Performance Of Secondary Network Research Articles

Performance Analysis of NOMA-Based Spectrum Sharing System With Imperfect SIC

This paper presents a non-orthogonal multiple access (NOMA)-based spectrum sharing scheme with imperfect successive interference cancellation (i-SIC), where the secondary user assists the primary to achieve cooperative multiplexing. The proposed scheme allows primary and secondary transmitters to transmit in alternate time slots and, hence, no primary transmitter's (PT) interference at the secondary receiver (SR). However, since the relay node and secondary transmitter (ST) are transmitting simultaneously on the same frequency spectrum, ST causes interference to the primary user. Therefore, the proposed scheme imposes the variable interference threshold constraint (v-ITC) to ST transmit power to improve the performance of both primary and secondary networks. We derive the closed-form expressions for the outage probability and ergodic rate of the proposed system. Furthermore, numerical results are presented to manifest the advantages of the v-ITC scheme on outage performance and the ergodic rate of the secondary network (SN).

Throughput Optimization for NOMA Cognitive Relay Network with RF Energy Harvesting Based on Improved Bat Algorithm

Due to the shortcomings of the standard bat algorithm (BA) for multi-parameter optimization, an improved bat algorithm is proposed. The benchmark function test shows that the proposed algorithm has better realization of high-dimensional function optimization by introducing multiple flight modes, adopting adaptive strategy based on group trend, and employing loudness mutation flight selection strategy based on Brownian motion. Aiming at the characteristics of complex networks structure and multiple design variables of energy harvesting non-orthogonal multiple access cognitive relay networks (EH-NOMA-CRNs), we utilize the proposed hybrid strategy improved bat algorithm (HSIBA) to optimize the performance of EH-NOMA-CRNs. At first, we construct a novel two-hop underlay power beacon assisted EH-NOMA-CRN, and derive the closed-form expressions of secondary network’s outage probability and throughput. Then, the secondary network performance optimization is formulated as the throughput maximation problem with regard to EH ratio and power allocation factors. Subsequently, the HSIBA is employed to optimize the above parameters. Numerical results show that the proposed HSIBA can achieve optimization to the constructed EH-NOMA-CRN with faster convergence speed and higher stability.

On the outage performance of decode-and-forward based relay ordering in cognitive wireless sensor networks

In this paper, the issue of secondary network access in cognitive wireless sensor networks is investigated. An efficient scheme (in terms of both power and spectrum) named decode-and-forward based multi-relay scheme with relay ordering (DF-MRRO) is proposed for secondary network access. More important, this scheme is used to enhance the performance of secondary network. In an effort to assess the performance, the received signal-to interference-plus-noise ratio of both the primary and secondary links are derived, from which new exact closed-form expressions for the outage probability of primary and secondary networks are derived. Moreover, the diversity order is calculated for both the primary and secondary network. It is also shown that full diversity order can be achieved if the condition of power requirement is satisfied. Finally, simulation results obtained for the outage performance of the proposed scheme in primary and secondary networks prove the effectiveness of the proposed scheme. It also demonstrates that a maximum of 7 dB SNR gain can be achieved in the proposed DF-MRRO scheme.

NOMA Enhanced UAV-Assisted Communication System With Nonlinear Energy Harvesting

This work investigates the performance of a laser-powered unmanned aerial vehicle (UAV) based hybrid wireless network consisting of a UAV-mounted base station (UAV-BS), cellular user, a low-power IoT user, and a secondary IoT network consisting of a group of multiple IoT devices. Communication among these devices takes place in two different phases. In the first phase of transmission, UAV-BS fulfills its power requirements by harvesting power from a distributed laser charging-based laser power transfer and uses non-orthogonal multiple access (NOMA) signaling to transmit the information to both the users. Further, in the second phase of transmission, the IoT user harvests power using power-splitting (PS) protocol and uses it to communicate with the selected IoT device, selected using a signal to interference-plus-noise ratio based selection strategy from the secondary IoT network, while the cellular user transmits uplink information to UAV-BS. We discuss the effect of non-linear energy harvesting on the performance of secondary IoT network and UAV-BS. Next, we analyze the performance of the proposed system by deriving the closed-form expressions of the outage probabilities, throughput, and ergodic capacity of both the users, the secondary IoT network, and UAV-BS. Furthermore, we find the optimal values of power coefficient and target rates that maximize the throughput of the IoT user while attaining a desired throughput for the cellular user. We also demonstrate that a judicious choice of the power allocation coefficient is essential in order to maximize the sum throughput of the system and hence the energy efficiency. Simulation results verify the accuracy of derived expressions and validate the effectiveness of proposed algorithms.

