Secondary Receiver Research Articles

Buffer-aided cooperative spectrum sharing with full-duplex wireless-powered relay

A buffer-aided wireless energy harvesting and information transfer protocol is proposed for full-duplex cooperative cognitive radio networks. In particular, during a transmission block, a secondary transmitter (ST) as a full-duplex relay first scavenges dedicated radio frequency (RF) energy signal transmitting from primary transmitter (PT), and then assists to transmit primary signals by using the harvested energy in exchange for the opportunity of spectrum sharing, where the primary and secondary signals are combined linearly. A buffer with limited-size is implemented on the ST and secondary receiver (SR) to storage the decoded current primary data. The SR performs successive interference decoding and cancelation to obtain desired secondary signal. The primary receiver (PR) detects the desired primary signal by treating the secondary signal as interference. Based on this, the closed-form expressions of the exact outage probabilities for both the primary and secondary systems are derived. Optimal energy harvesting duration and power allocation factor are determined by maximizing the achievable throughput of secondary system while maintaining the transmission performance of the primary system. Simulation results demonstrate that the proposed scheme achieves effective primary transmission while provides a superior transmission performance for the secondary system.

Performance Analysis of Cell-Center Users in SM-Based Cooperative Spectrum Sharing Systems

This letter presents full-rate cooperative spectrum sharing protocol where both primary and secondary transmitters are allowed to transmit simultaneously on the same frequency channel by using orthogonal spatial modulation technique. This proposed scheme can optionally enable secondary receiver as a full-duplex fixed decode-and-forward cooperative relay to maintain quality-of-service (QoS) of the cell-edge users. Considering two different modes, i.e., cooperative relay mode for cell-edge users and cooperative non-relay mode for cell-center users, we derive the closed-form expressions for the average bit error rate (BER) of both primary and secondary receivers.

Secure transmission in underlay cognitive radio network with outdated channel state information

This paper investigates the secrecy performance of an underlay cognitive radio network (CRN) with outdated channel state information (CSI) for two practical scenarios, i.e., scenario 1: the CSI of an eavesdropper’s channel is unavailable at the secondary transmitter and scenario II: the CSI of an eavesdropper is available at the secondary transmitter. The selection combining (SC) and maximal ratio combining (MRC) techniques are utilized at the secondary receiver while MRC is also employed at both eavesdropper and primary receiver. For the scenario I, the compact expressions of exact and asymptotic secrecy outage probability (SOP), intercept probability and ϵ- outage secrecy capacity are derived, and simulations are conducted to verify analytical results. Our results reveal that the secrecy performance of the system degrades when the CSI of the main channel is outdated. Additionally, in scenario II, a comprehensive analysis of average secrecy capacity is performed, and new closed-form expressions for exact and asymptotic average secrecy capacity are derived which are valid for an arbitrary number of antennas at secondary receiver and eavesdropper. Finally, we investigate the high signal to noise ratio (SNR) slope and high SNR power offset which characterize the impact of the outdated CSI of the main channel and eavesdropper’s channel on average secrecy capacity.

Opportunistic Spectrum Sharing Based on OFDM With Index Modulation

In this paper, a novel opportunistic spectrum sharing scheme, based on orthogonal frequency division multiplexing with index modulation (OFDM-IM), is proposed for cognitive radio (CR) networks. In the considered OFDM-IM based CR (OFDM-IM-CR) model, the primary transmitter (PT) communicates with the primary receiver with the aid of an amplify-and-forward (AF) relay by transmitting OFDM-IM signals. Meanwhile, the secondary transmitter (ST) passively senses the spectrum and transmits its own information over those inactive subcarriers of the primary network to the secondary receiver if the signal-to-noise ratio of the PT <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\to $ </tex-math></inline-formula> ST link is above a predefined threshold; otherwise, the ST stays in silent mode. Two different types of maximum-likelihood (ML) detectors are designed for the primary network, based on the knowledge of either the estimated channel state information or the statistical channel information of the secondary network. A complexity-reducing method, which is applicable to both types and achieves near optimal performance, is further proposed. To evaluate the performance, a tight upper bound on the bit error rate (BER) is derived, assuming the first type of ML detection. Simulation results corroborate the analysis and show that OFDM-IM-CR has the potential of outperforming OFDM-CR and OFDM-IM-AF in terms of BER with higher spectral efficiency.

