Peak Interference Power Constraint Research Articles

Network-Coded Cooperative Systems in Cognitive Radio Networks

We study the performance of a network-coded cooperative (NCC) system in an underlay cognitive radio network (CRN). The primary network (PN) consists of a single transmitter-receiver pair, and the secondary network (SN) is an NCC system with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> users, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula> relays, and a single destination. The relays employ decode-and-forward (DF) protocol and use network coding (NC). We study the performance of the SN under two types of power constraints: i) the combined peak interference power constraint on the PN and maximum transmit power constraint at the SN; and ii) the single peak interference power constraint on the PN. For the SN, an exact closed-form expression and an asymptotically tight end-to-end outage probability are derived, and the diversity order and coding gain are quantified. Compared to the existing literature, the proposed CRN NCC has four main distinguishable features: i) it applies to general CRN NCC network settings with an arbitrary number of users and relays; ii) it considers general relay selection mechanism and independent and non-identically distributed (i.n.i.d.) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Nakagami-m$ </tex-math></inline-formula> fading channels; iii) it assumes secondary-to-primary and primary-to-secondary interference links; and iv) it provides a generalization of previous work and includes existing results in the literature as special cases.

Secrecy Performance of Underlay Cognitive Radio Networks With Primary Interference

This work explores the physical layer security of an underlay cognitive radio network (CRN) in the presence of a powerful interferer called a primary transmitter (PT) under peak interference power constraint. Under this scenario, the secondary transmitter (Alice) transmits secret information on a single antenna with the highest signal-to-interference plus noise ratio (SINR) to a legitimate receiver (Bob), and an eavesdropper (Eve) attempts to intercept that information. Depending upon the availability of channel state information (CSI) of the eavesdropper channel, we investigate the secrecy performance of the proposed network in the Rayleigh fading environment for both passive and active eavesdropping scenarios. We obtain analytical expressions for the secrecy outage probability, intercept probability, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\epsilon$</tex-math></inline-formula> -outage secrecy capacity in a passive eavesdropping scenario. A complete investigation of the average secrecy capacity (ASC) has been made, and novel expressions for the exact and asymptotic ASC have been obtained for active eavesdropping. Bolstering these results, we also define a high SINR power offset, which quantifies the significance of main system parameters on the ASC explicitly. Further, the effect of outdated CSI of Alice to primary receiver link on the various performance metrics with the concept of interference-outage is also studied.

Underlay Cognitive Radio With Instantaneous Interference Constraint: A Secrecy Performance

We examine the secrecy performance of the receive antenna selection scheme in interference-limited underlay cognitive radio network (CRN) where the antenna that results in the highest signal-to-interference ratio at the secondary receiver is chosen to improve the secrecy performance of the secondary transmission. Exact and asymptotic expressions for the secrecy outage probability and intercept probability are derived for an interference-limited scenario over a general fading scenario with the assumption that the channel state information (CSI) on the secondary transmitter (ST)- primary receiver (PR) channel is perfect. However, CSI on the ST-PR channel may be outdated due to the time-varying properties or feedback latency from the PU. If the ST allocates transmission power using this outdated CSI, PR's interference constraint will not be satisfied. Therefore, we investigate the impact of outdated CSI on the secrecy performance of an interference-limited CRN when interference from the primary transmitter to SU exits under peak interference power constraint.

Spectrum sharing systems capacity under η-μ fading environments

This paper presents general, closed-form, and exact expressions for cumulative distribution function, probability density function and average value for the ratio of independent η-μ random variables, with arbitrary parameters. More specifically, the outage capacity with peak interference power constraint, the delay-limited capacity, and the ergodic capacity considering constraints on the interference power are derived for non-homogeneous environments containing multipath waves clusters. Numerical curves are presented to evaluate the effects of the general fading variables in spectrum sharing systems. Besides, the results are validated by performing Monte-Carlo simulations. Notably, the provided results find important applications in cognitive radio systems considering the spectrum sharing approach and channels modeled by η-μ distribution.

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 &amp; Sons, Inc.

