Serkan Ozturk

DWT-SVD based image watermarking using Particle Swarm Optimizer

Several watermarking schemes have been proposed with the purpose of copyright protection and access control for multimedia objects. In this paper, an optimal discrete wavelet transform-singular value decomposition (DWT-SVD) based image watermarking scheme using particle swarm optimizer (PSO) is presented. Proposed DWT-SVD based watermarking algorithm initially decomposes the host image into subbands, afterwards the singular values of each subband of the host image are modified by different scaling factors to embed the watermark image. Modifications are optimized using PSO to obtain the highest possible robustness without losing the transparency. Experimental results show improvement both in transparency and robustness under certain attacks.

A novel fragile watermarking based on Particle Swarm Optimization

In this paper, a novel fragile watermarking scheme based on discrete cosine transform (DCT) using particle swarm optimization (PSO) algorithm is presented. Embedding watermarks in frequency domain can usually be achieved by modifying the least significant bits (LSBs) of the transformation coefficients. After embedding process is completed, a number of rounding errors appear due to conversion of real numbers into integers in the process of transformation of image from frequency domain to spatial domain. A population based stochastic optimization technique (PSO) is proposed to correct these rounding errors. Simulation results show the feasibility of employing PSO for watermarking and the accuracy of this novel method.

A novel clonal selection algorithm based fragile watermarking method

In this paper, a novel fragile watermarking method based on clonal selection algorithm (CSA), CLONALG, is presented. In Discrete Cosine Transform (DCT) based fragile watermarking techniques, there occurs some degree of rounding errors because of the conversion of real numbers into integers in the process of transformation of image from frequency domain to spatial domain. In this paper, the rounding errors caused by this transformation process are corrected by using CLONALG. Simulation results show that extracted watermark is obtained exactly the same as embedded watermark and optimum watermarked image transparency is achieved. In addition, the performance comparison of CLONALG and genetic algorithm (GA) based methods is realized.

Reaching spatial or networking saturation in VANET

In this article, we investigate the network transition between non-saturation and saturation regimes for a Vehicular Ad hoc Network (VANET) which is composed of mobile nodes. We combine vehicular traffic theory, queuing model, and Markov chain to evaluate the performance of the network under spatial or networking saturation for multiple data classes over control channel and service channel. Our results indicate that the vehicle density growth can result in saturation of wireless medium around the roadside unit (RSU), further resulting in buffer overflows at on board units (OBUs). We also investigate the network saturation points for different transmission ranges of a RSU. Our results show that RSUs transmission coverage has to be chosen with respect to data patterns of OBUs, minimal distance between vehicles, and number of lanes in order to avoid network saturation condition.

On non-saturation regime in IEEE 802.11p based VANET with mobile nodes

In this paper, we investigate the IEEE 802.11p based Vehicular Ad-hoc Network transition between non-saturation and saturation regimes with mobile nodes. We combine vehicular traffic theory, queuing model and Markov chain to evaluate the performance of the network under spatial or networking saturation for mutiple data classes over control and service channels with different transmission rates depending on the vehicles distance from the roadside unit (RSU). Our results show that the vehicle density growth can result in saturation of wireless medium around the RSU, further resulting in buffer overflows at on board units.

Video communications over IEEE 802.11p using single channel devices

IEEE 802.11p is a new communication standard for wireless access in vehicular environment (WAVE), intended to support road safety messages, electronic toll collection, infotainment services, and other as well as a number of other intelligent transportation systems (ITS) applications. In this paper, we focus on the impact of the dwelling time on the control channel (CCH) vs. that on the SCH (i.e., the duty cycle) on the performance of video communication on the service channel (SCH), using a novel analytical model. We show that a range of duty cycles allows for satisfactory performance of video traffic on SCH as well as timely delivery of safety messages on CCH.

Tasarsiz ağlarda yönlendirme protokollerinin başarimlarinin değerlendirilmesi

In this work we investigate the performance of Ad-hoc on-demand distance vector routing (AODV), Dynamic source routing (DSR), Temporary ordered routing (TORA), Optimized link state routing (OLSR) and Geographic routing (GRP) protocols in wireless ad-hoc networks by using OPNET simulation program. In ad-hoc networks consisting of fixed and mobile stations, routing protocols are compared for different packet sizes and different number of stations.

Ayrik kosinüs dönüşümü ve ayrik dalgacik dönüşümü tabanli Çoklu resim damgalama yöntemi

In recent years, due to the development of computer, internet and mobile technologies the copyright protection of the multimedia documents such as digital audio, image and video has become important. Digital watermarking has become the most popular method for protecting multimedia documents. In this work, a novel robust image watermarking method based on Discrete Cosine Transform, Discrete Wavelet Transform and Arnold Transform is presented. The experiment results show that the proposed method is robust against different attacks.

The MAC Layer of VANETs

The design of the Medium Access Control (MAC) layer for vehicular networks should carefully cope with fast changing topologies caused by vehicle mobility, short connection lifetimes, harsh propagation environments, high node density, and heterogeneous traffic nature and quality demands. This chapter provides a detailed description of MAC functions (i.e., channel access rules, prioritization schemes, frame types, and formats), as specified by the IEEE 802.11p and ETSI ITS-G5 standards, and the multichannel operation. By discussing the main challenges which the MAC has to deal with, the chapter also presents the main evaluation tools (analytics, simulations, field-tests) that can be used to analyze the MAC performance.

Capacity limits in a variable duty cycle IEEE 802.11p-based VANET

In this paper, we investigate the capacity limits in an variable duty cycle VANET that uses the IEEE 802.11p standard. We show that the default value of duty cycle that allocates time equally between control and service channels (CCH and SCH, respectively) leads to unbalanced performance, and that the performance of typical traffic on those channels can be greatly improved by judicious choice of the value for duty cycle. We also find the values of spatial density of vehicular traffic that lead to spatial saturation of network traffic.