Beam Selection and Discrete Power Allocation in Opportunistic Cognitive Radio Systems With Limited Feedback Using ESPAR Antennas

We consider an opportunistic cognitive radio (CR) system consisting of a primary user (PU), secondary transmitter (SUtx), and secondary receiver (SUrx), where SUtx is equipped with an electrically steerable parasitic array radiator (ESPAR) antenna with beam steering capability for sensing and communication, and there is a limited feedback channel from SUrx to SUtx. Taking a holistic approach, we develop a framework for integrated sector-based spectrum sensing and sector-based data communication. Upon sensing the channel busy, SUtx determines the beam corresponding to PU's orientation. Upon sensing the channel idle, SUtx transmits data to SUrx, using the selected beam corresponding to the strongest channel between SUtx and SUrx. We formulate a constrained optimization problem, where SUtx- SUrx link ergodic capacity is maximized, subject to average transmit power and interference constraints, and the optimization variables are sensing duration, thresholds of channel quantizer at SUrx, and transmit power levels at SUtx. Since this problem is non-convex we develop a suboptimal computationally efficient iterative algorithm to find the solution. Our numerical results quantify the capacity improvement provided by the ESPAR antenna and demonstrate that our CR system yields lower outage and symbol error probabilities, compared with a CR system that its SUtx has an omni-directional antenna.

Multi-relay Antennas for Energy Harvesting Cognitive Radio Networks using Energy-Assisted Decode Forward Method

The single antenna relay energy-assisted decode forward (EDF) was not applicable for multi cognitive users that has less data rates. In order to achieve higher data rates with increased user demands energy harvesting or Simultaneous Wireless Information and Power Transfer (SWIPT) enabled networks with multi antenna relays are highly recommended. The proposed work considers multi relay EDFSWIPT for 5G systems with presence of transmitter and an antenna array. The transmitter affords data and power towards various numerous single-antenna secondary receivers (SR). The SR outfitted with a power splitter receiving system where multiple primary relays are introduced. The goal of proposed work is to amplify weighted sum rate harvested energy for SR using multi relay EDF. The simulation considers the capacity, outage probability, and throughput for both primary and secondary networks with respect to both single multi relay EDF. The simulation results afford that multi relay EDF has better performance than single antenna array EDF.

Cognitive UAV Communication via Joint Maneuver and Power Control

This paper investigates a new scenario of spectrum sharing between unmanned aerial vehicle (UAV) and terrestrial wireless communication, in which a cognitive/secondary UAV transmitter communicates with a ground secondary receiver (SR), in the presence of a number of primary terrestrial communication links that operate over the same frequency band. We exploit the UAV's mobility in three-dimensional (3D) space to improve its cognitive communication performance while controlling the co-channel interference at the primary receivers (PRs), such that the received interference power at each PR is below a prescribed threshold termed as interference temperature (IT). First, we consider the quasi-stationary UAV scenario, where the UAV is placed at a static location during each communication period of interest. In this case, we jointly optimize the UAV's 3D placement and power control to maximize the SR's achievable rate, subject to the UAV's altitude and transmit power constraints, as well as a set of IT constraints at the PRs to protect their communications. Next, we consider the mobile UAV scenario, in which the UAV is dispatched to fly from an initial location to a final location within a given task period. We propose an efficient algorithm to maximize the SR's average achievable rate over this period by jointly optimizing the UAV's 3D trajectory and power control, subject to the additional constraints on UAV's maximum flying speed and initial/final locations. Finally, numerical results are provided to evaluate the performance of the proposed designs for different scenarios, as compared to various benchmark schemes. It is shown that in the quasi-stationary scenario the UAV should be placed at its minimum altitude while in the mobile scenario the UAV should adjust its altitude along with horizontal trajectory, so as to maximize the SR's achievable rate in both scenarios.