Performance Analysis of Optimum Combiner in Power Limited Cognitive Radios with Multiple Primary Interferers

This paper investigates the performance of power limited Cognitive Radio system with optimum combining at the cognitive user receiver under the influence of interference from multiple primary users’ transmitters (Lt) in flat Rayleigh fading channels. An approximate analytical result of the probability density function of maximum signal-to-interference ratio at the output of CR-OC receiver is derived. Using this derived PDF, the closed form expressions for the performance metrics viz. Average post processed SIR, Ergodic capacity, Average bit error rate and outage probability of CR-OC system are derived by taking into account peak interference power constraint denoted by ‘Q’ at PU-Rx. Based on the achieved result, it is concluded that the performance of the proposed system degrades when number of primary interferers exceeds from Lt=3. Analytical results for CR-OC system are validated through Monte Carlo simulations also.DOI: http://dx.doi.org/10.5755/j01.eie.24.1.20159

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.

Secure EE maximisation in green CR: guaranteed SC

Physical-layer security from an energy-efficient perspective is of crucial importance in cognitive radio (CR). A CR network is considered where a secondary user (SU) coexists with a primary user in the presence of an eavesdropper and channel fading. Secure energy efficiency (EE) maximisation problems are formulated in secure green CR based on the condition that a minimum secrecy capacity (SC) of a SU is guaranteed. A peak interference power constraint and an average (ATP)/peak transmit power (PTP) constraint are imposed in the SU's Tx. Using fractional programming and the Lagrange dual method, energy-efficient optimal power allocation strategies are proposed to efficiently solve the secure EE maximisation problems. It is shown that the secure EE of the SU achieved under the ATP constraint is higher than that obtained under the PTP constraint. The tradeoff is elucidated between the secure EE and the SC of the SU.

Performance analysis of SIMO spectrum sharing networks over correlated [formula omitted]-[formula omitted] shadowed fading relying on MRC reception

The real-world wireless channels are accurately modeled by the composite multipath fading and shadowing channel models. The performance of a typical cognitive spectrum sharing (SS) network under a composite fading and shadowing model is rarely analyzed, and hence, needs considerable attention. In this paper, a cognitive SS network is considered having multiantenna at the secondary/cognitive receiver (SR), and the signals received at different antennas are combined using maximal ratio combining scheme. The channels at SR are considered to be spatially correlated κ-μ shadowed distributed. The analytical expressions for the outage probability and the ergodic capacity are derived under peak interference power constraint (PIPC) of the primary receiver (PR). It is shown that the performance of the SS network degrades as the spatial correlation increases at SR. It is also observed that the severity of fading/shadowing at the interfering link is favorable to the secondary user’s communication up to a certain value of PIPC of PR.

Cooperative Hybrid Spectrum Sharing: A NOMA-based Approach

Non-orthogonal multiple (NOMA) access using successive interference cancellation and cognitive radio are two promising techniques for enhancing the spectrum efficiency and utilization for future wireless communication systems. This paper presents a NOMA-based cooperative hybrid spectrum sharing protocol for cognitive radio networks. A two phase decode-and- forward (DF) relaying scheme in a multi-relay scenario is considered. Each secondary transmitter is grouped into one of the two clusters: a non-cooperative cluster (NCC) and a cooperative cluster (CC). The cluster head (CH) of the CC working as the best DF relay for the primary system is permitted to transmit its own signal superimposed on the primary signal using a NOMA approach in exchange for cooperation. On the other hand, the CH of the NCC transmits in parallel with the primary system satisfying a predefined peak transmit power and peak interference power constraints that guarantee a given primary quality of the service requirement. It is demonstrated that the performances of both the primary and secondary systems increase with the increasing number of secondary nodes. The simulation and theoretical results affirm the efficacy of the proposed protocol compared to the traditional overlay and underlay models in terms of the outage probability and the ergodic capacity.

Analysis of capacity limits over fading environment with imperfect channel state information for cognitive radio network

In this paper, we have explored an optimal power allocation scheme for the spectrum sharing with imperfect channel state information between the cognitive/secondary user (CU) and licensed/primary user (PU) in the Rayleigh fading environment. We have analyzed the ergodic capacity of CU link under the combination of peak transmit power and peak/average interference power constraints with or without the primary user interference. In addition to this, the outage capacity with multiple primary users’ interference is also analyzed with the error variance under the joint peak transmit power and peak interference power constraint as well as individual peak interference power constraint. Moreover, the power disbursement is also investigated to achieve the lower limit of ergodic and outage capacity. The minimum mean square channel estimation technique is used for the channel estimation between CU and PU. Further, the convex optimization method is used for the optimal power allocation.

