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Pilot spoofing attack brings new challenges to physical layer secure transmission. However, this method will not work without any knowledge about the pilot sequence and active eavesdropping can be detected by constructing random pilot sequence. Intelligent reflecting surface (IRS), with the real-time programmable features for wireless channels, provides new possibilities for effective pilot spoofing. In this paper, the IRS is deployed near the legitimate users and the legitimate signal can always be passively reflected. Then the control strategy is embedded into the communication process under time-division duplex mode to assist eavesdroppers to conduct pilot spoofing. By setting different phase shifts at the IRS during the uplink phase and downlink phase, the channel reciprocity disappears, and thus secure beamforming vector is biased towards the eavesdropper. Furthermore, in order to overhear more information, the average secrecy rate minimization problem based on statistical channel state information is established by carefully designing the phase shifts, which is non-trivial to solve. With alternating optimization and Charnes-Cooper transformation technique, the original problem is transformed into convex form and a near optimal solution is achieved. Finally, simulation results show that our proposed scheme can pose serious secure threat without any energy footprint. What's more, if the IRS is not utilized by the internal users properly, it will bring more threat.

Physical layer secret key generation is a promising candidate to achieve one-time-pad encryption approach for the wireless communication system. However, in a static environment, the secret key rate is low due to the lack of channel time-variation. To solve this problem, this letter proposes a novel secret key generation scheme assisted by an intelligent reflecting surface with discrete phase shifts. In the scheme, legitimate nodes construct the dynamic time-varying channel by rapidly and randomly switching the phase of IRS elements. Then, channel coefficients are used to generate the secret key. Based on the IRS channel model, we derive the probability distribution of the channel coefficient and the expressions of the secret key rate. Furthermore, we optimize the secret key rate by adjusting the switching time of the IRS phase. Monte Carlo simulation and numerical results show that our proposed scheme can update the secret key in a static environment.

This paper proposes a tractable analysis framework to evaluate the reliability, security and secrecy energy efficiency (SEE) performance in a communication network with mobile sinks via a threshold-based access scheme and multi-antenna technique. Specifically, the mobile sinks, legitimate receivers and eavesdroppers are deployed randomly. To achieve reliable results for general communication scenarios, this paper assumes both line-of-sight and non-line-of-sight paths with Rayleigh fading for air-to-ground channel model. In particular, we first exploit the association probability of a randomly located receiver and the activation probability of mobile sinks. Then, we analyze the security, reliability, and SEE of the networks with mobile sinks. Simulation results are finally provided to show the effect of the predetermined access threshold, the transmitter’s resource block, the height of mobile sinks, the density of legitimate receivers, and the density of eavesdroppers on the reliability as well as security performance, and determine the optimal design parameters for a given network with mobile sinks to maximize the SEE.

Existing handover authentication schemes are implemented in the upper layer through cryptographic techniques with different protocols and parameters involved under different handover scenarios, introducing high latency and complexity especially in the next generation (5G) highly heterogeneous network (HetNet). The authors propose to introduce wireless link signatures decided by users' locations as handover authentication data to achieve unified and fast handover authentication at the physical layer in 5G software defined networking-based HetNet. Specifically, the unique wireless channel characteristics between a user and the serving access point (AP) are extracted as the secure context information (SCI) and transferred to the target AP. The latter determines whether the user is the legitimate one who has already been authenticated according to the received SCI. They then analyse the authentication performance relating to multiple attributes and results demonstrate that the authentication strength can be adaptively adjusted. Furthermore, they find that optimum performance can be achieved by setting a proper decision threshold and derive the sub-optimal performance by iterative search. Lastly, analysis and simulations on latency and overhead compared with existing ones are conducted and results prove the effectiveness of the proposed scheme.

This paper develops a tractable analysis framework to evaluate the reliability and security performance of cooperative non-orthogonal multiple access (co-NOMA) in cognitive networks, where both a primary base station (PBS) and a NOMA-strong primary user (PU) send confidential messages to multiple uniformly distributed PUs in the presence of randomly located external eavesdroppers. For constricting the interference to the PUs imposed by cognitive femto base stations (CFBSs), a mobile association scheme is introduced. Moreover, an eavesdropper-exclusion zone is introduced around the PBS for improving the secrecy performance of the primary networks. To characterize the security-reliability tradeoff of the considered network, we first derive the activation probability of CFBSs and the conditional probability density function associated with the distance between the relay user and other PUs. Then, the connection outage probability (COP) and the secrecy outage probability (SOP) of each PU with NOMA (co-NOMA) or non-cooperative NOMA (nco-NOMA) are separately derived to obtain the overall COP and SOP in the primary networks. Finally, the tradeoff between COP and SOP with co-NOMA (identified as transmission SOP) is investigated for simultaneously reflecting the security and reliability. Numerical results demonstrate the performance improvements of the proposed co-NOMA scheme in comparison to that of the nco-NOMA scheme in terms of different parameters. Furthermore, the security-reliability tradeoff performance of co-NOMA is shown.

