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With the ellipsoid‐bounded channel state information (CSI) errors, this study investigates the robust secrecy energy efficiency (SEE) optimisation in a wireless powered heterogeneous network. Specifically, the authors consider the network where multiple femtocell base stations (FBSs) are deployed under the coverage of one macrocell base station (MB...
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The new paradigm of wirelessly powered two-tier heterogeneous networks (HetNets) is considered in this paper. Specifically, the femtocell base station (FBS) is powered by apower beacon (PB) and transmits confidential information to a legitimate femtocell user (FU) in the presence of a potential eavesdropper (EVE) and a macro base station (MBS). In...
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... By jointly optimizing the power allocation at all users, PS factor and relay beamforming under the constraints on the QoS, EH and transmit power, the sum achievable secrecy rate (ACSR) metric has been aimed to be maximized for communications security purposes. The authors of [196] have focused on the robust secrecy energy efficiency (SEE) optimization in a wirelessly-powered HetNet by considering ellipsoid-bounded CSI uncertainties. Here, the network is considered as to consist of a macrocell BS that covers multiple femtocell BSs. ...
Increasing number of devices connected to the networks, applications and demands of new generation wireless communications cause very high energy consumption resulting in large amount of carbon emission. Thus, energy harvesting solutions together with accomplishing information transmission are required for energy efficient communications of new wireless communications generations such as 5G and 6G (i.e., 5G+). As such, due to the promise of energy efficient green communications, simultaneous wireless information and power transfer (SWIPT) techniques are expected to be indispensable component of 5G+. In this survey, the literature of multiuser SWIPT communications is reviewed for 5G+. Different multiuser SWIPT scenarios including multi-antenna communications, cooperative communications, network coding, communications security, and unmanned aerial vehicle (UAV)-enabled communication systems based on multiuser diversity and multiple access methods are thoroughly reviewed. The experimental studies are also discussed.
... en, centralized and distributed secure beamforming schemes are discussed, respectively. Furthermore, in [7], the authors explore the robust secrecy energy efficiency maximization designs under deterministic channel state information (CSI) error, and a suboptimal algorithm based on alternative direction multiplier method is proposed. However, existing works have some drawbacks. ...
In this paper, secure transmission in a simultaneous wireless information and power transfer technology-enabled heterogeneous network with the aid of multiple IRSs is investigated. As a potential technology for 6G, intelligent reflecting surface (IRS) brings more spatial degrees of freedom to enhance physical layer security. Our goal is to maximize the secrecy rate by carefully designing the transmit beamforming vector, artificial noise vector, and reflecting coefficients under the constraint of quality-of-service. The formulated problem is hard to solve due to the nonconcave objective function as well as the coupling variables and unit-modulus constraints. Fortunately, by using alternating optimization, successive convex approximation, and sequential Rank-1 constraint relaxation approach, the original problem is transformed into convex form and a suboptimal solution is achieved. Numerical results show that the proposed scheme outperforms other existing benchmark schemes without IRS and can maintain promising security performance as the number of terminals increases with lower energy consumption.
... In this context, many multi-antenna related physical-layer security works have been developed to investigate secure transmission schemes (e.g, [3][4][5][6]). Additionally, these multi-antenna secure transmission schemes have been fully investigated over the various wireless communications systems, including conventional cellular systems [7], wireless powered heterogeneous network [8,9], hybrid satellite-terrestrial relay network [10], device-to-device underlaid cellular network [11], energy harvesting cognitive radio network [12] etc. Generally speaking, most of the multi-antenna secure transmission schemes fall into two broad categories: transmit beamforming [12-17] and joint optimisation of beamforming and artificial noise (AN) [9,[18][19][20][21]. To cater to the legitimate receiver and interfere with the eavesdroppers, these two types of approaches depend on the amount and degree of channel state information at the transmitter (CSIT) heavily. ...
... In step 1, with the reduction to absurdum, we prove that the optimal solution to (8), ...
... Otherwise, by plugging β ⋆ and the corresponding R ⋆ (β ⋆ ) = log 2 τ ⋆ (β ⋆ ) into (8), we solve (8) and take its optimal solution as W ⋆ , Q z ⋆ . Similarly, we actually solve (8) via its equivalent SDP below: ...
The probabilistic robust beamforming with the help of artificial noise (AN) is investigated in this study, where a multiple‐input‐single‐output wiretap scenario with K single‐antenna eavesdroppers is considered. Based on a more practical assumption that the transmitter derives imperfect legitimate user's channel state information (LCSI) and statistical eavesdroppers' channel state information (ECSI), secrecy rate maximisation (SRM) under a total transmit power constraint and K probabilistic secrecy outage constraints are studied. To deal with it, the K probabilistic constraints are firstly approximated to the deterministic worst‐case ones by resorting to sphere bounding. Secondly, by introducing a slack variable the approximated worst‐case SRM can be further recast as a series of semi‐definite programmings. In this way, the jointly optimised robust beamforming vector and the AN covariance are determined in a tractable convex fashion. Moreover, the authors can prove that the derived AN‐aided secure robust beamforming actually is the optimal solution to the approximated worst‐case SRM problem. Numerical results reveal that the proposed AN‐aided probabilistic secure robust beamforming could achieve outage secrecy rate improvement in comparison with the existing optimal worst‐case robust beamforming without AN, optimal outage constrained robust beamforming without AN, the non‐robust isotropic AN transmission, and the non‐robust AN‐aided beamforming scheme.
In this paper, we design and experiment a far-field wireless power transfer (WPT) architecture based on distributed antennas, so-called WPT DAS, that dynamically selects transmit antenna and frequency to increase the output dc power. Uniquely, spatial and frequency diversities are jointly exploited in the proposed WPT DAS with low complexity, low cost, and flexible deployment to combat the wireless fading channel. A numerical experiment is designed to show the benefits using antenna and frequency selections in spatially and frequency selective fading channels for single-user and multi-user cases. Accordingly, the proposed WPT DAS for single-user and two-user cases is prototyped. At the transmitter, we adopt antenna selection to exploit spatial diversity and adopt frequency selection to exploit frequency diversity. A low-complexity over-the-air limited feedback using an IEEE 802.15.4 RF interface is designed for antenna and frequency selections and reporting from the receiver to the transmitter. The proposed WPT DAS prototype is demonstrated in a real indoor environment. The measurements show that WPT DAS can boost the output dc power by up to 30 dB in single-user case and boost the sum of output dc power by up to 21.8 dB in two-user case and broaden the service coverage area in a low cost, low complexity, and flexible manner.
In this paper, we design and experiment a far-field wireless power transfer (WPT) architecture based on distributed antennas, so-called WPT DAS, that dynamically selects transmit antenna and frequency to increase the output dc power. Uniquely, spatial and frequency diversities are jointly exploited in the proposed WPT DAS with low complexity, low cost, and flexible deployment to combat the wireless fading channel. A numerical experiment is designed to show the benefits using antenna and frequency selections in spatially and frequency selective fading channels for single-user and multi-user cases. Accordingly, the proposed WPT DAS for single-user and two-user cases is prototyped. At the transmitter, we adopt antenna selection to exploit spatial diversity and adopt frequency selection to exploit frequency diversity. A low-complexity over-the-air limited feedback using an IEEE 802.15.4 RF interface is designed for antenna and frequency selections and reporting from the receiver to the transmitter. The proposed WPT DAS prototype is demonstrated in a real indoor environment. The measurements show that WPT DAS can boost the output dc power by up to 30 dB in single-user case and boost the sum of output dc power by up to 21.8 dB in two-user case and broaden the service coverage area in a low cost, low complexity, and flexible manner.
