“…Unlike the aforementioned studies that focus only on energy efficiency [ 3 , 4 , 5 , 6 , 7 , 13 , 14 , 15 , 16 , 17 ] or PLS [ 18 , 19 , 20 , 21 , 22 , 23 , 24 ], secrecy energy efficiency (SEE), which is defined as the ratio of the secrecy rate to dissipated power, was suggested to achieve a balance between energy efficiency and secure communication [ 25 , 26 , 27 , 28 , 29 , 30 ]. For example, resource allocations including transmit power and beamforming vectors were optimized to maximize the SEE in CRNs [ 25 , 27 ] and multi-antenna systems [ 26 , 28 ], respectively.…”