Under the case of imperfect channel state information (CSI), this paper investigates the robust secrecy energy efficiency (SEE) optimization for the heterogeneous networks (HeNets) supported by simultaneous wireless information and power transfer. Specifically, we first consider a two-tier HeNet composed of a macrocell base station (MBS) and several femtocell base stations (FBSs), where the MBS serves multiple macrocell users (MUs) while each FBS serves an information receiver (IR) and an multiple-antenna energy receiver (ER). Meanwhile, a malicious multiple-antenna eavesdropper (Eve) attempts to wiretap the downlink information of MUs and the ER acts as a potential Eve to eavesdrop the confidential information for IR in the same femtocell. To enhance the secrecy performance, artificial noise (AN) is injected into the downlink information beams of the MBS and FBSs. By considering the user fairness, the problem of SEE maximization of the whole network is formulated via a cross-tier multi-cell coordinated beamforming design. The resulting problem contains infinite constraints caused by CSI error, which is nonconvex and cannot be solved directly. To this regard, we resort to the successive convex approximation, S-procedure and semi-definite relaxation techniques to obtain a solvable form of it. Furthermore, to reduce the overhead of information exchange among coordinated BSs, we develop a distributed solution based on alternative direction multiplier method (ADMM) that can achieve a good approximation performance. Finally, simulation results verify the validity of the proposed AN-aided cross-tier multi-cell coordinated beamforming design and distributed ADMM-based design.

Delay and security are both highly concerned in massive internet of things (IoT) which is a promising application scenario in 5G wireless communication system. In this study, the authors develop an integrated framework to study delay performance and secrecy performance in massive IoT. First, stochastic geometry and queuing theory are applied to model the spatially location of IoT devices and the temporal arrival of packets. To enhance the physical layer security of massive IoT with limited overhead increment at IoT devices, a low-complexity noise injection scheme is applied. Then, the packet delay and packet secrecy outage probability are derived to characterise delay performance and secrecy performance. It is demonstrated that the IoT device intensity and power allocation coefficient arouse a tradeoff between the delay and security. Furthermore, optimal power allocation coefficient that maximises secrecy transmission rate can be derived, which can improve the delay-security tradeoff. The analytical and simulation results show the effects of power allocation coefficient and IoT device intensity on the tradeoff between delay performance and secrecy performance.

To solve the problem that key is susceptible to eavesdroppers in the correlated channel scenarios, in this paper, we propose a native security scheme based on physical layer chain keys, which can be used for encryption and authentication. First, the physical layer chain key is generated by performing XOR operation on the updated key and the previous chain key, where the updated key is obtained by the current channel state information. The proposed scheme uses the chain key as the authentication root, and the authentication relationship is continuously transferred as the chain grows. Then, CRC is used to realize identity authentication and message verification simultaneously. Finally, the derivation based on information theory proves the security of chain key for encryption and authentication. The simulation results show that the proposed chain key scheme can leak less information and have a lower probability of successful attack than the traditional physical layer key in the correlated channel scenarios.

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.

We study physical layer secure transmission with limited feedback in heterogeneous cellular networks. A transmission protocol is designed to obtain more secure and accurate channel state information (CSI) for enhancing the secrecy performance. Under the proposed protocol, we derive expressions of coverage probability and secrecy outage probability to analyze the security performance with different system parameters such as feedback CSI length and number of antennas. Furthermore, an iteration algorithm is proposed to balance the tradeoff between the feedback and transmission time, and maximize the average secrecy throughput under coverage and secrecy outage constrains. Numeric results demonstrate the optimal feedback overhead and the maximum average secrecy throughput are influenced by the number of antennas.

Due to the channel estimation error, most of the physical layer secret key generation schemes need information reconciliation to correct error key bits, resulting in reduced efficiency. To solve the problem, this work proposes a novel secure communication scheme based on a equivalent interference channel. Different keys generated from imperfect channel state information are directly applied to signal scrambling and descrambling, which is equivalent to the process of a signal passing through an interference channel. Legitimate communication parties can reduce interference with the help of similar keys and channel coding without sending additional signals, while the eavesdropper channel is deteriorated due to the spatial decorrelation. For this kind of schemes, we first establish a discrete memoryless broadcast channel model to derive the expressions of bit error rate (BER), channel capacity, and security capacity for performance analysis. Simulation results verify the derivations that the proposed scheme achieves secure communication with a correlated eavesdropping channel and has a higher upper bound of transmission rate. Furthermore, we design a new metric to evaluate the efficiency and the result shows that the proposed scheme has superior performance on error reconciliation efficiency, despite its slight increase in BER.

