Secondary Source Nodes Research Articles

Outage performance of underlay cognitive radio networks over mix fading environment

In this paper, the underlay cognitive radio network over mix fading environment is presented and investigated. A cooperative cognitive system with a secondary source node S, a secondary destination node D, secondary relay node Relay, and a primary node P are considered. In this model system, we consider the mix fading environment in two scenarios as Rayleigh/Nakagami-m and Nakagami-m/Rayleigh Fading channels. For system performance analysis, the closed-form expression of the system outage probability (OP) and the integral-formed expression of the ergodic capacity (EC) are derived in connection with the system's primary parameters. Finally, we proposed the Monte Carlo simulation for convincing the correctness of the system performance.

Outage analysis of cognitive non‐orthogonal multiple access downlink system with secondary source selection in Nakagami‐m fading environment

SummaryCognitive inspired non‐orthogonal multiple access (Cognitive‐NOMA) technique allows multiple primary and secondary users to utilize the same time and frequency resources to explore the reliability and spectral efficient requirements of 5G communication networks. In this paper Cognitive‐NOMA downlink system with multiple secondary source (SS) nodes is proposed. An optimal SS node is selected based on the signal to interference plus noise ratio (SINR) requirements of both near and far primary users and the secondary user node. Each optimal SS node incorporates simultaneous wireless information and power transfer (SWIPT) and full‐duplex technique to harvest energy and transceiver operation. Analytical outage probability expressions of the proposed system are derived over Nakagami‐m fading environment with the assumption that SS transmission links are correlated. Numerical results infer that the outage performance of the proposed system depends on the number of SS nodes, self‐interference at the SS node, and the SINR constraint for the selection of optimal SS node.

Performance of multi-hop cognitive MIMO relaying networks with joint constraint of intercept probability and limited interference

In this paper, we propose a multi-hop multiple input multiple output (MIMO) decode-and-forward relaying protocol in cognitive radio networks. In this protocol, a multi-antenna secondary source attempts to send its data to a multi-antenna secondary destination with assistance of multiple intermediate multi-antenna nodes, in presence of a multi-antenna secondary eavesdropper. A primary network includes a primary transmitter and a primary receiver which are equipped with multiple antennas, and use transmit antenna selection (TAS) and selection combining (SC) to communicate with each other. Operating on the underlay spectrum sharing method, the secondary source and relay nodes have to adjust their transmit power so that the outage performance of the primary network is not harmful and satisfy the quality of service (QoS). Moreover, these secondary nodes also reduce their transmit power so that the intercept probability (IP) at the eavesdropper at each hop is below a desired value. To improve the outage performance of the secondary network under the joint constraint of IP and limited interference, the TAS/SC method is employed to relay the source data hop-by-hop to the destination. We derived exact closed-form expressions of the end-to-end (e2e) outage probability (OP) and IP of the proposed protocol over Rayleigh fading channels. Monte Carlo simulations are then performed to verify the theoretical derivations.

On performance of multihop energy harvesting CRN in the presence of co-channel interferers

ABSTRACT In this paper, the performance of a multihop cognitive radio network is investigated in the presence of co-channel interference (CCI) which affects the primary receiver and secondary receiver nodes. A deterministic expression for the maximum allowable transmit power of the secondary nodes is derived based on the tolerable outage probability of the primary network. The system considers radio frequency energy harvesting at the secondary source and intermediate secondary nodes from the primary user transmitter as well as from the various CCIs present around the nodes. We analyse secondary outage probability and derive a closed-form analytical expression for secondary outage probability. We present the impact of PU-TX transmit power and efficiency of harvester circuit on the secondary outage probability. The optimum number of intermediate relays is indicated for several number of CCIs which minimises outage probability of secondary network.

A cooperative phase-steering technique in spectrum sharing-based military mobile ad hoc networks

Abstract In military applications, mobile ad hoc networks are commonly used due to the autonomy, self-configuration, and flexibility. In addition, spectrum sharing-based communication protocols are being actively considered due to spectrum shortage. We propose a cooperative phase-steering (CPS) technique for a spectrum sharing-based military mobile ad hoc network which consists of a single secondary source (SS) node, multiple secondary relay (SR) nodes, a single secondary destination (SD) node, and multiple primary destination (PD) nodes. In the proposed technique, the SR nodes that succeeded the packet decoding cooperatively adjust the phase of their transmit signals such that the received signals at the SD node from the SR nodes are aligned to a certain angle, while the SR nodes control the transmit power such that the received power at all PD nodes is lower than a certain threshold. Through extensive computer simulations, it is shown that the proposed technique outperforms the conventional cooperative relaying scheme in terms of outage probability.

