Özgür Can Turna

İstanbul University-Cerrahpaşa · Department of Computer Engineering

In this study, Earth’s magnetic field signals have been investigated to de-termine mobile user’s location. In theory, Earth’s magnetic field does not change during the day at a certain point. But, the various noise effects that are exposed during the measurement causes deviations in the measured sig-nal. In this study; Kalman Filter, LOESS, Savitzk...

Computer networks are one of the major slices of the global energy consumption. Since 2009, a couple of standards have been developed for energy conservation in passive optical networks. These standards and most of the researches are based on improvements on Optical Network Unit side. In this study, a novel energy efficiency algorithm, which is bas...

Access Point (AP) selection in WiFi hotspots is driven by stations and it is based on the measured strongest RSSI (Received Signal Strength Indicator) level: Any station connects to the AP that provides the higher physical data rate. Although simple and effective in low crowded scenarios with low-medium traffic load, this strategy performs ineffici...

In parallel with the enormous spread of Internet usage, the tendency of users for high capacity applications (HDTV, Online Games, P2P File Transfer) are rising. This increase in needs of data communication, compel the service providers to act to end users better than before. At this point, Passive Optical Networks (PONs) distinguish in access netwo...

In this thesis, general overview about PON systems is presented and existing PON mechanisms and classification are investigated. After, a novel dynamic bandwidth allocation algorithm for EPON is introduced. This proposed algorithm is named as “Half Cycling Dynamic Bandwidth Allocation-hcDBA” by the inspiration of its half cycling processing mode. L...

This study is about a prediction approach for our previous dynamic bandwidth allocation algorithm for Ethernet Passive Optical Networks (EPON). Our previous work (hcDBA) is based on half cycle timing for bandwidth allocation. That can be handled as a middle way between online and offline bandwidth allocation schemes. In PONs, prediction is used for...

Metropolitan ring networks are usually used to connect the high speed backbone networks with access networks. Until now, the metropolitan network and the access network are gained much attention of researchers. However they have been investigated in separate ways. There is no work in which the end- to-end performance from end-users of the access ne...

Nowadays, fiber optic networks that make transmission possible in high capacities become widespread. There is a partial decrease in network problems with the capabilities provided by these networks such as telephone, wide area network, Internet, video conference on a single fiber line. Also in optical networks, optical burst switching that is a new...

This article presents a comparative study between Optical Burst Switching (OBS) and Optical Packet Switching (OPS) with variable-size packets on mono-service and multi-service network with Quality of Service (QoS) support. In terms of performance criteria, loss rate in byte and access delay are considered. A 2-state Markov Modulated Poisson Process...

A performance comparison according to different number of wavelengths and topologies on OBS has been studied in this paper. Preemptive Channel Scheduling Algorithm (PCSA) has been used as reservation mechanism in OBS. In terms of performance criteria, loss rate in bytes, access delay and end-to-end delay are considered. A 2-state MMPP (Markov Modul...

This paper presents a comparative study between JET (Just Enough Time) and a number of new preemptive channel scheduling algorithms in Optical Burst Switching (OBS) with QoS (Quality of Service) requirement. In terms of performance criteria, loss rate in byte, access delay and end-to-end delay are considered. A 2-state MMPP (Markov Modulated Poisso...

In this study, a wavelength grouping approach has been proposed for core nodes in OBS in order to control byte drop rates for different classes of traffic. Preemptive Channel Scheduling Algorithm (PCSA) has been used for channel scheduling in OBS. In terms of performance criteria, loss rate in bytes is considered. A 2-state MMPP (Markov Modulated P...

This paper presents a comparison of reservation protocols used in optical burst switches (OBS) with quality of service (QoS). In terms of performance criteria, byte loss rate, end-to-end delay and access delay are considered. A 2-state MMPP(Markov modulated Poisson process) traffic generator on a 14-node mesh network topology illustrating NSFNET is...