Secrecy outage performance analysis of MIMO underlay cognitive radio networks with delayed CSI and transmitter antenna selection

SummaryCognitive radio network is an emerging solution to deal with spectrum scarcity and to utilize the radio spectrum in opportunistic and efficient manner. Secure data transmission is one of the important issues in these kind of networks. This work studies the secrecy outage performance of a multiple‐input multiple‐output underlay cognitive wiretap radio network system over Rayleigh fading channel with delayed channel state information. This work considers that the secondary transmitter is equipped with multiple antennas and confidential information is transmitted from to multiantenna receiver in the presence of multiantenna eavesdropper. Further, the transmit antenna selection scheme is considered at secondary transmitter to reduce the complexity of antenna selection and to make it more practicable. To improve the quality of signal, this work considers maximal ratio combining (MRC) at secondary receiver, while selection combining and MRC techniques are utilized at the eavesdropper. The closed form expression for exact, asymptotic, and intercept secrecy outage probability has been derived, and the simulation is done for the validation of analytical results. The derived results reveal deterioration of channel secrecy performance with outdated channel state information, and the eavesdropper with outdated channel state information has also an adverse effect. Moreover, the diversity order that can be achieved in underlay cognitive radio network with outdated channel state information is unity.

A numerical analysis of the energy and entropy generation rate in a Linear Fresnel Reflector using computational fluid dynamics

This work presents an energy and entropy generation analysis of a Linear Fresnel Reflector using the Computational Fluid Dynamics. It consists of 25 mirrors oriented to a receiver tube, which is located inside a Compound Parabolic Concentrator. The formulation of the entropy generation rate considers the phenomena of viscous dissipation, heat transfer and radiation, it is performed in a local and global way and implemented by user-defined functions. Results of the incident radiation, absorbed radiation, radiation temperature, temperature gradients, air velocity contours, Nusselt number and optical efficiency, are presented. Results show that the maximum values of the absorbed radiation (7800 W m−2), incident radiation (30,000 W m−2) and radiation temperature were located at the receiver tube. Also, the maximum value of the temperature gradient (39,000 K m−1) was obtained on the lower half of the receiver tube and the upper part of the secondary receiver. Moreover, the highest values of the entropy generation rate were located at the upper part of the secondary receiver for each phenomenon considered. It is concluded that the entropy generation rate due to heat transfer phenomenon is the most dominant (97.4% of the total), followed by radiation (2.59%) and then by viscous dissipation (negligible).

Secure Primary Transmission Assisted by a Secondary Full-Duplex NOMA Relay

In this paper, secure primary transmission is proposed by using a multi-antenna secondary full-duplex non-orthogonal multiple access (NOMA) relay in cognitive radio (CR) networks. First, the primary signal is transmitted from the primary transmitter to the relay. Artificial noise is generated by using part of the antennas at the relay to disrupt eavesdropping, without affecting the primary transmission. Then, superimposed signals are transmitted from the relay to the primary receiver and secondary receivers via NOMA. The primary security is guaranteed by the modified decoding order and beamforming optimization, which is converted to convex and solved by an iterative algorithm. Simulation results are presented to show the effectiveness of the proposed scheme in guaranteeing the primary security in CR networks.

Cognitive Non-Orthogonal Multiple Access With Energy Harvesting: An Optimal Resource Allocation Approach

We consider a cognitive radio system, in which a secondary transmitter harvests energy from a primary transmitter's RF signal. The secondary transmitter, which provides decode-and-forward relaying service for the primary system, transmits its own data by using downlink non-orthogonal multiple access (NOMA). A time-switching protocol is used by the secondary transmitter to harvest energy and decode the primary transmitter's information. Our objective is to achieve maximal secondary throughput, by optimally selecting the time portion used for energy harvesting and the secondary transmitter's power allocation in NOMA transmission. In this paper, two optimization problems are formulated, in which the secondary receiver performs or does not perform successive interference cancellation (SIC), respectively. Although the two problems are nonconvex, we devise a method to transform the problems into equivalent problems under different cases. Then, we theoretically prove that the objective functions of the equivalent problems are quasiconcave, based on which we develop two-level bisection search algorithms to solve the equivalent problems. Interestingly, we show that performing SIC at the secondary receiver does not always guarantee a higher secondary throughput than the case without performing SIC. Computer simulation demonstrates that our algorithm performs better than an equal power allocation algorithm and an orthogonal multiple access algorithm.

