| Summary: | Abstract This paper considers an unmanned aerial vehicle -enabled multicast-unicast transmit system, in which downlink non-orthogonal multiple access (NOMA) is applied. Since two types of information are broadcast simultaneously, the security of information transmission is a matter of concern. Based on this, we investigate the problem of maximizing the secrecy rate of the particular unicasting user subject to the quality-of-service (QoS) requirements of the multicasting users and the power budget constraint of the UAV base station (BS). Such a problem is non-convex and hard to tackle, and a two-stage procedure is proposed to solve it optimally by dealing with a sequence of semidefinite relaxation (SDR) counterparts. First, fixing the maximal signal to interference plus noise ratio (SINR) of unicasting information in other users, we obtain the corresponding SINR of unicasting information at the particular user. Then, the maximal secrecy unicasting rate is derived by a one-dimension search over the intercepted SINR of unicasting information in other users. Furthermore, two suboptimal solutions with lower complexity are also proposed. Numerical simulation shows that the proposed NOMA assisted schemes always have a better security performance for UAV-enabled transmission.
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