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Öğe Bandwidth-aware scaling for internet video streaming(2004) Tunali T.; Özbek N.; Anar K.; Kantarci A.In this study, we propose a bandwidth-aware scaling mechanism for rate adaptive video streaming. This mechanism involves estimation of the capacity of the network dynamically by measuring bottleneck bandwidth and available bandwidth values. By taking the available bandwidth as an upper limit, the sender adjusts its output rate accordingly. While increasing the quality of the video, using a bandwidth estimator instead of probing prevents the congestion generated by the streaming application itself. The results of the bandwidth-aware algorithm are compared with that of a similar algorithm with no bandwidth-aware scaling and the improvement is demonstrated with measurements taken over WAN. © Springer-Verlag 2004.Öğe A cluster based target tracking algorithm for targets moving rapidly in wireless sensor networks [Telsiz duyarga aglarinda hizli hareket eden hedefler için küme tabanli hedef i·zleme algoritmasi](2009) Alaybeyoglu A.; Dagdeviren O.; Kantarci A.; Erciyes K.Due to the advancements in low cost embedded processors and wireless transmission technologies, wireless sensor networks have been commonly used in many civil and military applications. In this study, we propose a cluster based target tracking algorithm for targets moving rapidly in wireless sensor networks. In the existing studies found in the literature, the current leader node at time t predicts the location only for time t+1. In case the target moves in high speed, it can pass by a group of nodes very fast without being detected. With our algorithm, we plan to implement target tracking systems that will predict the future locations of the target and awaken the corresponding leader nodes in order the nodes along the trajectory to self organize to form the necessary structures to collect data related to the target in advance and thus reduce the target misses. ©2009 IEEE.Öğe Design and Implementation of a Streaming System for MPEG-1 Videos(2003) Kantarci A.; Tunali T.A new streaming application has been developed for the Internet environment. The system has client-server structure together with multithreaded architecture and pipelining. RTP protocol is used to transmit packets belonging to MPEG videos. RTCP protocol collects transmission statistics. System is adaptive in the sense that it reacts to dynamic network conditions. A feedback mechanism controls both the frame interval and frame rate depending on the frame-loss statistics and buffered video level at the client. A flow control module at the client side controls buffer underflows and overflows. Performance results of the implementation are reported and discussed. The performance of the proposed buffering strategy is compared with other proposed methods from the literature. The comparisons showed that the proposed strategy is more robust than other methods.Öğe A distributed wakening based target tracking protocol for wireless sensor networks(2010) Alaybeyoglu A.; Dagdeviren O.; Kantarci A.; Erciyes K.We propose a two layer protocol for tracking fast targets in sensor networks. At the lower layer, the Distributed Spanning Tree Algorithm (DSTA) [12] partitions the network into clusters with controllable diameter and constructs a spanning tree backbone of clusterheads rooted at the sink. At the upper layer, we propose a target tracking algorithm which wakes clusters of nodes by using the estimated trajectory beforehand, which is different from existing studies [3] in which target can be detected only when the nodes close to the target are awake. We provide the simulation results and show the effect of fore-waking operation by comparing error and miss ratios of existing approaches with our proposed target tracking algorithm. © 2010 IEEE.Öğe A Dynamic Distributed Tree Based Tracking Algorithm for Wireless Sensor Networks(2010) Alaybeyoglu A.; Kantarci A.; Erciyes K.We propose a dynamic, distributed tree based tracking algorithm for very fast moving targets in wireless sensor networks, with speeds much higher than reported in literature. The aim of our algorithm is to decrease the miss ratio and the energy consumption while tracking objects that move in high speeds. In order to do this, the root node which is determined dynamically in accordance with the node's distance to the target, forms lookahead spanning trees along the predicted direction of the target. As the miss ratio decreases, the usage of recovery mechanisms which are employed to detect a target again that is moving away from the predicted trajectory also decreases. This decrease reduces the energy consumption and increases the network lifetime. We describe all the phases of the algorithm in detail and show by simulations that the proposed algorithm performs well to track very fast moving targets. We also compare the algorithm with the generic cluster, generic tree and dynamic multi cluster based tracking algorithms in terms of miss ratio and energy consumption. © Springer-Verlag Berlin Heidelberg 2010.