Focusing on the problem of information leakage and communication cost in information reconciliation, this paper introduces a non-reconciliation secret Keys based transmission scheme(NASKT) for machine to machine(M2M) communications in Internet of Things(IoT) networks, which uses polar codes to guarantee no error transmission. First, the improved Kalman filter preprocessing algorithm is used to reduce the quantized bit error rate(QBER). Then, QBER is modeled as the transmission bit error rate of the additional white Gaussian noise (AWGN) channel. Finally, the polar codes are designed based on the equivalent AWGN channel and system performance requirements to guarantee the security of transmitted information. Numerical simulations verify that the secure M2M transmission scheme based on the Non-reconciliation secret Keys using polar codes can realize the One-Time Pad lightweight security.

In a heterogeneous simultaneous wireless information and energy transfer (SWIPT) network, the beamforming scheme for multi-users is significantly influenced by the imperfect channel state information (CSI). A joint beamforming scheme for multiple eavesdroppers in two-layer SWIPT network is proposed, jointly design the information and energy beam in the presence of imperfect CSI to serve the several users in the cell. In the meantime, using the signals between macro and pico base stations as the equivalent artificial noise to protect the security and improve the energy efficiency. To this end, an optimization algorithm is designed to approximate the optimal beamforming matrix for maximizing the overall minimum secure energy efficiency. the successive convex approximation (SCA) and semi-positive definite relaxation (SDR) techniques are used to simplify and solve this non-convex optimization problem. The simulation results verifies the security and effectiveness of the scheme.

Most of the existing works on group secret key (GSK) generation are based on pairwise key which wasting the total time and power of the group users. We present a cooperative GSK generation algorithm via star topology with one central node and one reference node. After channel estimation, secure network coding technique is employed by the central node to help all the group users exploit the randomness of reference channel with nothing about that leaking to the eavesdropper. Then all the group users agree on a secret key from the correlative observations of the reference channel in one information reconciliation phase. In addition, the expression of achievable secret key rate is derived. Theoretical and Monte Carlo simulation results validate the performance of our proposed algorithm.

Resource allocation in secure communication is of primary importance due to the fact that the next-generation wireless network (5G) aims to achieve high spectral efficiency and a high level of security. Different from previous studies, we study the resource allocation for secure transmission in $K$ -tier dynamic heterogeneous cellular networks jointly considering the randomness of base stations (BSs) in spatial dimension and user equipment (UE) arrival and departure processes in temporal dimension. First, we develop a 3-D stochastic model by jointly taking into account the randomness of BSs in two spatial dimensions and UE arrival and departure processes in one temporal dimension. Second, we analyze the connection outage probability and secrecy outage probability of the typical UE. Their expressions admit quite simple closed-forms in some plausible special cases. Based on the outage analysis, the reliability and security performances of the network are evaluated, respectively. Third, we investigate the network-wide secrecy throughput in virtue of the outage analysis. Furthermore, we derive the optimal resource allocation factors of different tiers to maximize the secrecy throughput. Since the objective function of the maximization problem is not in closed form and non-convex, the concave upper and lower bounds are deduced and utilized, which leads to near-optimal solutions of the resource allocation factors of different tiers. It is demonstrated that apart from the spatial intensity and transmission power of each BS, UE arrival and departure processes are also key elements influencing the resource allocation factors of different tiers. Finally, numerical results show the usefulness and correctness of our theoretical conclusions.

This paper investigates the physical-layer security of uplink non-orthogonal multiple access (NOMA) in the cellular Internet of Things (IoT) with invoking stochastic geometry. Poisson cluster process-based model is applied to characterize the NOMA uplink transmission scenario, where IoT terminals are located around the serving base station. Considering the severe interference brought by a large number of IoT terminals, inter-cell interference is also taken into account. To enhance the physical-layer security of uplink NOMA transmission with limited overhead increment at IoT terminals, the base stations not only receive the signals from IoT terminals but also keep emitting jamming signals all the time to degrade the performance of any potential eavesdroppers. In order to characterize the physical-layer security performances, we derive expressions of coverage probability and secrecy outage probability. To obtain further insights, network-wide secrecy throughput (NST) and network-wide secrecy energy efficiency (NSEE) are analyzed. It is demonstrated that the security performance can be improved by the proposed full-duplex base station jamming scheme at the cost of reliable performance. The analytical and simulation results show the effects of BS intensity and jamming power on network performances. We also verify that NST and NSEE can be significantly enhanced by our proposed scheme. Using these results, the security of confidential information transmitted by low-complexity IoT terminals can be protected from overhearing.

