A. Emre Harmanci

Color image segmentation using histogram multithresholding and fusion

Abstract A novel method for multiband image segmentation has been proposed. The method is based on segmentation of subsets of bands using multithresholding followed by the fusion of the resulting segmentation “channels”. For color images the band subsets are chosen as the RB, RG and BG pairs, whose two-dimensional histograms are processed via a peak-picking algorithm to effect multithresholding. The segmentation maps are first fused by running a label concordance algorithm and then smoothed by a spatial–chromatic majority filter. It is shown that for multiband images, multithresholding subsets of bands followed by a fusion stage results in improved performance and running time.

A new population based adaptive domination change mechanism for diploid genetic algorithms in dynamic environments

In this paper, an adaptive domination change mechanism for diploid genetic algorithms with discrete representations is presented. It is aimed at improving the performance of existing diploid genetic algorithms in changing environments. Diploidy acts as a source of diversity in the gene pool while the adaptive domination mechanism guides the phenotype towards an optimum. The combined effect of diploidy and the adaptive domination forms a balance between exploration and exploitation. The dominance characteristic of each locus in the population is adapted through feedback from the ongoing search process. A dynamic bit matching benchmark is used to perform controlled experiments. Controlled changes to implement different levels of change severities and frequencies are used. The testing phase consists of four stages. In the first stage, the benefits of the adaptive domination mechanism are shown by testing it against previously proposed diploid approaches. In the second stage, the same adaptive approach is applied to a haploid genetic algorithm to show the effect of the diploidy on the performance of the proposed approach. In the third stage, the levels of diversity introduced by diploidy on the genotype and maintained by the adaptive domination mechanism on the phenotype are explored. In the fourth stage, tests are performed to examine the robustness of the chosen approaches against different mutation rates. Currently, the dominance change mechanism can be applied to di-allelic or multiallelic discrete representations and promising results are obtained as a result of the tests performed.

Robust Image Transmission Over Wireless Sensor Networks

Robust image and video communications have become more imperative due to the ubiquitous proliferation of multimedia applications over wireless sensor networks. In this work, the transmission distortions on the image data induced by both channel and instant node failures for Wireless Sensor Networks (WSN) are considered. The effect of two techniques and their integration with multipath transmission are investigated to compensate the multimedia distortions at the expense of incurring additional energy consumption and/or wasting bandwidth resources. First technique is watermarking based error concealment utilizing discrete wavelet transform for embedding downsized replicas of original image into itself. The other is conventional Reed–Solomon (RS) coding utilizing additional information bits to correct bit/symbol errors. Performance results obtained from extensive simulations utilizing a communication and energy model applicable to WSN show that error concealment (EC) integrated schemes, especially EC with multipath fusion (ECMF), are more promising to compensate losses than RS-coding-integrated and pure multipath transmission techniques in WSN.

ITUbee: A Software Oriented Lightweight Block Cipher

In this paper, we propose a software oriented lightweight block cipher, ITUbee. The cipher is especially suitable for resource constrained devices including an 8-bit microcontroller such as sensor nodes in wireless sensor networks. For a sensor node one of the most important constraints is the low energy consumption because of the limited battery power. Also, the memory on sensor nodes are restricted. We have simulated the performance of ITUbee in the AVR ATtiny45 microcontroller using the integrated development platform Atmel Studio 6. We have evaluated the memory usage and clock cycles needed for an encryption. The number of clock cycles gives a metric for energy consumption. The simulation results show that ITUbee is a competitive block cipher on 8-bit software platforms in terms of energy consumption. Also, less memory requirement of the cipher is remarkable. In addition, we have shown that the attacks which are effective on software oriented lightweight block ciphers can not reduce the 80-bit security level of ITUbee.

Impossible differential cryptanalysis of reduced-round LBlock

In this paper, we improve the impossible differential attack on 20-round LBlock given in the design paper of the LBlock cipher. Using relations between the round keys we attack on 21-round and 22-round LBlock with a complexity of 269.5 and 279.28 encryptions respectively. We use the same 14-round impossible differential characteristic observed by the designers to attack on 21 rounds and another 14-round impossible differential characteristic to attack on 22 rounds of LBlock.

