S. El-Rabaie

Proposed relay selection scheme for physical layer security in cognitive radio networks

In this study, the physical layer security for cognitive radio network (CRN) will be investigated in which a secondary user transmitter (SU-Tx) sends confidential information to a SU receiver (SU-Rx) on the same frequency band of a primary user (PU) in the presence of an eavesdropper receiver. Moreover, relay selection scheme is proposed for the security constrained CRNs with single eavesdropper, multiple eavesdroppers and PUs. The proposed scheme selects a trusted decode and forward relay to assist the SU-Tx and maximise the achievable secrecy rate that is subjected to the interference power constraints at the PUs for the different number of eavesdroppers and PUs under available channel knowledge. The SU cooperates with relays only when a high secrecy rate is achieved. Secrecy rate and secrecy outage probability are the two performance metrics that are used to verify the effectiveness of the proposed scheme although asymptotic approximations of the secrecy outage probability are also derived. Simulation and analytical results demonstrate that the performance improvement of the proposed scheme reaches to the double relative to the conventional scheme for the secrecy capacity.

Homomorphic image encryption

This paper presents a new homomorphic image cryptosystem. The idea of this system is based on encrypting the reflectance component after the homomorphic transform and embedding the illumination component as a least significant bit watermark into the encrypted reflectance component. A comparison study is held between the RC6 block cipher algorithm and the chaotic Baker map algorithm for the encryption of the reflectance component. We present a security analysis for the proposed cryptosystem against the entropy, brute-force, statistical, and differential attacks from a strict cryptographic viewpoint. Experimental results verify and prove that the proposed homomorphic image cryptosystem is highly secure from the cryptographic viewpoint. The results also prove that this cryptosystem has a very powerful diffusion mechanism (a small change in the plain text makes a great change in the cipher image). The homomorphic encryption using RC6 algorithm is more secure than that using the chaotic Baker map algorithm but not robust to noise. Thus, the proposed homomorphic cryptosystem can be used in different applications, depending on the core algorithm used.

Image fusion based on principal component analysis and high-pass filter

Several commercial earth observation satellites carry dual-resolution sensors, which provide high spatial resolution panchromatic image and low spatial resolution multi-spectral image. Image fusion techniques are therefore useful for integrating a high spectral resolution image with a high spatial resolution image, to produce a fused image with high spectral and spatial resolutions. Some image fusion methods such as IHS, PC and BT provide superior visual high-resolution multi-spectral images but ignore the requirement of high-quality synthesis of spectral information. The high-quality synthesis of spectral information is very important for most remote sensing application based on spectral signatures, such as lithology, soil and vegetation analysis. Another family of image fusion techniques such as HPF operates on the basis of the injection of high-frequency components from the high spatial resolution panchromatic image into the multi-spectral image. This family of methods provides less spectral distortion. In this paper we propose to integrate between the two families PCA and HPF to provide pan sharpened image with superior spatial resolution and less spectral distortion. The experiments have shown that the proposed fusion method retains the spectral characteristics of the multi-spectral image and improves at the same time the spatial resolution of the fused image.

A New Method for Encrypting Images with Few Details Using Rijndael and RC6 Block Ciphers in the Electronic Code Book Mode

ABSTRACT In this paper, we propose an efficient method for encrypting images with few details using Rijndael and RC6 block ciphers in Electronic Code Book (ECB) mode. Images with few details are images with large areas of similar gray levels such as medical images, infrared images, and logo images. This leads to encryption leakage if the Rijndael or RC6 block ciphers are used. The proposed method solves this problem by using a preprocessing step to eliminate the repeated patterns before encryption. A comparison is held between encryption of images with few details with preprocessing and encryption without preprocessing. Experimental results verify that the proposed preprocessing method gives the encryption algorithms the ability to encrypt images with few details in an efficient manner in the ECB mode.

An efficient designed prototype technique for OFDM PAPR reduction using FPGA

In this paper, a proposed designed technique to reduce Orthogonal Frequency Division Multiplexing (OFDM) Peak-to-Average Power Ratio (PAPR) value is done. This designed technique contains new block which is inserted in the OFDM system. This proposed block is applied to WiMAX system as an example of OFDM technology. Afterwards, several MATLAB programs are executed to discuss the behavior and the characteristics of this proposed block. In addition, the effect of its insertion on the original system is studied. Due to this insertion, 0 dB OFDM PAPR value can be achieved. Furthermore, it can be synthesized practically. This proposed system is implemented over Field Programmable Gate Array (FPGA). The designed circuit is characterized by both its low complexity and its high speed. Moreover, it is portable circuit. This means that it can be implemented over any FPGA kit regardless of its technology.