This paper investigates the physical layer security in heterogeneous networks (HetNets) supported by simultaneous wireless information and power transfer (SWIPT). We first consider a two-tier HetNet composed of a macrocell and several femtocells, where the macrocell base station (BS) serves multiple users in the presence of a malicious eavesdropper, while each femtocell BS serves a couple of Internet-of-Things (IoT) users. With regard to the energy constraint of IoT users, SWIPT is performed at the femtocell BSs, and IoT users accomplish the reception of information and energy in a time-switching manner, where information secrecy is to be protected. To enhance the secrecy performance, we inject artificial noise (AN) into the transmit beam at both macrocell and femtocell BSs, and for the sake of achieving green communications, we formulate the problem of maximizing secrecy energy efficiency while considering the fairness in a cross-tier multi-cell coordinated beamforming (MCBF) design. To handle this resulting nonconvex max-min fractional program problem, we propose an iterative algorithm by applying successive convex approximation method. Then, we further develop a decentralized solution based on alternative direction multiplier method (ADMM), which reduces the overhead of information exchange among coordinated BSs and achieves good approximation performance. Finally, simulation results demonstrate the performance of the proposed AN-aided cross-tier MCBF design and verify the validity of distributed ADMM-based approach.

Spectral efficiency (SE) and energy efficiency (EE) in secure communications is of primary importance due to the fact that 5G wireless networks aim to achieve high throughput, low power consumption and high level of security. Nevertheless, maximizing SE and EE are not achievable simultaneously. In this paper, we investigate the SE and EE tradeoff for secure transmission in cognitive relay networks where all nodes are randomly distributed. We first introduce the opportunistic relay selection policy, where each primary transmitter communicates with the primary receiver with the help of a secondary user as a relay. Then, we evaluate the secure SE and secure EE of the primary network based on the outage probabilities analysis. Thirdly, by applying a unified SE-EE tradeoff metric, the secure SE and EE tradeoff problem is formulated as the joint secure SE and EE maximization problem. Considering the non-concave feature of the objective function, an iterative algorithm is proposed to improve secure SE and EE tradeoff. Numerical results show that the opportunistic relay selection policy is always superior to random relay selection policy. Furthermore, the opportunistic relay selection policy outperforms conventional direct transmission policy when faced with small security threat (i.e., for smaller eavesdropper density).

This paper studies a simultaneous wireless information and power transfer system with multiple external eavesdroppers and internal curious users. We model the random network by Poisson cluster process in consideration of the case where eavesdroppers hide around certain targets. Focusing on the users that work in harvesting-transmitting mode with time switching receivers, we establish communication model via time division multiple access. On this basis, we propose a lightweight secure transmission scheme based on dual-thresholds for physical-layer security enhancement, which consists of two protocols applied to the downlink (DL) and uplink (UL) transmission respectively. In the DL, we design a dynamic information-power switching transmission protocol based on signal-to-noise ratio threshold, which provides an opportunistic approach to reform the fixed period allocation of information and power transfer; in the UL, an energy threshold is proposed for users to control the transmission, which is called a user-led on-off transmission protocol. Furthermore, we give a comprehensive performance analysis for the proposed scheme in terms of delay, reliability, security and secrecy throughput. Based on the analysis results, we optimize the two thresholds and the DL-UL allocation coefficient to maximize the secrecy throughput. Simulation results show the proposed scheme can bring about a substantial secrecy gain.

The ever increasing wireless data services, such as imaging, video, audio, multimedia, etc., have demands for the very high speed wireless communications and network, which are unfortunately a bottleneck when combining with the wireline core network. Users' are now expecting high quality of experience with low-cost devices, ubiquitous connectivity, energy efficiency, high reliability, or even ultra-low latency if a vehicle terminal is applied.

Key generation technique generates symmetric keys based on the temporal variation, reciprocity and spatial decorrelation of the wireless channel. Most key generation schemes, however, assume that the eavesdropping channels are independent of the main channel and neglect the influence of the eavesdroppers. In this paper, we analyze the secret key capacity taking into account the information leaked to eavesdroppers, and the security analysis shows the eavesdropping channel correlation will reduce the secret key capacity. Then we propose a security channel estimating (SCE) scheme to resist eavesdroppers and the scheme is shown to be efficient. Finally, we use the Monte Carlo simulation verifies the theoretical analysis results.

In order to deal with the performance degradation caused by resource contention due to the sharing of physical resources between VNFs in the network slicing, we proposed a network slicing deployment method for guaranteeing service performance. Firstly, estimate the basic performance level of VNF from the perspective of resource supply and demand. Then select the candidate deployment servers for VNF, the candidate servers can guarantee the basic performance level of both new incoming and already deployed VNFs. Finally, to reduce deployment costs, our approach uses the candidate server on the shortest path as the final deployment server. The simulation results show that this method not only can reduce performance degradation on physical servers, but also can reduce operating costs.

