Average Interference Power Research Articles

IRS-Assisted RF-Powered IoT Networks: System Modeling and Performance Analysis

Emerged as a promising solution for future wireless communication systems, intelligent reflecting surface (IRS) is capable of reconfiguring the wireless propagation environment by adjusting the phase-shift of a large number of reflecting elements. To quantify the gain achieved by IRSs in the radio frequency (RF) powered Internet of Things (IoT) networks, in this work, we consider an IRS-assisted cellular-based RFpowered IoT network, where the cellular base stations (BSs) broadcast energy signal to IoT devices for energy harvesting (EH) in the charging stage, which is utilized to support the uplink (UL) transmissions in the subsequent UL stage. With tools from stochastic geometry, we first derive the distributions of the average signal power and interference power which are then used to obtain the energy coverage probability, UL coverage probability, overall coverage probability, spatial throughput and power efficiency, respectively. With the proposed analytical framework, we finally evaluate the effect on network performance of key system parameters, such as IRS density, IRS reflecting element number, charging stage ratio, etc. Compared with the conventional RF-powered IoT network, IRS passive beamforming brings the same level of enhancement in both energy coverage and UL coverage, leading to the unchanged optimal charging stage ratio when maximizing spatial throughput.

Effects of Jamming Attacks on Wireless Networked Control Systems Under Disturbance

Jamming attacks on wireless networked control systems are investigated for the scenarios where the system dynamics face exogenous disturbance. In particular, the control input packets are assumed to be transmitted from a controller to a remotely located linear plant over an insecure wireless communication channel that is subject to jamming attacks. The time-varying likelihood of transmission failures on this channel depends on the power of the jamming interference signal emitted by an attacker. We show that jamming attacks can prevent stability when the system faces disturbance, even if the attacked system without disturbance is stable. We also show that stability under jamming and disturbance can be achieved if the average jamming interference power is restricted in a certain way that we characterize in this article. We illustrate our results on an example networked control system with a fading wireless channel, where the outage probability is affected by jamming attacks.

Optimal Power Allocation for Achieving Secure Green Cognitive Radio Networks

In cognitive radio networks, wireless nodes adapt to the surrounding radio environment and utilize the spectrum of licensed users. The cognitive radio environment is dynamic, and wireless channels are accessible by both legitimate and illegitimate users. Therefore, maintaining the security of cognitive radio networks is a challenging task, which must be addressed thoroughly. Further, with the recent exponential surge in wireless nodes and associated high data rate requirements, energy consumption is also growing at an unprecedented rate. Hence, energy efficiency becomes an important metric that must be considered in the design of future wireless networks. Accordingly, by considering the great ecological and economic benefits of green wireless networks, this work focus on energy-efficient resource allocation in secure cognitive radio networks. Since physical-layer security is an emerging technique that improves the security of communication devices, in this paper, an ergodic secure energy efficiency problem for a cognitive radio network is formulated with a primary user, a secondary user, and an eavesdropper. As the formulated problem is non-convex, a concave lower bound is applied to transform the original non-convex problem into a convex one. Further, by adopting the fractional programming and dual decomposition techniques, optimal power allocation strategies are obtained with the aim of maximizing the ergodic secure energy efficiency of the secondary user with constraints on the average interference power and average transmit power. Numerical examples are used to demonstrate the effectiveness of the proposed algorithm.

Energy-efficient cooperative spectrum sensing over imperfect reporting channels with collision constraint

Recently, energy-efficient cooperative spectrum sensing (CSS) has been studied extensively in cognitive radio networks (CRNs). Most studies assume that the occupancy state of the primary user (PU) remains constant during the transmission of secondary users (SUs). However, the PU could change its activity multiple times during the transmission period, resulting in collisions with each other. In this paper, the energy efficiency (EE) maximization problem for CRNs with CSS is examined by explicitly considering the collision probability of the PU state to transition while the SU transmits data. Specifically, two types of interference based on the sensing errors and PU re-occupancy as well as imperfect reporting channels are considered simultaneously. The goal is to achieve the maximum average EE of SUs while ensuring detection accuracy by jointly optimizing the number of collaborative SUs, frame duration and transmission power, subject to the constraints of collision probability, average transmission power, average interference power and data rate. To address the non-convex optimization problem, the optimal frame duration is obtained first based on the properties of collision probability. Then, based on Dinkelbach’s method, an energy-efficient CSS iterative power control algorithm is developed. Numerical results verify the effectiveness of the proposed algorithm. It is shown that the proposed algorithm is better to the existing schemes regarding to EE. The impacts of the PU traffic parameters, reporting errors, transmission power and rate constraints on the collision probability and EE are evaluated.