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.

Performance analysis of cognitive decode-and-forward dual-hop relay networks over [formula omitted] shadowed channels

In this paper, a decode-and-forward relay based dual-hop spectrum-sharing network is considered in cognitive radio perspective. The channels at all links are assumed to be κ–μ shadowed distributed with arbitrary fading and shadowing parameters. The κ–μ shadowed fading is a composite channel model of multipath fading and shadowing, unifying many classical fading models. The outage probability and the ergodic capacity of the considered network are derived under peak interference power constraint of the primary (licensed) network. It is shown that when channels at all links are identically distributed, the secondary user’s communication is favored by the severe channel conditions for a low peak interference power constraint of the primary network. For high values of peak interference power, the secondary network shows improved performance under less severe channel conditions. Two simple forms of the outage probability and the ergodic capacity are also evaluated when the channels between secondary nodes are Nakagami-m and Rician/Rician-shadowed distributed. In all scenarios, the analytical results are validated by Monte-Carlo simulations.

Energy-Efficient Resource Allocation for OFDM-Based Cognitive Radio Networks with Imperfect Spectrum Sensing

In this study, energy-efficient (EE) resource allocation in orthogonal frequency division multiplexing-based cognitive radio networks with imperfect spectrum sensing is investigated. We present a new EE model by considering the sensing errors. Optimizing such an EE expression saves valuable resources, such as battery life, by selectively allocating power to underutilized subcarriers, and also achieves EE gain compared with general EE expression. Given that the primary user’s interference tolerance can be defined as either the Peak Interference Power (PIP) constraint or Average Interference Power (AIP) constraint for all subchannels, we compare the EE performance for the two interference power constraints. Finally, we propose an optimal EE resource allocation scheme based on the quasiconcave relation between the EE and transmit power. Simulations show that the new EE design improves EE compared with the conventional EE design, and the EE is higher with AIP constraint than that with PIP constrain under certain interference power.

Full-Duplex Spectrum Sharing in Cooperative Single Carrier Systems

We propose cyclic prefix single carrier full-duplex transmission in amplify-and-forward cooperative spectrum sharing networks to achieve multipath diversity and full-duplex spectral efficiency. Integrating full-duplex transmission into cooperative spectrum sharing systems results in two intrinsic problems: 1) the residual loop interference occurs between the transmit and the receive antennas at the secondary relays and 2) the primary users simultaneously suffer interference from the secondary source ( $\textsf {SS}$ ) and the secondary relays ( $\textsf {SR}\text{s}$ ). Thus, examining the effects of residual loop interference under peak interference power constraint at the primary users and maximum transmit power constraints at the $\textsf {SS}$ and the $\textsf {SR}\text{s}$ is a particularly challenging problem in frequency selective fading channels. To do so, we derive and quantitatively compare the lower bounds on the outage probability and the corresponding asymptotic outage probability for max–min relay selection, partial relay selection, and maximum interference relay selection policies in frequency selective fading channels. To facilitate comparison, we provide the corresponding analysis for half-duplex. Our results show two complementary regions, named as the signal-to-noise ratio (SNR) dominant region and the residual loop interference dominant region, where the multipath diversity and spatial diversity can be achievable only in the SNR dominant region, however the diversity gain collapses to zero in the residual loop interference dominant region.

Outage Probability and Ergodic Capacity of Spectrum-Sharing Systems with MRC Diversity

AbstractThe spectrum sharing system employing maximum ratio combining (MRC) is analyzed in Nakagami fading environment, for the case when the interference from the primary user is present at the input of the secondary user receiver. The closed-form expressions for the probability density function of the signal-to-interference-and-noise ratio, the outage probability and the ergodic capacity of the SU link are derived under both peak interference and maximal transmit power constraints. Asymptotical expressions are provided for the important region where peak interference power constraint dominates and the case when the interference from the primary user’s is dominant compared to the noise at the secondary user’s receiver. The obtained expressions are presented for both cases of outdated and mean-value based power allocation and verified by using Monte Carlo simulation method.

