Hybrid Outage Probability Research Articles

Multiuser-scheduling and resource allocation using max-min technique in wireless powered communication networks

Wireless <span>powered communication network (WPCN) is a promising research area for improving network security and speed. The transmission power of the source during the uplink functions as a random variable in WPCN due to the intrinsic power transfer process, whereas it is a constant in typical cooperative networks, culminating in the signal to noise ratio of the source-access point and all the source-relay-access point being mutually correlated. As a result of the massive increase in communication devices powered by battery, the goal of prolonging their life is critical. To get the most throughput in the shortest amount of time, the best uplink and downlink time allocations were calculated. For high throughput and secrecy performance, the proportional max-min fairness algorithm was used in this paper for secure communication in hybrid relays integrated with WPCN. This method allows for multi-user scheduling with optimum targets to provide reliable hybrid outage probability, secrecy outage probability, and energy outage probability. Efficacy of the proposed system was demonstrated regarding throughput, outage probability, and confidentiality. The performance of the model was compared to that of various energy harvesting models like random user scheduling, best user scheduling, and several others, and was found to outperform them for secure transmission.</span>

Q-Learning-Based Power Allocation for Secure Wireless Communication in UAV-Aided Relay Network

Unmanned aerial vehicle (UAV)-aided wireless relay networks are at risk of eavesdropping activities due to their open nature. In this paper, we study the security of a UAV-aided selective relaying wireless network in which $N$ UAVs are employed as decode-and-forward (DF) relays linking a ground base station (BS) with $L$ legitimate users on the ground in the presence of a passive eavesdropper ( $Eave$ ). Direct links between the ground BS and both the ground users and the eavesdropper are assumed to be blocked. The ground-to-air and air-to-ground channels are assumed to follow Rician fading model with opportunistic scheduling scheme for UAVs and users selection. In order to secure data transmissions against such an interception action, the UAV of the worst UAV-selected user link transmits a jamming artificial noise (AN) signal to degrade $Eave$ ability in decoding the confidential information successfully. The transmission outage probability, intercept probability, and hybrid outage probability are derived and analyzed. Due to the heavy computation burden raised by increasing the number of UAVs and users as well as the difficulty in estimating the instantaneous channel state information (CSI), existing traditional optimization methods are not highly efficient in solving the considered power allocation problem. Therefore, we propose a dynamic power control scheme based on Q-learning algorithm combined with statistical CSI where the hybrid outage probability is minimized. Simulation results show that the proposed algorithm efficiently reduces the hybrid outage probability with a noticeable reduction in the computational time.

Secure Multiuser Scheduling for Hybrid Relay-Assisted Wireless Powered Cooperative Communication Networks With Full-Duplex Destination-Based Jamming

In this paper, we investigate secure communication in a hybrid relay (HR)-assisted wireless powered cooperative communication network (WPCCN), where an eavesdropper tries to intercept the data transmitted by a source user and the HR simultaneously. The HR has the ability to wireless powered the energy-constrained multiple users in the downlink and to relay the received confidential information in the uplink. In particular, the full-duplex destination-based jamming (FD-DBJ) strategy is exploited to improve the secrecy performance. Moreover, in order to conduct effective secure communications, we design two multiuser scheduling schemes, i.e., random user selection (RUS), and best user selection (BUS) based on the main channel quality. In order to evaluate the secrecy performance, we analytically derive the energy outage probability (EOP), the secrecy outage probability (SOP), and the hybrid outage probability (HOP), respectively. As such, we formulate the secrecy throughput (ST) maximization problem to optimize the predetermined transmission rate. Our analysis and numerical results reveal that: 1) The BUS scheme has better security performance. 2) Both of the energy conversion efficiency and the number of users have a positive effect on secrecy performance. 3) The FD-DBJ scheme is an effective method to achieve secure communications. 4) The time-switching factor and predetermined transmission rate have a crucial influence on the secrecy performance, which should be considered carefully in system design.

Insecure Region Around Receiver for Downlink Transmissions With Randomly Located Active Eavesdropper

This letter studies a challenging physical layer security problem for downlink transmissions when facing a randomly located active eavesdropper. Artificial noise (AN) is transmitted in conjunction with a confidential signal to defend against the eavesdropper. However, the active eavesdropper with changeable location can perform both eavesdropping and malicious jamming simultaneously, which yields the secrecy outage probability as an unsuitable performance metric. In this case, a more appropriate metric, the hybrid outage probability which takes both the transmission outage probability and secrecy outage probability into consideration, is derived to evaluate the security performance. Based on the hybrid outage probability, we can optimize the power allocation to the confidential and AN signals. Furthermore, an insecure region is defined to restrict the location of the eavesdropper. Additionally, the insecure range is defined as a valuable indicator of a circular insecure region. Simulation results are provided to depict the region around receiver is insecure.

