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.

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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.

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While the amplitude, frequency and phase, are the well-known carrier features that can be modulated according to digital data stream, there is still another unexploited sinusoidal feature. Sinusoidal damping factor is the suggested modulation technique that can be used in carrier communication. In this paper, damping shift keying (DSK) is proposed as a new modulation space that can be combined with conventional modulation techniques to increase the data rate per symbol. In addition to the complex amplitude modulation, the carrier can be modulated using multi-damping factors according to the data stream. Combination of DSK with quadrature amplitude modulation (QAM) increases the data rate of the so called Damped QAM (D-QAM). Simulation results measures the performance of the proposed D-4PSK (carrying 3 bits/symbol) against conventional QPSK (carrying 2 bits/symbol). The proposed scheme …

Single tone M-ary frequency shift keying (MFSK) enjoys constant envelop transmission at the expense of much lower spectral efficiency (SE). Many research efforts were given for enhancing the SE of MFSK. In this paper, SE of coherent single tone MFSK is improved by filling up the same allocated spectral band-width by larger number of uniformly spaced non-orthogonal tones. The main idea resides in two main points, first, regarding the detection task as an operation of super-resolution (SR) spectral line estimation, second, highlighting implicit sparsity construction of MFSK scheme. Compressive sensing (CS) based SR approaches are enabled for resolving activated atom from over-complete dictionary. Moreover, more general keying schemes can be performed on learned dictionary instead of the classical Fourier (sinusoidal) dictionary, where each atom may occupy the whole allocated spectrum instead of …

Jointly enhancing both energy efficiency (EE) and spectrum efficiency (SE) of modulation schemes becomes one of the main issues for 5G mobile communications. Recently, an indexed modulation (IM) technique provides an interesting tradeoff between EE and SE. Data can be conveyed through the combination of subcarriers pattern that can be divided between activated/non-activated subcarriers in the frequency domain. Maximum SE can be attained at half subcarrier activation, hence producing symbols with half energy of the conventional orthogonal frequency-division multiplexing (OFDM) system. In this paper, alternatively, the new concept of sparsely indexing modulation (SIM) on overall subcarrier space is clarified. Sparse (few) subcarrier activations provide much higher EE, while the combinatorial indexing of the sparse subcarriers on the overall subcarriers as a single group spans huge combinatorial …