Underlay Radar-Massive MIMO Spectrum Sharing: Modeling Fundamentals and Performance Analysis

In this work, we study underlay radar-massive MIMO cellular coexistence in LoS/near-LoS channels, where both systems have 3D beamforming capabilities. Using mathematical tools from stochastic geometry, we derive an upper bound on the average interference power at the radar due to the 3D massive MIMO cellular downlink under the worst-case `cell-edge beamforming' conditions. To overcome the technical challenges imposed by asymmetric and arbitrarily large cells, we devise a novel construction in which each Poisson Voronoi (PV) cell is bounded by its circumcircle to bound the effect of the random cell shapes on average interference. Since this model is intractable for further analysis due to the correlation between adjacent PV cells' shapes and sizes, we propose a tractable nominal interference model, where we model each PV cell as a circular disk with an area equal to the average area of the typical cell. We quantify the gap in the average interference power between these two models and show that the upper bound is tight for realistic deployment parameters. We also compare them with a more practical but intractable MU-MIMO scheduling model to show that our worst-case interference models show the same trends and do not deviate significantly from realistic scheduler models. Under the nominal interference model, we characterize the interference distribution using the dominant interferer approximation by deriving the equi-interference contour expression when the typical receiver uses 3D beamforming. Finally, we use tractable expressions for the interference distribution to characterize radar's spatial probability of false alarm/detection in a quasi-static target tracking scenario. Our results reveal useful trends in the average interference as a function of the deployment parameters (BS density, exclusion zone radius, antenna height, transmit power of each BS, etc.).

Energy efficient resource allocation in delay-aware UAV-based cognitive radio networks with energy harvesting

In this paper, we study an UAV-based cognitive radio network with energy harvesting (EH-UAV-CRN) in delay-aware scenarios. First, based on the sensing results of the primary user, the energy harvesting-enabled UAV dynamically adapts the transmission power to obtain spectrum efficiency for data transmission. In addition, the process of UAV collecting renewable energy is described by compound Poisson distribution approximately. Our goal is to obtain the maximum energy efficiency (EE) of EH-UAV-CRN under the constraints of average energy, multiple minimum rate outage probability (MMROP), average transmission power, and average interference power. As the EE maximization is a non-tractable optimal problem with multiple complex constraints, one so-called delay-related approximate optimization strategy (De-AOS) is proposed. Specifically, the primitive optimal problem is firstly transformed into a tractable counterpart by the proposed De-AOS. Moreover, the optimal resource allocation solution is obtained by taking advantage of the Lagrange duality method and one-dimensional linear programming. Simulation results demonstrate that our strategy can be used flexibly in various delay-related scenarios by setting different MMROP thresholds. Moreover, compared with the traditional quality of service-based minimum rate constraint scheme, our algorithm can obtain significant EE gains under the same constraints of energy, interference and transmission power.

Modeing and Robust Continuous Power Allocation Strategy with Imperfect Channel State Information in Cognitive Radio Networks

A robust continuous power allocation strategy for secondary users (SUs) with imperfect channel state information (CSI) in the cognitive radio networks is proposed. Modeling the error of CSI by normbounded distribution, we address the optimization of the transmit power allocation at SU under the constraints of average transmit power at SU and average interference power at the primary user. Simulation results show that the proposed robust rools can improve the system performance of the SU.

