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Sparse code multiple access (SCMA) is a novel multiple-access strategy used in 5G wireless networks that combines Orthogonal Frequency Division Multiple Access (OFDMA) and Code Division Multiple Access (CDMA). Recent interest in CDMA has been on the use of multi-level orthogonal coding to facilitate spreading. The orthogonal code is used to disseminate the modulated data symbols of each user. The set of spreading codes employed controls how much the signals interfere with each other, and thus impacts the system's performance at the receiver. Grey Inverse Grey (GIG) orthogonal spreading codes are constructed in this study employing grey and inverse grey code, which provide higher correlation features than traditional binary code families such as Hadamard and gold code. This research assesses the Bit Error Rate (BER) performance of CDMA using the Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK) modulation techniques. The performance of a DS-CDMA communication system is examined utilizing GIG orthogonal spreading codes in the Additive White Gaussian Noise (AWGN) and Rayleigh fading channels. The scrambling impact on GIG codes is also investigated. Under the same test settings, the results reveal that DS-CDMA systems using GIG spreading codes outperform binary spreading codes in terms of BER. [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplexing (OFDM) is an efficient multiplexing/demultiplexing technique studied and developed over several years to accommodate the rapid growth in communication networks. OFDM was recently entered the optical communication field due to its promising features, especially in the optical domain such as high data rate, high spectral efficiency, immunity against dispersion, and improving the received signal. OFDM is classified into three categories based on implementation process of fast Fourier transform (IFFT/FFT) these categories are electrical OFDM, Optical OFDM (O-OFDM), and all-optical OFDM (AO-OFDM). From O-OFDM to AO-OFDM various methods existed to accomplish them. This paper investigated optical OFDM in general case and deeply focused on all-optical OFDM by highlighting on the various techniques existed to implement it until now, comparing between these methods in terms of multiplexing/demultiplexing and concluded the best method to implementing AO-OFDM. [ABSTRACT FROM AUTHOR]

Optical code-division multiple-access (OCDMA) is considered as a good technique to provide optical layer security. Many research works have been published to enhance optical network security by using optical signal processing. The paper, demonstrates the design of the AWG (arrayed waveguide grating) router-based optical network for spectral-amplitude-coding (SAC) OCDMA networks with Walsh Code to design a reconfigurable network codec by changing signature codes to against eavesdropping. In this paper we proposed a code reconfiguration scheme to improve the network access confidentiality changing the signature codes by cyclic rotations, for OCDMA system. Each of the OCDMA network users is assigned a unique signature code to transmit the information and at the receiving end each receiver correlates its own signature pattern a(n) with the receiving pattern s(n). The signal arriving at proper destination leads to s(n)=a(n). [ABSTRACT FROM AUTHOR]

In the present work, the Total Focusing Method (TFM) is used to image defects in a High Density Polyethylene (HDPE) pipe. The viscoelastic attenuation of this material corrupts the images with a high electronic noise. In order to improve the image quality, the Decomposition of the Time Reversal Operator (DORT) filtering is combined with spatialWalsh-Hadamard coded transmissions before calculating the images. Experiments on a complex HDPE joint demonstrate that this method improves the signal-to-noise ratio by more than 40 dB in comparison with the conventional TFM. [ABSTRACT FROM AUTHOR]

Certain matrices lexicographically ordered are written using the elements of …. The relations between the codes generate by these matrices and Hadamard codes are given. [ABSTRACT FROM AUTHOR]

The manuscripts presents a novel acoustic OFDM data embedding by deploying reversible Walsh-Hadamard transform. The classical acoustic OFDM embedding method was replacing the high band of the acoustic signal with power adjusted OFDM data which brings two shortcoming of degrading the spectral efficiency of the acoustic signal for the listener and dependency to the acoustic carrier signal for estimation of high band envelope. Despite the classical method, the proposed approach not only preserves the spectrum of the acoustic signal, but also it is independent from acoustic carrier signal. The proposed approach encodes the OFDM data signal by a weighted reversible Walsh-Hadamard transform via a linear combination of acoustic signal samples and OFDM signal samples. The efficiency of the approach in data transmission as well as listener subjective quality of acoustic carrier signal for different level of background noise has been clarified, and optimum values of the weighting matrix has been obtained by the evaluation of implementation of the system. [ABSTRACT FROM AUTHOR]