Secure transmission for uplink and downlink non-orthogonal multiple access system with imperfect channel state information

In this paper, we design a secure transmission scheme in uplink and downlink of non-orthogonal multiple access (NOMA) system. scenario, two pairs base stationuser can operate under the presence eavesdropper. The relay plays an important role to forward signals from group stations serve distant users. However, eavesdropper overhear signal which leads performance need be reconsidered. To provide performance, derive closed-form expressions for strictly positive secrecy capacity (SPSC). addition, rely on enlarge coverage area. channel conditions meet imperfect state information (CSI) shows degraded performance. Results confirm relationship between transmit power at source SPSC how many main parameters affecting metric. Furthermore, simulation results show that NOMA technique improves low region. We further conduct analysis by using Monte-Carlo simulations.