El-Sayed M. El-Rabaie

Speech enhancement with an adaptive Wiener filter

This paper proposes an adaptive Wiener filtering method for speech enhancement. This method depends on the adaptation of the filter transfer function from sample to sample based on the speech signal statistics; the local mean and the local variance. It is implemented in the time domain rather than in the frequency domain to accommodate for the time-varying nature of the speech signals. The proposed method is compared to the traditional frequency-domain Wiener filtering, spectral subtraction and wavelet denoising methods using different speech quality metrics. The simulation results reveal the superiority of the proposed Wiener filtering method in the case of Additive White Gaussian Noise (AWGN) as well as colored noise.

C42. PAPR reduction for LFDMA using a reduced complexity PTS scheme

Three subcarrier mapping schemes are used for single carrier frequency division multiple access (SC-FDMA) system: interleaved (IFDMA), distributed (DFDMA) and localized (LFDMA) subcarrier mapping. Comparison between these schemes showed that the peak to average power ratio (PAPR) for both IFDMA and DFDMA systems is less than that of LFDMA system. In this paper, a low complexity Partial Transmit Sequence (PTS) technique is proposed for the reduction of PAPR in LFDMA system by generating the candidates using the time domain cyclical shift of each sub-block sequence and combining them in a recursive manner. This enables the detector to recover the original signal without needing side information. In this paper, mathematical analysis is explained in details for both the conventional PTS (C-PTS) scheme and the proposed PTS (P-PTS) scheme. Also, computational complexity comparison is performed between the C-PTS and P-PTS schemes.

Robust and secure fractional wavelet image watermarking

This paper presents an efficient fractional wavelet transform (FWT) image watermarking technique based on combining the discrete wavelet transform (DWT) and the fractional Fourier transform (FRFT). In the proposed technique, the host image is wavelet transformed with two resolution levels, and then, the middle frequency sub-bands are FRFT transformed. The watermark is hidden by altering the selected FRFT coefficients of the middle frequency sub-bands of the 2-level DWT-transformed host image. Two pseudo-random noise (PN) sequences are used to modulate the selected FRFT coefficients with the watermark pixels, and inverse transforms are finally applied to get the watermarked image. In watermark extraction, we just need the same two PN sequences used in the embedding process and the watermark size. The correlation factor is used to determine whether the extracted pixel is one or zero. The proposed fractional wavelet transform (FWT) image watermarking method is tested with different image processing attacks and under composite attacks to verify its robustness. Experimental results demonstrated improved robustness and security.

Chaotic Interleaving for Robust Image Transmission with LDPC Coded OFDM

This paper presents a new technique for progressive image transmission over low-density parity-check coded orthogonal frequency division multiplexing (LDPC-OFDM) system. This technique adopts chaotic Baker map to improve the performance and reduce the peak-to-average power ratio (PAPR) of the OFDM signal. It helps improving the error resilient ability and also enhancing the efficiency of progressive image transmission over frequency selective fading channels. The proposed technique can effectively resist the fading impact of the frequency selective channels using simple frequency domain equalization. The proposed technique also utilizes the set partitioning in hierarchical trees as a source coding algorithm for the transmitted images. The distinctive feature of the proposed technique is that the transmitted data sequence has less data correlation, which leads to minimizing the PAPR. Simulation results show that the proposed technique improves the visual quality of the received images and reduces the PAPR of the OFDM signal as well.

Optimal Power Allocation for Sensing-Based Spectrum Sharing in MIMO Cognitive Relay Networks

With most of the radio spectrum already allocated, cognitive radio acts as a promising solution to the spectrum scarcity problem. Increasing the secondary throughput without making interference to the primary user (PU) is a major challenge. In this paper, the secondary throughput is maximized under power constraints by obtaining an optimum value of the relay amplification factor. Comparison between using single antenna, double antennas at all the nodes of the cognitive relay network (CRN), and double antennas at the relay node only is performed. The mathematical analysis of the system is investigated for two cases: (1) The opportunistic access case, where the secondary user (SU) can transmit data only in the vacant bands of the allocated spectrum to the PU; and (2) The sensing-based spectrum sharing case, where the SU can transmit data all the time but with different transmit powers depending on the sensing information. Simulation results show that the achieved secondary throughput can be maximized at a given value of the relay amplification factor. Moreover, using double antennas at all the nodes of the CRN increases the maximum achievable throughput and improves the detection capabilities compared with using single antenna or using double antennas at the relay node only. Finally, results show that the SU can achieve more throughput under the sensing-based spectrum sharing case compared with that achieved under the opportunistic access case.