Öğe Implementation of a video streaming system using scalable extension of H.264(2005) Kantarci A.Scalable video coding (SVC) offers flexible adaptation of video bitrate through spatial, temporal and SNR scalability. Recently, it has been shown that SVC can achieve comparable coding performance with the state of the art nonscalable codec H.264 and since then, SVC has regained its popularity among researchers. In this work, a streaming system for scalable H.264 videos has been implemented. In the system, a flexible rate adaptation module selects an appropriate bitstream by considering motion dynamics of video in cases of packet loss in the network and buffer drain at the receiver. In this paper, the developed system has been introduced and the performance results of the implementation have been reported. Experimental results show that the system reacts to congestion and buffer drains in a flexible way and maintains interrupt-free display througout the whole video. © Springer-Verlag Berlin Heidelberg 2005.Öğe A lightweight method for time synchronization in wireless sensor networks [Kablosuz algilayici aglarinda saat eşzamanlamasi i·çin yükte hafif bir yöntem](2011) Yildirim K.S.; Kantarci A.A distributed time synchronization protocol whose objective is to provide a common notion of time between the sensor nodes is mandatory for many applications in wireless sensor networks. This paper presents Simple Time Synchronization (STS) protocol whose main objective is to achieve networkwide synchronization with microsecond precision using a simple and lightweight method. STS achieves synchronization by fast flooding synchronization messages which are periodically broadcasted by a reference node and uses a simple averaging strategy for drift compensation. STS is implemented on Iris platform using TinyOS and evaluated on a testbed setup including 16 sensor nodes. Experimental results show that the prototype implementation of STS outperforms Flooding Time Synchronization Protocol which is the de facto protocol for time synchronization in wireless sensor networks. © 2011 IEEE.Öğe A new operating system for embedded systems: EGİS [Gömülü sistemler i·çin yeni bir i·sletim sistemi: EGİS](2007) Yildirim S.; Kantarci A.Many embedded applications need a real-time and embedded operating system that provides an simple operation environment. Embedded operating systems that give service to embedded applications must be configurable and restructurable in contrast to general purpose operating systems. In this work, eGİS (Ege Gömülü İşletim Sistemi) which is a real-time, portable, configurable, object oriented and embedded operating system is implemented. In this paper, the developed system is introduced and some experimental results are presented.Öğe Performance evaluation of h.264/avc slice structured coding modes with content complexities and GOP structures(2008) Alaybeyoglu A.; Kantarci A.In this study, performances of different slice modes defined in H.264 video codec are tested. Results show that slice structured coding decreases the coding efficiency by increasing the overhead. To observe the error propagation and the effects of error concealment of the H.264 codec, four different GOP structures are used in the experiments. In addition, to observe the effect of video content, videos with different content complexities are chosen for simulations. Measurements indicate that, increment in content complexity results in quality decrease after error concealment.Öğe Quality of service management for the streaming of scalable videos [Ölçeklenebilir videolarin akişlandirmasinda servis kalitesi yönetimi](2006) Kantarci A.In this paper, a streaming system developed for scalable videos is introduced. The system adapts to the status of network and clients by considering motion dynamics of video. Performace results show that the system can be employed in an environment similar to the Intermet. © 2006 IEEE.Öğe Robust quality adaptation for internet video streaming(2005) Tunali E.T.; Kantarci A.; Ozbek N.Internet video streaming is a widely popular application however, in many cases, congestion control facilities are not well integrated into such applications. In order to be fair to other users that do not stream video, rate adaptation should be performed to respond to congestion. On the other hand, the effect of rate adaptation on the viewer should be minimized and this extra mechanism should not overload the client and the server. In this paper, we develop a heuristic approach for unicast congestion control. The primary feature of our approach is the two level adaptation algorithm that utilizes packet loss rate as well as receiver buffer data to maintain satisfactory buffer levels at the receiver. This is particularly important if receiver has limited buffer such as in mobile devices. When there is no congestion, to maintain best buffer levels, fine grain adjustments are carried out at the packet level. Depending on the level of congestion and receiver buffer level, rate shaping that involves frame discard and finally rate adaptation by switching to a different pre-encoded video stream are carried out. Additive increase multiplicative decrease policy is maintained to respond to congestion in a TCP- friendly manner. The algorithm is implemented and performance results show that it has adaptation ability that is suitable for both local area and wide area networks. © 2005 Springer Science + Business Media, Inc.