Enabling NOMA in Overlay Spectrum Sharing in Hybrid Satellite-Terrestrial Systems

In this paper, a hybrid satellite-terrestrial spectrum sharing system allows terrestrial secondary network to cooperate with a primary satellite network and to further provide higher spectrum efficiency. For massive connections design, we implement non-orthogonal multiple access (NOMA) technique to form cognitive radio based satellite-terrestrial (CR-NSHT) system relying on NOMA and further achieve more benefits compared with traditional schemes. The secondary network only remains its stable operation when the outage probability of such system is guaranteed, and thereby, to explore advantages of spectrum sharing opportunities. Considering Shadowed-Rician fading for satellite links, and Nakagami- $m$ as well as Rician fading for terrestrial links, we derive the closed-form expressions of the outage probability to evaluate the performance of secondary network. We consider further system performance metrics including ergodic capacity, energy efficiency and multi-user scenarios. We also demonstrate the impacts of power allocation factors, transmit signal-to-noise ratio (SNR) at the source, parameters of satellite links, target rates, and fading severity parameters on the system performance. Numerical and simulation results validate our analysis and highlight the performance gains of the proposed schemes for CR-NSHT with relay link serving secondary network and direct link serving the primary network.

Performance Analysis of Piece-Wise Linear Model of Energy Harvesting-Based Multiuser Overlay Spectrum Sharing Networks

In this article, we investigate the performance of a piece-wise linear model of energy harvesting-based multiuser overlay spectrum sharing system. Herein, an energy-constrained secondary node acts as a cooperative relay to assist the information transmission between a primary transmitter and multiple primary receivers. In return for the cooperation, the secondary node enjoys access to the primary user's spectrum for its own information transfer. Specifically, by employing a time-switching based receiver, the secondary node harvests energy from the received radio-frequency signal of primary transmitter during a dedicated energy harvesting phase. In the subsequent information transfer phase, the secondary node splits the harvested power to forward the primary data as well as its own information intended for another secondary user. We analyze the impact of decoding primary's information at the secondary receiver on the performance of secondary network. Importantly, we propose an improved energy harvesting-based relaying scheme which makes an efficient use of available degrees of freedom and thereby enhances the performance of both primary and secondary networks significantly. For this analytical framework, we derive the expressions of outage probability for primary and secondary networks. Numerical and simulation results are obtained to extract various useful insights and to validate our theoretical developments.

Impact of the Arrival Distribution of Primary User Traffic in Dynamic Spectrum Access

Abstract In dynamic spectrum access (DSA) a primary user shares the spectrum with one or more secondary users, with or without the primary user knowing the existence of the secondary users and offering assistance to the secondary users. When the primary user is inactive in the channel, the secondary users use the spectrum for data communication. When the primary user becomes active, the secondary users back off to return the spectrum back to the primary user. It is therefore that an arrival of the primary user traffic interrupts the ongoing communication among the secondary users. The arrivals of the primary user traffic are, in general, random, and thus secondary users cannot predict the arrivals accurately. However, when the primary user engages in non-interactive communications, it has a degree of flexibility in distributing its transmissions of data in the time domain. The paper studies the impact of the arrival distribution of primary user traffic on secondary users in terms of the secondary user network performance. Based on a state conservation scheme in DSA, the paper studies how the change of the arrival distribution of primary user traffic may affect the average network throughput, packet delay, and network power consumption of the secondary user network.

Hierarchical Cooperation Improves Delay in Cognitive Radio Networks with Heterogeneous Mobile Secondary Nodes