Analysis of FD-NOMA Cognitive Relay System With Interference From Primary User Under Maximum Average Interference Power Constraint

Analysis of FD-NOMA Cognitive Relay System With Interference From Primary User Under Maximum Average Interference Power Constraint

Product and Ratio of Product of Fisher-Snedecor ℱ Variates and Their Applications to Performance Evaluations of Wireless Communication Systems

This article considers the product, and the ratio of the product of Fisher-Snedecor $\mathcal {F}$ random variables (RVs), which can be used in modeling fading conditions that are encountered in realistic wireless transmission. To this end, exact analytical expressions are derived for the probability density function (PDF) and cumulative distribution function (CDF) of the product of $N$ statistically independent, but not necessarily identically distributed, Fisher-Snedecor $\mathcal {F}$ RVs. Capitalizing on these, exact analytical expressions are then derived for the outage probability, average channel capacity and average bit error probability over cascaded fading channels. Moreover, some important statistical metrics such as amount of fading, channel quality estimation index, kurtosis, and skewness are also provided, since they provide useful insights on the characteristics of the encountered fading conditions. In addition, with the aid of the central limit theorem, an approximation for the PDF of $N*$ Fisher-Snedecor $\mathcal {F}$ RVs is proposed using a lognormal density, and its accuracy is quantified in terms of the resistor-average distance. Finally, novel expressions for the PDF and CDF of the $N$ -fold product ratio of Fisher-Snedecor $\mathcal {F}$ RVs are also derived. As a potential application of our new results, a spectrum sharing network is considered, for which exact analytical expressions for the outage probability, delay-limited capacity, and ergodic capacity are derived. For the cascaded fading scenario and the spectrum sharing network, numerical examples are provided to show the impact of different channel-related parameters, such as fading severity, shadowing, peak and average interference power on the system performance, which is rather useful in the design of conventional and emerging wireless communication systems. Monte-Carlo simulation results are provided to corroborate the presented mathematical analysis.

Distributed Rate Control in Downlink NOMA Networks With Reliability Constraints

Non-orthogonal multiple access (NOMA) has been identified as a promising technology for future wireless systems due to its performance gains in spectral efficiency when compared to conventional orthogonal schemes (OMA). This gain can be easily translated to an increasing number of served users, but imposes a challenge in the system reliability which is of vital importance for new services and applications of coming cellular systems. To cope with these issues we propose a NOMA rate control strategy that makes use only of topological characteristics of the scenario and the reliability constraint. We attain the necessary conditions so that NOMA overcomes the OMA alternative, while we discuss the optimum allocation strategies for the 2-user NOMA setup when operating with equal rate or maximum sum-rate goals. In such scenario we show that the user with the largest target error probability times the ratio between the average receive signal power and the average interference power, should be scheduled to be decoded first for optimum performance. We compare numerically the performance of our allocation scheme with its ideal counterpart requiring full CSI at the BSs and infinitely long blocklength, and show how the gap increases as the reliability constraint becomes more stringent. Results also evidence the benefits of NOMA when the co-interference can be efficiently canceled, specially when the goal is to maximize the sum-rate.

Modified reference window for two‐dimensional CFAR in radar target detection

The constant false alarm rate (CFAR) technology plays an important role in radar target detection. In cell averaging CFAR detectors, a reference window is usually adopted to estimate the average interference power in the range–Doppler matrix and to obtain the detection threshold, which should be set high enough to limit false alarm rate to a tolerably small rate. The conventional rectangular window, cross window, and column window are investigated in this study, which may suffer from a degraded detection performance due to involving some extraneous reference cells. Therefore, a modified reference window for two-dimensional CFAR is proposed to improve performance, depending on the distribution characteristics of radar targets in range and Doppler dimensions. The experimental results demonstrate its performance advantages on detection probability, CFAR loss, and figure of merit.

Energy‐Efficient Outage Capacity in Sensing‐Based Spectrum Sharing Cognitive Radio Networks

Energy efficiency (EE) is an important metric for a Cognitive radio network (CRN). We focus on the EE maximization problem in a sensing-based spectrum sharing CRN for delay-sensitive applications. With the aid of one-dimension exhaustive search, fractional programming and Lagrange duality method, two energy-efficient optimal sensing time and power allocation policies are derived with the consideration of Average/Peak transmit power (ATP/PTP) constraints and Average interference power (AIP) constraints, respectively. Simulation results show that the proposed policies can achieve higher EE compared to the conventional spectrum sharing schemes.