EFFICIENT DETECTION OF LANDMINES FROM ACOUSTIC IMAGES

The Laser Doppler Vibrometer (LDV)-based Acoustic to Seismic (A/S) landmine detection system is one of the reliable and powerful landmine detection systems. The interpretation of the LDVbased A/S data is performed off-line, manually, depending heavily on the skills, experience, alertness and consistency of a trained operator. This takes a long time. The manually obtained results suffer from errors, particularly when dealing with large volumes of data. This paper proposes some techniques for the automatic detection of objects from the acoustic images which are obtained from the LDV-based A/S landmine detection system. These techniques are based on Corresponding author: F. E. Abd El-Samie (fathi sayed@yahoo.com).

Automatic Modulation Recognition in Wireless Multi-carrier Wireless Systems with Cepstral Features

Automatic digital modulation recognition (ADMR) has become an interesting problem in wireless communication systems with various civil and military applications. In this paper, an ADMR algorithm is proposed for both orthogonal frequency division multiplexing and multi-carrier code division multiple access systems using discrete transforms and mel-frequency cepstral coefficients (MFCCs). The proposed algorithm uses one of the discrete cosine transform, discrete sine transform, and discrete wavelet transform with MFCCs to extract the modulated signal coefficients, and uses also either a support vector machine (SVM) or an artificial neural network (ANN) for modulation classification. Simulation results show that the proposed algorithm provides higher recognition rates than those obtained in previous studies, in addition to a superiority of SVM performance compared to ANN performance at low signal-to-noise ratios.

Efficient Transmission of Encrypted Images with OFDM in the Presence of Carrier Frequency Offset

AbstractIn this paper, the impact of carrier frequency offset (CFO) and CFO compensation on the transmission of encrypted images with different orthogonal frequency division multiplexing (OFDM) versions is studied. The investigated OFDM versions are the fast Fourier transform OFDM, the discrete cosine transform OFDM, and the discrete wavelet transform OFDM. A comparison between four encryption algorithms with images transmitted through different OFDM versions is presented. These algorithms are data encryption standard, advanced encryption standard, RC6, and chaotic Baker map. This comparison aims to select the most appropriate version of OFDM, and the most suitable image encryption algorithm for efficient image transmission. In the simulation experiments, the peak signal-to-noise ratio at the receiver is used as an evaluation metric for the decrypted image quality.

Block-based SVD image watermarking in spatial and transform domains

The idea of this paper is to implement an efficient block-by-block singular value (SV) decomposition digital image watermarking algorithm, which is implemented in both the spatial and transforms domains. The discrete wavelet transform (DWT), the discrete cosine transform and the discrete Fourier transform are exploited for this purpose. The original image or one of its transforms is segmented into non-overlapping blocks, and consequently the image to be inserted as a watermark is embedded in the SVs of these blocks. Embedding the watermark on a block-by-block manner ensures security and robustness to attacks such like Gaussian noise, cropping and compression. The proposed algorithm can also be used for colour image watermarking. A comparison study between the proposed block-based watermarking algorithm and the method of Liu is performed for watermarking in all domains. Simulation results ensure that the proposed algorithm is more effective than the traditional method of Liu, especially when the watermarking is performed in the DWT domain.

Relay-based throughput maximization in multiple antennas cognitive radio networks

Cognitive radio is a promising technology that solves the problem of spectrum scarcity. A major challenge in cognitive radio is how to increase secondary throughput without interfering the primary user transmissions. In this paper, the effect of using multiple antennas at the relay is studied, and an optimal power allocation strategy is used to maximize the secondary throughput under power constraints by simply seeking an optimum value of the relay amplification factor. The analysis of the system is performed and simulation results show that there is an optimum value of the relay amplification factor at which the secondary throughput is maximized. Compared to using single antenna, the results show that using multiple antennas at the relay network increases the maximum achievable throughput and also improves the detection capability.