Performance Of Cognitive Relay Networks Research Articles

Performance of cognitive relay network with energy harvesting relay under imperfect CSI

SummaryThis paper evaluates the performance of an underlay cognitive relay network under imperfect channel state information (CSI) where a secondary user (SU) transmits using a secondary relay (SR) based on decode and forward scheme. The outage probability (OP) of SU is investigated in a scenario where the decode and forward relay harvests energy from radio frequency signal of SU. The relay uses a fraction of time for harvesting in time switching–based relaying (TSR) while a fraction of received power is used for harvesting in power splitting–based relaying (PSR) scheme. The SU and relay control their transmit power using a scaling factor, based on CSI of the interfering links (ie, links from SU transmitter and SR to the primary user [PU] receiver) to protect the quality of service of PU. The available CSI at the SU and SR are imperfect due to practical limitation. Analytical expressions of the OP are derived for TSR‐ and PSR‐based schemes. The impact of harvesting time, power splitting ratio, imperfect CSI, PU outage constraint and interference threshold on the OP of the SU network, and average transmit power of SR is indicated. Further, the impact of multiple SRs is also shown.

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.

Performance of cognitive relay network with novel hybrid spectrum access schemes with imperfect CSI

SummaryTwo novel spectrum access schemes, a hybrid spectrum access scheme (HSAS) and a modified HSAS combining underlay mode and overlay mode, are proposed for a relay based cognitive radio (CR) network. The CR employs the underlay mode with imperfect channel state information of the interfering link between CR transmitter and primary user receiver if primary user is sensed to be present else it employs overlay mode. In both the schemes, transmission of CR is assisted by relay working in amplify and forward scheme by maintaining interference below an interference threshold in underlay mode and a collision constraint in overlay mode. In HSAS, CR transmits either in underlay mode or in overlay mode only during the transmission slot of a detection cycle, whereas in modified HSAS, the CR transmits for the entire frame including the sensing time. The outage probability of CR user is considered as the performance metric. Novel expressions of outage probability for both the schemes have been developed. Impact of several sensing parameters such as sensing time, correlation coefficient, and tolerable interference threshold has been investigated. Copyright © 2016 John Wiley & Sons, Ltd.

Outage Performance of Cognitive Relay Networks With Wireless Information and Power Transfer

In this paper, we consider underlay cognitive radio (CR) networks with one primary receiver, one cognitive transmitter–receiver pair, and one energy harvesting relay. The transmission power of the secondary source is opportunistically determined by its interference to the primary receiver, and the relay transmission is powered by the energy harvested from the radio-frequency observations at the relay. For the considered CR networks with simultaneous wireless information and power transfer (SWIPT), we derive analytical expressions for the outage probability, as well as their high signal-to-noise ratio (SNR) approximations in closed form. The developed analytical results demonstrate that the use of SWIPT will not cause any loss in diversity gain, but the outage probability achieved by the SWIPT-CR scheme asymptotically decays as ${\log \mbox{SNR}}/\mbox{SNR}$ , whereas a decaying rate of ${\mbox{1}}/\mbox{SNR}$ is achieved by a conventional CR network. Computer simulation results are also provided to demonstrate the accuracy of the presented analysis.

Performance analysis of amplify‐and‐forward cognitive relay networks with interference power constraints over Nakagami‐m fading channels

With the wide-spread wireless applications and services, the spectrum scarcity has become a challenging problem. Thus, it is necessary to find a solution to have more spectrum bands. One from these solutions is the cognitive relay network, where we can increase the spectrum utilization by combining the cognitive radio (CR) with cooperative spectrum sharing systems. In this paper, the performance of cognitive relay networks under interference power constraints from the primary user (PU) is studied. Here, the system models are studied by utilizing different scenarios. The first scenario is by using a single amplify-and-forward (AF) relay, and the second one is by using a single AF relay with selection diversity. Tabulated expressions for the outage probability (OP) are derived over independent and non-identically distributed Nakagami-m fading channels. Numerical results show that the cooperative spectrum sharing transmission with a single AF relay and selection diversity outperforms both the direct transmission and the transmission using a single AF relay for the underlay cognitive relay networks. Furthermore, the results show that the outage performance depends on the minimum fading severity parameters of the two hops of the secondary user (SU) and the OP decreases as the PU moves away from the SU network.

