Outage Probability Of Network Research Articles

Secrecy outage analysis in a hybrid cognitive relay network with energy harvesting

SummaryIn this paper, we investigate the physical layer security of a hybrid cognitive relay network using an energy harvesting relay in presence of an eavesdropper. In the hybrid scheme, a secondary user (SU) as well as a cognitive relay works either in underlay or in overlay mode. In underlay, the transmit power of the SU as well as the relay is limited by the maximum acceptable interference at primary user (PU) receiver as required by an outage constraint of PU, a quality of service for PU. The secondary network consists of a decode and forward relay that harvests energy from radio frequency signal of secondary transmitter as well as PU transmitter to assist the SU in forwarding the information signal to the destination. A time switching relaying protocol is used at the relay. We evaluate the secrecy outage probability of secondary relay network assuming that channel state information of the interfering links from both the SU and relay transmitter to PU receiver is imperfect. Our results reveal the impact of imperfect channel state information, energy harvesting time, tolerable interference threshold, and PU outage constraint on the secrecy outage probability of SU.

Influence of Channel Information Imperfection on Outage Probability of Cooperative Cognitive Networks with Partial Relay Selection

Influence of channel information imperfection on outage probability of cooperative cognitive networks with partial relay selection over independent and non-identical Rayleigh fading channels and under peak transmit power constraint and interference power constraint is thoroughly analyzed in this paper. To eliminate time-consuming simulations, we propose both exact and asymptotic outage probability expressions in closed-form, which facilitate in quickly evaluating this influence in key operation parameters and acquiring useful insights into performance limits. For comparison, we also derive similar expressions for two benchmark communications schemes in cognitive radio networks, namely direct transmission and dual-hop communications with partial relay selection. Various results show considerable system performance deterioration and performance saturation owing to channel information imperfection, and superiority of cooperative communications to direct transmission and dual-hop communications.

Transmission Capacity of Clustered Ad Hoc Networks With Virtual Antenna Array

In this paper, a clustered ad hoc network with virtual antenna array is investigated. Considering the random distribution of the nodes in ad hoc networks, the nodes are modeled as a Poisson point process (PPP). Different from prior analyses, interference in the ad hoc network is taken into account. Outage probability and transmission capacity of a single-hop network are first derived, and the accuracy of the analytical results is verified by simulation results. It is found that the outage probability decays as $\Theta(\lambda_c^{-(2/\alpha)})$ , where $\lambda_c$ is the intensity of potential cooperative nodes, and $\alpha$ is the path-loss exponent. That is, the outage probability obeys an inverse- $\mbox{2}/\alpha$ law with the intensity of cooperative nodes $\lambda_c$ . Moreover, there exists a unique optimal packet transmission rate to maximize the transmission capacity, and the optimal rate is shown to be within a specific interval that is only related to a path-loss exponent. Finally, the analysis of transmission capacity is extended to a multihop network. The results show that multihop transmission is not beneficial to the transmission capacity, but it does improve the outage performance. The analytical results are meaningful and can provide theoretical guidance on the network design.

Performance Evaluation of Amplify-Quantize and Forward Protocol for Multi-relay Cooperative Networks

Fading which occurs during the process of information transmission can significantly degrade system performance. The cooperative communication system is a well-known diversity technique that is able to mitigate the impact of fading. The relay protocol is the core of such systems. In this research, we evaluated the performance of amplify-quantize and forward (AQF) relays using a hybrid of two protocols: amplify-and-forward (AF) and quantize-and-forward (QF). The outage probability and throughput of multi-relay cooperative networks were derived, and computer simulation was used to evaluate the impact of a number of parameters on the performance of the AQF relay for multi-relay cooperative networks. We also compared the outage probability and throughput of AF, QF, and direct link networks. The outage probability of AQF decreased as the number of relays increased, whereas the throughput increased. We demonstrated that amplification values and quantization levels have a significant impact on the performance of AQF multi-relay networks. Overall, AQF performed better in terms of outage probability and throughput than AF and QF, for multi-relay cooperative networks.

