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Interference has been a key roadblock against the effectively deployment of applications for end-users in wireless networks including fifth-generation (5G) and beyond fifth-generation (B5G) networks. Protocols and standards for various communication types have been established and utilised by the community in the last few years. However, interference remains a key challenge, preventing end-users from receiving the quality of service (QoS) expected for many 5G applications. The increased need for better data rates and more exposure to multimedia information lead to a non-orthogonal multiple access (NOMA) scheme that aims to enhance spectral efficiency and link additional applications employing successive interference cancellation and superposition coding mechanisms. Recent work suggests that the NOMA scheme performs better when combined with suitable wireless technologies specifically by incorporating antenna diversity including massive multiple-input multiple-output architecture, data rate fairness, energy efficiency, cooperative relaying, beamforming and equalization, network coding, and space–time coding. In this paper, we discuss several cooperative NOMA systems operating under the decode-and-forward and amplify-and-forward protocols. The paper provides an overview of power-domain NOMA-based cooperative communication, and also provides an outlook of future research directions of this area.

This paper studies the cell-edge user’s performance of a secure multiple-input single-output non-orthogonal multiple-access (MISO-NOMA) system under the Rayleigh fading channel in the presence of an eavesdropper. We suppose a worst-case scenario that an eavesdropper has ideal user detection ability. In particular, we suggest an optimization-based beamforming scheme with MISO-NOMA to improve the security and outage probability of a cell-edge user while maintaining the quality of service of the near-user and degrading the performance of the eavesdropper. To this end, power allocation coefficients are adjusted with the help of target data rates of both the users by utilizing a simultaneous wireless information and power transfer with time switching/power splitting protocol, where the near-user is used to forward the information to cell-edge user. The analytical results demonstrate that our beamformer analysis can achieve reduced outage probability of cell-edge user in the presence of the eavesdropper. Moreover, the provided simulation results validate our theoretical analysis and show that our approach improves the overall performance of a two-user cooperative MISO-NOMA system.

Images play a vital role in scientific research and its capturing are different in nature, so that few images are bad in quality because of bad circumstances like bad lightening, undesirable conditions, error in capturing device itself etc. Contrast enhancement plays an important role for better visualization, to get suitable results and for the improvement of quality of image. In this paper, we proposed a technique for the contrast enhancement of both types of images the color images as well as gray scale images. The proposed method calculate two parameters statistics and phase congruency of the image. Furthermore we use optimal histogram method which is RIQMC (reduced reference image quality metric for contrast changes) based and histogram equalization which is non parametric is used to perform the contrast enhancement. We presented two methodologies, purpose of one is the brightness of the image remain preserve and other is used to adaptively increase its brightness. Subjective comparison is performed by considering the improved contrast and absence of useless artifacts. Analyses of the contrast enhancement images are also perform by the quantitative measure. Simulation results on the different images conclude the significance of our proposed model.