Image Segmentation by Relaxation Using Constraint Satisfaction Neural Network

Abstract The problem of image segmentation using constraint satisfaction neural networks (CSNN) has been considered. Several variations of the CSNN theme have been advanced to improve its performance or to explore new structures. These new segmentation algorithms are based on interplay of additional constraints, of varying the organization of the network or modifying the relaxation scheme. The proposed schemes are tested comparatively on a bank of test images as well as real world images.

Investigation of new operators for a diploid genetic algorithm

This study involves diploid genetic algorithms in which a diploid representation of individuals is used. This type of representation allows characteristics that may not be visible in the current population to the preserved in the structure of the individuals and then be expressed in a later generation. Thus it prevents traits that may be useful from being lost. It also helps add diversity to the genetic pool of the population. In conformance with the diploid representation of individuals, a reproductive scheme which models the meiotic cell division for gamete formation in diploid organisms in nature is employed. A domination strategy is applied for mapping an individuals genotype onto its phenotype. The domination factor of each allele at each location is determined by way of a statistical scan of the population in the previous generation. Classical operators such as cross-over and mutation are also used in the new reproductive routine. The next generation of individuals are chosen via a fitness proportional method from among the parents and the offspring combined. To prevent early convergence and the population overtake of certain individuals over generations, an age counter is added. The effectiveness of this algorithm is shown by comparing it with the simple genetic algorithm using various test functions.

Image Quality Estimation in Wireless Multimedia Sensor Networks: An Experimental Study

Multimedia applications in wireless sensor networks (WMSN) have stringent quality of service (QoS) requirements. In this paper, we study image quality distortions due to packet losses in multi hop WMSN. An experimental simulation and real testbed environment has been setup to estimate the quality of the test images over 30,000 transmissions. Two scenarios are considered: in the first scenario, images are watermarked with their replicas at the source node and an error concealment (EC) algorithm is employed at the sink. In the second scenario, raw images are transmitted without any encoding. The empirical results have revealed that there is a strong correlation between Peak-Signal-To-Noise-Ratio (PSNR) values of the distorted images and packet loss rate of the transmission route (PER). Moreover, the relationship is linear when EC technique is used with an achievement over 25dB PSNR for PER less than 0.6. This correlation is useful when designing QoS based transport schemes.

Preserving Diversity through Diploidy and Meiosis for Improved Genetic Algorithm Performance in Dynamic Environments

Genetic algorithms have been applied to a diverse field of problems with promising results. Using genetic algorithms modified to various degrees for tackling dynamic problems has attracted much attention in recent years. The main reason classical genetic algorithms do not perform well in such problems is that they converge and lose their genetic diversity. However, to be able to adapt to a change in the environment, diversity must be maintained in the gene pool of the population. One approach to the problem involves a diploid representation of individuals. Using this representation with a dynamic dominance map mechanism and meiotic cell division helps preserve diversity. In this paper, the effects of using diploidy and meiosis with such a dominance mechanism are explored. Experiments are carried out using a variation of the 0-1 knapsack problem as a testbed to determine the effects of the different aspects of the approach on population diversity and performance. The results obtained show promising enhancements.

Perceptual quality‐based image communication service framework for wireless sensor networks

Wireless multimedia sensor networks (WMSNs) have an increasing variety of multimedia-based applications including image and video transmission. In these types of applications, multimedia sensor nodes should ideally maximize perceptual quality and minimize energy expenditures in communication. For the required perceptual quality to be obtained, quality-aware routing is a key research area in WMSNs. However, mapping the system parameters to the end users perceptual quality-of-service measures is a challenging task because of incomplete identification metrics. Unfortunately, unless disputable assumptions and simplifications are made, optimal routing algorithm is not tractable. In this paper, we propose a novel image transmission framework to optimize both perceptual quality and energy expenditure in WMSNs. Our framework aims to provide acceptable perceptual quality at the end user by using an analytical distortion prediction model that is able to predict the image distortion resulting from any given error pattern. The innovation of the proposed scheme lies in the combined use of a content-aware packet prioritization with an energy-aware and quality-aware routing protocol, named as image quality-aware routing. Additionally, it does not only propose an energy-efficient route selection policy but also manages the network load according to the energy residues of nodes, thus leading to a great energy economy. The results reveal that the framework is capable of identifying true metrics for mapping required image quality to network parameters. Copyright (c) 2011 John Wiley & Sons, Ltd.