This paper characterizes the throughput and delay performance of Cognitive Radio Networks (CRNs), where both primary and secondary networks coexist in a unit torus. Specifically, the primary network consists of static primary nodes (PNs) of density $n$ n , which have a higher priority to access the spectrum. In contrast, the secondary network consists of mobile secondary nodes (SNs) of density $m=n^{\beta }$ m = n β with $\beta \geq 1$ β ≥ 1 , which move according to a hybrid random walk mobility model and have opportunistic access to the spectrum without affecting primary packet transmissions. Motivated by the fact that cooperation between primary and secondary nodes leads to possible improvement on the performance of CRNs, as well as the fact that the heterogeneous moving regions of secondary nodes will bring about further improvement, we propose a novel hierarchical cooperative scheduling mechanism, where secondary nodes serve as relays for primary packet transmissions by exploiting their mobility heterogeneity and geographic information. Our findings include: (i) For the primary network, stronger mobility heterogeneity of secondary nodes leads to better delay performance of the primary network, and meanwhile the delay scaling can be significantly reduced to $\Theta (n^{\sqrt{\beta /{(4\;\log n)}}}\log ^{3/2}n)$ Θ ( n β / ( 4 log n ) log 3 / 2 n ) when a near-optimal per-node throughput of $\Theta ({1}/{\log n})$ Θ ( 1 / log n ) is obtained. (ii) For the secondary network, we also adopt a similar hierarchical cooperative scheduling mechanism, and obtain a near-optimal per-node throughput of $\Theta {(1/{\log m})}$ Θ ( 1 / log m ) with the delay scaling of $\Theta ({m^{1-(1/\sqrt{\log m})}})$ Θ ( m 1 - ( 1 / log m ) ) . (iii) The delay of secondary source-destination pairs is determined by the moving region of destinations and has no relation with sources. Our work provides deeper understandings of the cooperation, heterogeneous mobility, and geographic information on the performance of CRNs, and sheds light on designing more efficient CRNs.

NOMA based cognitive relaying: Transceiver hardware impairments, relay selection policies and outage performance comparison

This paper considers cognitive radio (CR) inspired non-orthogonal multiple-access (NOMA). Such NOMA users with performance improvement can be achieved as deploying relay selection schemes. In this investigation, NOMA and CR scheme are considered as promising techniques to introduce new model of CR-NOMA and to improve spectral efficiency and energy efficiency. In this paper, problem of hardware impairment-aware design is studied to evaluate practical performance as deployment of CR-NOMA in practical. Especially, we examine outage performance of secondary network where contains relay selection strategy under limitation of interference of secondary source and secondary relay on primary destination. The closed-form expressions of outage performance are provided as main metric to exhibit performance analysis. Simulation results show that outage performance is till remained by using NOMA compared to the conventional orthogonal multiple access (OMA). It is also indicated that the performance of Opportunistic Relay Selection (ORS) is better than Partial Relay Selection (PRS) scheme.

Optimizing Performance of Co-Existing Underlay Secondary Networks

In this paper, we analyze sum throughput and (asymptotic) sum ergodic rate performance of two co-existing downlink multiuser underlay secondary networks employing either fixed-rate transmission (FRT) or (channel aware) adaptive rate transmission (ART). In the considered scenario in which two secondary sources may transmit simultaneously, intelligent apportioning the interference temperature limit (ITL) is vital. We consider cases when this ITL apportioning is based on statistical properties of the channels, or on full (or partial) knowledge of the channel gains. For these cases, proper network management (NM) strategies are evolved to maximize sum throughput or sum ergodic rate of the secondary networks. Each NM strategy determines whether both secondary sources should transmit concurrently or not, and also determines their transmit powers. We demonstrate that a channel aware NM strategy is superior to an optimal fixed NM strategy. With secondary sources employing non-opportunistic user selection, in case of FRT (ART), we demonstrate that there exists a critical target-rate (ITL) below which it is advantageous to operate both secondary networks concurrently. We present closed form expressions of critical parameters that influence sum throughput and sum ergodic rate. Computer simulations are presented to corroborate the derived expressions.

Throughput of cognitive radio networks with improved energy detector under security threats

SummarySpectrum sensing in cognitive radio networks (CRNs) is subjected to some security threats such as primary user emulation (PUE) attack and spectrum sensing data falsification (SSDF) attack. In PUE attack, a malicious user (MUPUE) transmits an emulated primary signal throughout the spectrum sensing interval to secondary users (SUs) to forestall them from accessing the primary user (PU) spectrum bands. In SSDF attack, malicious users (MUSSDF) intentionally report false sensing decisions to the fusion center (FC) to influence the overall decision. While most of the existing literatures have studied the effects of these 2 types of attacks separately, the present paper evaluates the secondary network performance in terms of throughput under both the PUE and SSDF attacks with improved energy detectors (IEDs) where SU's spectrum access is hybrid, ie, either in overlay or in underlay mode. An analytical expression on throughput of SU under the simultaneous influence of both of these attacks is developed. Impact of several parameters such as IED parameter, attacker probabilities, and attacker strength on the throughput of SU is investigated. Performance of the present scheme is also compared with only PUE and only SSDF attacks. A simulation test bed is developed in MATLAB to validate our analytical results.