Outage Probability of Cognitive Selective DF Relay Networks with Multiple Primary Nodes and Heterogenous Non-Identical Constraints

Outage probability analysis of cognitive selective DF relay networks with selection combining technique taking into account all the following issues is important: multiple SU relays, multiple PUs, non-identical independent Rayleigh fading channels, non-identical interference power limits of PUs, non-identical maximum transmission power limits of SUs, and non-identical noise powers in signals. However, no existing works solve this task exactly. In this paper, to overcome the complexity in analyzing such non-identical-parameter networks directly, we conduct the analysis in two steps indirectly. In the first step, we obtain outage probability expressions of identical-parameter networks. Then in the second step, we propose a method for transforming a non-identical-parameter network into a new identical-parameter network, meanwhile guaranteeing that the distributions of end-to-end signal to noise ratio of the two networks before and after the transformation are identical. Thus the outage probability of the identical-parameter network can be regarded as outage probability of the corresponding non-identical-parameter network. Numerical simulations validate our analysis results and confirm the feasibility of the two-step indirect analysis approach.

An Analysis on Secure Communication in Millimeter/Micro-Wave Hybrid Networks

The secrecy outage of millimeter wave (mmWave) overlaid micro-wave ( $\mu $ Wave) networks under the impact of blockages is analyzed, and closed form as well as integral expressions are provided. Specifically, using a network model that accounts for uncertainties both in node locations and blockages, we characterize the conditional connection outage probability and the secrecy outage probability of hybrid networks with multiple eavesdroppers under basic factors, such as density of eavesdropping nodes, antenna gain, and blockage density. The upper and lower bounds of the conditional secrecy outage probability for both the line-of-sight and non-line-of-sight links are derived. As a desirable side effect, certain factors, such as blockages and reduced antenna gain, can decrease the secrecy outage probability in mmWave networks. This can be considered as a tradeoff between outage capacity and secrecy outage capacity with respect to blockages. Hence, blockages that have been proved to be detrimental to achieving higher data rates in mmWave systems, can be helpful for systems with secrecy constraints. Finally, we have shown the coexistence of mmWave and $\mu $ Wave networks from a secrecy perspective.

Cooperative amplify‐and‐forward partial relay selection with outdated channel information in spectrum‐sharing systems

AbstractRecently, cooperative relaying techniques have been integrated into spectrum‐sharing systems in an effort to yield higher spectral efficiency. Many investigations on such systems have assumed that the channel state information between the secondary transmitter and primary receiver used to calculate the maximum allowable transmit secondary user transmit power to limit the interference is known to be perfect. However, because of feedback delay from the primary receiver or the time‐varying properties of the channel, the channel information may be outdated, which is an important scenario to cognitive radio systems. In this paper, we investigate the impact of outdated channel state information for relay selection on the performance of partial relay selection with amplify and forward in underlay spectrum‐sharing systems. We begin by deriving a closed‐form expression for the outage probability of the secondary network in a Rayleigh fading channel along with peak received interference power constraint and maximum allowable secondary user transmit power. We also provide a closed‐form expression for the average bit‐error rate of the underlying system. Moreover, we present asymptotic expressions for both the outage probability and average bit‐error rate in the high signal‐to‐noise ratio regime that reveal practical insights on the achievable diversity gain. Finally, we confirm our results through comparisons with computer simulations. Copyright © 2016 John Wiley & Sons, Ltd.

Research on Outage Performance Optimization of Cognitive Relay Network with Cooperative Sensing

In this work, cooperative spectrum sensing technology is applied to optimize the outage probability of cognitive relay networks. The outage performance optimization problem of cognitive relay networks is resolved by designing the sensing time and fusion rule threshold appropriately. The outage probability by high signal to noise ratio (SNR) approximation under Rayleigh fading channels is derived theoretically, and the solution of optimal fusion rule threshold is given. Theoretical analysis and simulation results illustrate that the optimal sensing time and fusion rule threshold exist to minimize the outage probability. The outage performance of cognitive relay networks is significantly improved under the assistance of cooperative sensing compared with that of non-cooperative sensing scheme. ACM CCS (2012) Classification : Networks → Network components → Wireless access points, base stations and infrastructure → Cognitive radios; Networks → Network performance evaluation → Network performance analysis *To cite this article: Y. Song et al ., Research on Outage Performance Optimization of Cognitive Relay Network with Cooperative Sensing, CIT. Journal of Computing and Information Technology , vol. 24, no. 2, pp. 111–119, 2016.