Service Enhancement for User Equipments in LTE-A Downlink Physical Layer Network

In this paper, we propose a real LTE-A downlink physical layer network with multiple relay stations (RSs). RSs improve the weak received signal at user equipments (UEs). LTE-A with RSs can be used to increase the coverage area of BSs and increase the system capacity. It also enhances the service of the user at cell edge and cover shadowed areas. The performance of the proposed LTE-A network is illustrated and modeled. We also take the effect of different environments scenarios of the WINNER Phase II channel model. The received signals of UEs scenarios are mathematically derived and analyzed in this paper. The weighted least square method for signal combining is mathematically analyzed. The performance of LTE-A with RSs is evaluated by calculating the SER and the capacity for a certain range of SNRs. The SER and capacity are calculated for different UEs scenarios to investigate the effect of RSs in LTE-A network. Simulation results reveal that UEs which receive multiple signals from RSs have low SER values for a certain range of SNRs and enhances the service performance of the UEs at cell edge.

Sharpening Misrsat-1 data using Super-Resolution and HPF fusion methods

Spatial resolution enhancement is usually required in the remote sensing field. Super-Resolution (SR) is a fusion process for reconstructing a High-Resolution (HR) image from several Low-Resolution (LR) images covering the same region in the world. It is difficult, however, for some satellite remote sensing arrangements to get several images of the same scene in a short time, especially for highly dynamic scenes. In this paper, we study the SR process of Misrsat-1 data using sub-pixel shifts between bands 1, 3, and the Panchromatic (PAN) sub-band. Due to the difference in radiometry between the different bands, we propose performing the SR process between the high-pass details extracted from bands 1, 3, and the PAN, and then using the High-Pass Filter (HPF) fusion method for sharpening the Multi-Spectral (MS) image of Misrsat-1 using the super-resolved high-pass details. The comparison of the proposed method with the cubic convolution interpolation method has shown an enhancement in the image entropy, Point Spread Function (PSF), and Modulation Transfer Function (MTF).

FET SMALL-SIGNAL MODELING USING MEL-FREQUENCY CEPSTRAL COEFFICIENTS AND THE DISCRETE COSINE TRANSFORM

In this paper, a novel neural technique is proposed for FET small-signal modeling. This technique is based on the discrete cosine transform (DCT) and the Mel-frequency cepstral coefficients (MFCCs). The input data to traditional neural systems for FET small-signal modeling are the scattering parameters and the corresponding frequencies in a certain band, and the outputs are the circuit elements. In the proposed technique, the input data are considered random, and the MFCCs are calculated from these inputs and their DCT. The MFCCs are used to give a few features from the input random data sequence to be used for the training of the neural networks. The objective of using MFCCs is to characterize the random input sequence with features that are robust against measurement errors. The MFCCs extracted from the DCT of the inputs increase the robustness against measurement errors. There are two benefits that can be achieved using the proposed technique; a reduction in the number of neural inputs and hence a faster convergence of the neural training algorithm and a robustness against measurement errors in the testing phase. Experimental results show that the technique based on the DCT and MFCCs is less sensitive to measurement errors than using the actual measured scattering parameters.

Peak power reduction of OFDM signals using trigonometric transforms

This paper presents a new technique, based on trigonometric transforms, to solve the peak to average power ratio (PAPR) problem associated with orthogonal frequency division multiplexing (OFDM) signals. In the proposed technique, both the in-phase and in-quadrature components of the OFDM signals after the inverse fast Fourier transform (IFFT) are transformed using either the discrete sine transform (DST) or the discrete cosine transform (DCT). It is known that both the DCT and the DST have an energy compaction property concentrating most of the signal energy in the first few samples after the application of the transform and leaving the rest of samples close to zero. This property can be exploited for PAPR reduction by interchanging the first half of samples of the in-phase component by the last half of samples of the in-quadrature component after applying the discrete transform on both of them, separately. The OFDM signal is transmitted in this format. By this process of replacement, it can be guaranteed that if either the in-phase or the in-quadrature component of the OFDM signal is large, the other will be small.

Peak power reduction of OFDM signals using chaotic baker maps

This paper presents a new approach for peak to average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems. This approach is based on the chaotic Baker map. It is known that OFDM transmitted signals are in complex format, having in-phase and in-quadrature components. If a chaotic randomization process is performed on each component, separately, prior to transmission, the likelihood that both the real and imaginary components of the transmitted signal at a certain time are of large amplitude gets lower. As a result, a reduction of the PAPR can be achieved. Simulation results show that the proposed PAPR reduction method achieves a performance improvement in the OFDM system.