University of Sistan and Baluchestan International Journal of Communications and Information Technology 2322-4606 1 2 2011 09 20 Watermarking Scheme Based on Multiple Chaotic Maps 1 9 94 10.22111/cit.2011.94 EN J. Ayubi University of Sistan and Baluchestan F. Mohanna University of Sistan and Baluchestan S. Mohanna University of Sistan and Baluchestan M. Rezaei University of Sistan and Baluchestan Journal Article 2011 02 01 a watermarking scheme for Grayscale image is proposed based on a family of the chaotic maps and discrete cosine transform. Jacobian Elliptic mapis employed to encrypt of watermarked logo. Piecewise nonlinear chaotic map is also used to determine the location of DCT coefficients for the watermark embedding. The purpose of this algorithm is to improve the shortcoming of watermarking such as small key space and low security. Therefore the size of key space for initial conditions and control parameters is computed about and this key space is large enough to resist the attacks. Toevaluate the robustness and effectiveness of proposed method, several attacks are applied to the

https://cit.usb.ac.ir/article_94_956a72097dca392b5b9792a6a9b8c539.pdf

University of Sistan and Baluchestan International Journal of Communications and Information Technology 2322-4606 1 2 2011 09 20 A Recursive Approximation Approach of non-iid Lognormal Random Variables Summation in Cellular Systems 10 14 95 10.22111/cit.2011.95 EN R. Abaspour University of Sistan and Baluchestan M. Mehrjoo University of Sistan and Baluchestan S. Mohanna University of Sistan and Baluchestan M. Rezaei University of Sistan and Baluchestan Journal Article 2011 02 01 Co-channel interference is a major factor in limiting the capacity and link quality in cellular communications. As the co-channel interference is modeled by lognormal distribution, sum of the co-channel interferences of neighboring cells is represented by the sum of lognormal Random Variables (RVs) which has no closed-form expression. Assuming independent, identically distributed (iid) RVs, the sum of lognormal RVs has been approximated by another log-normally distributed RV in the literature. In practice, the co-channel interference RVs have identical standard deviations (SDs) and different means. In this paper, first a new method based on curve fitting is proposed to approximate the sum of two log-normally distributed RV's with identical SDs and different means. Then a recursive method using the surface fitting is developed for approximating the sum of more than two lognormal RVs. Results show that the proposed method can approximate the first and the second moments of the resulting RV very well.

https://cit.usb.ac.ir/article_95_6805158886914e6c18d95d2996e67479.pdf

University of Sistan and Baluchestan International Journal of Communications and Information Technology 2322-4606 1 2 2011 09 20 A Hidden Node Aware Network Allocation Vector Management System for Multi-hop Wireless Ad hoc Networks 15 18 96 10.22111/cit.2011.96 EN M. Najimi Department of Electrical Engineering, K. N. Toosi University of Technology M. Sayad Haghighi Department of Electrical Engineering, K. N. Toosi University of Technology Journal Article 2011 02 01 Many performance evaluations for IEEE 802.11 distributed coordination function (DCF) have been previously reported in the literature. Some of them have clearly indicated that 802.11 MAC protocol has poor performance in multi-hop wireless ad hoc networks due to exposed and hidden node problems. Although RTS/CTS transmission scheme mitigates these phenomena, it has not been successful in thoroughly omitting these drawbacks. We argue that when eliminating hidden node effect with a given protocol is not feasible, one may sometimes earn more throughput by controlling or even wisely creating this phenomenon. In this paper we propose a novel solution to improve the performance of IEEE 802.11 MAC protocol in multi-hop networks through modifying NAV timer. We may call this method Dynamic NAV (DNAV) since the NAV timer operation changes dynamically with the change of environment variables. Simulation results show that our approach noticeably increases the throughput in multi-hop wireless ad-hoc networks.

https://cit.usb.ac.ir/article_96_d68806ecafeaf38116691f6ea712a046.pdf

University of Sistan and Baluchestan International Journal of Communications and Information Technology 2322-4606 1 2 2011 09 20 Add-Drop and Channel-Drop Optical Filters Based on Photonic Crystal Ring Resonators 19 24 97 10.22111/cit.2011.97 EN A. Tavousi University of Sistan and Baluchestan M. A. Mansouri-Birjandi University of Sistan and Baluchestan M. Saffari University of Sistan and Baluchestan Journal Article 2011 02 01 Here, we propose an add-drop and a channel drop filter based on two-dimensional photonic crystal all circular ring resonators. These structures are made of a square lattice of silicon rods with the refractive index n1=3.464 surrounded by air (with refractive index n2=1). The broadest photonic band gap occurs at the filling ratio of r/a = 0.17. Two linear defect W1 waveguides couple to the ring. Our add-drop and channel drop filters form by the appropriate coupling distance between the ring and waveguide. The dropping efficiency of both filters in their operational window - the C (1.535-1.565μm) and L (1.565-1.625μm) bands of optical telecommunications - is almost %100 and corresponds to a deca-pole degenerated resonant mode. Normalized frequencies (a/λ), in degenerated mode equal to 0.3684 and 0.3645. Resonant modes of the all circular ring resonator with their corresponding degenerated poles and the transmission spectra are calculated using the PWE, and 2D-FDTD methods respectively.