A Cooperative Phase-Steering Technique with On-Off Power Control for Spectrum Sharing-Based Wireless Sensor Networks.

With the growth of the number of Internet of Things (IoT) devices, a wide range of wireless sensor networks (WSNs) will be deployed for various applications. In general, WSNs are constrained by limitations in spectrum and energy resources. In order to circumvent these technical challenges, we propose a novel cooperative phase-steering (CPS) technique with a simple on-off power control for generic spectrum sharing-based WSNs, which consists of a single secondary source (SS) node, multiple secondary relay (SR) nodes, a single secondary destination (SD) node, and multiple primary destination (PD) nodes. In the proposed technique, each SR node that succeeds in packet decoding from the SS and for which its interference power to the PD nodes is lower than a certain threshold is allowed to transmit the signal to the SD node. All SR nodes that are allowed to transmit signals to the SD node adjust the phase of their transmit signal such that the phase of received signals at the SD node from the SR nodes is aligned to a certain angle. Moreover, we mathematically analyze the outage probability of the proposed scheme. Our analytical and simulation results show that the proposed technique outperforms the conventional cooperative relaying schemes in terms of outage probability. Through extensive computer simulations, it is shown that the analytical results match well with the simulated outage probability as a lower bound.

Secrecy Performance Enhancement for Underlay Cognitive Radio Networks Employing Cooperative Multi-Hop Transmission with and without Presence of Hardware Impairments.

In this paper, we consider a cooperative multi-hop secured transmission protocol to underlay cognitive radio networks. In the proposed protocol, a secondary source attempts to transmit its data to a secondary destination with the assistance of multiple secondary relays. In addition, there exists a secondary eavesdropper who tries to overhear the source data. Under a maximum interference level required by a primary user, the secondary source and relay nodes must adjust their transmit power. We first formulate effective signal-to-interference-plus-noise ratio (SINR) as well as secrecy capacity under the constraints of the maximum transmit power, the interference threshold and the hardware impairment level. Furthermore, when the hardware impairment level is relaxed, we derive exact and asymptotic expressions of end-to-end secrecy outage probability over Rayleigh fading channels by using the recursive method. The derived expressions were verified by simulations, in which the proposed scheme outperformed the conventional multi-hop direct transmission protocol.

Joint Multiple Relay Selection and Time Slot Allocation Algorithm for the EH-Abled Cognitive Multi-User Relay Networks

The wireless energy harvesting (EH) technique is regarded as a new way to provide an energy supply for energy-constrained cognitive relay networks (CRNs). A novel wireless EH cognitive multi-user relay network (CMRN) for the underlay protocol is investigated in this paper. In this system, there are multiple primary users (PUs) and multiple secondary users (SUs). The SUs can share the licensed spectrum and harvest energy from ambient signals. The problems of multiple relay selection by the SUs and of finding the optimal EH ratio are considered. We analytically derive the exact expression of the throughput of a secondary network. In it, there are four constraints: for the permitted peak interference with each primary transmitter (PT); for the sum interference for each PT; that the transmit power of secondary source nodes (SSNs) and secondary relays (SRs) should be less than the energy harvested; and that each secondary source node/secondary destination node (SSN-SDN) pair can only choose one SR. To obtain the optimal performance of the secondary network’s throughput, we should optimize the multiple relay selection scheme and the EH ratio. Actually, it is a classic integer optimization problem to design an optimal multiple relay selection scheme. However, the selection of the optimal EH ratio is a continuous optimization problem. The joint multiple relay selection and time slot allocation is a classical hybrid optimization problem. So, we propose a novel quantum sine cosine algorithm (QSCA) for resolving the difficulty with optimization of multiple relay selection and the EH ratio. Our simulation results verify our proposed solution by showing the influence of different parameters for the proposed model and by demonstrating good performance under the QSCA.