The particularity of security threats for multi-tier heterogeneous cellular networks (HCNs) is causedby the nonuniformity between the tiers and the complex and unplanned topology. To promote the study of secrecy transmission in HCNs, we utilize stochastic geometry tools and physical-layer security technologies to obtain theexpressions for the secrecy coverage probability and average secrecy rate under different scenarios such as nocooperation, only macrocell base stations (MBSs) involved in cooperation, all base stations (BSs) involved incooperation, and with/without channel measurements between the cooperative BSs and the mobile users. Furthermore,we simulate and analyze the influences on security performance caused by the fraction of transmit powerused for transmitting artificial noise, the fraction of cooperative power used for transmitting artificial noise, thesecrecy rate threshold, the number of transmission antennas for an MBS, and the eavesdropper density. Basedon the simulation results, we propose a security-performance-oriented strategy for cooperative transmission andjamming in HCN.

This study proposes a tractable approach to analyze the physical-layer security in the downlink of a multi-tier heterogeneous cellular network. This method is based on stochastic geometry, has low computational complexity, and uses the two-dimensional Poisson point process to model the locations of K-tier base stations and receivers, including those of legitimate users and eavesdroppers. Then, the achievable secrecy rates for an arbitrary user are determined and the upper and lower bounds of secrecy coverage probability derived on the condition that cross-tier interference is the main contributor to aggregate interference. Finally, our analysis results reveal the innate connections between information-theoretic security and the spatial densities of legitimate and malicious nodes.

This paper focuses on the problem of secure transmission in a cellular system. A full-duplex base station using artificial noise is adopted to improve both the uplink and downlink secrecy rate via pairing terminals which reverses the downlink and uplink of each other. We give the designs of artificial noise and the user's desired signal, and derive the pairing prin-ciple between terminals. Moreover, the influence of self-interference cancellation on secrecy rate is ex-plored. Simulation results show that the secrecy rate can get much better performance by adopting full-duplex artificial noise scheme and proposed pair-ing method. The downlink secrecy rate decreases with the distance between terminals. Besides the uplink secrecy rate is sensitive to the ability of self-interference cancellation.

We consider a cellular network with a full-duplex base station, multiple uplink users and an eavesdropper. The full-duplex base station transmits jamming signals to degrade the eavesdropper channel when receiving secure multi-user signals. To maximize the secrecy rate of uplink communications, we propose a distributed ascending-clock auction (ACA) algorithm to allocate subcarriers and jamming power. Specifically, the impact of the self-interference of the full-duplex base station on the secrecy rate is considered. The proposed algorithm consists of two parts. Firstly, subcarriers and the jamming power are respectively priced by the base station. Secondly, users select the subcarrier and the jamming power based on the price. Moreover, the convergence of the proposed auction algorithm is mathematically proved. Simulation results show that the proposed auction algorithm is more beneficial to improve the uplink secrecy performance compared to traditional auction algorithms.

A multiple relays aided secret key generation algorithm is proposed to improve the generated secret key rate for Internet of things when the wireless channels change slowly. First, the two legitimate users and relays send training sequences in turn to estimate the channels. Then, the relays employ secure network coding technique to help the two legitimate users exploit the randomness of relay channels. Finally, the two legitimate users agree on a secret key without the help of relays. In addition, the optimal relays selection with optimal power allocation algorithm is present to further improve the secret key rate when relay selection is needed. The performances of the proposed algorithms are verified by Monte Carlo simulation results.

In device-to-device (D2D) underlaying cellular networks, interference generated by D2D communications can be exploited to improve secrecy rate of cellular users (CUE). The security-oriented distributed access selection algorithm is proposed, in which each D2D pair decides whether to access to radio resources according to its local channel state information without considering the locations of D2D pairs and Eve. The ergodic secrecy rate of CUE and the data rate of D2D pairs in the proposed scheme are investigated. Simulation results show that the proposed scheme can achieve an impressive secrecy performance gain.

Recent researches show that millimeter wave (mmWave) communication offers the promise of orders of magnitude increases in the cellular network capacity. Due to the severe path loss, relay aided transmission has been regarded as an effective way to extend mmWave communication range. In this paper, we apply an opportunistic relay selection (ORS) scheme for range extension to mmWave networks and develop a framework to analyze the connection outage probability (COP) and secrecy outage probability (SOP) using stochastic geometry. We first introduce the ORS scheme where each base station transmits its data in first time slot and the best relay is selected by competition to forward the infirmation in second time slot. Then the COP, SOP and secrecy throughput in direct transmission and ORS transmission are derived, respectively. By comparing the reliability and security performance of the two transmission schemes, it is demonstrated that ORS scheme enhances the reliability of the communication, but unfortunately increases the risk that confidential information be intercepted by an eavesdropper. We also find the secrecy throughput of ORS scheme is higher than that of direct conventional transmission.

