## 1 Introduction  
Recently, Internet-of-Things (IoT) has emerged to be considered as one of the key technological concepts as a basic precondition implementing Industry 4.0 [1]. The recent developments in the IoTapplication, wireless sensor networks (WSNs), have played a significant role in connecting tens of thousands of wireless devices over the Internet in many applications, especially healthcare services, electronic instrumentation, transportation, and environmental assessment [2]. A WSN generally contains many sensor nodes (SNs) that is capable of perceiving their external environment, which can perform communicate and computations [3]. Unfortunately, because SN are battery-powered, the working lifetime of the entire WSNs is limited by energy consumption due to the energy restriction at SN [4]. In order to overcome these limitation, there are many investigations on enabling technologies for energy sustainability in WSNs [5]. The emergence of mobile devices has resulted in a continuously growing requirement for wireless applications, such as an ultra-wide radio coverage, an ultra-high data service, and an ultra-large number of smart devices. Recently, a promising solution to cater for this requirement has been the fifth generation (5G) wireless technology [6; 7]. Therefore, the deployment of low-cost femtocell base stations (FBSs) underlaid in the macrocell can provide ubiquitous coverage and extremely high data rate [8]. In this regard, to accommodate the explosive cell density and growing data traffic, heterogeneous networks (HetNets) have emerged as one of the most promising approaches in the 5G wireless systems by increasing the off-load portion of their traffic [9; 10]. In recent years, by integrating the WPT with traditional wireless information transmission (WIT), simultaneous wireless information and power transfer (SWIPT) have been recognised as among the main candidate technologies for green communications [11; 12; 13; 14; 15], which has been shown to be in a position to improve the WPT performance in HetNets [16; 17; 18]. The idea of using SWIPT to implement wireless recharging of the batteries in HetNets was first studied in [16], where two integer linear programming methods were proposed to help wireless nodes to scavenge ambient energy. [PERSON] et al. [17] provided a essential study of the QoS-constrained energy efficiency optimization problem for coordinated multi-point (CoMP)-SWIPT HetNets, a decoupled approach was proposed in which the power allocation procedure and beamforming design were separated. Considering multiple Power splitting (PS)-based heterogeneous users in [18], [PERSON] et al. investigated the optimal transmit power minimization design problem of SWIPT systems to achieve green communication design under non-linear energy harvesting model, where the semidefinite relaxation (SDR) are employed to solve and the globe optimal solution was theoretically guaranteed. On the other hand, depending on the presence of the broadcasting nature of wireless channel and the multi-tier dynamic topology in SWIPT HetNets, the useful messages which intended to the information users may be entirely possible to be eavesdropped by the energy users, which brings huge technical challenges to secure SWIPT in HetNets [19]. Recently, physical-layer security (PLS) has emerged as a prominent technique to guarantee the secrecy communication by exploiting the characteristics of physical wireless channels, while defending against the eavesdroppers [20; 21]. Various PLS techniques in SWIPT networks have been studied in MISO and MIMO systems [22; 23; 24; 25; 26; 27; 28; 29]. More specifically, [PERSON] et al. [29] studied jointly optimize design of the transmit beamforming and AN of the macrocell base station (MBS) and the femtocell base stations (FBS), the secrecy rate maximization problem of the eavesdropper macrocell users was reformulated by utilizing the one-dimensional line search and successive convex approximation.