This paper investigates the covertness and reliability of unmanned aerial vehicle (UAV) relay communications assisted by a friendly jammer in the presence of co-channel interference (CCI). In the considered scenario, communication from a source to a destination is relayed by a UAV, while a malicious node attempts to monitor the transmission behaviors of both the source and the UAV. To enhance the system’s covertness, we propose a friendly jammer aided covert communication (FJACC) scheme, which leverages a friendly jammer to degrade the detection capability of the malicious monitoring node by sending artificial noise. We analyze the covertness and reliability of the FJACC scheme by deriving closed-form expressions of the outage probability and detection error probability under CCI, considering that the wireless channels are characterized by Nakagami-mfading for UAV-to-ground links and Rayleigh fading for terrestrial links. Numerical results confirm the superior covertness of the proposed FJACC scheme over traditional non-friendly jammer aided transmission scheme. Furthermore, increasing the number of co-channel interferers or their transmit power exhibits a dual effect: it enhances covertness at the expense of reliability.

This paper studies the physical-layer security (PLS) for an unmanned aerial vehicle (UAV)-aided non-orthogonal multiple access (NOMA) network, where transmissions from a base station (BS) to a trusted near user (TNU) and an untrusted far user (UFU) are assisted by an UAV relay in the face of multiple non-colluding external eavesdroppers (Es). The traditional strategies such as artificial noise-aided friendly jammer (TAN-FJ), artificial noise with non-friendly jammer (TAN-NFJ), and reconfigurable intelligent surface (RIS)-aided schemes fail to simultaneously guarantee the secrecy for both TNU and UFU, thus how to guarantee the PLS for NOMA users becomes an urgent issue to be solved. In this context, we propose an artificial noise (PAN) scheme aided with digital network coding (DNC). Specifically, the artificial noise signals generated by UAV are resorted to encrypt confidential signals with the assistance of DNC, which realizes one-time pad, thus the PLS of TNU and UFU can be ensured. We resort security-reliability tradeoff (SRT) as a metric to evaluate the PLS for our proposed PAN scheme. Hence, the exact and asymptotic expressions of outage probability (OP) and intercept probability (IP) are derived to quantify the reliability and security. Moreover, numerical simulations validate the correctness of our theoretical results and reveal that: 1) the PAN scheme enhances the SRT performance of near user compared to the TAN-FJ, TAN-NFJ, and RIS-aided schemes, while far user by the PAN scheme achieves almost the same SRT performance as the TAN-FJ scheme and significantly better performance than the TAN-NFJ and RIS-aided schemes, which indicates that the PAN scheme realizes the fairness of secrecy transmissions for NOMA users; 2) the SRT performance of TNU benefits from multiple antennas at BS and UAV, which has ignorable effect on the SRT performance of UFU; 3) the antenna number at UAV has more obvious impact on the SRT of TUN than the antenna number at BS.

As a novel category of beyond-diagonal (BD)-reconfigurable intelligent surfaces (RISs), the fully-connected (FC)-RIS represents an unprecedented advancement in RIS technology for wireless networks. To unlock the full potential of FC-RISs for physical-layer surveillance, this paper investigates a wireless surveillance system assisted by an aerial FC-RIS. Specifically, a legitimate monitoring station exploits an unmanned aerial vehicle (UAV)-borne FC-RIS to enhance the channels related to the monitoring station for facilitating its monitoring of a signal transmitted from a suspicious source. Meanwhile, this signal is decoded at the suspicious destination. Capitalizing on the unparalleled configuration flexibility of FC-RISs, we reduce the implementation complexity associated with jointly optimizing both antenna selection and RIS configuration. In particular, we opportunistically select a antenna at the legitimate multi-antenna monitoring station for signal reception without requiring iterative RIS optimization. Accordingly, several schemes are proposed, each differentiated by their specific selection criteria: 1) round-robin antenna selection and FC-RIS-aided (RAS-FR), 2) antenna selection combined with known FC-RIS reflecting channels (ASC-FRRC), 3) threshold-based antenna selection with known FC-RIS reflecting channels (TAS-FRRC). Considering that successful monitoring can be achieved when the monitoring channel conditions surpass those of the suspicious channels, we derive closed-form expressions for monitoring success probabilities (MSPs) of the RAS-FR, ASC-FRRC, and TAS-FRRC schemes, respectively. Furthermore, when part of small-scale channel state information (CSI) is unavailable due to the inherent non-cooperative nature of suspicious party, the surveillance performance can be further improved by optimizing the UAV-borne FC-RIS location. Numerical results not only validate our closed-form MSP analysis, but also verify that the considered UAV-borne FC-RIS aided surveillance system outperforms the conventional diagonal-RIS or terrestrial-RIS-assisted surveillance systems in terms of MSP. Moreover, compared with non-channel-aware schemes or antenna selection with CSI of all sub-links in cascaded links, the proposed AS-FRRC framework dramatically reduces the computational complexity for selection and RIS optimization without introducing performance loss. Additionally, the TAS-FRRC scheme can achieve a more favourable performance-complexity tradeoff than the RAS-FR and ASC-FRRC schemes.