Delay analysis for cognitive radio networks

In this article, we derive the waiting time and total delay of packets for cooperative cognitive radio networks. In the primary network, there are primary transmitter (PT) and receiver (PR). In the secondary network, there are a source, M relays and a destination. Our results are valid for any number of relays and different relaying protocols: opportunistic amplify and forward (AF), partial AF, reactive AF and reactive DF. The analysis is carried out for nodes with fixed and adaptive transmit power. For fixed transmit power (FTP), we cannot guarantee that interference to PR is less than threshold T. Therefore, some relays are inactive because they generate harmful interference to PR. For adaptive transmit power (ATP), the power of a relay node is fixed so that peak interference power (PIP) or average interference power (AIP) constraints are verified. We also take into account interference from the primary transmitter (PT) by analyzing the delays based on signal to interference plus noise ratio (SINR). © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Stability and Dynamic Control of Underlay Mobile Edge Networks

This paper studies the stability and dynamic control of underlay mobile edge networks. First, the stability region for a multiuser edge network is obtained under the assumption of full channel state information. This result provides a benchmark figure for comparing performance of the proposed algorithms. Second, a centralized joint flow control and scheduling algorithm is proposed to stabilize the queues of edge devices while respecting the average and instantaneous interference power constraints at the core access point. This algorithm is proven to converge to a utility point arbitrarily close to the maximum achievable utility within the stability region. Finally, more practical implementation issues such as distributed scheduling are examined by designing efficient scheduling algorithms taking advantage of communications diversity. The proposed distributed solutions utilize mini slots for contention resolution and achieve a certain fraction of the utility optimal point. The performance lower bounds for distributed algorithms are determined analytically. The detailed simulation study is performed to pinpoint the cost of distributed control for mobile edge networks with respect to centralized control.

Throughput of Cooperative HARQ protocols for Underlay Cognitive Radio Networks using Adaptive and Fixed Transmit Power

In this paper, we study theoretically and by simulations the throughput of cooperative hybrid automatic repeat request (HARQ) protocols for underlay cognitive radio networks (CRN). Both fixed and adaptive power transmission are studied. Different relay selection techniques with amplify and forward (AF) and decode and forward (DF) relaying are investigated. For fixed transmit power, some relays are not available due to interference constraints. The best relay is selected among the available ones. For adaptive transmit power, all relays adapt their power so that interference to primary receiver is always lower than a predefined threshold T. In this case, all relays will be available for retransmitting the secondary source packet. Both average interference power (AIP) and peak interference power constraints (PIP) are studied. We also analyse the effect of primary interference on secondary throughput.

Performance Assessment for Cognitive Cooperative Multiple Relays Network (CCMRN) With Imperfect Channel State Information

In the underlay spectrum sharing approach, cognitive radios have limited coverage area to keep interference protection for the licensed users. Multiple cooperative relays have shown benefit for allowing reliable communication with an increase in the radio coverage area. The performance of an underlay cognitive cooperative multiple relays network (CCMRN) is evaluated in case of imperfect channel state information (CSI). In this paper, CCMRN will be treated as a secondary network with multiple decode and forward relays, whereas the secondary user (SU) transmitter will select a single relay from the available set of relays. The relay selection process is based on obtaining maximum end-to-end effective capacity ( $C_{\text {eff}}$ ) as seen by the SU. By assuming cooperation between the licensed primary network and the unlicensed secondary network, the SU and the selective secondary relay can share the spectrum with occupying two orthogonal channels of two different primary users (PUs). According to the average interference power constraint of the PUs, the SU allowed maximum power transmission will be obtained. Network performance is assessed in terms of the SU maximum end-to-end $C_{\text {eff}}$ as well as outage probability ( $P_{\text {out}}$ ). Mathematical expressions for $C_{\text {eff}}$ and $P_{\text {out}}$ are derived for practical multipath Rayleigh faded channel. The analytical results illustrate the effect of the imperfect CSI on the performance metrics with applying various constraints such as available multiple relays group size, statistical delay quality of service, and average interference power.

