Secure Energy Efficiency for mmWave-NOMA Cognitive Satellite Terrestrial Network

In this letter, we investigate secure energy efficiency (SEE) for millimeter-wave non-orthogonal multiple access (mmWave-NOMA) cognitive satellite terrestrial network (CSTN), where the primary satellite network coexists with the secondary terrestrial network in the same mmWave bands. In the terrestrial network, there are multiple legitimate receivers (LRs) and an eavesdropper (Eve). Based on this, we divide the LRs into multiple clusters and design the hybrid analog/digital precoding. The LRs belonging the same cluster are served by NOMA. Considering the spectrum sharing issues of the CSTN and imperfect channel state information of the Eve, a power allocation optimization problem is formulated to maximize the SEE. To solve the non-convex optimization problem, we transform the fractional SEE problem to a subtractive form. Moreover, the subtractive-form problem is transformed into a semidefinite program by Dinkelbach, successive convex approximation and S-procedure technologies. Finally, an iterative algorithm is proposed to solve the SEE problem. The simulation results are provided to verify the performance of the proposed schemes.