A novel power control based on a relaxed constraint in cognitive system

AbstractThe next‐generation 5G networks will integrate two technologies, cognitive radio and cooperative communication, which use radio spectrum opportunistically and efficiently. In addition, they enhance the reliability and the capacity of the system. In this paper, we present a novel power control scheme based on a relaxed constraint in cognitive network under both the outage probability limit (OPL) of the primary system and the interference constraint limit (ICL). We show how to transform the optimization problem of the condition on the OPL and the ICL into a condition on the channel so that the cognitive user observes the channel from cognitive source to primary receiver and control its transmit power based on the channel condition. Moreover, we extend the studies to the cognitive relay network. We derive the closed‐form expressions of the outage probabilities over independent but not necessarily identically distributed Nakagami‐m fading channels. By using the theoretical analysis and from the numerical results, firstly, we show that the proposed power control scheme, which is based on both the OPL and the ICL, achieves better performance in underlay spectrum rather than the traditional one, which is based only on the interference constraints. Secondly, we show that the proposed scheme allows lower power consumption at cognitive side while the performance of cognitive relay network is improved, and the QoS of primary system is guaranteed in parallel. Copyright © 2016 John Wiley & Sons, Ltd.

Impact of the CSI on the Performance of Cognitive Relay Networks With Partial Relay Selection

In a cognitive relay network, a secondary cooperative transmission, sharing the same spectrum band with $N$ primary transmissions, is considered. Assuming imperfect channel state knowledge of the interference channels (from secondary transmitters to primary receivers) at the secondary nodes, we investigate the problem of secondary achievable rate maximization under a constraint on the interference caused at the primary receivers. Different scenarios are defined based on the accuracy of estimating the interference channels at the primary receivers and the number of feedback quantization bits. For each scenario, we derive expressions for both the secondary achievable rate and the primary interference probability. Then, we investigate the associated power allocation problem and provide a sub-optimal solution. Finally, analytical and simulation results illustrate the efficiency of the provided solution in terms of secondary achievable rate and primary interference probability.

Secure Cognitive Reactive Decode-and-Forward Relay Networks: With and Without Eavesdropper

In this paper, we study performances of cooperative relay networks in cognitive radio with reactive multiple decode-and-forward (DF) relays. In particular, we first derive exact and asymptotic expressions of outage probability for the considered scheme with K-th best relay selection over Rayleigh fading channel. Next, in the presence of an eavesdropper and the same relay selection scheme, secrecy performance of the cognitive relay network is also evaluated, in terms of average secrecy capacity. We then perform Monte-Carlo simulations to verify the theoretical derivations. Our results have presented the significance of using relay networks to enhance the system and secrecy performance of cognitive reactive DF relay networks.

Analysis of Network Path Selection Based on Outage Probability in Cognitive Relay Networks

This paper evaluates the outage performance of cognitive relay networks with mutual interference between secondary users and primary users under the underlay approach, while adhering to the interfe...

Cognitive Relay Networks: Opportunistic or Uncoded Decode-and-Forward Relaying?

This paper analyzes the outage performance of cognitive relay networks operating in the same frequency band of a primary transceiver. Different from previous works, opportunistic decode-and-forward (ODF) and uncoded decode-and-forward (UDF) relaying schemes are considered, in which the relay makes either a hard decision on whether or not to transmit or generates soft information of the received signal by using the maximum-likelihood (ML) detection. To facilitate the coexistence between the cognitive user (CU) and the primary user (PU), the transmit power of both the source and the relay should be optimized to minimize the outage probability of the CU, while satisfying both the outage probability constraint on the PU and their transmit power constraints. The resulting optimization problem for the ODF scheme is generally nonconvex, but the suboptimal solution can be obtained when the decoding rate threshold of the relay is sufficiently small. Whereas for the UDF scheme, the suboptimal solution is obtained by minimizing the upper bound of its outage probability. For comparison, traditional DF relaying with optimal power allocation and direct transmission are also investigated. Simulation results confirm the tightness of suboptimal solutions and the negligible performance gap for both the ODF and the UDF schemes, and demonstrate the performance improvement provided by both schemes, particularly when the relay is far from the primary receiver.

Outage Analysis of Orthogonal Space–Time Block Code Transmission in Cognitive Relay Networks With Multiple Antennas

The outage performance of cognitive relay networks (CRNs) for a decode-and-forward (DF) protocol in a spectrum sharing scenario with orthogonal space-time block code (OSTBC) transmission is presented in this paper. Both the exact formulas of the outage probability and its approximation in a high-SNR region are derived over Rayleigh fading channels. The theoretical results are validated by simulations. It shows that there is an outage saturation phenomenon due to both the maximum transmit power limit and the interference power constraint, which is similar to CRNs with a single antenna. Meanwhile, our results also show that increasing the number of antennas may not improve the outage performance when the interference power constraint or the transmit power constraint is very small; however, it will significantly improve the outage performance when the number of antennas is large enough. Through the asymptotic analysis, it shows that the CRN where the source and the relay are both equipped with N antennas can achieve full degree of diversity, i.e., 2N-order diversity.