Energy-Efficient Cooperative Spectrum Sensing With Reporting Errors in Hybrid Spectrum Sharing CRNs

Recently, cooperative spectrum sensing (CSS) in cognitive radio networks has been extensively researched. However, most of the studies mainly focus on maximizing the spectral efficiency while the energy consumption is generally ignored. However, since the secondary users (SUs) are usually battery-powered devices, energy saving is very important. This paper studies the mean energy efficiency (EE) maximization problem of the CSS system using the hybrid spectrum sharing (HSS) scheme. Specifically, the effects of imperfect spectrum sensing and reporting channel errors on the EE are considered. Our goal is to maximize the mean EE of SUs while maintaining the detection accuracy by jointly optimizing the sensing time and the number of cooperative SUs, subject to the SUs' average/peak transmission power constraints (ATPC/PTPC) and minimum data rate constraint, and the average interference power constraint of primary user. To address the non-convexity of the optimization problem, an energy-efficient iterative power allocation algorithm is developed. Simulations compare the achievable mean EE under ATPC/PTPC with three hard combining fusing rules using the HSS scheme and the opportunistic spectrum access (OSA) scheme, respectively; the results show that our proposed HSS scheme can obtain higher mean EE than the conventional OSA scheme and that the EE achieved under ATPC is better than that under PTPC. Moreover, among the three hard combining fusing rules, the Majority rule has the best EE.

Interference Analysis in Wireless Power Transfer

This letter studies the effect of co-channel interference (CCI) generated by wireless power transfer on information delivery for three widely used setups, i.e., power beacon (PB), hybrid access point (HAP), and simultaneous wireless information and power transfer (SWIPT). It focuses on the comparison of CCI from these three schemes in terms of the average interference power, the ergodic capacity, and the bit error rate. Numerical results show that the extra interference caused by wireless power transfer indeed degrades the system performance. Moreover, SWIPT has the largest degradation, while PB and HAP have the same degradation when proper parameters are chosen.

Energy-Efficient Optimal Power Allocation in Integrated Wireless Sensor and Cognitive Satellite Terrestrial Networks.

This paper proposes novel satellite-based wireless sensor networks (WSNs), which integrate the WSN with the cognitive satellite terrestrial network. Having the ability to provide seamless network access and alleviate the spectrum scarcity, cognitive satellite terrestrial networks are considered as a promising candidate for future wireless networks with emerging requirements of ubiquitous broadband applications and increasing demand for spectral resources. With the emerging environmental and energy cost concerns in communication systems, explicit concerns on energy efficient resource allocation in satellite networks have also recently received considerable attention. In this regard, this paper proposes energy-efficient optimal power allocation schemes in the cognitive satellite terrestrial networks for non-real-time and real-time applications, respectively, which maximize the energy efficiency (EE) of the cognitive satellite user while guaranteeing the interference at the primary terrestrial user below an acceptable level. Specifically, average interference power (AIP) constraint is employed to protect the communication quality of the primary terrestrial user while average transmit power (ATP) or peak transmit power (PTP) constraint is adopted to regulate the transmit power of the satellite user. Since the energy-efficient power allocation optimization problem belongs to the nonlinear concave fractional programming problem, we solve it by combining Dinkelbach’s method with Lagrange duality method. Simulation results demonstrate that the fading severity of the terrestrial interference link is favorable to the satellite user who can achieve EE gain under the ATP constraint comparing to the PTP constraint.

Distributed ON/OFF switching and dynamic channel allocation: Decreasing complexity and improving energy efficiency

AbstractHeterogeneous network (HetNet) has emerged as a promising and viable approach to deliver higher‐rate data services. In HetNets, switching OFF base stations (BSs) is known as an effective solution to reduce the energy consumption of networks and thus enables the “greener” networks concept. In this paper, we investigate the impact of the number of energy‐saving modes for BSs on improving energy efficiency. We assume that BSs are able to switch among several modes, ie, different transmission power levels. We apply a no‐regret learning algorithm to choose the BS's operation mode while modeling the BS's operation under dynamic traffic with a Markov process. As a result, we face a trade‐off between energy savings and computational complexity. Furthermore, we use a distributed channel allocation algorithm based on the average cochannel interference power. Simulation results show that energy consumption reduces with increased number of modes. However, increasing the number of modes beyond a certain limit will not have a significant effect on energy efficiency.