Elastic bandwidth allocation scheme with softened peak interference power constraint for the dynamic cognitive radio systems

The popularity of diverse wireless communication systems has led to increased strains on the unlicensed spectrum. However, investigations have shown that vast portions of the licensed spectrum remain underutilized across frequency, space and time. To improve the utilization of the existing radio spectrum, cognitive radio (CR) allows a secondary system to access the licensed spectrum as long as the primary system's operation is not compromised. Two main CR transmission modes, spectrum overlay and underlay have been proposed. In the spectrum overlay mode, challenges in quality-of-service (QoS) provisioning arise due to the necessity for secondary users to vacate the channels when a primary user appears. In the underlay model, interference caused to the primary system has to be carefully managed resulting in a constraint of the secondary system's transmit power, which causes difficulty in QoS provisioning. In this paper, we propose an elastic bandwidth allocation scheme to make concurrent use of both spectrum overlay and underlay transmission modes. Different from existing hybrid transmission strategy, our scheme employ a novel softened peak interference power constraint to improve the performance of the secondary system while still granting the superior protection to the primary system transmissions. This allows the proposed scheme to achieve a superior transmission capacity in the CR network while avoiding the weaknesses of the both spectrum overlay and spectrum underlay transmission modes.

Ergodic Sum-Rate Maximization for Fading Cognitive Multiple-Access Channels Without Successive Interference Cancelation

In this paper, the ergodic sum rate of a fading cognitive multiple-access channel (C-MAC) is studied, where a secondary network (SN) with multiple secondary users (SUs) transmitting to a secondary base station shares the spectrum band with a primary user (PU). An interference power constraint (IPC) is imposed on the SN to protect the PU. Under such a constraint and the individual transmit power constraint (TPC) imposed on each SU, we investigate the power allocation strategies to maximize the ergodic sum rate of a fading C-MAC without successive interference cancelation (SIC). In particular, this paper considers two types of constraints: 1) average TPC and average IPC and 2) peak TPC and peak IPC. For the first case, it is proved that the optimal power allocation is dynamic time-division multiple access (D-TDMA), which is exactly the same as the optimal power allocation to maximize the ergodic sum rate of the fading C-MAC with SIC under the same constraints. For the second case, it is proved that the optimal solution must be at the extreme points of the feasible region. It is shown that D-TDMA is optimal with high probability when the number of SUs is large. Moreover, we show that when the SUs can be sorted in a certain order, an algorithm with linear complexity can be used to find the optimal power allocation.

QoS‐based power allocation for cognitive radios with AMC and ARQ in Nakagami‐m fading channels

AbstractThis paper presents power allocation schemes to maximize the effective capacity (EC) of a secondary user (SU) communications link using adaptive modulation and coding (AMC) in an underlay cognitive radio Nakagami‐m block‐fading environment to meet target quality‐of‐service (QoS) requirements in terms of delay‐outage probability and packet error rate constraints. The SU transmission parameters are chosen such that the primary user imposed interference power constraint (IPC) is satisfied. Three different types of IPCs, namely average interference power, peak interference power and interference power outage, are considered. For each IPC, the analytical solutions for choosing the AMC mode and power allocation in each fading block, and the corresponding SU achievable EC under given QoS requirements are derived. Furthermore, we investigate the performance of a hybrid automatic repeat request (ARQ)/AMC and obtain the closed‐form packet loss rate expression. Illustrative results show the effects of the IPC, fading duration and fading severeness on the SU achievable EC under given QoS requirements. It is shown that for loose delay‐outage requirements, average interference power and interference power outage constraints give higher SU EC than peak interference power constraint. However, for more stringent delay‐outage requirements, the SU achievable EC for the three IPC is significantly reduced. The results also indicate that ARQ is helpful to significantly reduce the packet loss rate for loose delay constraint. However, ARQ increases the delay and is not effective for stringent delay‐outage requirements. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Outage Probability Analysis of MIMO Cognitive Radios with Single Transmit and Receive Antenna Selection

For multiple-input multiple-output cognitive radio systems, we propose an optimal single transmit and receive antenna selection scheme which maximizes the signal-to-interference-and-noise ratio. Considering peak interference power constraint, peak transmit power constraint, and interference from primary transmitter to cognitive receiver, we theoretically derive the exact system outage probability. It is shown that the theoretical results match simulation results.