Secure Relay Selection of Cognitive Two-Way Denoise-and-Forward Relaying Networks

In this paper, secrecy performance of a cognitive two-way denoise-and-forward relaying network consisting of two primary user (PT and PD) nodes, two secondary source (SA and SB) nodes, multiple secondary relay ($${\textit{SR}}_i$$) nodes and an eavesdropper (E) node is considered, where SA and SB exchange their messages with the help of one of the relays using a two-way relaying scheme. The eavesdropper tries to wiretap the information transmitted between SA and SB. To improve secrecy performance of the network, two relay selection schemes called maximum sum rate and maximum secrecy capacity based relay selection (MSRRS and MSCRS) are proposed and analyzed in terms of intercept probability. It is proved that the MSRRS and MSCRS schemes have the same secrecy performance. Two parameters called average number gain and average cost gain are proposed to show the performance of the proposed relay selection schemes. Numerical results demonstrated that with 10 relay nodes, the proposed relay selection schemes can achieve, respectively, 3.7 dB and 1.9 dB’s improvements in terms of the reduced intercept probability and the enhanced secrecy capacity compared to the traditional round-robin scheme.

Performance Evaluation of Relay Selection Schemes in Beacon-Assisted Dual-Hop Cognitive Radio Wireless Sensor Networks under Impact of Hardware Noises.

To solve the problem of energy constraints and spectrum scarcity for cognitive radio wireless sensor networks (CR-WSNs), an underlay decode-and-forward relaying scheme is considered, where the energy constrained secondary source and relay nodes are capable of harvesting energy from a multi-antenna power beacon (PB) and using that harvested energy to forward the source information to the destination. Based on the time switching receiver architecture, three relaying protocols, namely, hybrid partial relay selection (H-PRS), conventional opportunistic relay selection (C-ORS), and best opportunistic relay selection (B-ORS) protocols are considered to enhance the end-to-end performance under the joint impact of maximal interference constraint and transceiver hardware impairments. For performance evaluation and comparison, we derive the exact and asymptotic closed-form expressions of outage probability (OP) and throughput (TP) to provide significant insights into the impact of our proposed protocols on the system performance over Rayleigh fading channel. Finally, simulation results validate the theoretical results.

Relay Selection for Broadcast Underlay Cognitive Radio Networks Using AF and DF Relaying

A degree of cooperative diversity has been achieved with the introduction of relay nodes in wireless networks. However, such approach suffers from spectral efficiency loss. Therefore, different relay selection techniques have been proposed in the literature to mitigate this loss. In this paper, the problem of relay selection for broadcast cognitive radio networks (CRNs) is investigated. The CRN is composed of a primary transmitter and receiver, a secondary source and several destination nodes. It is assumed that the secondary source broadcasts a signal to N secondary destinations. We implicitly split the destination nodes into two sets: reliable nodes having an signal-to-noise ratio (SNR) larger than a predefined threshold (T) and unreliable nodes with SNR lower than T. The paper proposes several relay selection techniques based on the average SNR, instantaneous SNR, and best direct link. Relay selection is performed by a central node taking into account the interference level at primary receiver and channel state information between nodes of the secondary CRN. In addition, the paper provides the mathematical derivation and analysis of the bit error probability (BEP) of relay selection in broadcast CRNs for both amplify and forward and decode and forward relaying. We propose to select a single relay among reliable nodes that verify interference constraints (interference to primary receiver lower than the interference threshold \(\beta \)) to help the remaining unreliable nodes. The threshold T is optimized numerically to yield the lowest BEP. Our theoretical results are confirmed by simulation.

A Bandwidth-Efficient Transmission Scheme Based on Spectrum Sensing Results in CR Networks

A bandwidth-efficient transmission scheme based on conservative spectrum sensing results without a common reporting channel is proposed for cognitive radio (CR) networks. A secondary relay node can assist a secondary source node for both spectrum sensing and data transmission. The secondary source node determines when it needs to cooperate with the secondary relay node by checking the sensing results reported from the destination and relay nodes. The CR relay transmission mode is restricted to necessary condition when the directed link between the source node and destination node fails, which improves the bandwidth efficiency of secondary data transmission. Furthermore, spectrum sensing time is optimized to maximize the expected bandwidth efficiency under the constraints of spectrum sensing requirements. Numerical results verify the effectiveness of our scheme .