This article studies the secrecy performance for a dual-hop nonorthogonal multiple access (NOMA)-aided unmanned aerial vehicle (UAV) network in the face of a passive untrusted far user (UFU). A new artificial noise (AN) scheme is proposed, where AN generated in the first hop can be used to encrypt confidential signals by XOR operation in the second hop. Based on the proposed AN (PAN) scheme, we analyze the exact and asymptotic outage probabilities (OPs) for both NOMA users and intercept probability (IP) for trusted near user (TNU). Simulation results verify the correctness of our theoretical analysis and demonstrate that the PAN scheme significantly improves the security for TNU at the cost of negligible reliability of UFU compared to the benchmark schemes.

This article investigates the physical-layer security (PLS) of a satellite-terrestrial integrated network (STIN) consisting of a satellite (S), a destination (D), and several friendly jammers in the presence of an eavesdropper (E). For improving PLS of the STIN, we propose three friendly jammer assisted communication schemes to help S securely send confidential information to D, i.e., the random jammer selection assisted communication (RJSC) scheme, the optimal jammer selection assisted communication (OJSC) scheme, and the multiple jammers assisted communication (MJC) scheme. For performance comparison, the nonjammer assisted communication (NJC) scheme is also presented. We analyze secrecy performance of the NJC, RJSC, OJSC, and MJC schemes by carrying out their closed-form secrecy outage probability (SOP) expressions, respectively. Numerical results unveil that the RJSC, OJSC, and MJC schemes exceed the NJC scheme with regard to their SOPs (e.g., as shown inFig. 2, when the signal-to-noise ratio is 25 dB, SOP of the STIN drops from 70% to 3%), and the OJSC scheme can get the best secrecy performance, showing the secrecy benefits of adopting friendly jammers assisted communication schemes against eavesdropping. Additionally, by increasing the number of friendly jammers, the secrecy performance of the OJSC and MJC schemes can be significantly enhanced, while that of the RJSC scheme remains unchanged.

This paper studies the optimization of reconfigurable intelligent surface (RIS)-assisted unmanned aerial vehicle (UAV)-enabled Internet of Things (IoT) communication networks. In this framework, a rotary-wing UAV is dispatched to collect data form multiple ground IoT devices, leveraging the signal enhancement capabilities of an RIS to improve communication efficiency. We aim to enhance the overall energy efficiency (EE), taking into account both the system transmission rate and UAV propulsion power consumption, while satisfying the UAV initial/final position constraints, transmit power limits, and RIS unit-modules phase shift requirements. To achieve this goal, we first establish a closed-form analytical model for the EE of RIS-assisted UAV-enabled IoT wireless systems. Based on this model, we subsequently formulate the EE maximization (EEM) problem by jointly optimizing time allocation, transmit power control, RIS reflection coefficients, and UAV trajectory. Due to the non-convex nature of the proposed EEM problem, we decompose it into three subproblems: 1) RIS phase shift optimization with given resource allocation and UAV trajectory, 2) time and power allocation under fixed UAV trajectory and RIS configuration, and 3) UAV trajectory design based on provided resource allocation and RIS parameters. Particularly, the optimal phase shift solution is derived in a closed form to ensure phase alignment of signals from multiple transmission paths, while the non-convex resource allocation subproblem is solved through introducing relaxation variables. For UAV trajectory design, a hybrid optimization strategy combing Dinkelbach’s method and successive convex approximation approach is adopted to transform the non-convex EE optimization problem into a convex one. Numerical simulations demonstrate that the proposed EEM scheme obtains superior EE performance compared to benchmarks with fixed trajectory or without RIS deployment.