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.

Functional Movement Assessments Are Not Associated with Risk of Injury During Military Basic Training.

Musculoskeletal injuries (MSK-I) in the U.S. military accounted for more than four million medical encounters in 2017. The Military Entrance Processing Screen to Assess Risk of Training (MEPSTART) was created to identify MSK-I risk during the first 180 days of military service. Active duty applicants to the United States Army, Navy, Air Force, and Marine Corps between February 2013 and December 2014 who consented completed a behavioral and injury history questionnaire and the MEPSTART screen [Functional Movement Screen (FMS), Y-Balance Test (YBT), Landing Error Scoring System (LESS), and Overhead Squat assessment (OHS)] the day they shipped to basic training. Male (n = 1,433) and Female (n = 281) applicants were enrolled and MSK-I were tracked for 180 days. Binomial logistic regression and multivariate Cox proportional hazards modeling were used to assess relationships among MEPSTART screens and MSK-I independent of age, BMI, sex, Service, injury history, and smoking status. Analyses were finalized and performed in 2017. The only functional screen related to injury was the LESS score. Compared to those with good LESS scores, applicants with poor LESS scores had lower odds of MSK-I (OR = 0.54, 95% CI = 0.30-0.97, p = 0.04), and a lower instantaneous risk of MSK-I during the first 180 d (HR = 0.58, 95%CI = 0.34-0.96, p = 0.04). However, secondary receiver operator characteristic (ROC) analyses revealed poor discriminative value (AUC = 0.49, 95%CI = 0.43-0.54). Functional performance did not predict future injury risk during the first 180 days of service. Poor LESS scores were associated with lower injury risk, but ROC analyses revealed little predictive value and limited clinical usefulness. Comprehensive risk reduction strategies may be preferable for mitigating MSK-I in military training populations.

A POMDP‐based long‐term transmission rate maximization for cognitive radio networks with wireless‐powered ambient backscatter

SummaryWireless energy harvesting enables wireless‐powered communications to accommodate data services in a self‐sustainable manner over a long operational time. Along with energy harvesting, an ambient backscatter technique helps a secondary transmitter reflect existing radio frequency (RF) signal sources to communicate with a secondary receiver when the primary channel (PC) is utilized. However, secondary system performance is significantly affected by factors such as the availability of the primary channel, imperfect spectrum sensing, and energy‐constrained problems. Therefore, we propose a novel approach for wireless‐powered cognitive radio networks (CRNs) to improve the transmission performance of secondary systems. To reduce the dependence of the secondary system on RF sources, in the paper, we provide a new paradigm by integrating ambient backscattering with both RF and non‐RF wireless‐powered communications to facilitate secondary communications. On the basis of the sensing result in a time slot, the secondary transmitter can dynamically select the operational action: (a) backscattering, (b) harvesting, or (c) transmitting to maximize the long‐term achievable data transmission rate at the secondary receiver. In addition, the optimal action set for CRNs with wireless‐powered ambient backscatter is selected by the partially observable Markov decision process (POMDP), which maximizes an expected transmission rate calculated over a number of subsequent time slots. The proposed scheme aims to improve long‐term transmission rate of CRNs with wireless‐powered ambient backscatter in comparison with conventional schemes where an action is taken only to maximize the immediate reward in every single time slot.

Aided Opportunistic Jammer Selection for Secrecy Improvement in Underlay Cognitive Radio Networks

In this paper, we consider the physical-layer security for the primary system in an underlay cognitive radio model which comprises of a primary source–destination pair, a secondary receiver (SR), K secondary transmitters (STi, i = 1,…,K) and an eavesdropper (E). To protecting the transmission confidentiality of the primary transmission system against eavesdropping, we propose secondary transmitter (ST) aided opportunistic jamming transmission protocols. In our protocols, the selection of ST plays a crucial role. To this end, we propose the optimal secondary transmission selection (OSTS) and the Optimal Cooperative Jammer Selection (OCJS), respectively. For the non-security management, OSTS, OCJS schemes, we derive the closed-form expressions of the outage probability and the intercept probability for primary system, respectively. Furthermore, we also derive the closed-form expressions of the outage probability for the secondary user for the selective schemes. Numerical results show that the OCJS scheme has the best security performance and the conventional non-security management scheme has the worst security performance for primary system. In addition, the outage performances of OSTS and OCJS are better than the conventional non-security protocol in high secondary transmitting SNR region.

