Mohamed E. Nasr

LDPC coded MIMO OFDM-based IEEE 802.11n wireless LAN

Recently, to meet higher data rate requirements, LDPC coded MIMO-OFDM systems are investigated widely. Multiple-input multiple-output (MIMO) wireless technology in combination with orthogonal frequency division multiplexing (OFDM) is an attractive solution for next-generation wireless local area networks (WLANs). Space-time block coded OFDM is capable of achieving substantial diversity gains, while supporting high bit-rates in wireless communications. By concatenating a space-time block coded OFDM scheme with powerful channel codes, such as Low-Density Parity-Check (LDPC) coding, the performance of the system can be further enhanced. In this contribution the performance of the latest WLAN standard, IEEE 802.11n, based on MIMO-OFDM with LDPC coding is being investigated. The achievable performance is studied as a function of MIMO mode, code rate, bandwidth, and modulation type.

A new secure and fast hashing algorithm (SFHA-256)

This paper presents a new secure and fast hashing algorithm based on the generic 3C construction. This construction is obtained by modifying the Merkle-Damgard (M-D) iterated construction used to construct iterated hash functions arid it is more resistant against the recent differential multi-blocks attacks and the extension attacks than the M-D iterated hash construction. Also the M-D construction is not practical construction by itself, while the generic 3C is a practical construction which preserves the collision resistance of the compression function in a much better way compared to the hash functions that followed the M-D construction. These advantages are at the expense of one extra iteration of the compression function compared to the M-D construction, his disadvantage by proposing a step function with a reduced number of operations. All tests performed in this paper show that SFHA-256 is more secure and has a better performance than SHA-256 which makes it preferred in many applications.

Planar array for signal tracking using sliding window approach

The problem of determining the directions of arrival (DOAs) of multiple sources arises in a number of radar applications. Most of the direction-finding (DF) algorithms have been presented in the context of estimating a single angle per source (e.g., azimuth only), generalizations to the azimuth-elevation case are very important. The main goal of this paper is to develop a planar array model for beamforming and estimating movement parameters of the targets as a generalization to the local polynomial approximation (LPA) approach. So, the problem of narrowband direction of arrival tracking using sliding window is applied using LPA technique. The LPA beamformer performance expressions and the problem of window length choice are studied. The optimization of window length is based on the bias-to-variance tradeoff. This is valid for a wide class of time-varying single source cases, as well as multiple source cases with a sufficient source separation in angle or angular velocity.

Modified LPA beamformer for localizing and tracking rapidly accelerated moving sources

Smart antennas are urgently needed in the expanding field of communications. Thus, the problem of beamforming is primarily considered. A modified windowed local polynomial approximation (LPA) including the acceleration term in Taylor series expansion is considered in this paper. The weighted least squares approach is applied for localizing and tracking rapidly accelerated moving sources. In this paper, LPA-beamformer performance expressions and the problem of the optimal window choice are studied.

Performance enhancement of IEEE802.11n wireless LAN using irregular LDPCC

The need for flexible network structures has created a successful Wireless Local Area Network (WLAN) market, promising to replace many wired LANs in the near future. The latest draft of IEEE 802.11n offers the potential of throughputs beyond 200 Mbps, based on physical layer data rates up to 600 Mbps. IEEE 802.11n standard adopts low density parity check coding as optional coding scheme to offer higher reliability in PHY level. LDPC may end up as the standard scheme in a host of sectors including communications, broadcasting and even hard disk drives. This paper presents LDPC efficient encoder and decoder then the performance of LDPC based on IEEE 802.11n standard is studied. Different modulation and coding schemes were compared to get the best choice.

An Integrated Image Fusion Technique for Boosting the Quality of Noisy Remote Sensing Images

To better identify the objects in remote sensing images, the muItispectral images with high spectral resolution and low spatial resolution, and the panchromatic images with high spatial resolution and low spectral resolution need to be fused. Many fusion techniques are discussed in the recent years to obtain images with high spectral resolution and also high spatial resolution. In this paper an image fusion technique, based on integrating both the intensity-hlue-saturation (IHS) and the discrete wavelet frame transform (DWFT), is proposed for boosting the quality of remote sensing images. A panchromatic and multispectral image from Landsat-7(ETM+) satellite has been fused using this new approach. Experimental results show that the proposed technique improves the spectral and spatial qualities of the fused images. Moreover, when this technique is applied to noisy and de-noised remote sensing images it can preserve the quality of the fused images. Comparison analyses between different fusion techniques are also presented and show that the proposed technique outperforms the other techniques.

