The fifth-generation (5G) mobile communications emerges as the key enabler to meet the growing demands of future wireless applications, including ultra-high data rates, ubiquitous coverage, a massive number of connected devices, and very low latency. In this way, 5G changes from a mere evolution of 4G and becomes the greatest enabler of the next Industrial Revolution. Therefore, it is evident that a huge amount of confidential information will be transmitted via wireless channels on 5G and future networks, thus providing an effective security service is a top priority in the design and implementation of such networks. In this sense, the traditional approach to providing information security through cryptographic techniques is no longer sufficient to meet the highly diverse requirements of the new services and applications of the vertical industries that will be formed from the 5G network. Regarding this deficiency, security at the physical layer has been growing as a complementary solution that offers great advantages for the protection of information in wireless communications. On the other hand, the scarcity and underutilization of the radio frequency spectrum is another critical point that 5G and future networks need to work around to provide access to a massive number of connected devices. In order to guarantee spectral efficiency in access, the non-orthogonal multiple access (NOMA) technique has recently been proposed to enable the transmission of data to different users within the same frequency and time channel. To allow access to multiple users on the same channel through NOMA, they can be differentiated by different power levels or different codes. In this perspective, the present project aims to evaluate the performance of a NOMA network in the power domain, considering that the nearest user employs successive interference cancellation (SIC). Performance is evaluated in terms of security at the physical layer. For this purpose, it will be considered the down link of a network of three legitimate nodes, one base station and two users operating in NOMA. In addition, the existence of an eavesdropper is considered in the network, thus the secrecy capacity and the outage probability of the network is evaluated via Monte Carlo simulations for the cases with perfect and imperfect SIC.
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