| | Parameter | Meaning/expression | | , , , | complex channel vectors of the PT-ST, ST-SR, ST-ME, and ST-PR, respectively | | , | Channel coefficients of the PT-PR and the PT-ME | | Duration of energy harvesting | | T | Total block time | | , | Transmit dedicated energy signal and confidential signal at PT | | , | Decoded primary signal and secondary signal at ST | | PT’s transmission power | | , , , | Received AWGN at ST, PR, ME, and SR | | Energy conversion efficiency from signal power to circuit power | | , , , | Achievable rate at ST, PR, ME, and SR, respectively | | , | Overall transmission rates at PR and ME | | Secrecy rate of the primary system | | , | Relaying beamforming vector and cognitive beamforming vector | | Initial power at the ST | | Minimal transmission rate requirement for the secondary system | | An auxiliary optimization variable to bound the achievable rate of the eavesdropper ME | | Power allocation coefficient |
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