In this paper, the authors consider a multi-antenna downlink network where a Secure User (SU) coexists with a passive eavesdropper. There are two design requirements for such a network. First, the information should be transferred in a secret and efficient manner. Second, the Quality of Service (QoS), i.e. delay sensitivity, should be taking into consideration to satisfy the demands of real-time wireless services. In order to fulfill the two requirements, they combine the physical layer security technique based on switched beam beam forming with an energy efficient power allocation. The problem is formulated as the maximization of the secrecy energy efficiency subject to delay and power constraints. By solving the optimization problem, they derive an energy-efficient power allocation scheme.