The 5th-generation mobile communication system (5G) has higher security requirements than previous systems. Accordingly, international standard organizations, operators, and equipment manufacturers are focusing extensively on 5G security technology. This paper analyzes the security requirements of 5G business applications, network architecture, the air interface, and user privacy. The development trends of 5G security architecture are summarized, with a focus on endogenous defense architecture, which represents a new trend in 5G security development. Several incremental 5G security technologies are reviewed, including physical layer security, lightweight encryption, network slice security, user privacy protection, and block chain technology applied to 5G.

This paper investigates the physical layer security in simultaneous wireless information and power transfer (SWIPT)-enabled cooperative non-orthogonal multiple access (NOMA) transmissions. Taking the malicious eavesdropper into account, we study on the problem of artificial noise (AN)-aided transceiver optimization. To guarantee the quality of service (QoS) at cell-edge users and promote the average performance of system, we consider the multi-cell beam-forming (MCBF) and formulate the problem of maximizing the secrecy spectral efficiency fairness (SSEF) among multiple coordinated cells. As the formulated problem is nonconvex and difficult to solve with existing methods, we apply the semi-definition relaxation (SDR) technique and propose an iterative algorithm based on successive convex approximation (SCA) for complexity reduction. Furthermore, we analyze the complexity of the proposed algorithm. Finally, simulations results demonstrate our analysis and illustrate the validity of AN-aided MCBF transmission scheme.

Security and delay are both of extremely important due to the fact that the fifth generation (5G) wireless networks aims to achieve high level of security and low delay. In this paper, considering the randomness of base stations in space and dynamic user traffic arrivals in time, we first develop a novel traffic-aware spatio-temporal mathematical framework in an open access A"-tier heterogeneous cellular network (HCN) based on stochastic geometry theory and queuing theory. On the basis of the spatio-temporal framework, we then investigate the security and delay performance. It is demonstrated that there is a tradeoff between packet transmission delay and secrecy transmission rate, which is caused by the packet arrival probability. Finally, simulation experiments are conducted to validate the correctness and usefulness of our theoretical conclusions.

In the original publication [1] the name of author Yajun Chen was spelled wrong. The original article was updated to rectify this error.

Device-to-device (D2D) communication has been deemed as a promising technology in the next generation 5G wireless communication. Due to the openness nature of the transmission medium, secure transmission is also a critical issue in the D2D-enabled cellular network as well as other wireless systems. In this paper, we investigate secure communication for the cellular downlink in this hybrid network. We consider a case in which each base station has no channel state information (CSI) from D2D transmitters which are generally deployed in the cell edge. To guarantee the secure communication of the cellular link, each base station employs the artificial noise assisted transmission strategy. Firstly, we derive the close-form expression and asymptotic expression of the secrecy outage probability of the cellular link in different scenarios: (I) eavesdroppers having no multi-user decedability; (II) eavesdroppers having the multi-user decedability. Then, we comprehensively discuss the impacts of some main system parameters on the performance to provide some system design guidances. To characterize the reliable communication of the typical D2D link, the close-form expression and asymptotic expression of the connection outage probability are, respectively, derived and some comprehensive analysis are presented. Finally, simulation results are provided to validate the effectiveness of theoretical analysis.

In this paper, we investigate secure communication over cellular uplinks in device-to-device (D2D)-enabled cellular networks. We consider a more general scenario, in which multiple D2D pairs could simultaneously share the same resource block with a specific cellular user. First, an opportunistic access control scheme based on wireless channel gains is proposed, by which the candidate selected set of D2D pairs sharing the same resource block is determined. The proposed scheme could guarantee reliable communications for both cellular users and D2D pairs, and further could combat eavesdroppers while keeping the legitimate cellular user as non-intrusive as possible, regarding D2D pairs as friendly jammers in a non-collaborative way. Then, we derive theoretical results to characterize the security and reliability of the typical cellular and D2D links, respectively. To further support the performance of this hybrid network, we next present an interference threshold optimization model. Our aim is to minimize the connection outage probability (COP) of D2D pairs subject to the secrecy requirement of the cellular user. Finally, simulation results are presented to validate the effectiveness of our proposed scheme.

Delay and security are both highly concerned in the Internet of Things (IoT). In this paper, we set up a secure analytical framework for IoT networks to characterize the network delay performance and secrecy performance. Firstly, stochastic geometry and queueing theory are adopted to model the location of IoT devices and the temporal arrival of packets. Based on this model, a low-complexity secure on-off scheme is proposed to improve the network performance. Then, the delay performance and secrecy performance are evaluated in terms of packet delay and packet secrecy outage probability. It is demonstrated that the intensity of IoT devices arouse a tradeoff between the delay and security and the secure on-off scheme can improve the network delay performance and secrecy performance. Moreover, secrecy transmission rate is adopted to reflect the delay-security tradeoff. The analytical and simulation results show the effects of intensity of IoT devices and secure on-off scheme on the network delay performance and secrecy performance.

