work status to the monitoring point of collection, establishment of enforcement points is currently working conditions database. When a busy executive spots, it will pass on the work of monitoring points, processing, monitoring points, such as busy work, it can point the current status of work from the implementation of the database to find a free and appropriate implementation of the work points to pass on the work of turn found in the implementation of enforcement points. Case, the whole grid environment, resources will be fully utilized, and to reach the whole system performance optimization.

碩士
國立高雄大學
資訊工程學系碩士班
99
In wireless sensor network, there are several sensors and targets. All targets have to be monitored by sensors. Each target has a coverage level requirement. The targets can satisfy requirements by opening a part of the sensors. The paper research how to schedule the sensors. The power consumption can be reduced, and the network life time can be extended. The traditional methods almost use the greedy methods and the heuristic algorithms to solve the problem. In this paper, we employ Game Theory to solve it. The sensor selects whether to open the power or not. We prove that the game we defined can converge to a stable state, and the simulation result show it can extend the network life time. But the time that a game converges to a stable state has to be regarding as a cost. We propose two solutions to get the stable state more quickly. By simulation result, reaching stable state quickly leads to the little reduction of the network life time. The result is very good.

碩士
國立中正大學
資訊工程研究所
99
The IEEE 802.16 standard is defined to meet the high-speed and wide-range data transmission in an efficient way. The purpose of this thesis is to study how to minimize the energy consumption of mobile stations so as to maximize the network lifetime. We consider the real-time connections and focus on the resource scheduling which includes time slots allocation, QoS guarantee of real-time flows, interference-free on each link, and spectral reuse for the channel. The proposed energy-aware link scheduling algorithms construct a mathematical model of the energy consumption problem and provide a computationally efficient scheme to solve the problem. Comparing with traditional algorithm for real-time flows, simulation results show that the proposed scheme significantly improves the life cycle of mobile stations.

Network lifetime is a key issue in wireless sensor networks where sensor nodes, distributed typically in remote/hostile sensing areas, are powered by finite energy batteries which are not easily replaced/recharged. Depletion of these finite energy batteries can result in a change in network topology or in the end of network life itself. Hence, prolonging the life of wireless sensor networks is important. Energy consumed in wireless sensor nodes can be for the purpose of i) sensing functions, ii) processing/computing functions, and ii) communication functions. For example, energy consumed by the transmit and receive electronics constitute the energy expended for communication functions. Our focus in this thesis is on the efficient use of energy for sensing. In particular, we are concerned with energy efficient algorithms for scheduling the sensing activity of sensor nodes. By scheduling the sensing activity we mean when to activate a sensor node for sensing (active mode) and when to keep it idle (sleep mode). The novel approach we adopt in this thesis to achieve efficient scheduling of sensing activity is an information coverage approach, rather than the widely adopted physical coverage approach. In the physical coverage approach, a point is said to be covered by a sensor node if that point lies within the physical coverage range (or the sensing radius) of that sensor, which is the maximum distance between the sensor and the point up to which the sensor can sense with acceptable accuracy. Information coverage, on the other hand, exploits cooperation among multiple sensors to accurately sense a point even if that point falls outside the physical coverage range of all the sensors. In this thesis, we address the question of how to schedule the activity of various sensor nodes in the network to enhance network lifetime using information coverage. In the first part of the thesis, we are concerned with scheduling of sensor nodes for sensing point targets using information coverage – example of a point-target being temperature or radiation level at a source or point that needs to be monitored. Defining a set of sensor nodes which collectively can sense a point-target accurately as an information cover, we propose an algorithm to obtain Disjoint Set of Information Covers (DSIC) that can sense multiple point-targets in a given sensing area. Being disjoint, the resulting information covers in the proposed algorithm allow a simple round-robin schedule of sensor activation (i.e., activate the covers sequentially). We show that the covers obtained using the proposed DSIC algorithm achieve longer network life compared to the covers obtained using an Exhaustive-Greedy-Equalized Heuristic (EGEH) proposed recently in the literature. We also present a detailed complexity comparison between the DSIC and EGEH algorithms. In the second part of the thesis, we extend the point target sensing problem in the first part to a full area sensing problem, where we are concerned with energy efficient ‘area-monitoring’ using information coverage. We refer to any set of sensors that can collectively sense all points in the entire area-to-monitor as a full area information cover. We first propose a low-complexity heuristic algorithm to obtain full area information covers. Using these covers, we then obtain the optimum schedule for activating the sensing activity of various sensors that maximizes the sensing lifetime. The optimum schedules obtained using the proposed algorithm is shown to achieve significantly longer sensing lifetimes compared to those achieved using physical coverage. Relaxing the full area coverage requirement to a partial area coverage requirement (e.g., 95% of area coverage as adequate instead of 100% area coverage) further enhances the lifetime. The algorithms proposed for the point targets and full area sensing problems in the first two parts are essentially centralized algorithms. Decentralized algorithms are preferred in large networks. Accordingly, in the last part of the thesis, we propose a low-complexity, distributed sensor scheduling algorithm for full area sensing using information coverage. This distributed algorithm is shown to result in significantly longer sensing lifetimes compared to those achieved using physical coverage.