Outage Probability Analysis in Power-Beacon Assisted Energy Harvesting Cognitive Relay Wireless Networks

We study the performance of the secondary relay system in a power-beacon (PB) assisted energy harvesting cognitive relay wireless network. In our system model, a secondary source node and a relay node first harvest energy from distributed PBs. Then, the source node transmits its data to the destination node with the help of the relay node. Also, fading coefficients of the links from the PBs to the source node and relay node are assumed independent but not necessarily identically distributed (i.n.i.d) Nakagami-m random variables. We derive exact expressions for the power outage probability and the channel outage probability. Based on that, we analyze the total outage probability of the secondary relay system. Asymptotic analysis is also performed, which provides insights into the system behavior. Moreover, we evaluate impacts of the primary network on the performance of the secondary network with respect to the tolerant interference threshold at the primary receiver as well as the interference introduced by the primary transmitter at the secondary source and relay nodes. Simulation results are provided to validate the analysis.

Relay-Assisted Primary and Secondary Transmissions in Cognitive Radio Networks

We assume a set of cognitive relay nodes that assists both primary and secondary transmissions in a time-slotted cognitive radio networks. To regulate the channel access of the various nodes in the network, we propose an overlapped spectrum sensing strategy for channel sensing, where the secondary source node senses the channel from the beginning of the time slot and the cognitive relay nodes sense the channel for double the sensing time used by the secondary source node to detect the activities of both the primary and secondary source nodes. Hence, the secondary source node has an intrinsic priority over the relay nodes. The relay nodes help both the primary user and the secondary user to deliver their unsuccessfully decoded packets at their destinations. In a given time slot, the scheduled relay node for data transmission starts its transmission when both the primary and secondary users are sensed to be inactive (i.e. have no data to transmit). We propose two optimization-based formulations with quality-of-service (QoS) constraints involving average queueing delay and average service rate requirements.We investigate both cases of perfect and imperfect spectrum sensing. To further enhance the usersʼ QoS requirements, we propose three packet decoding strategies at the relay nodes and compare their performance. We derive an upper bound on the secondary queue average service rate to determine which decoding strategy can achieve that bound. Our numerical results show the benefits of relaying and its ability to enhance the performance of both the primary and secondary users. Moreover, the performance of the proposed schemes is close to the derived upper bound.

On Multicast Capacity and Delay in Cognitive Radio Mobile Ad Hoc Networks

In this paper, we focus on the capacity and delay tradeoff for multicast traffic pattern in cognitive radio mobile ad hoc networks (MANETs). In our system model, the primary network consisting of n primary nodes overlaps with the secondary network consisting of m secondary nodes in a unit square. Assume that all nodes move according to an independent and identically distributed mobility model, and each primary node serves as a source that multicasts its packets to kp primary destination nodes, whereas each secondary source node multicasts its packets to ks secondary destination nodes. Under the cell partitioned network model, we study the capacity and delay for the primary networks under two communication schemes, i.e., noncooperative scheme and cooperative scheme. The communication pattern considered for the secondary network is cooperative scheme. Given that m = n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">β</sup> (β > 1), we show that per-node capacities O(1/k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ) and O(1/k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) are achievable for the primary network and the secondary network, with average delays Θ(n log k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ) and Θ(m log k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ), respectively. Moreover, to reduce the average delay in the secondary network, we employ a redundancy scheme and prove that a per-node capacity O(1/k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> √m log k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) is achievable with average delay Θ(√m log k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ). We find that the fundamental delay-capacity tradeoff in the secondary network is delay/capacity ≥ O(mk <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> log k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) under both cooperative and redundancy schemes.

Full Duplex Relay Based Cognitive Radio System with Physical Layer Network Coding

In this paper, a full duplex relay (FDR) based cognitive radio (CR) system is proposed with two secondary source nodes and two secondary destination nodes. The concept of physical layer network coding (PLNC) is applied on decode and forward (DF) FDR to ensure that both source nodes can transmit data to both destination nodes. Further, the availability of multiple spectrum bands enables CR system to decode source symbols at destination nodes. The major advantage of the proposed system with FDR and PLNC is that it requires only one time slot to send the data from both the source nodes to both the destination nodes. If FDR is replaced with half duplex relay (HDR), 2 time slots are required for the CR system. If PLNC is not applied at the DF relay, the CR system would require 2 or 4 time slots when FDR or HDR is employed, respectively. In Nakagami-$$m$$m fading channels environment, analytical expressions are derived for end-to-end outage performance of the proposed PLNC based system in the presence of echo interference at the FDR and with HDR in the place of FDR. The outage performance of the proposed CR system is analyzed for various scaling and shape parameters of Nakagami-$$m$$m fading channels.

