In this letter, we consider a multi-antenna downlink network where a secureuser (SU) coexists with a passive eavesdropper. There are two designrequirements for such a network. First, the information should be transferredin a secret and efficient manner. Second, the quality of service (QoS), i.e.delay sensitivity, should be take into consideration to satisfy the demands ofreal-time wireless services. In order to fulfill the two requirements, wecombine the physical layer security technique based on switched beambeamforming with an energy-efficient power allocation. The problem isformulated as the maximization of the secrecy energy efficiency subject todelay and power constraints. By solving the optimization problem, we derive anenergy-efficient power allocation scheme. Numerical results validate theeffectiveness of the proposed scheme.
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