This paper studies the physical layer security of uplink (UL) transmission in simultaneous wireless information and power transfer (SWIPT) deployed in wireless sensor networks (WSNs). Firstly, we model the random network as Poisson cluster process (PCP) to focus on the case where eavesdroppers hide around certain targets to intercept the confidential information successfully. Then, the communication model of time division multiple access (TDMA) is established to avoid inter-node interferences and extend the time for energy harvesting (EH). After that, aiming at the sensor nodes that work in “harvesting-transmitting” (H-T) mode with time switching (TS) receiver, we derive the energy outage probabilities (EOP), connection outage probabilities (COP) and secrecy outage probabilities (SOP) through comprehensive analysis on downlink (DL) and UL transmissions, based on which the uplink secrecy throughput (STP) is obtained to characterize the overall performance. Finally, our theoretical derivations are verified and the influences of various parameters on uplink STP are revealed by the simulation results, which indicate the existence of an optimal energy threshold and a partition coefficient of DL and UL period that can achieve the best secrecy performance.

The existing secure transmission methods based on fountain codes require a quite dominant quality of the main channel. In this paper, we propose a novel feedback-based method for fountain code to achieve stronger security. In the binary erasure channel model, the legitimate user shares the decoding situation with transmitter via feedback messages. The transmitter updates the coding process based on the feedback so as to weaken the connection of coding before and after the feedback. By doing that, the superiority of the main channel is accumulated and expanded. Numerical results indicate that the proposed method can significantly reduce the rate of intercepted symbols at the eavesdropper under the same channel conditions and the performance is even better when the quality of the main channel and the wiretap channel are close.

In this paper, we consider the secure communication of the cellular downlink between the base station and the cellular user underlaying D2D communication. Base stations, cellular users, D2D transmitters and eavesdroppers are modeled as the independent homogeneous Poisson point processes (PPPs). We consider a worst case in which each base station has no channel state information (CSI) from D2D transmitters which are generally deployed in the cell edge. In order to guarantee the secure transmission for cellular links, each multi-antenna base station employs the artificial noise assisted transmission strategy to keep the confidential message from being intercepted by the malicious eavesdropper having the multi-user decedability. Firstly, we derive the secrecy outage probability for the typical cellular link in the interference-limited network in which the additive noise is neglected. Then, the connection outage probability for the typical D2D link in the hybrid network is derived and some comprehensive analysis are presented. Finally, Finally, simulation results are provided to validate the effectiveness of theoretical analysis.

This paper studies the physical-layer secrecy performance of the downlink transmission in Simultaneous Wireless Information and Power Transfer (SWIPT) deployed in Internet of Things (IoT), where the Energy Receivers (ERs) are curious about the confidential messages of Information Receivers (IRs). Firstly, the locations of IoT users are modeled as the Poisson Point Process (PPP) to characterize the random deployment. Then, the communication model among the Resource Center (RC) and multiple IoT users is established via Time Division Multiple Access (TDMA). Furthermore, considering the energy requirements of nodes that work in "harvesting-transmitting" mode, two thresholds of eavesdropping are proposed to analyze the eavesdropping behaviors of ERs in different scenarios, based on which the curiosity probabilities are respectively obtained. Finally, the average secrecy outage probability is derived through the comprehensive analysis on different links in an entire period. The simulation results show that there exits an optimal transmitting power that can achieve the best performance and the proposed thresholds can improve the accuracy of the analysis.

Secure communication in Heterogeneous cellular networks (HCNs) is of primary importance due to the fact that the fifth generation (SG) wireless networks aim to achieve high level of security. Different from previous works, we study the physical layer security (PLS) performance jointly considering the randomness of base stations in spatial dimension and user equipment (UE) arrival and departure processes in temporal dimension. Firstly, we develop a novel spatio-temporal mathematical framework in an open access K-tier HCN based on stochastic geometry theory and queuing theory. Secondly, we evaluate the reliability and security performances based on the connection outage probability (COP) and secrecy outage probability (SOP) analysis. Thirdly, in order to jointly evaluate the reliability and security performances, we analyze the network-wide secrecy throughput based on the outage probability analysis. Furthermore, we derive the optimal UE arrival rate to maximize the network-wide secrecy throughput. Finally, simulation experiments are conducted to validate the correctness and usefulness of our theoretical conclusions.