Queueing Models for Cognitive Radio Networks: A Survey

Cognitive radio networks (CRNs) are an emerging paradigm for next generation wireless communication systems allowing for more efficient radio spectrum utilization. In order to harness the full potential that CRNs may offer, many challenges and problems need to be overcome and addressed. One of the critical questions is the performance of secondary networks under primary user activity constraints. In this respect, queueing assumes a primary role in characterizing the delay, throughput and other performance metrics for secondary users, which in turn has implications for resource allocation, medium access control and quality of service provisioning. This survey presents an overview and classification of the various queueing models and techniques which have been proposed in the literature in the context of CRNs. Furthermore, open problems, future research directions and further potential applications related to queueing for CRNs are identified.

Performance Study of a UCRN Over Nakagami- ${m}$ Fading Channels in the Presence of CCI

In this paper, the impact of co-channel interference (CCI) on the performance of an underlay cognitive radio network over Nakagami- ${m}$ fading channels is thoroughly presented and analysed. More precisely, a decode-and-forward relay protocol for a cognitive cooperative network is considered. In this study, the impact of both the primary transmitter interference and CCI on the secondary system performance are considered. First, an exact expression for the equivalent signal-to-interference-plus-noise ratio of the secondary system is obtained. Then, the corresponding exact and asymptotic cumulative distribution functions are derived. From this, the exact outage performance for the secondary network is investigated. Furthermore, the equivalent probability density function is obtained and discussed. In addition, approximate expressions for the average error probability and the system ergodic capacity performances are derived. From the results, it can be inferred that the presence of the CCI and primary network interference severely degrades the system performance. Moreover, a higher value of the shape parameter of the desired fading channel gives better performance and diversity gain. In addition, despite the impact of interferences, the secondary network performance gives better results in comparison to the Rayleigh fading channels scenario.

Cognitive two‐way relay systems with multiple primary receivers: exact and asymptotic outage formulation

This study is concerned with outage performance analysis of a cognitive two-way relay system having a primary network of one transmitter and multiple receivers over Nakagami- m fading channels. In the considered cognitive radio system, the secondary network facilitates information exchange between source nodes with the aid of multiple decode-and-forward two-way relays. In the presence of multiple relays, opportunistic relay selection is employed to obtain a relay with the best channel quality for reliable information recovery. To analyse the performance of the considered cognitive radio system, exact and asymptotic closed-form expressions of outage probability (OP) are derived in this study. The derived theoretical OP expressions are in good agreement with related empirical values which show that using relays can enhance the performance of secondary networks without sacrificing that of the primary network.

Performance of Secondary Network With Primary Beamforming-Assisted Energy Harvesting Transmitters

In this paper, we consider a novel energy-harvesting (EH) cognitive radio framework in which the primary source beamforms excess available energy to an EH secondary transmitter (ST) so as to enable it to share the spectrum. In the first phase of transmission, the multi-antenna primary source optimally beamforms symbols to its decode and forward relay while beamforming all excess energy to a selected EH ST. In the second phase while the relay transmits symbols to a selected primary receiver, the EH ST transmits symbols using underlay principles to its secondary receiver. Assuming peak interference constraints at the STs, we derive approximate expressions for outage probability and ergodic rate of the secondary link with the optimal beamformer . Using asymptotic expressions for outage and ergodic rate, we derive useful insights into performance of the system. We show that diversity equal to the number of secondary transmitters is achieved by the considered system. Computer simulations confirm accuracy of the derived expressions.

Design of Cooperative Non-Orthogonal Multicast Cognitive Multiple Access for 5G Systems: User Scheduling and Performance Analysis

Non-orthogonal multiple access (NOMA) is emerging as a promising, yet challenging, multiple access technology to improve spectrum utilization for the fifth generation (5G) wireless networks. In this paper, the application of NOMA to multicast cognitive radio networks (termed as MCR-NOMA) is investigated. A dynamic cooperative MCR-NOMA scheme is proposed, where the multicast secondary users serve as relays to improve the performance of both primary and secondary networks. Based on the available channel state information (CSI), three different secondary user scheduling strategies for the cooperative MCR-NOMA scheme are presented. To evaluate the system performance, we derive the closed-form expressions of the outage probability and diversity order for both networks. Furthermore, we introduce a new metric, referred to as mutual outage probability to characterize the cooperation benefit compared to non-cooperative MCR-NOMA scheme. Simulation results demonstrate significant performance gains are obtained for both networks, thanks to the use of our proposed cooperative MCR-NOMA scheme. It is also demonstrated that higher spatial diversity order can be achieved by opportunistically utilizing the CSI available for the secondary user scheduling.

