A modified Orthogonal Frequency Division MuItiplexing (OFDM) system for robust progressive image transmission is proposed in this paper. A joint sOUfce-channel coder (JSC C ) is employed in the modified OFDM system. The set partitioning hierarchical trees (SPTHT) used as SOUfce code, and The Low-Density Parity-C heck (LDPC ) used as a channel coder. The SPTHT coder is modified to generate fOUf different groups of bit stream relative to its significances. An unequal error protection (UEP) is suggested for data groups with the LDPC coder. Also, the modified OFDM system includes an adaptive c1ipping technique as a Peak to average power ratio (PAPR) reduction technique for OFDM signal. This proposed PAPR reduction technique is based on adaptive c1ipping for the amplitude of the input signal, where each of signals related to the different fOUf groups of the modified SPTHT coder is c1ipped with a …

We introduce an optimal approach to colour image compression using a new scan method. We propose efficient methods to increase the compression ratio for colour images by dividing the colour image into non-overlapping blocks and applying a different compression ratio for these blocks depending on the classification of blocks into edge and non-edge blocks. In an edge block (a region that contains important information) the compression ratio is reduced to prevent loss of information, while in a non-edge block (a smooth region which does not have important information), a high compression ratio is used. The new proposed scan is used instead of the zigzag scan. A particular implementation of this approach was tested, and its performance was quantified using the peak signal-to-noise ratio. Numerical results indicated general improvements in visual quality for colour image coding.

In the Orthogonal Frequency Division Multiplexing (OFDM) systems, where the data symbols are transmitted in parallel on different carriers, the length of a symbol is extended. This extension of the symbol length causes the OFDM system to be less sensitive to channel dispersion than a single carrier system transmitting data symbols at the same data rate. However, at the edges of the OFDM symbol, the channel dispersion still causes distortion, and hence introduces interference between successive symbols (ie Inter-Symbol Interference, ISI) and interference between different carriers within the same symbol (ie Inter-Carrier Interference, ICI). Different guard interval techniques for the OFDM transmission were suggested to reduce the interference between successive symbols. The most commonly used guard interval is the cyclic prefix (CP). In this paper, the impact of replacing the CP by zero insertion (ZI) before the Inverse Fast Fourier Transform (IFFT) process on the OFDM transmitter is studied. The motivation of using the ZI instead of the CP is the reduction in the transmission rate and the high performance in reducing the channel distortion. Moreover, the proposed ZI-OFDM system is suitable to minimize the effect of the fading channel when the channel characteristics are unknown or difficult to be estimated. Another approach to enhance the OFDM system is also introduced in this paper. A signal denoising approach is suggested to be added in the receiver to reduce the effect of the additive white Gaussian noise (AWGN) channel. In this approach, the Radio Frequency signal (RF) is enhanced using a wavelet thresholding technique instead of …

In cooperative communications, multiple sources communicate with a single destination in the presence of relay nodes. Network coding in cooperative communications allows the relay nodes to combine the data received from the sources and send the linear combination to the destination. The difference in complexity, reliability and overhead is a critical issue when we compare among the different decoders. In this paper, soft-decision maximum a posterior (MAP) decoder that has an optimal reliability and neglected overhead is proposed. Moreover, the Sphere decoder is used to reduce the complexity of the proposed MAP decoder. The proposed implementation proves that the sphere decoder can be used to reduce the complexity of the MAP decoder to about 3% related to the original complexity of the decoder.

Direct sequence spread spectrum (DSSS) signal is generated by modulating the pseudo random noise (PN) sequence with the data signal. The receiver must generate the same PN sequence to extract the direct sequence signal and then get the data signal. This paper presents a method to separate the PN sequence and data sequence from DSSS signal using adaptive blind deconvolution technique which utilizes the normalized cumulant of the adaptive signal. To minimize the computation burden the process gain is first estimated and is used in the adaptation process. The process gain estimator is also based on the computation of the normalized cumulant. Moreover, an efficient method that can enhance the direct-sequence spread spectrum (DSSS) signal at the receiver is introduced without complicating traditional slipping and tracking schemes. Both theoretical analysis and computer simulations verify the validity of the proposed method.

this paper examined the applicability of quantum genetic algorithms to solve optimization problems posed by satellite image enhancement techniques, particularly superresolution, and fusion. We introduce a framework starting from reconstructing the higher-resolution panchromatic image by using the subpixel-shifts between a set of lower-resolution images (registration), then interpolation, restoration, till using the higher-resolution image in pan-sharpening a multispectral image by weighted IHS+ Wavelet fusion technique. For successful superresolution, accurate image registration should be achieved by optimal estimation of subpixel-shifts. Optimal-parameters blind restoration and interpolation should be performed for the optimal quality higher-resolution image. There is a trade-off between spatial and spectral enhancement in image fusion; it is difficult for the existing methods to do the best in both aspects. The objective here is to achieve all combined requirements with optimal fusion weights, and use the parameters constraints to direct the optimization process. QGA is used to estimate the optimal parameters needed for each mathematic model in this framework “Super-resolution and fusion.” The simulation results show that the QGA-based method can be used successfully to estimate automatically the approaching parameters which need the maximal accuracy, and achieve higher quality and efficient convergence rate more than the corresponding conventional GA-based and the classic computational methods.

In this paper a novel scheme for video object extraction based on the second generation of the curvelet transform which is called Fast Discrete Curvelet Transform (FDCT) via wrapping is introduced. The main advantages of using FDCT are the approximate properties and the high directional sensitivity of this transform. An imaginary component of the curvelet coefficients to extract the moving objects in the video sequence is used. The proposed algorithm is mainly divided into two steps. The first step is based on estimating the static background from the initial frames using FDCT, the seconded step is based on subtracting the background from each video frame for obtaining the moving objects. Experimental results show a promising results than traditional wavlelet transform, where the accuracy ratios of each video frame is maximized while the error ratios are minimized compared with the wavelet transform.

NULL

Many wireless channel behavior exhibits approximate sparse modeling in time domain, therefore compressive sensing (CS) approaches are applied for more accurate wireless channel estimation than traditional least squares approach. However, the CS approach is not applied for multicarrier data information recovery because the transmitted symbol can be sparse neither in time domain nor in frequency domain. In this paper, a new Sparse Frequency Division Multiplexing (SFDM) approach is suggested to generate sparse multicarrier mapping in frequency domain based on the huge combinatorial domain. The subcarriers will be mapped in sparse manner according to data stream for taking advantages of multicarrier modulation with lower number of subcarriers. The number of activated subcarriers is designed to achieve the same as Orthogonal Frequency–Division Multiplexing data rate under lower signal-to-noise ratio. The proposed approach exploits the double sparsity of data symbol in the frequency domain, and channel sparsity in the time domain. The same CS approach for both data recovery and adaptive channel estimation in a unified sparsely manner is used. The suggested framework can be used with any non-orthogonal waveform shaping and can work efficiently without any prior information about neither the channel sparsity order nor searching for the optimum pilot patterns.

NULL