Distributed space‐time–frequency block code for cognitive wireless relay networks

In this study, the authors consider cooperative transmission in cognitive wireless relay networks (CWRNs) over frequency-selective fading channels. They propose a new distributed space-time–frequency block code (DSTFBC) for a two-hop non-regenerative CWRN, where a primary source node and multiple secondary source nodes convey information data to their desired primary destination node and multiple secondary destination nodes via multiple cognitive relay nodes with dynamic spectrum access. The proposed DSTFBC is designed to achieve spatial diversity gain as well as allow for low-complexity decoupling detection at the receiver. Pairwise error probability is then analysed to study the achievable diversity gain of the proposed DSTFBC for different channel models including Rician fading and mixed Rayleigh–Rician fading.

MSE-Based Source and Relay Precoder Design for Cognitive Multiuser Multi-Way Relay Systems

We consider joint design of source and relay precoders in a cognitive multiuser multi-way relay system, which supports simultaneous transmission of multiple secondary users concurrently with primary network with the help of a relay station. The design criterion is minimum mean-square error (MMSE) of all secondary users under a transmit power constraint for each transmitting node and a constraint on the interference to primary network assuming complete knowledge of the channel state information is available. To solve this non-convex optimization problem, an iterative algorithm is proposed to iteratively solve the precoding matrices at secondary source nodes and relay node, and the decoding matrices at secondary nodes, where each subproblem is convex. To reduce the computational complexity, a matrix distance based non-iterative algorithm which can be implemented in a distributed manner is also proposed. Given the fact that perfect channel state information is usually non-realistic, a robust precoder design is also proposed to address this problem. Simulation results show the effectiveness of our proposed algorithms.

Outage Probability and SER of Amplify-and-Forward Cognitive Relay Networks

This letter considers amplify-and-forward (AF) cognitive relay networks with interference power constraint and transmit power constraint in a spectrum-sharing context. In particular, we impose the interference power constraint on secondary source node, and impose the interference power constraint and the transmit power constraint on secondary relay node. We derive the exact outage probability and the lower bound on symbol error rate (SER) of cognitive transmission over Rayleigh fading channels. Our results show that the outage probability and SER saturation phenomenons occur when the interference power constraint or the transmit power constraint reaches a specified value. Monte Carlo simulations are shown to validate the accuracy of the analytical results.

End-to-End Performance of Cooperative Relaying in Spectrum-Sharing Systems With Quality of Service Requirements

We propose adopting a cooperative relaying technique in spectrum-sharing cognitive radio (CR) systems to more effectively and efficiently utilize available transmission resources, such as power, rate, and bandwidth, while adhering to the quality of service (QoS) requirements of the licensed (primary) users of the shared spectrum band. In particular, we first consider that the cognitive (secondary) user's communication is assisted by an intermediate relay that implements the decode-and-forward (DF) technique onto the secondary user's relayed signal to help with communication between the corresponding source and the destination nodes. In this context, we obtain first-order statistics pertaining to the first- and second-hop transmission channels, and then, we investigate the end-to-end performance of the proposed spectrum-sharing cooperative relaying system under resource constraints defined to assure that the primary QoS is unaffected. Specifically, we investigate the overall average bit error rate (BER), ergodic capacity, and outage probability of the secondary's communication subject to appropriate constraints on the interference power at the primary receivers. We then consider a general scenario where a cluster of relays is available between the secondary source and destination nodes. In this case, making use of the partial relay selection method, we generalize our results for the single-relay scheme and obtain the end-to-end performance of the cooperative spectrum-sharing system with a cluster of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$L$</tex></formula> available relays. Finally, we examine our theoretical results through simulations and comparisons, illustrating the overall performance of the proposed spectrum-sharing cooperative system and quantify its advantages for different operating scenarios and conditions.