For an uncrewed aerial vehicle (UAV)-aided energy-harvesting non-orthogonal multiple access (EH-NOMA) network, where an untrusted far user (UFU) overhears the confidential transmissions from base station (BS) to the trusted near user (TNU), how to ensure the security of TNU and achieve the reliability of UFU becomes an open issue. The traditional artificial noise (TAN) scheme just guarantees the security of TNU without focusing on the reliability of UFU, while the non-artificial noise (NAN) scheme only ensures the reliability of UFU but sacrifices the security of TNU. Thus, the TAN and NAN schemes are unable to guarantee the fairness between TNU and UFU. To this end, we employ digital network coding to encrypt confidential signals with artificial noise signals, and the proposed artificial noise (PAN) scheme not only protects the confidential transmissions of TNU but also guarantees the reliability of UFU. We use security-reliability tradeoff (SRT) and interference-reliability tradeoff (IRT) to evaluate the performance of TNU and UFU, respectively. Additionally, we derive the exact and asymptotic expressions of outage probabilities for both TNU and UFU, and the intercept probability for TNU. Numerical results verify the accuracy of our theoretical results and demonstrate that: 1) the SRT and IRT performance of the PAN scheme is better than that of the TAN and NAN schemes; 2) the PAN scheme achieves better secrecy for TNU compared to the TAN scheme. Meanwhile, the reliability of UFU in the PAN scheme is almost the same as the NAN scheme, indicating the PAN scheme simultaneously realizes the security of TNU and the reliability of UFU and the fairness of NOMA users is achieved by the PAN scheme.

In this article, we analyze the security and reliability tradeoff (SRT) performance of a unmanned aerial vehicle (UAV) relays assisted cognitive network consisting of a cognitive source (S), multiple cognitive UAV relays (Rs), a cognitive destination (D) in the face of an eavesdropper (E). We consider a practical scenario where mutual interference exists between the primary users and cognitive users. In order to protect the wireless transmission against the eavesdropping attack, we propose two UAV relay selection schemes, namely, noninterference aware relay selection (NIARS) scheme and interference aware relay selection (IARS) scheme. Specifically, in the NIARS scheme, a relay having the best instantaneous (R-D) link (spanning from Rs to D) is selected to forward message. By contrast, a relay maximizing the main channel capacity is selected, which relies not only on the channel state informations (CSIs) of main links but also on the CSIs of the interference links. For the purpose of comparison, we present the round robin (RR) scheme as a baseline. To evaluate the SRT performance, we derive the closed-form intercept probability (IP) and outage probability (OP) expressions for RR, NIARS, and IARS schemes under the impact of hardware impairments (HIs) over Nakagami-$m$fading channels. Numerical results show that the proposed IARS and NIARS schemes perform better than RR scheme in terms of SRT performance. Additionally, the HI at D has a negative impact on SRT performance, while HI at E has a positive impact on SRT performance.

This article investigates physical-layer security (PLS) for an energy-harvesting cognitive network with nonorthogonal multiple access (EHCN-NOMA), where a cognitive base station (CBS) communicates with two cognitive users named cognitive near user (CNU) and cognitive far user (CFU) by adopting the NOMA principle under an active or passive eavesdropper (Eve) attack. By means of energy harvesters, the CBS collects the radio frequency energy from the primary source (PS) by a time-switching protocol; meanwhile, the cognitive transmit power is limited by the interference threshold of primary destination (PD) to guarantee the Quality of Service (QoS) of primary transmissions. To evaluate the impact of active and/or passive eavesdroppings on system performance, we derive closed-form expressions in terms of outage probabilities (OPs), intercept probabilities (IPs), as well as effective secrecy throughputs (ESTs). The numerical results verify the correctness of our theoretical derivations and confirm that there exists a tradeoff between security and reliability for the EHCN-NOMA transmissions. Moreover, the EST improvement depends on the competition between security and reliability. Furthermore, the maximum EST performance can be achieved for both eavesdropping scenarios by adjusting the time allocation between that of the energy transfer phase and the information transmission phase.