Capacity and Power Scaling Laws for Finite Antenna MIMO Amplify-and-Forward Relay Networks

We study amplify-and-forward (AF) relay networks operating with source and relay amplifier distortion, where the distortion dominates the noise power. The diversity order is shown to be $0$ for fixed-gain (FG) and $1$ for variable-gain (VG) if distortion occurs at the relay; if distortion occurs only at the source, the diversity order will be $1$ for both. With $\epsilon_\beta=N_0/\eta_\beta$ ($N_0$ the noise power, $\eta_\beta$ the distortion power at node $\beta\in\{S,R\}$, the source or relay), we demonstrate the emergence of what we call an $\epsilon$-critical signal-to-noise plus distortion ratio (SNDR) threshold (a threshold that emerges when $\min\{\epsilon_\beta\}$ becomes small) for both forwarding protocols. We show that crossing this threshold in distortion limited regions will cause a phase transition (a dramatic drop) in the network's outage probability. Thus, small reductions in the required end-to-end transmission rate can have significant reductions in the network's outage probability.

Saddle Point Approximation for Outage Probability Using Cumulant Generating Functions

This letter proposes the use of saddle point approximation (SPA) to evaluate the outage probability of wireless cellular networks. Unlike traditional numerical integration-based approaches, the SPA approach relies on cumulant generating functions (CGFs) and eliminates the need for explicit numerical integration. The approach is generic and can be applied to a wide variety of distributions, given that their CGFs exist. We illustrate the usefulness of SPA on channel fading distributions such as Nakagami-$m$, Nakagami-$q$ (Hoyt), and Rician distributions. Numerical results validate the accuracy of the proposed SPA approach.

Outage Analysis of Underlay Cognitive Radio Networks With Multihop Primary Transmission

In this letter, we investigate an underlay cognitive radio network consisting of a single-hop secondary network coexisting with a multihop primary network. In the secondary network, the secondary destination receives the same interference signals from primary terminals over different time, which are cancelled by successive interference cancellation. We analyze the outage probability of the primary network and that of the secondary network. The validity of our analysis is verified by computer simulations.

Heterogeneous Cellular Network With Energy Harvesting-Based D2D Communication

The concept of mobile user equipment (UE) relay (UER) has been introduced to support device-to-device (D2D) communications for enhancing communication reliability. However, as the UER needs to use its own power for other UE’s data transmission, relaying information in D2D communication may be undesirable for the UER. To overcome this issue, motivated by the recent advances in energy harvesting (EH) techniques, we propose a D2D communication provided EH heterogeneous cellular network (D2D-EHHN), where UERs harvest energy from an access point (AP) and use the harvested energy for D2D communication. We develop a framework for the design and analysis of D2D-EHHN by introducing the EH region (EHR) and modeling the status of harvested energy using Markov chain. The UER distribution is derived, and a transmission mode selection scheme including the efficient UER selection method is proposed. The network outage probability is derived in close form to measure the performance of D2D-EHHN. Based on our analysis results, we explore the effects of network parameters on the outage probability and the optimal offloading bias in terms of the outage probability. Particularly, we show that having a high EH efficiency enhances the performance of D2D-EHHN, but can also degrade, especially for dense network.

Outage Probability of Energy Harvesting Relay-Aided Cooperative Networks Over Rayleigh Fading Channel

Energy harvesting technique is a potential way for relay node energy supply in cooperative networks with respect to deployment flexibility and maintenance charge reduction. However, unlike traditional power source, it is intuitive that the fluctuation of harvested energy flow can degrade the benefit resulted from relay-aided cooperative transmission. To this end, this paper focuses on the performance analysis of an energy harvesting relay-aided cooperative network under slow fading channel from a perspective of outage behavior and attempts deriving the closed-form expression of outage probability of the proposed cooperative protocol. Compared with simple direct transmission protocol, it is proved that a multiplicative gain for improving system performance in terms of minimizing outage probability can be obtained by energy harvesting relay-aided cooperative transmission. In particular, if there are multiple available relay nodes around the environment or the energy-exhausted probability of relay node is small, it is very profitable to employ relay-aided cooperative transmission protocol.

