Underlay CR Research Articles

Error Mitigation in Noma for Underlay CR Networks with Imperfect Successive Interference Cancellation

Error Mitigation in Noma for Underlay CR Networks with Imperfect Successive Interference Cancellation

Joint Trajectory and Primary-Secondary Transmission Design for UAV-Carried-IRS Assisted Underlay CR Networks

Joint Trajectory and Primary-Secondary Transmission Design for UAV-Carried-IRS Assisted Underlay CR Networks

Joint power allocation and collaborative beamforming for physical layer security in underlay CR NOMA relay systems

In this paper, we investigate the problem of joint power allocation and collaborative beamforming for physical layer security in underlay cognitive radio non-orthogonal multiple access relay systems. We consider two relaying schemes, i.e., amplify-and-forward and decode-and-forward, with the goal of maximizing the secrecy rate for the central user subjective to the transmit power constraint at the source node, individual transmit power constraints at relays, rate requirements at the cognitive users and the interference power constraint at the primary receiver. The optimization problems are nonconvex and hard to solve. We propose an efficient iterative algorithm by the constrained concave–convex procedure to solve the nonconvex optimization problems. For a comparison, we provide another method, namely alternating optimization (AO) algorithm. In addition, simulations are provided to show the superiority of our proposed methods with comparison to the AO algorithm and traditional orthogonal multiple access schemes.

Throughput maximization for underlay CR multicarrier NOMA network with cooperative communication

Throughput maximization for underlay CR multicarrier NOMA network with cooperative communication

Relay Selections for Cooperative Underlay CR Systems With Energy Harvesting

In this paper, we consider a cooperative underlay cognitive radio system in which one secondary user ( ${S}$ ) transmits its data to a secondary receiver with the assistance of multiple relays. In the considered underlay spectrum sharing scenario, the transmit power levers at ${S}$ and forwarding relays are adjusted simultaneously according to a given threshold interference power that the primary user can tolerate. We also consider that relays adopt threshold decode-and-forward relay scheme and harvest energy from the primary transmitter with finite energy storage capacity under time switching scheme. Three best relay selection (RS) schemes, optimal source-relay link with wireless energy harvesting (WEH), optimal relay-destination link with WEH and optimal source-relay-destination link with WEH schemes, are proposed and studied. Closed-form analytical expressions for the outage probability of these three best RS schemes are derived, respectively. Finally, our analytical results are verified by Monte-Carlo simulations.

Impact of Multiple Primaries and Partial CSI on Transmit Antenna Selection for Interference-Outage Constrained Underlay CR

Transmit antenna selection is a low-complexity multiple-antenna technique that exploits spatial diversity using only one radio frequency chain. We investigate it for an underlay cognitive radio system that operates in the presence of multiple primary receivers and is subject to a constraint on the interference outage it causes at any of the primary receivers. The selection is based on a practically motivated and general partial channel state information (CSI) model in which the secondary transmitter (STx) only knows the channel power gains to a subset of the primary receivers. We derive a novel and general antenna selection rule that provably minimizes the symbol error probability (SEP) of the secondary system. We also derive insightful analytical expressions for its average SEP and interference-outage probability. These apply to a general class of channel fading models and any number of transmit and receive antennas, and include the special cases in which the STx knows channel power gains of all or none of the primary receivers. Our numerical results bring out a new insensitivity of the average SEP of the optimal rule to the interference power threshold when the CSI available is partial.

A Survey of Cognitive Radio Reconfigurable Antenna Design and Proposed Design using Genetic Algorithm

Cognitive radio network (CRN) is a recent paradigm of techniques for enhancing the quality of radio communication systems through the efficient utilization of frequency spectrum. It is characterized by overlay and underlay CR. Antennas designed for overlay CR must possess the capability to sense the channel and communicate over a portion of it. CR overlay antennas can be implemented as two-port, where one port supports UWB, and the other is narrowband and frequency reconfigurable. Further, they can be designed as one-port antenna, in which the same port is used for both sensing as well as communicating, and therefore should switch between wideband and narrowband operations. Evolutionary computation methods like the genetic algorithm (GA) are able to design new kinds of antennas with challenging and counterintuitive designs. A binary coded genetic algorithm can be utilized to optimize the geometry of an antenna to achieve maximum possible frequency bands with minimum number of switches for achieving a wideband performance from a single CR antenna.

Underlay cooperative af relaying in cellular networks: performance and challenges

Cognitive radio is a promising technique to resolve the growing scarcity of the indispensable spectrum resources in wireless applications. Among its three major implementation paradigms, namely, interweave, overlay and underlay, underlay CR is the most flexible. However, the transmit power of secondary users (SUs) having to be strictly limited by the prescribed tolerable interference power dictated by primary users (PUs), confines underlay CR to short-range communications. To address this limitation, cooperative amplify-and-forward (AF) relaying techniques can be exploited to extend the coverage area and reduce the interference region of secondary transmission with low implementation complexity. Nevertheless, despite the significant potential of cooperation in underlay CR systems, advances in this context have been limited so far, mainly due to the extreme difficulty of mathematical tractability involved in the performance evaluation and design of these systems. This article aims to overview recent advances in this area. In particular, important dominating factors on system performance of underlay cooperative AF relaying in cellular networks are identified, in terms of cochannel interference coming from concurrent primary transmission, relay selection, number of relaying hops, and imperfect channel state information (CSI). Moreover, we outline some future research topics in this exciting area.

Effects of spatial correlation on QoS‐driven power allocation over Nakagami‐m fading channels in cognitive radio systems

AbstractCognitive radio (CR) technology is a revolutionary wireless communication paradigm that targets at the efficient and flexible utilization of the limited radio spectrum resource. This paper considers a spectrum underlay CR system operating in a fading environment, where the secondary users (SUs) have specific communication quality requirements. In this system, the unlicenced SUs may coexist with the licenced primary users, as long as the average interference‐power that they cause to the primary users does not exceed a threshold value.The concept of spatial correlation (cross‐correlation) of Nakagami‐m fading channels is introduced in the quality of service‐driven CR system. Specifically, we present a power allocation scheme that aims at maximising the SU's effective capacity, and we study the effects of the spatial channel correlation on the performance of the proposed scheme. In order to investigate thoroughly the impact of fading correlation, two different scenarios are studied, depending on which links are considered correlated, the receive correlation model and the transmit correlation model. The performance of the proposed allocation scheme is evaluated through simulations. Finally, the effects of spatial channel correlation for different system requirements and scenarios are presented and discussed. Copyright © 2013 John Wiley & Sons, Ltd.