Research on Cognitive Power Allocation for Secure Millimeter-Wave NOMA Networks

Millimeter-wave (mmWave) non-orthogonal multiple access (NOMA) networks are considered to be a promising network architecture to address spectrum scarcity, massive connectivity and low latency in the Internet of Things (IoT). This paper investigates the cognitive power allocation scheme to evaluate the reliability and secrecy performance of secondary user in mmWave NOMA networks, where a base station (BS) provides services for primary and secondary users distributed in different regions in the presence of randomly located eavesdroppers. In the proposed cognitive power allocation scheme, under the condition that both the security and quality of service (QoS) of the primary user are first satisfied, the opportunistic service is provided to the secondary user. In addition, a sector eavesdropper-exclusion zone is introduced around BS to ameliorate the secrecy performance of the networks. Considering the path loss and blockage model of mmWave channels, and the secrecy performance of secondary user is comprehensively studied by using the stochastic geometry from three aspects: connection outage probability (COP), secrecy outage probability (SOP), and secrecy throughput (ST). The performance evaluation results have demonstrated that when the security constraint of the primary user is heightened, the secondary user's secrecy performance is weakened to varying degrees, but the tradeoff between security and reliability is improved. Moreover, the ST of the mmWave NOMA communication networks with cognitive power allocation outperforms the equivalent networks with mmWave OMA scheme.