https://cit.usb.ac.ir/article_97_6c1403e353f8b98ef7b2b761bc5d5eec.pdf

University of Sistan and Baluchestan International Journal of Communications and Information Technology 2322-4606 1 2 2011 09 20 A Novel Small E–Ring Shaped Monopole Antenna with Dual Band-Notch Function for UWB Wireless Communications 25 28 98 10.22111/cit.2011.98 EN N. Ojaroudi Islamic Azad University, Ardabil Branch M. Ojaroudi Islamic Azad University, Ardabil Branch S. Amiri Iranian Research Organization for Science and Technology (IROST) Journal Article 2011 02 01 This paper presents an E-ring shaped printed monopole antenna for UWB applications with dual notched bands performance. In order to generate single frequency band notch function, we applied a U-ring shaped monopole antenna, and by inserting a rectangular ring in the centre of it an E-ring shaped radiating patch created and a dual band-notch function can be achieved. The measured bandwidth of the proposed antenna is from 2.75 GHz to 11.43 GHz (110%) for VSWR < 2. The proposed antenna offers two notched bands, covering all the 5.2/5.8GHz of WLAN, 3.5/5.5 GHz of WiMAX and 4-GHz of C bands ranges. Good radiation behavior within the UWB frequency range has been obtained. The antenna has a small dimension of 10 *17 mm2.

https://cit.usb.ac.ir/article_98_1d23fd92d23dfe803a7aaa5ac9212b99.pdf

University of Sistan and Baluchestan International Journal of Communications and Information Technology 2322-4606 1 2 2011 09 20 Users as the Biggest Threats to Security of Health Information Systems 29 33 99 10.22111/cit.2011.99 EN A. Bakhtiyari-Shahri Faculty of Computer Science and Information Systems Universiti Teknologi Malaysia (UTM) Z. Ismail Faculty of Computer Science and Information Systems, Universiti Teknologi Malaysia (UTM) Journal Article 2011 02 01 There are a lot of researches in the world about attacks on information systems (IS). Although there have been many attempts to classify threats of IS’s especially in Health Information Systems (HIS), it is still necessary for all health organization to identify new threats and their sources which threaten security of health care domain. The main aim of this paper is to present a research agenda of threats to HIS and identify issues and human factors that assist the implementation and adoption of health information security within the developing countries. In doing so, the authors try to provide a cohesive completeness identification of all threats about HIS and highlight the role of human in all of them. More than 70 threats to HIS are identified by using a large number of disparate data sources. Then they are classified in 30 subjects and finally categorized in seven areas whichuser’s activities are the biggest threat at the core of risks to HIS.

https://cit.usb.ac.ir/article_99_7e15494714f4f3e95791e7854197dd23.pdf

University of Sistan and Baluchestan International Journal of Communications and Information Technology 2322-4606 1 2 2011 09 20 A Block-Grouping Method for Image Denoising by Block Matching and 3-D Transform Filtering 34 38 100 10.22111/cit.2011.100 EN M. Shirdel University of Sistan and Baluchestan M. Rezaei University of Sistan and Baluchestan F. Mohanna University of Sistan and Baluchestan J. Ahmadi-Shokouh University of Sistan and Baluchestan Journal Article 2011 02 01 Image denoising by block matching and threedimensional transform filtering (BM3D) is a two steps state-ofthe- art algorithm that uses the redundancy of similar blocks in noisy image for removing noise. Similar blocks which can have some overlap are found by a block matching method and grouped to make 3-D blocks for 3-D transform filtering. In this paper we propose a new block grouping algorithm in the first step of BM3D that improves the performance of denoising algorithm especially in heavy noise conditions. In heavy noise conditions, BM3D causes some artifacts in the filtered image. These artifacts are reduced by the proposed block grouping algorithm. In the proposed block grouping method, beside of a similarity measure used for block matching, the amount of overlap between blocks is considered. Experimental results show that the proposed block grouping method can improve the performance of BM3D in terms of both peak signal-to-noise ratio (PSNR) and visual quality.

https://cit.usb.ac.ir/article_100_56cecc250dace49fe5ae496193d32607.pdf