Coexisting with the dynamic PU, the effect of PU‐returns on a secondary network

SummaryCoexisting with a dynamic primary user network is a challenge in cognitive radio networks, since the rate at which primary user reoccupies the spectrum is high. Therefore, it is important to investigate deeply the effect of primary traffic dynamics on secondary network performance metrics. To do that, interference due to both sensing error and primary user re‐occupancy must be formulated and considered in throughput and collision probability. Besides them, secondary packet retransmissions due to such interference should be considered in metrics such as average energy consumption and average packet delay. In this study, we formulate the mentioned secondary network metrics regarding to such kinds of interference and secondary packet retransmission. Numerical results along with discussions are given to clarify derived expressions. Simulations are also performed to justify the theoretical results, and optimum operating point for secondary network settings is derived by genetic algorithm.

System Times and Channel Availability for Secondary Transmissions in CRNs: A Dependability-Theory-Based Analysis

Reliability is of fundamental importance for the performance of secondary networks in cognitive radio networks (CRNs). To date, most studies have focused on predicting reliability parameters based on prior statistics of traffic patterns from user behavior. In this paper, we define a few reliability metrics for channel access in multichannel CRNs that are analogous to the concepts of reliability and availability in classical dependability theory. Continuous-time Markov chains are employed to model channel available and unavailable time intervals based on channel occupancy status. The impact on user access opportunities based on channel availability is investigated by analyzing the steady-state channel availability and several system times such as mean channel available time and mean time to first channel unavailability. Moreover, the complementary cumulative distribution function for channel availability is derived by applying the uniformization method, and it is evaluated as a measure of guaranteed availability for channel access by secondary users. The precision and the correctness of the derived analytical models are validated through discrete-event-based simulations. We believe that the reliability metric definitions and the analytical models proposed in this paper have their significance for reliability and availability analysis in CRNs.

Cognitive full-duplex relay networks under the peak interference power constraint of multiple primary users

This paper investigates the outage performance of cognitive spectrum-sharing multi-relay networks in which the relays operate in a full-duplex (FD) mode and employ the decode-and-forward (DF) protocol. Two relay selection schemes, i.e., partial relay selection (PRS) and optimal relay selection (ORS), are considered to enhance the system performance. New exact expressions for the outage probability (OP) in both schemes are derived based on which an asymptotic analysis is carried out. The results show that the ORS strategy outperforms PRS in terms of OP, and increasing the number of FD relays can significantly improve the system performance. Moreover, novel analytical results provide additional insights for system design. In particular, from the viewpoint of FD concept, the primary network parameters (i.e., peak interference at the primary receivers, number of primary receivers, and their locations) should be carefully considered since they significantly affect the secondary network performance.

Resource Allocation for Underlay Cognitive Radio Networks: A Survey

For conventional wireless networks, the main target of resource allocation (RA) is to efficiently utilize the available resources. Generally, there are no changes in the available spectrum, thus static spectrum allocation policies were adopted. However, these allocation policies lead to spectrum under-utilization. In this regard, cognitive radio networks (CRNs) have received great attention due to their potential to improve the spectrum utilization. In general, efficient spectrum management and resource allocation are essential and very crucial for CRNs. This is due to the fact that unlicensed users should attain the most benefit from accessing the licensed spectrum without causing adverse interference to the licensed ones. The cognitive users or called secondary users have to effectively capture the arising spectrum opportunities in time, frequency, and space to transmit their data. Mainly, two aspects characterize the resource allocation for CRNs: 1) primary (licensed) network protection and 2) secondary (unlicensed) network performance enhancement in terms of quality-of-service, throughput, fairness, energy efficiency, etc. CRNs can operate in one of three known operation modes: 1) interweave; 2) overlay; and 3) underlay. Among which the underlay cognitive radio mode is known to be highly efficient in terms of spectrum utilization. This is because the unlicensed users are allowed to share the same channels with the active licensed users under some conditions. In this paper, we provide a survey for resource allocation in underlay CRNs. In particular, we first define the RA process and its components for underlay CRNs. Second, we provide a taxonomy that categorizes the RA algorithms proposed in literature based on the approaches, criteria, common techniques, and network architecture. Then, the state-of-the-art resource allocation algorithms are reviewed according to the provided taxonomy. Additionally, comparisons among different proposals are provided. Finally, directions for future research are outlined.