Defending Against Randomly Located Eavesdroppers by Establishing a Protecting Region.

The security problem in wireless sensor networks faces severe challenges, due to the openness of the sensor network channel and the mobility and diversity of the terminals. When facing randomly located eavesdroppers, the situation is much more complex. This paper studies the security performance of a wireless sensor network where randomly located passive and active eavesdroppers are both considered. Compared to a passive eavesdropper, an active eavesdropper can perform both eavesdropping and malicious jamming simultaneously in a wireless sensor network. Based on beamforming and artificial noise (AN), we propose a practical way to defend against the eavesdropper by establishing a protecting region. An appropriate metric, the hybrid outage probability, which takes both the transmission outage probability and the secrecy outage probability into consideration, is utilized to evaluate the security performance. In addition, the concept of safe transmission range is defined to evaluate the security performance. Simulation results are provided to depict the insecure region and verify the harm of the active eavesdropper to the transmission in the wireless sensor network.

Secure Communication via Multiple RF-EH Untrusted Relays With Finite Energy Storage

This article investigates secure communication between a source and a destination via multiple radio frequency (RF) energy harvesting (EH) relays, in which the RF-EH relays are untrusted and apply the amplify-and-forward policy. On the one hand, to prevent the untrusted relays from eavesdropping the confidential information, the destination-aided jamming is employed, in which the destination emits jamming signal to interfere the relays while the source transmits information signal. On the other hand, the power splitting (PS) policy is adopted at the relays to harvest energy and process information, in which every relay has a finite energy storage to accumulate the energy harvested from the source’s information signal and destination’s jamming signal. To achieve energy-efficient and fully distributed implementation, we propose an energy-aware distributed beamforming (EADB) scheme, in which each relay only needs local information to decide whether to assist the source-destination communication. To evaluate the secrecy performance of the EADB scheme, the charging and discharging behaviors of the relays’ energy storage are first tracked using the Markov chain. On this basis, we derive analytical expressions for the hybrid outage probability (HOP) and secure energy efficiency (SEE) of the considered network. Finally, numerical results show that the EADB scheme has a better secrecy performance than the existing scheme. In addition, despite the curiousness of the untrusted relays, deploying more relays and increasing their energy storage capacity can enhance the security of the considered network.

Secure Wireless Powered Cooperative Communication Networks With Finite Energy Storage

This paper investigates secure transmission in a wireless powered cooperative communication network (WPCCN) over Nakagami- $m$ fading channels, where multiple intermediate energy harvesting (EH) nodes with finite energy storage are deployed to assist the secure transmission between source and destination in the presence of an eavesdropper. Specifically, the intermediate EH nodes first harvest and accumulate energy from the source's signal and then forward the confidential signal or emit jamming signal to interfere the eavesdropper according to actual requirements. In order to exploit the intermediate EH nodes for secure improvement, considering both energy storage status and channel gains, three relay-and-jammer selection schemes at the intermediate nodes are proposed, namely: energy threshold based best-relay and random-jammer (ETBR), energy threshold based random-relay and best-jammer (ETRB), and energy threshold based best-relay and best-jammer (ETBB). For understanding the impact of critical parameters on the secrecy performance, we first capture the evolution of the EH nodes’ storages using finite-state Markov chain (FSMC) and then derive the analytical expressions for hybrid outage probability (HOP) and secrecy throughput (ST). Furthermore, numerical results demonstrate that our proposed selection schemes outperform the existing schemes (bR-rJ, rR-bJ, bR-bJ) due to the consideration of energy accumulation and storage status. In addition, there is a suitable value of the energy threshold for each proposed scheme to achieve the optimal secrecy performance.