Secure full-duplex small-cell networks in a spectrum sharing environment

In this paper, we propose three relay selection schemes for full-duplex heterogeneous networks in the presence of multiple cognitive radio eavesdroppers. In this setup, the cognitive small-cell nodes (secondary network) can share the spectrum licensed to the macro-cell system (primary network) on the condition that the quality-of-service of the primary network is always satisfied subjected to its outage probability constraint. The messages are delivered from one small-cell base station to the destination with the help of full-duplex small-cell base stations, which act as relay nodes. Based on the availability of the network’s channel state information at the secondary information source, three different selection criteria for full-duplex relays, namely: 1) partial relay selection; 2) optimal relay selection; and 3) minimal self-interference relay selection, are proposed. We derive the exact closed-form and asymptotic expressions of the secrecy outage probability for the three criteria under the attack of non-colluding/colluding eavesdroppers. We demonstrate that the optimal relay selection scheme outperforms the partial relay selection and minimal self-interference relay selection schemes at the expense of acquiring full channel state information knowledge. In addition, increasing the number of the full-duplex small-cell base stations can improve the security performance. At the illegitimate side, deploying colluding eavesdroppers and increasing the number of eavesdroppers put the confidential information at a greater risk. Besides, the transmit power and the desire outage probability of the primary network have great influences on the secrecy outage probability of the secondary network.

Secure Full-Duplex Spectrum-Sharing Wiretap Networks with Different Antenna Reception Schemes

In this paper, we investigate the secrecy performance of full-duplex multi-antenna spectrum-sharing wiretap networks in which a jamming signal is simultaneously transmitted by the full-duplex secondary receiver (Bob) based on the zero forcing beamforming (ZFB) algorithm. For the security enhancement, we propose the two antenna reception schemes: 1) random selection combining (RSC) where Bob selects $L_{\mathrm{B}}$ antennas at random to combine the received signals and 2) generalized selection combining (GSC) where Bob selects $L_{\mathrm{B}}$ strongest antennas to combine the received signals. We derive the exact closed-form expressions for the secrecy outage probability of full-duplex multi-antenna spectrum-sharing wiretap networks with ZFB algorithm. In order to explore a new design of the proposed schemes, we provide tractable asymptotic approximations for the secrecy outage probability in high signal-to-noise ratio regime under two distinct scenarios. From the analysis, we demonstrate that: 1) when the main channel is much better than the eavesdropper’s channel, GSC/ZFB scheme achieves full diversity $N_{\mathrm{B}}$ , while RSC/ZFB scheme only achieves partial diversity $L_{\mathrm{B}}$ and 2) GSC/ZFB scheme achieves better secrecy performance than RSC/ZFB with different antenna numbers at Bob.

Secrecy Outage Probability in Multi-RAT Heterogeneous Networks

Practical difficulty in examining all base stations (BSs) to choose the best one providing secure transmission in heterogeneous networks (HetNets), we impose a BS association constraint in this letter that the BSs providing an average received signal power at the legitimate user greater than a predetermined receiving threshold can be candidate serving BSs. With this constraint, we derive closed-form expressions for secrecy outage probability (SOP) of both homogeneous networks and $K$ -tier HetNets based on stochastic geometry. Our analysis reveals that security performance can be improved by deploying more low-power BSs in high path-loss environments. Besides, the SOP stays unchanged when the receiving threshold is below a critical point and increases rapidly when exceeding that point. These results depict features of SOP with practical constraint, which could provide new insights into the physical layer security in HetNets.