Synchronized double watermark audio watermarking scheme based on a transform domain for stereo signals

Digital watermarking technology is interested in solving the problem of copyright protection, data authentication, content identification, distribution, and duplication of the digital media due to the great developments in computers and Internet technology. Recently, protection of digital audio signals has taken a great attention from the researchers. This paper proposed a new audio watermarking scheme based on Discrete Wavelet Transform (DWT), Singular Value Decomposition (SVD), and Quantization Index Modulation (QIM) with synchronization code embedded within double encrypted watermark images or logos into stereo audio signal. In the algorithm, an original audio signal is split into blocks and each block is decomposed into two levels discrete wavelet transform, and then the approximate low frequency sub-band coefficients are decomposed by the SVD transform, obtaining a diagonal matrix. The prepared watermarking and synchronization code bit stream is embedded into the diagonal matrix using Quantization Index Modulation (QIM). After that, we apply ISVD and IDWT to obtain the watermarked audio signal. The watermark can be blindly extracted without knowledge of the original audio signal. Experimental results show that the transparency and imperceptibility of the proposed algorithm is satisfactory, and robustness is strong against popular audio signal processing attacks. High watermark payload is achieved and performance analysis is presented.

C5. Time difference of arrival by IEEE 802.11a, g based on practical estimation

Localization and tracking have recently gained a special importance. A common system for positioning in outdoor environment as e.g. the Global Positioning System (GPS) exists already. GPS is useless for indoor positioning because its signals are weakened or even blocked. This motivated the use of another wireless system to accomplish positioning. Wireless Local Area Network (WLAN) Access Points (APs) are already installed inside buildings, making them a suitable replacement for GPS. Many techniques exist for extracting and calculating location information form the WLAN signals. Among them are super resolution algorithms such as Root Multiple Signal Classification (Root-MUSIC), Estimation of Signal Parameters via Rotational Invariance Technique (ESPRIT), and Matrix Pencil (MP). Many researchers applied these techniques on a specially designed WLAN signals. To apply these techniques in real applications, they should be tested on true wireless signals. In this paper, the performance of super resolution techniques is practically tested on a WLAN transceiver using the communication signals without any modifications.

Efficient transmission of 1D and 2D chaotic map encrypted images with orthogonal frequency division multiplexing

Image transmission takes place as an important research branch in multimedia broadcasting communication systems in the last decade. Our paper presents image transmission over a FFT-OFDM (Fast Fourier Transform Orthogonal Frequency Division Multiplexing). The need for encryption techniques increase with the appearance of the expression which said that our world became small village, and the use of image application such as conference and World Wide Web which increase rapidly in recent years. Encryption is an effective method for protecting the transmitted data by converting it into a form being invisible over transmission path and visible in receiver side. This paper presents a new hybrid encryption technique based on combination of Backer maps and logistic map. This proposed technique aims to increase PSNR and reduce the noise in the received image. The encryption is done by shuffling the positions of a pixel image using two dimensional Baker maps then encrypt using XOR operation with logistic map to generate cipher image over orthogonal frequency multiplexing (OFDM). The encryption approach adopted in this paper is based on chaotic Baker maps because the encoding and decoding steps in this approach are simple and fast enough for HDTV applications. The experimental results reveal the superiority of the proposed chaotic based image encryption technique using two logistic maps and two dimensional Backer map over normal Backer map.

Blocking performance for all optical wavelength routed WDM networks under wavelength conversions

Wavelength converters relax the wavelength continuity constrain in wavelength routed WDM all optical networks. Since wavelength converter is an expensive component with respect to other components in optical network researches are constrained in minimizing this coast keeping the blocking performance as optimum as we can. Sparse wavelength converters, limited range wavelength converters, shared node wavelength converters and node shared wavelength converters are examples used to optimize this problem. In this paper blocking performance optimization for convertible routers in WDM optical networks are examined using simulation. Simulation results show that full wavelength converters for large paths give significant enhancement in blocking performance than the non wavelength converter router path of the same number of nodes. wavelength converters depends on many factors such as network topology, number of wavelengths available, and traffic patterns