Öğe A study on scene change detection in H.264/AVC videos [H.264/AVC videolarinda sahne degişiminin belirlenmesi üzerine bir çalişma](2008) Kuştutan S.; Kantarci A.This study focuses on testing and improving the available scene change detection methods developed for bit streams compressed with the latest coding standard H.264/AVC. ©2008 IEEE.Öğe A study on segment aware streaming of medical videos [Tip videolarinin bölüte uyumlu akitimi üzerine bir çalişma](2007) Kantarci A.In this study, a streaming model for educational medical videos that reduces the bandwidth consumption and hence the risk of packet loss and delay during streaming has been proposed. Experimental results indicate that the model can succesfully be used in medical video streaming.Öğe Subantimicrobial-dose doxycycline and cytokine-chemokine levels in gingival crevicular fluid.(2011) Emingil G.; Gürkan A.; Atilla G.; Kantarci A.The present randomized, double-masked, placebo-controlled, parallel-arm study examines the impact of adjunctive subantimicrobial-dose doxycycline (SDD) on the local inflammatory response through cytokine and chemokine levels in gingival crevicular fluid (GCF) samples from patients with chronic periodontitis. Forty-six patients with chronic periodontitis received scaling and root planing with or without adjunctive SDD. GCF samples were collected and clinical parameters including probing depth, clinical attachment level, gingival index, and plaque index were recorded every 3 months for 12 months. GCF tumor necrosis factor-?, interleukin (IL)-6, IL-4, IL-10, IL-13, IL-17, macrophage inhibitory protein 1?, macrophage inhibitory protein 1ß, monocyte chemoattractant protein 1, and regulated on activated normal T-cell expressed and secreted protein levels were determined by xMAP multiplex immunoassay. Significant improvements were observed in all clinical parameters in both groups over 12 months (P <0.0125), whereas the SDD group showed significantly better reduction in gingival index, probing depth, and gain in clinical attachment compared to the placebo group (P <0.05). Decrease in IL-6 in the SDD group was significantly higher compared to the placebo group at 6 and 9 months in deep pockets (P <0.05), whereas tumor necrosis factor-? was significantly reduced in moderately deep pockets (P <0.05). SDD resulted in a stable IL-4 and IL-10 response while reducing the monocyte chemoattractant protein 1 levels at 3 months (P <0.05). These results show that SDD, as an adjunct to non-surgical periodontal therapy, stabilizes the inflammatory response by promoting the suppression of proinflammatory cytokines and increasing the anti-inflammatory cytokines. The chemokine activity would account for the regulation of the inflammatory response to SDD therapy.Öğe Tracking fast moving targets in wireless sensor networks(2010) Alaybeyoglu A.; Erciyes K.; Kantarci A.; Dagdeviren O.We propose a dynamic distributed algorithm for tracking objects that move fast in a sensor network. In the earlier efforts in tracking moving targets, the current leader node at time t predicts the location only for time t + 1 and if the target moves in high speed, it can pass by a group of nodes very fast without being detected. Therefore, as the target increases its speed, the probability of missing that target also increases. In this study, we propose a target tracking system that predicts future k locations of the target and awakens the -corresponding leader nodes so that the nodes along the trajectory self organize to form the clusters to collect data related to the target in advance and thus reduce the target misses. The algorithm first -provides detection of the target and forms a cluster with the neighboring nodes around it. After the selection of the cluster leader, the coordinates of the target is estimated using localization methods and cooperation -between the cluster nodes under the control of the leader node. The coordinates and the speed of the target are then used to estimate its trajectory. This information in turn provides the location of the nodes along the estimated trajectory which can be awaken, hence providing tracking of the moving object. We describe the algorithm, analyze its efficiency and show by simulations that it performs well to track very fast moving objects with speeds much higher than reported in literature. Copyright © 2009 by the IETE.Öğe A video streaming application on the internet(Springer Verlag, 2000) Kantarci A.; Tunali T.A new software only streaming application is being developed for the Internet. The application is based on multithreaded architecture. RTP (Real¬time Transport Protocol) is being used for the transmission of video data. The system is adaptive to dynamic network conditions. In this paper, performance results of the implementation are reported. © Springer-Verlag Berlin Heidelberg 2000.