Cooperative Diversity in Secondary Systems: Efficient Relaying Protocol for Cognitive Radio

This paper considers half-duplex cooperative spectrum sharing scheme where both primary and secondary systems mutually cooperate with each other to exploit cooperative diversity in both the systems. Unlike existing cooperative schemes, this proposed protocol achieves cooperative diversity at the secondary (unlicensed) user without degrading the spectral efficiency and bit error rate (BER) performance of the primary (licensed) user. We present the closed-form expression for average BER of both primary and secondary receivers. Moreover, we compare our results with the recently proposed schemes to substantiate the efficacy of our protocol.

스펙트럼 공유 MIMO 인지 무선 통신 환경에서 다중 부사용자를 고려한 부사용자 수신기 SINR 분석

스펙트럼 공유 MIMO 인지 무선 통신 환경에서 다중 부사용자를 고려한 부사용자 수신기 SINR 분석

Protocol design and resource allocation for power optimization using spectrum sharing for 5G networks

In this paper, we propose a spectrum sharing protocol wherein the sharing is performed in a situation without introducing a secondary transmitter in assisting the primary system. Specifically, in the primary system, the primary receiver after achieving its target rate helps a secondary receiver to achieve its target using the remaining power left with it. We study the optimization of power with increased QoS and Experience for both the primary systems and the secondary receivers while the former has a higher priority. Additionally Hidden Markov Model has been used for resource allocation in the proposed model to achieve high spectrum efficiency and energy efficiency. The main emphasis of the model is in an urban deployment scenario as we are heading towards ultra-dense network for next generation networks. Extensive simulations have been carried out and the results demonstrate the performance of the proposed spectrum sharing protocol in comparison to some other power allocation techniques and opportunistic spectrum sharing model. The proposed model achieves high power optimization, increased throughput and access rate along with better QoE. The results confirm the efficiency of the proposed protocol for both the primary and the secondary system.

Performance analysis of wireless-powered cognitive radio networks with ambient backscatter

Ambient backscatter is a promising wireless communication technique where low-power users communicate with each other without any dedicated power source. These communicating users transmit their information by reflecting ambient radio-frequency (RF) signals. In this paper, we propose an ambient backscatter communications-assisted wireless-powered underlay cognitive radio network (CRN). The proposed CRN consists of a single primary transmitter (PT) and multiple primary receivers (PRs), secondary transmitters (STs), and secondary receivers (SRs). For efficient utilization of radio resources, the STs in the proposed scheme dynamically adopt either harvest-then-transmit mode or backscatter mode. Furthermore, PRs cooperate with STs to select an appropriate mode for their communication with SRs. To evaluate the performance of our proposed scheme, we conduct system-level simulations. Numerical results show that the performance of the secondary system can be improved in terms of throughput with minimum effect on the communication of primary users.

Performance of cluster-based cognitive multihop networks under joint impact of hardware noises and non-identical primary co-channel interference

In this paper, we evaluate outage probability (OP) of a cluster-based multi-hop protocol operating on an underlay cognitive radio (CR) mode. The primary network consists of multiple independent transmit/receive pairs, and the primary transmitters seriously cause co-channel interference (CCI) to the secondary receivers. To improve the outage performance for the secondary network under the joint impact of the CCI and hardware imperfection, we employ the best relay selection at each hop. Moreover, the destination is equipped with multiple antennas and uses the selection combining (SC) technique to enhance the reliability of the data transmission at the last hop. For performance evaluation, we first derive an exact formula of OP for the primary network which is used to calculate the transmit power of the secondary transmitters. Next, an exact closed-form expression of the end-to-end OP for the secondary network is derived over Rayleigh fading channels. We then perform Monte-Carlo simulations to validate the derivations. The results present that the CCI caused by the primary operations significantly impacts on the outage performance of the secondary network.