This paper investigates the physical layer security for a distributed antenna system, where a base station (BS) equipped with multiple distributed antennas transmits signals to a legitimate user (U) through an opportunistic antenna. Meanwhile, multiple non-colluding eavesdroppers (Es) attempt to tap the information transmission between the BS and U. To enhance the physical layer security, a friendly jammer (J) is employed to create a potential interference to Es by emitting artificial noise. However, since U is not aware of the information sent by J, it can be affected by the interference. In this context, this paper proposes adaptive jamming (AJ) scheme and interference cancellation (IC) scheme to mitigate the interference’s impact on U and consequently improve secrecy performance. Specifically, the AJ scheme avoids interference from having a negative effect on the system security by setting an interference threshold, activating the jammer only when the interference to U is below the threshold value. By contrast, the IC scheme designs an advanced special signal to eliminate the interference from J to U. For comparison, we present conventional non-jammer (NJ) scheme as a benchmark. Exact and asymptotic secrecy outage probability expressions for NJ, AJ, and IC schemes are derived over Nakagami-mfading channels. Numerical results show that the proposed AJ and IC schemes perform better than NJ scheme in terms of secrecy outage probability. Additionally, the physical layer security of all schemes can be improved by increasing the number of distributed antennas.

Abstract In this paper, the secrecy performance in a MIMO cognitive radio (CR) relay network with energy harvesting (EH) and transmit antenna selection/maximal ratio combining (TAS/MRC) is invstigated, where the DF relaying protocol and multiple colluding passive eavesdroppers are considered. To improve the security of wireless transmission, two antenna selection schemes are proposed, namely, the optimal transmit antenna selection (OTAS) scheme and suboptimal transmit antenna selection (STAS) scheme. For the purpose of comparison, the space‐time transmission (STT) scheme is introduced as a baseline. The exact and asymptotic closed‐form secrecy outage probability (SOP) expressions for OTAS, STAS and STT schemes are derived over Rayleigh fading channels. An extension of the TAS framework to an artificial noise (AN) aided MIMO network is further presented and an AN aided transmit antenna selection (AN‐TAS) scheme is proposed, in which the unselected antennas at R are used to emit AN for interfering with Es. Numerical results show that the OTAS and STAS schemes perform better than STT scheme in terms of SOP. Meanwhile, the SOP of AN‐TAS scheme is much smaller than that of OTAS, STAS and STT schemes in the high SNR region, indicating the benefit of applying AN in MIMO network.

Timely status updates are significant for some critical Internet of Things applications. However, due to the transmission delay of status packets, the status information arriving at the destination is not fresh enough. Especially, when the transmission delay is large, the destination cannot know the current status of the target well. In this article, the prediction technology is introduced into status update systems to solve this problem. First, we study a prediction-based status update scheme for machine-type communications (MTCs) and use the recently proposed metric, Age of Information (AoI), to characterize the status update performance. With the scarce spectrum resources, an MTC device (MTCD), as an unlicensed user, adopts the overlay mode to reuse the spectrum resource of the primary user and sends status packets to the central controller (CC). Then, we consider prediction errors and packet decoding errors to characterize the reliability of MTC, analyze the status update process in the prediction-based scheme, and derive the closed-form expression of the average AoI. Finally, in the proposed prediction-based scheme, we analyze the tradeoff between the status update performance and energy consumption and design an optimization algorithm to improve the status update performance by adjusting the transmit power and prediction horizon of the MTCD. Simulation results verify the correctness of the theoretical analysis and show that the proposed scheme can help the MTCD effectively improve the status update performance.

This paper investigates the secrecy performance of a spectrum sharing network, where${N}$legitimate source-destination pairs orderly access the shared spectrum for communication, while an eavesdropper (E) attempts to tap the legitimate information transmission. To improve the physical layer security, we propose two jamming strategies that can intelligently switch between jamming and non-jamming, namely, suboptimal jammer selection (SJS) scheme and optimal jammer selection (OJS) scheme. Specifically, when a user pair is assigned to access the shared spectrum, another source is chosen as a friendly jammer in order to create intentional interference at E. For the purpose of comparison, we present the non-jammer selection (NJS) scheme as a benchmark. Analytical closed-form secrecy outage probability expressions of NJS, SJS and OJS schemes are derived over Nakagami-${m}$fading channels. We further present an asymptotic secrecy outage probability analysis to evaluate the secrecy diversity gain performance of NJS, SJS and OJS schemes. Numerical results show that the secrecy outage probability performance of OJS scheme is better than SJS and NJS schemes in the low average channel power gain${\mathop \Omega \nolimits _{D} }$region. Furthermore, the secrecy outage probabilities of NJS as well as SJS and OJS schemes converge to each other with the increase of${\mathop \Omega \nolimits _{D} }$, due to the fact that the OJS and SJS scheme will switch to NJS scheme when${\mathop \Omega \nolimits _{D} }$tends to infinity.