Cooperative relaying is a promising technology that can improve the spectral and energy efficiency of cellular networks. However, the deployed relays consume a lot of energy and system resources. To improve the energy efficiency of the relay-assisted cellular networks, this paper considers the use of energy harvesting (EH) on relay nodes. A random sleeping strategy is also introduced in macro base stations (MBS) as a possible method to reduce energy consumption. In this paper, an analytical model is proposed to investigate the energy efficiency of cellular networks with EH relays and sleep mode strategy. Numerical results confirm a significant energy efficiency gain of the proposed networks comparing to the cellular networks with non-EH relays and MBSs without sleep mode strategy. The effects of the density and transmit power of MBSs on energy efficiency are also given through simulations.

The authentication of transmitting terminal in present physical-layer security method based on wireless channel character is implemented by checking the pilot signal sent by it, and missing detection often happens. A new kind of physical-layer authentication and key distribution mechanism based on equivalent channel is presented. The equivalent channel is built by encrypting keys with channel character of multi time slots, as a result difference of different channels is mapped onto transmitting distortion. And mutual information of delivering and receiving terminals channel characters can be told by correctness of the transmission, thus the key distribution and authentication are implemented at the same time. Analysis and simulation reveal that key distribution performance in this method is same as the existing one, and the attack can be recognized in circumstances of channels with strong correlation.

Cognitive heterogeneous cellular networks (CHCNs) are emerging as a promising approach to next-generation wireless communications owing to their seamless coverage and high network throughput. In this paper, we describe our reliance on multi-antenna technology and a secrecy transmission protocol to ensure the reliability and security of downlink underlay CHCNs. First, we introduce a two-tier CHCN model using a stochastic geometry framework, and derive the probability distribution of the indicator function for a secrecy transmission scheme. We then investigate the connection outage probability, secrecy outage probability (SOP), and transmission SOP of both primary and cognitive users under a secrecy guard scheme and a threshold-based scheme. Furthermore, we reveal some insights into the secrecy performance by properly setting the predetermined access threshold and the radius of detection region for the secrecy transmission scheme. Finally, simulation results are provided to show the influence of the antenna system, eavesdropper density, predetermined access threshold, and radius of the detection region on the reliability and security performance of a CHCN.

The mutual interference induced by the hybrid links can bring the secrecy gain for device-to-device (D2D) communication underlaying cellular networks, where there have been few works on studying its impact on the secrecy performance of the accessed D2D pairs. In this paper, our aim is to mainly analyze the secrecy performance gain of the accessed D2D pair brought by the mutual interference.Firstly,an opportunistic D2D pairs selection scheme based on the wireless channel direction information (CDI) is proposed. The proposed scheme determines a set of candidate D2D pairs with the required interference limitation for the cellular user. Then, the D2D pair with best channel condition is scheduled to share the same channel with cellular users for its own transmission. Further, the analytical expressions of the secrecy outage probability are derived with presence of multiple D2D pairs and multiple eavesdroppers. Finally, the secrecy performance of the proposed scheme is demonstrated by simulations.

For preventing the leakage of confidential messages sent to a marcocell user in dense heterogeneous networks, a physical layer security scheme based on base station cooperation is proposed in the paper. To improve transmission rate of confidential messages and make the downlink signals of other legitimate users interfere with eavesdroppers, the beamforming vectors at a macrocell base station and femtocell base stations are jointly optimized. The problem of maximizing the secrecy rate is modeled under the limitations of quality of service(QoS) and base station power. Due to the intractability, this problem is recast into a convex SemiDefinite Program(SDP) problem using the SemiDefinite Relaxation(SDR) technique and the successive convex approximation(SCA) algorithm. Simulation results validate the efficacy and the security of the scheme.

When extracting secret key from shared wireless channel between two legitimate moving terminals, its capacity is affected by the time difference of channel sampling, terminal's mobility, and additive noise. In order to quantitatively analyze their effects, a closed-form solution to physical layer secret key capacity in the time domain is derived over the uniform scattering environment. Afterwards, simulations in the uniform and non-uniform scattering environment are carried out to demonstrate its validity and applicability, respectively. Simula-tion results show that the derivation can be utilized to provide theoretical reference for physical layer secret key extraction between two moving terminals located among dense scatters.

To transmit the information in secret with MIMO (multi-input multi-output) system, the security scheme based on the random reference is presented. In this scheme, the independent parallel channels are obtained by doing singular value decomposition. Then, the random pilot is sent to one of these channels, which encrypts the information carried on other parallel channels. Because of the discrepancy from the main channel, with the eavesdropping channel, the eavesdropper cannot decompose the independent random pilot channel to recover the information sent by transmitter. By the theoretical analysis and the simulation about the security after symbol decision module, we get a conclusion that, comparing with the existing arti cial noise scheme, the random reference algorithm can be safer.