Computer Engineering / Bilgisayar Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/10
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Conference Object Citation - WoS: 37Graph Theoretic Clustering Algorithms in Mobile Ad Hoc Networks and Wireless Sensor Networks (survey)(Azerbaijan National Academy of Sciences, 2007) Erciyeş, Kayhan; Dağdeviren, Orhan; Çokuslu, Deniz; Özsoyeller, DenizClustering in mobile ad hoc networks (MANETs) and wireless sensor networks (WSNs) is an important method to ease topology management and routing in such networks. Once the clusters are formed, the leaders (coordinators) of the clusters may be used to form a backbone for efficient routing and communication purposes. A set of clusters may also provide the underlying physical structure for multicast communication for a higher level group communication module which may effectively be used for fault tolerance and key management for security purposes. We survey graph theoretic approaches for clustering in MANETs and WSNS and show that although there is a wide range of such algorithms, each may be suitable for a different cross-layer design objective.Conference Object Duyarga Ağları için Bir Γ Eşuyumcusu Tasarım ve Uygulaması(IEEE, 2008) Özsoyeller, Deniz; Erciyeş, Kayhan; Dağdeviren, OrhanImplementation of synchronous algorithms in distributed systems in general is less troublesome than the implementation of asynchronous algorithms. Synchronizers provide synchronous execution of an asynchronous algorithm in distributed systems. In this study, we propose a gamma synchronizer for Wireless Sensor Networks (WSNs). This synchronizer consists of a and beta synchronizers. In our work, the WSN is first divided into clusters and then these clusters are connected using a ring protocol. Synchronization is provided using the beta synchronizer in the cluster and a synchronizer among the clusters. We describe the clustering algorithm and the ring formation algorithm for the WSNs and give the results obtained so far.Conference Object Citation - Scopus: 15Gezgin Tasarsız Ağlar için Taşırma Tabanlı Yönlendirme Yordamı(IEEE, 2008) Çokuslu, Deniz; Erciyeş, KayhanMobile Ad Hoc Networks (MANETs) are videly in use in rescue, military operations, scientific and business areas. Many studies are addressed in MANETs because of their need to long lasting liveness, fault tolerance, dynamic addressing, collusion prevention, mobility management and security. Especially, self clustering, backbone construction and routing are the most interesting academic and industrial research areas in MANETs. A wide range of studies addressed the routing problem in MANETs. Many previous studies address the clustering and routing problems as seperate subjects. However, rowing approaches which are specific to the clustering methodologies may have many advantages in terms of efficiency and availability. In this study, a flooding based routing algorithm is proposed. First, a detailed description of the algorithm is explained, then the analysis and test results using the ns2 simulator are given which show that the designed algorithm is scalable and has favorable performance.Conference Object Citation - Scopus: 3Grid Resource Discovery Based on Web Services(Institute of Electrical and Electronics Engineers Inc., 2009) Çokuslu, Deniz; Hameurlain, Abdelkader; Erciyeş, KayhanThe size of grid systems has increased substantially in the last decades. Resource discovery in grid systems is a fundamental task which provides searching and locating necessary resources for a given process. Various different approaches are proposed in literature for this problem. Grid resource discovery using web services is an important approach which has resulted in many tools to become de facto standards of today's grid resource management. In this paper, we propose a survey of recent grid resource discovery studies based on web services. We provide synthesis, analysis and evaluation of these studies by classification. We also give a comparative study of different classes proposed.Conference Object Citation - WoS: 13Citation - Scopus: 14Performance Evaluation of Cluster-Based Target Tracking Protocols for Wireless Sensor Networks(Institute of Electrical and Electronics Engineers Inc., 2009) Alaybeyoğlu, Ayşegül; Dağdeviren, Orhan; Erciyeş, Kayhan; Kantarcı, AylinTarget tracking is an important application type for wireless sensor networks (WSN). Recently, various approaches [1-11] are proposed to maintain the accurate tracking of the targets as well as low energy consumption. Clustering is a fundamental technique to manage the scarce network resources [12-19]. The message complexity of an application can be significantly decreased when it is redesigned on top of a clustered network. Clustering has provided an efficient infrastructure in many existing studies [1-8]. The clusters can be constructed before the target enters the region which is called the static method [1-4] or clusters are created by using received signal strength (RSS) from target which is called the dynamic method [5-8]. In this paper we provide simulations of static and dynamic clustering algorithms against various mobility models and target speeds. The mobility models that we applied are Random Waypoint Model, Random Direct Model and Gauss Markov Model. We provide metrics to measure the tracking performance of both approaches. We show that the dynamic clustering is favorable in terms of tracking