Wireless Information and Power Transfer in Secure Massive MIMO Downlink With Phase Noise

To support downlink simultaneous wireless information and power transfer (SWIPT), energy harvesting mobile terminals (EMTs) need to be deployed closer to the base station than information mobile terminals (IMTs), in order to meet higher received power requirement. However, this raises a critical issue that the messages sent to IMTs are potentially eavesdropped on by EMTs, which experience better channels. In this letter, we study the effect of phase noise on the downlink SWIPT in secure massive MIMO systems, which degrades accuracy of the channel state information and in turn causes potential information leakage. We derive closed-form lower bounds on the worst-case secrecy rate achieved by each IMT and the energy harvested by each EMT. Numerical results reveal that the secrecy rate monotonically decreases as the phase noise variance increases, but the monotonicity does not hold for the harvested energy.