Safeguarding UAV Communications Against Full-Duplex Active Eavesdropper

Unmanned aerial vehicle (UAV) wireless communication has recently been recognized to be inevitable and prevalent in the fifth-generation (5G) wireless networks. In this paper, we propose a secure transmission scheme for a wiretap channel, where a source communicates with a legitimate UAV in the presence of an eavesdropper. We consider the full-duplex active eavesdropper, which performs both eavesdropping and malicious jamming simultaneously. The source transmits artificial noise (AN) signals, in addition to information signals, to confuse this eavesdropper. By considering the ground-to-UAV channel model, we analyze the hybrid outage probability, which takes both the transmission outage probability and the secrecy outage probability into consideration. We further provide the asymptotic hybrid outage probability in a more compact form, where both the transmit power at the source and the jamming power at the eavesdropper become large with a fixed ratio. Through the analysis and the numerical results, we determine the optimal power allocation factor between information signals and AN signals as well as the operating height of UAV that minimize the hybrid outage probability. We also provide the most harmful antenna configuration of the eavesdropper to the UAV communications, and this paper can be a useful framework for the design of confidential UAV communication system.

Full Duplex AF and DF Relaying Under Channel Estimation Errors for V2V Communications

In this paper, we investigate the outage performance of full-duplex (FD) and half-duplex (HD) vehicle to vehicle (V2V) networks. We consider two vehicular communication scenarios with the assistance of roadside unit (RSU), i.e., RSU-to-vehicle-to-vehicle (RVV) and vehicle-to-RSU-to- vehicle (VRV) scenarios. In particular, we analyze the outage performance of vehicular networks with the amplify-and-forward (AF) and decode-and-forward (DF) protocols under the effect of residual loop-back-interference (LBI) and channel estimation errors. For RVV scenario, the upper bounds for the outage probability of the AF based FD and HD relaying over double Rayleigh fading channels are derived. Moreover, we derive the approximate closed form expressions for the outage probability of the DF based FD and HD relaying protocol over Rayleigh fading channels; For VRV scenario, the exact closed-form expressions for the outage probability of the AF and DF relaying protocols are presented in case of FD and HD modes. Furthermore, we derive the approximate closed-form expressions for the outage probability of hybrid FD/HD mode on AF and DF relaying protocols. The numerical and simulation results corroborate our theoretical ones and quantify the impact of the data rates, channel estimation errors and the residual LBI on the system performance.

Optimal Transmission With Artificial Noise in MISOME Wiretap Channels

We investigate the optimal physical-layer secure transmission with artificial noise in the wiretap channel with N antennas at the transmitter, a single antenna at the receiver, and M antennas at the eavesdropper. We analyze the performance and determine the optimal transmission parameters for two distinct schemes: 1) an on-off transmission scheme and 2) an adaptive transmission scheme. For the on-off transmission scheme, where a channel-realization-independent secrecy rate is used for all transmission periods, we derive closed-form expressions for the secure transmission probability, the hybrid outage probability, and the effective secrecy throughput. For the adaptive transmission scheme, where a channel-realization-dependent secrecy rate is used for each transmission period, we derive closed-form expressions for the secure transmission probability, the secrecy outage probability, and the effective secrecy throughput. Using these closed-form expressions, we determine the optimal power allocation between information signals and artificial noise signals for both schemes to maximize the secure transmission probability. We also determine the optimal secrecy rate for both schemes to maximize the effective secrecy throughput. We explicitly examine the impact of N and M on the optimal power allocation and the optimal secrecy rate. Finally, we demonstrate the performance gain of the adaptive transmission scheme over the on-off transmission scheme.

Artificial Noise: Transmission Optimization in Multi-Input Single-Output Wiretap Channels

We analyze and optimize the secrecy performance of artificial noise (AN) in multi-input single-output wiretap channels with multiple antennas at the transmitter and a single antenna at the receiver and the eavesdropper. We consider two transmission schemes: 1) an on-off transmission scheme with a constant secrecy rate for all transmission periods, and 2) an adaptive transmission scheme with a varying secrecy rate during each transmission period. For the on-off transmission scheme, an easy-to-compute expression is derived for the hybrid outage probability, which allows us to evaluate the transmission outage probability and the secrecy outage probability. For the adaptive transmission scheme where transmission outage does not occur, we derive a closed-form expression for the secrecy outage probability. Using these expressions, we determine the optimal power allocation between the information signal and the AN signal and also determine the optimal secrecy rate such that the effective secrecy throughput is maximized for both transmission schemes. We show that the maximum effective secrecy throughput requires more power to be allocated to the AN signal when the quality of the transmitter-receiver channel or the transmitter-eavesdropper channel improves. We also show that both transmission schemes achieve a higher maximum effective secrecy throughput while incurring a lower secrecy outage probability than existing schemes.