In this paper, we investigate the physical layer security for a cognitive multiuser network which is composed of multiple cognitive sources, a cognitive destination and an eavesdropper under the joint impact of hardware impairments (HIs) and channel estimation errors (CEEs). We consider a practical scenario where mutual interference exists between the primary users and cognitive users. To achieve high physical layer security with low implementation complexity, we propose three pure user scheduling schemes, namely, selection combining (SC) scheme, threshold-based switched diversity (tSD) scheme and switch-and-examine combining with post-selection (SECps) scheme. To further improve physical layer security, we present an extension of our SC framework to a jammer aided multiuser network and propose a jammer aided SC (JSC) scheme. We derive the closed-form intercept probability (IP), outage probability (OP) and effective secrecy throughput (EST) expressions for SC, tSD, SECps and JSC schemes over Nakagami-$m$channels to analyze the system performance. Numerical results show that among the three pure multiuser scheduling schemes, the SC scheme achieves the best secrecy performance with the highest complexity, the SECps scheme obtains the worst secrecy performance with the lowest complexity. In addition, the secrecy performance of JSC scheme is better than that of SC scheme in the high SNR region.

This paper investigates an intelligent reflecting surface (IRS) aided secure wireless powered communication network (WPCN), where a transmitter first harvests energy from a power station (PS), and then uses the collected energy to transmit information to multiple internet of things (IoT) devices in the form of multicast in the presence of multiple eavesdroppers. An IRS is deployed to enhance the efficiency of wireless energy transfer (WET) and secure wireless information transfer (WIT). Considering that the PS and transmitter belong to different service providers, we model this energy interaction through a Stackelberg game and propose an IRS-aided energy trading and secure communication (IRS-ETSC) scheme, in which the transmitter needs to pay an energy price as an incentive for the PS energy service. Specifically, the transmitter as the leader can control the energy price, WET time, two-stage phase shifts, and beamforming vector, while the PS as the follower can adjust the transmit power. To solve the non-convex leader game problem, we propose a two-step approach to decompose the original problem into two subproblems. The first subproblem can be solved independently by an efficient alternating optimization (AO) based algorithm, in which the closed-form optimal beamforming vector and energy phase shifts are alternately optimized. Then, the second subproblem is relaxed by semidefinite relaxation (SDR) and solved by an iterative algorithm based on block coordinate descent (BCD), where the optimal energy price, optimal WET time, and suboptimal information phase shifts can be obtained by golden section method and successive convex approximation (SCA) respectively. Both subproblems can converge to a stationary point. Numerical results show that compared with the traditional non-IRS scheme, the proposed IRS-ETSC scheme achieves utility improvement for both the PS and transmitter.

In this paper, we investigate the physical-layer security in an energy-harvesting (EH) multiuser network with the help of a friendly jammer (J), where multiple eavesdroppers are considered to tap the information transmission from users (Us) to base station (BS). In this system, a power beacon (PB) transmits radio frequency (RF) signals to Us for charging. In order to enhance the security of wireless transmission, we propose non-energy-aware multiuser scheduling (NEAMUS) scheme and energy-aware multiuser scheduling (EAMUS) scheme. For the purpose of comparison, we introduce conventional round robin multiuser scheduling (CRRMUS) scheme. The closed-form outage probability (OP) and intercept probability (IP) expressions of NEAMUS, EAMUS, and CRRMUS schemes are derived over Rayleigh fading channels. Additionally, we analyze the security-reliability tradeoff (SRT) of NEAMUS, EAMUS, and CRRMUS schemes in terms of OP and IP. Numerical results show that the proposed EAMUS scheme is superior to the CRRMUS scheme and NEAMUS scheme in terms of SRT, demonstrating the advantage of the proposed EAMUS scheme in improving the physical-layer security and reliability. Moreover, SRT performance of NEAMUS and EAMUS schemes can also be improved by increasing the number of users.

