Browsing by Author "Tekkalmaz, Metin"
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Item Open Access Distributed construction and maintenance of bandwidth-efficient bluetooth scatternets(IEEE, 2005-05) Tekkalmaz, Metin; Sözer, Hasan; Körpeoǧlu, İbrahimBluetooth networks can be constructed as piconets or scatternets depending on the number of nodes in the network. Although piconet construction is a well-defined process specified in Bluetooth standards, scatternet construction policies and algorithms are not well specified. Among many solution proposals for this problem, only a few of them focus on efficient usage of bandwidth in the resulting scatternets. In this paper, we propose a distributed algorithm for scatternet construction problem, that dynamically constructs and maintains a scatternet based on estimated traffic flow rates between nodes. The algorithm is adaptive to changes and maintains a constructed scatternet for bandwidth-efficiency when nodes come and go or when traffic flow rates change. Based on simulations, the paper also presents the improvements in bandwidth-efficiency provided by the proposed algorithm. © 2005 IEEE.Item Open Access Distributed construction and maintenance of bandwidth-efficient bluetooth scatternets(2004) Tekkalmaz, MetinBluetooth is currently the mainstream technology used for short range wireless communication due to its low power and low cost properties. In order to communicate, Bluetooth enabled devices can form networks called piconets, which consist of at most eight members. To construct larger Bluetooth networks, which are called scatternets, any number of piconets can be combined. Although piconet construction process is standardized by Bluetooth Special Interest Group, scatternet construction policies and algorithms are not yet clarified. There have been many solution proposals for the scatternet construction problem each of which focuses on different aspects of it like the efficiency of the construction algorithm, ease of routing in the resulting scatternet and number of piconets that constitute it. Although various considerations came into picture, bandwidth efficiency of the resulting scatternet topology, which depends on the placement of nodes and communication demand among them, did not take much attention. In this thesis, we provide a distributed and adaptive algorithm that constructs a scatternet and based on collected traffic flow information, modifies it to minimize the overall bandwidth usage. As consequences of efficient use of available bandwidth, reduce in average latency and total energy consumption as well as increase in available bandwidth for new communication demand are also aimed. Moreover, performance of the proposed algorithm is presented, based on the evaluation criteria described.Item Open Access Gömülü sistemler için yazilim mimari çerçevesi(CEUR-WS, 2013) Tekinerdoğan, Bedir; Şeker, Şafak; Kahraman, Gökhan; Tekkalmaz, Metin; Erdoğan, Özgü ÖzköseItem Open Access A path-quality-aware peer-to-peer file sharing protocol for mobile ad-hoc networks: Wi-Share(IEEE, 2009-09) Karasabun, Efe; Ertemür, Doğuş; Sarıyıldız, Seyhun; Tekkalmaz, Metin; Körpeoğlu, İbrahimPeer-to-peer networks are rather well-studied and currently there are numerous systems based on peer-to-peer principles running on the Internet. On the other hand peer-to-peer networks for mobile ad-hoc networks have attracted attention only in the recent years. In this paper, we propose a novel peer-to-peer file sharing system particularly designed for mobile ad-hoc networks. The proposed system, namely Wi-Share, has both network and application layer aspects enabling efficient search and download of the shared files. Wi-Share uses reactive routing for the search operation combined with source discovery and uses the routing tables constructed during the search operation for the download operation. In order to increase the overall efficiency of the file sharing in the network, Wi-Share applies techniques to reduce the required traffic and to increase efficient parallelism of the download operation. These techniques include filtering search results, preferring the higher quality routing paths, using partitioned download scheme and allowing the nodes that have joined to the network recently to contribute to the ongoing downloads. Wi-Share is implemented to work on mobile computers and the results of several experiments are also presented in the paper. © 2009 IEEE.Item Open Access Power-source-aware adaptive routing in wireless sensor networks(2013) Tekkalmaz, MetinA wireless sensor network (WSN) is a collection of sensor nodes distributed over an area of interest to accomplish a certain task by monitoring environmental and physical conditions and sending the collected data to a special node called sink. Most studies on WSNs consider nodes to be powered with irreplaceable batteries, which limits network lifetime. There are, however, perpetual power source alternatives as well, including mains electricity and energy harvesting mechanisms, which can be utilized by at least some portion of the sensor nodes to further prolong the network lifetime. Our aim here is to increase the lifetime of such WSNs with heterogeneous power sources by centralized or distributed routing algorithms that distinguish battery- and mains-powered nodes in routing, so that energy consuming tasks are carried out mostly by mains-powered nodes. We first propose a framework for a class of routing algorithms, which forms and uses a backbone topology consisting of all mains-powered nodes, including the sinks, and possibly some battery-powered nodes, to route data packets. We propose and evaluate a set of centralized algorithms based on this framework, and our simulation results show that our algorithms can increase network lifetime by up to more than a factor of two. We also propose a fully distributed power-source-aware backbone-based routing algorithm (PSABR) that favors mains-powered nodes as relay nodes. We validate and evaluate our distributed algorithm with extensive ns-2 simulations and our results show that the proposed distributed algorithm can enhance network lifetime significantly with a low control messaging overhead. Besides wireless technology independent routing solutions, we also propose a technology specific power-source-aware routing solution (PSAR) for sensor and ad hoc networks which use 802.15.4/ZigBee as the wireless technology. Our solution is fully distributed, tree-based, and traffic-adaptive. It utilizes some protocol specific properties of ZigBee, such as distributed and hierarchical address assignment, to eliminate battery-powered nodes on the routing paths as much as possible. To validate and evaluate our ZigBee-specific algorithm, we first implemented ZigBee extensions to ns-2 simulator and then implemented and simulated our protocol in this extended ns-2 environment. Our results show that the proposed algorithm operates efficiently and can increase network lifetime without increasing the path lengths significantly, compared to the default ZigBee routing algorithm.Item Open Access Power-source-aware backbone routing in wireless sensor networks(IEEE, 2010-11) Tekkalmaz, Metin; Körpeoğlu, İbrahimDue to the limited energy-source and mostly unattended nature of the wireless sensor networks, efficient use of energy has a critical importance on the lifetime of the applications accomplished by such networks. Although in most of the cases sensor nodes are battery-powered, there are application scenarios in which battery- and mains-powered nodes coexist. In this paper, we present an approach and algorithms based on this approach that increase the lifetime of wireless sensor networks in such heterogeneous deployment cases. In the proposed approach, a backbone, which is composed of mains-powered nodes, sink, and battery-powered nodes if required, is constructed to relay the data packets. Simulation results show that, the proposed approach is able to increase the network lifetime up to more than a factor of two, compared to the case in which battery- and mains-powered nodes are not distinguished.