accuracy whereas the energy consumption of static clustering is significantly smaller. We also show that the target moving with Gauss Markov Model can be tracked more accurately than the other models.Conference Object Citation - WoS: 12Citation - Scopus: 20A Hierarchical Leader Election Protocol for Mobile Ad Hoc Networks(Springer Verlag, 2008) Dağdeviren, Orhan; Erciyeş, KayhanLeader Election is an important problem in mobile ad hoc networks and in distributed computing systems. In this study, we propose a hierarchical, cluster based protocol to elect a leader in a mobile ad hoc network. The initial phase of the protocol employs a clustering algorithm to group nodes of the network after which a leader for a cluster(clusterhead) is elected. The second phase is performed by forming a connected ring of these leaders using the Ring Formation Algorithm. Finally, Chang Roberts Leader Election Algorithm for rings is employed in the final phase to elect the super-leader among the clusterheads. We provide performance results of this protocol for various mobility parameters and analyze its time and message complexities.Conference Object Citation - WoS: 13Citation - Scopus: 12Distributed Algorithms To Form Cluster Based Spanning Trees in Wireless Sensor Networks(Springer Verlag, 2008) Erciyeş, Kayhan; Özsoyeller, Deniz; Dağdeviren, OrhanWe propose two algorithms to form spanning trees in sensor networks. The first algorithm forms hierarchical clusters of spanning trees with a given root, the sink. All of the nodes in the sensor network are then classified iteratively as subroot, intermediate or leaf nodes. At the end of this phase, the local spanning trees are formed, each having a unique subroot (clusterhead) node. The communication and data aggregation towards the sink by an ordinary node then is accomplished by sending data to the local subroot which routes data towards the sink. A modified version of the first algorithm is also provided which ensures that the obtained tree is a breadth-first search tree where a node can modify its parent to yield shorter distances to the root. Once the sub-spanning trees in the clusters are formed, a communication architecture such as a ring can be formed among the subroots. This hybrid architecture which provides co-existing spanning trees within clusters yields the necessary foundation for a two-level communication protocol in a sensor network as well as providing a structure for a higher level abstraction such as the γ synchronizer where communication between the clusters is performed using the ring similar to an α synchronizer and the intra cluster communication is accomplished using the sub-spanning trees as in the β synchronizers. We discuss the model along with the algorithms, compare them and comment on their performances.Conference Object Citation - WoS: 7Citation - Scopus: 12Time Synchronization Algorithms Based on Timing-Sync Protocol in Wireless Sensor Networks(Institute of Electrical and Electronics Engineers Inc., 2008) Kulaklı, Ali Burak; Erciyeş, KayhanWireless Sensor Networks(WSN) are large scale networks of sensors running on wireless environment. For an application running on a WSN, gathered data by the sensors are time critical in most of the cases. However, almost all the nodes suffer from a problem named clock drift. This problem causes clock difference among nodes as time goes because the processors do not run exactly at the same speed. There are many proposed solutions to remedy this problem. TPSN (Timing-sync Protocol for Sensor Networks) is one of the effective protocols proposed to synchronize sensor networks. In this paper, we propose enhancements over TPSN to synchronize nodes in a wireless sensor network more effectively with a lower message complexity and higher precision.Conference Object Citation - WoS: 1Citation - Scopus: 3A Replication-Based Fault Tolerance Protocol Using Group Communication for the Grid(Springer Verlag, 2006) Erciyeş, KayhanWe describe a replication-based protocol that uses group communication for fault tolerance in the Computational Grid. The Grid is partitioned into a number of clusters and each cluster has a designated coordinator that manages the states of the replicas within its cluster. The coordinators belong to a process group and the proposed protocol ensures the correct sequence of message deliveries to the replicas by the coordinators. Any failing node of the Grid is replaced by an active replica to provide correct continuation of the operation of the application. We show the theoretical framework along with illustrations of the replication protocol and its implementation results and analyze its performance and scalability.Conference Object Citation - WoS: 6Citation - Scopus: 6A Merging Clustering Algorithm for Mobile Ad Hoc Networks(Springer Verlag, 2006) Dağdeviren, Orhan; Erciyeş, Kayhan; Çokuslu, DenizClustering is a widely used approach to ease implementation of various problems such as routing and resource management in mobile ad hoc networks (MANET)s. We propose a new fully distributed algorithm for clustering in MANETs that merges clusters to form higher level clusters by increasing their levels. We show the operation of the algorithm and analyze its time and message complexities and provide results in the simulation environment of ns2. Our results conform that the algorithm proposed is scalable and has a lower time and message complexities than the other algorithms