In this paper, we investigate the security and reliability trade-off (SRT) for a wireless sensor network (WSN) which consists of one cluster head (CH), multiple users, and one eavesdropper (E), where the eavesdropper attempts to tap the confidential transmission between multiple users and CH. We first present two multiuser scheduling schemes, namely the selection combining (SC) scheme and the switch-and-examine combining with post-selection (SECps) scheme to enhance physical-layer security (PLS) of the WSN system. For comparison purposes, the round-robin scheduling (RRS) scheme is also considered as a baseline. Then, we analyze the SRT of the RRS, SECps, and SC schemes by deriving their closed-form outage and intercept probability expressions under the joint impact of hardware impairment (HI) and co-channel interference (CCI). And, secrecy diversity analysis of the three schemes is also carried out. Numerical results show that the SC and SECps scheme outperform the RRS scheme in terms of the SRT performance, where the SC scheme can achieve the best SRT performance at the cost of an increased channel estimation complexity. Moreover, a trade-off between the security and reliability can be achieved for each of the RRS, SECps, and SC schemes by adjusting the overall data rate and signal-to-noise ratio (SNR).

In this study, the authors investigate the security and reliability trade‐off (SRT) performance of a multiuser wireless network, where an eavesdropper attempts to overhear the confidential transmissions between a base station and multiple users under the impact of co‐channel interference. To enhance the SRT performance of the network, the authors propose two joint user and jammer selection schemes, namely the joint optimal user and random jammer selection (JOU‐RJS) scheme and the joint optimal user and optimal jammer selection (JOU‐OJS) scheme. For SRT performance comparison purposes, the traditional multiuser scheduling (TMUS) scheme is also considered. The authors derive closed‐form outage and intercept probability expressions for the JOU‐RJS and JOUOJS schemes. Simulation results show that the SRTs of both JOU‐RJS and JOU‐OJS schemes are better than that of the TMUS scheme, where JOU‐OJS achieves the best SRT performance. Additionally, this study also shows that an expected outage or intercept probability of the TMUS, JOU‐RJS, and JOU‐OJS schemes can be achieved by giving an appropriate overall rate. Finally, the sum of the outage and intercept probability can be minimised through an optimal power allocation between the selected user and friendly jammer for the proposed JOU‐RJS and JOU‐OJS.

In this paper, we analyze the secrecy outage probability and computation overhead of a multi-user multi-eavesdropper wireless system which is composed of one cluster head (CH) transmitting to multiple users, while multiple eavesdroppers attempt to tap the transmission from CH to multiple users in the presence of co-channel interference (CCI). To achieve high security and low computation overhead, we present two multi-user scheduling schemes, namely, the switch-and-examine combining with post-selection user scheduling (SECpsUS) scheme and the selection combining-based user scheduling (SCbUS) scheme. For the purpose of comparison, the conventional round-robin scheduling (RRS) is also considered as a benchmark scheme. Furthermore, we derive closed-form secrecy outage probability expressions and analyze computation overheads for the conventional RRS, SCbUS, and SECpsUS schemes. Numerical results and Monte Carlo simulations are provided to verify the correctness of our theoretical secrecy outage analysis and to demonstrate the effect of CCI on the system performance. It is shown that the SECpsUS and SCbUS schemes outperform the conventional RRS scheme in terms of their secrecy outage probabilities, where SCbUS achieves the best secrecy outage performance but at cost of the highest computation overhead, while the conventional RRS scheme has no computation overhead with the worst secrecy performance. Moreover, a flexible tradeoff between the secrecy outage performance and computation overhead can be achieved by the proposed SECpsUS scheme by adjusting a so-called switching threshold. In addition, as the number of users increases, the secrecy outage performance of the SECpsUS and SCbUS is improved significantly, whereas no secrecy benefit is achieved by the conventional RRS scheme.