Outage Analysis of Cognitive Relay Networks with Relay Selection under Imperfect CSI Environment

In this letter, we study the outage performance of cognitive relay networks with multiple primary users in imperfect channel state information environment. Specifically, an exact closed-form outage expression is derived, which provides an efficient means to evaluate the effect of system parameters. In order to gain more insights, simple expressions for the outage probability is obtained at asymptotic high SIR regime, which is only determined by the second hop of the considered system. Monte Carlo simulations are also provided, which corroborate the correctness of the analytical results. The finding suggests that the primary network only affects the coding gain of the considered system.

On the Study of Outage Performance for Cognitive Relay Networks (CRN) with the Nth Best-Relay Selection in Rayleigh-fading Channels

Relay selection is an effective way to achieve considerable performance gains in cognitive relay networks (CRN). In practice, the best relay may not always be selected, thus the study of the small Nth best relay selection will be very beneficial for CRN design. In this paper, performance analysis for underlay cognitive decode-and-forward relay networks with the small Nth best-relay selection scheme is studied over independent and identically distributed (i.i.d.) Rayleigh fading channels. Closed-form expression for the exact outage probability is derived, which can be used to evaluate the impact of the relay selection scheme, the number of relays, the interference power constraint and the transmit power limit on the outage performance. The theoretical analysis is validated by Monte-Carlo simulations. The results show that both the relay selection scheme and the number of relays have great impact on the outage performance of cognitive relay networks.

Outage Performance of Cognitive Relay Networks with Best Relay Selection in Nakagami-m Channels

This paper investigates the outage performance of a cognitive relay network considering best relay selection in Nakagami-m fading environment. The secondary user is allowed to use the spectrum when it meets the interference constraints predefined by primary user. Due to deep fading, cognitive source is unable to communicate directly with cognitive destination. As such, multiple relays are ready to deliver the signal from the cognitive source to cognitive destination. We select a single best relay and the selected relay uses decode-and-forward protocol. Specifically, we derive the exact outage probability expression, which provides an efficient means to evaluate the effects of several parameters. Finally, numerical simulation results are presented, which validate the correctness of the analytical analysis.

Outage Performance of Cognitive Relay Networks with Interference from Primary User

Cognitive relay networks employ cooperative relaying scheme in the cognitive secondary user transmission. In this letter, we theoretically derive a closed form expression and a lower bound of the outage performance for underlay cognitive relay networks considering the interference from the primary transmitter to the secondary receiver, the interference from the secondary transmitter to the primary receiver and the dependence introduced due to the interference power constraint. It is shown from simulation results that the derived closed form expression matches the simulated results.

Cognitive Relay Networks With Multiple Primary Transceivers Under Spectrum-Sharing

We examine the impact of multiple primary transmitters and receivers (PU-TxRx) on the outage performance of cognitive decode-and-forward relay networks. In such a joint relaying/spectrum-sharing arrangement, we address fundamental questions concerning three key power constraints: 1) maximum transmit power at the secondary transmitter (SU-Tx), 2) peak interference power at the primary receivers (PU-Rx), and 3) interference power at SU-Rx caused by the primary transmitter (PU-Tx). Our answers to these are given in new analytical expressions for the exact and asymptotic outage probability of the secondary relay network. Based on our asymptotic expressions, important design insights into the impact of primary transceivers on the performance of cognitive relay networks is reached. We have shown that zero diversity order is attained when the peak interference power at the PU-Rx is independent of the maximum transmit power at the SU-Tx.

Outage probability of cognitive radio networks with relay selection

In this study, the author investigates the outage performance of cognitive relay networks, in which the best relay is selected based on full and partial channel state information, respectively. The author derives exact closed-form expressions for both relay selection schemes, and study their asymptotic performance in terms of the diversity order based on the performance bound analysis. Simulation results are provided to confirm the accuracy of the analytical results, and highlight performance gains provided by the relay selection in cognitive radio networks.

Exact Outage Performance of Cognitive Relay Networks with Maximum Transmit Power Limits

In this letter, considering a cognitive relay network with the maximum transmit power limit in a spectrum sharing scenario, the exact outage probability of secondary system is derived over Rayleigh fading channels, and the theoretical analysis is validated by simulations. The results show that both the maximum transmit power limit and the interference power constraint cause the outage saturation phenomenon, and more relays for secondary system can provide better outage performance.

On the Performance of Cognitive Relay Networks Under Primary User's Outage Constraint

In this letter, we propose two relay selection schemes in cognitive relay networks. According to the proposed schemes, the number of relays involved in the opportunistic relaying is determined by the partial channel state information (CSI) of primary user link and partial CSI between the relays and the primary user receiver, so as to maintain the primary user's outage probability below a predetermined value. The exact outage probabilities of the secondary user are derived over Rayleigh fading channels. Finally, simulation results validate our analysis.