Secure Transmission in Cognitive MIMO Relaying Networks With Outdated Channel State Information

In this paper, we introduce transmit antenna selection/maximal-ratio combining (TAS/MRC) scheme in dual-hop randomize-and-forward (RaF) cognitive multiple-input multiple-output (MIMO) wiretap networks with outdated channel state information (CSI). In this network, the secondary transmitter adopts the TAS scheme to choose the antenna with the maximal received signal-to-noise ratio (SNR), while the secondary receiver and the eavesdropper adopt the MRC scheme to combine the received signals. To thoroughly assess the secrecy performance achieved by the TAS/MRC scheme and the impact of outdated CSI on the secrecy performance, we derive a new closed-form expression for the secrecy outage probability of dual-hop RaF cognitive MIMO wiretap networks. In order to achieve more insights on the application of TAS/MRC scheme, we further present tractable asymptotic secrecy outage probability at high SNR regimes under two distinct scenarios. From our analysis, several important concluding remarks are obtained as follows: 1) the RaF relaying strategy achieves better secrecy performance than that of the decode-and-forward relaying strategy for dual-hop cognitive MIMO wiretap networks; 2) outdated CSI decreases the secrecy diversity gain of the TAS/MRC scheme from ${N_{{R}}}\min \left ({ {{N_{{A}}},{N_{{B}}}} }\right )$ to $\min \left ({ {{N_{{R}}},{N_{{B}}}} }\right )$ ; and 3) although TAS/MRC scheme cannot attain full secrecy diversity gain for the considered system with outdated CSI, it still can achieve an extra secrecy coding gain compared with the random antenna selection/MRC scheme.

Secure Multi-Antenna Cognitive Wiretap Networks

In this paper, we investigate the secrecy performance of a multiantenna cognitive wiretap network, where the secondary transmitter (Alice) communicates with the secondary receiver (Bob) in the presence of an eavesdropper (Eve). Specifically, we consider both half-duplex (HD) and full-duplex (FD) operations. For the HD, maximal-ratio combining (MRC) is adopted at Bob, while for the FD, we propose two jamming schemes to deteriorate the quality of the eavesdropper's channel, i.e., selection combining/selection jammer (SC/SJ) and SC/zero forcing beamforming (SC/ZFB). Assuming Rayleigh fading, exact closed-form expressions for the secrecy outage probability of the cognitive wiretap network are derived. In addition, we also provide simple asymptotic approximations for the secrecy outage probability under two distinct scenarios, depending on the quality of the main and wiretap channels. From the analytical results and numerical simulations, it is concluded that all the proposed schemes outperform the SC scheme; all the proposed schemes achieve full diversity when the main channel is much better than the eavesdropper's channel; MRC outperforms SC/SJ and SC/ZBF in the low interference threshold regime, while the opposite holds in the high interference one; and SC/ZFB always achieves better performance than SC/SJ, albeit with higher complexity.

On the Throughput and Outage Probability of Multi-Relay Networks With Imperfect Power Amplifiers

This paper studies the energy-limited performance of multi-relay networks. Taking the properties of the power amplifiers (PAs) into account, we derive closed-form expressions for the optimal power allocation, the outage probability and the throughput in the cases with a sum consumed energy constraint. Moreover, we analyze the diversity and the multiplexing gains of the PA-aware systems. Finally, we investigate the performance of large-scale multi-relay networks and develop efficient multi-relay systems with low cooperation overhead. The numerical and the analytical results show that the inefficiency of the PAs affects the outage probability and the throughput of the multi-relay systems substantially.

Outage Probability of Ad Hoc Networks With Wireless Information and Power Transfer

This letter considers simultaneous wireless information and power transfer in ad hoc networks, where each transmitter (TX) is wirelessly powered by power beacons (PBs) and uses the aggregate received power from PBs to transmit to its desired receiver (RX). Using stochastic geometry, we formulate the total outage probability at a typical RX in terms of the power and channel outage probability. The former incorporates a power receiver activation threshold at TX while the latter incorporates maximum transmit power at TX and interference at RX. For the special case of path-loss exponent of 4, we derive accurate expressions for the power, channel and total outage probability and study the effect of the system parameters on the outage performance.