In this paper, we study a multiuser uplink network consisting of one base station (BS), multiple users and one eavesdropper (E), where the users are intended to transmit their confidential messages to BS, while the eavesdropper attempts to tap their transmissions. To improve the transmission secrecy, we propose two friendly jammer selection-aided multiuser scheduling schemes, namely, the random jammer selection-aided multiuser scheduling (RJS-MUS) without knowing the eavesdropper's channel state information (CSI) and the optimal jammer selection-aided multiuser scheduling (OJS-MUS), where the CSIs of eavesdropper are available. For comparison purposes, the conventional non-jammer selection-aided multiuser scheduling (NJS-MUS) scheme is considered as a benchmark. We derive exact and asymptotic closed-form secrecy outage probability expressions for the conventional NJS-MUS as well as proposed RJS-MUS and OJS-MUS schemes. The numerical results show that the proposed RJS-MUS and OJS-MUS schemes with equal power allocation between the selected friendly jammer and scheduled user perform worse than the conventional NJS-MUS approach in terms of the secrecy outage probability in the low signal-to-noise ratio (SNR) region. As the SNR increases, the secrecy outage performance of RJS-MUS and OJS-MUS schemes substantially improves, which is, in turn, better than that of conventional NJS-MUS approach. Moreover, the secrecy advantage of RJS-MUS and OJS-MUS over NJS-MUS becomes more significant with an increasing SNR. Also, it is shown that for both the RJS-MUS and OJS-MUS schemes, a better secrecy performance can be achieved through an optimal power allocation (OPA) between the scheduled user and friendly jammer. In addition, the proposed RJS-MUS and OJS-MUS schemes with OPA strictly outperform the conventional NJS-MUS approach in terms of the secrecy outage probability.

This paper analyzes the secrecy outage probability of a cellular downlink system which consists of multiple users, one base station (BS), and one eavesdropper in the presence of co-channel interferers, where the BS transmits its signals to users which are distributed according to a Poisson point process with a fixed density, while the eavesdropper attempts to tap the transmission from the BS to the users. To enhance the transmission security against eavesdropping, we propose two multiuser scheduling schemes, namely, the partial channel state information (CSI) aided user scheduling (PCSI-US) scheme where only the CSIs of users are available without knowing the co-channel interferers' CSIs and the full CSI aided user scheduling (FCSI-US) scheme which requires the CSIs of both users and interferers. For comparison purposes, the conventional round-robin scheduling scheme is also considered as a baseline. We derive closed-form expressions of the secrecy outage probability for the proposed PCSI-US and FCSI-US as well as conventional round-robin scheduling schemes in co-channel interference (CCI) environments. Numerical results show that the proposed FCSI-US and PCSI-US schemes outperform the conventional round-robin scheduling in terms of their secrecy outage probabilities, where FCSI-US achieves the best secrecy outage performance in CCI environments. It is also demonstrated that increasing the mean number of users has a marginal effect on the secrecy performance of conventional round-robin scheduling, which can significantly decrease the secrecy outage probabilities of PCSI-US and FCSI-US schemes. This further validates the secrecy effectiveness of the proposed user scheduling methods in terms of combating the CCI.

Adaptive modulation selection plays an important role in wireless communication and wireless sensor network since the wireless channel condition is time-varying due to some factors e.g. path-loss and multipath propagation. Therefore, using one modulation type cannot fulfill all the channel conditions and receivers. Conventional adaptive modulation selection schemes are based on packet loss statistics or SNR measurement. However, all of these methods are indirect approaches because they utilize the packet loss rate or SNR information to estimate the BER approximately and the modulation selection that based on these approximate results is not exactly. Therefore, in this paper, we propose to utilize the error estimating code (EEC) which directly represents the BER information to realize a new adaptive modulation selection scheme. Compared to traditional adaptive modulation type selection schemes, our scheme needs only a small amount of overhead and very little computational cost for the same performance.

Distributed Compressed Video Sensing (DCVS) has developed as one of the efficient solutions that guarantee low complexity video compression. In this paper, a novel DCVS algorithm with unequal protection of the video signal's elements is proposed. The new algorithm utilizes not only the sparsity and probability distribution of the video signal but also its particular unequal significance feature. Based on this feature, we design the structured irregular low-density sensing matrix to sample the signal. From the analysis and simulation results, it is confirmed that our method has higher recovery quality than the conventional Bayesian Compressed Sensing (CS) using Belief Propagation (BP). Moreover, the excellent noise-resilience of BP is preserved in our algorithm comparing to the DCVS schemes using optimization recovery.