Outage Probability Performance Research Articles

Outage Performance of Underlay CR-NOMA-based D2D Communications under Imperfect CSI and SIC

Background: Non-orthogonal multiple access (NOMA) is a promising technique for improving wireless communication performance in the future. In addition to NOMA, cognitive radio (CR) is another technology that can address the issue of limited spectrum availability and meet the increasing demands for wireless connectivity. Methods: This paper focuses on investigating underlay CR-NOMA-based D2D communications. The study assumes a decode-and-forward (DF) mode used in the system, where nearby users (D1, D2) act as helper users to assist distant users (D3, D4). The paper derives the closed-form expressions for outage probability (OP) and throughput at the far users in three scenarios: (1) Perfect successive interference cancellation (SIC) and perfect channel state information (CSI), (2) Imperfect CSI, and (3) Imperfect SIC. Results: In CR-NOMA mode, the results indicate that the performance of user D4 was better than user D3. Additionally, the OP performance of distant users employing CR-NOMA mode surpasses that of users using CR-OMA mode. The optimal power allocation (PA) values are investigated. Conclusion: The presence of imperfect CSI and SIC has an unfavorable influence on the outage performance. Monte Carlo simulations are used to validate the derived analytical expressions.

Outage performance analysis of antenna selection schemes in UAV-assisted networks

In this paper, we investigate the performance of various antenna selection (AS) techniques in an unmanned aerial vehicle (UAV)-assisted relay communication system, wherein a UAV is deployed as a flying relay to establish and sustain a communication link between source and destination nodes. The AS schemes under study encompass transmit antenna selection/maximal ratio combining (TAS/MRC), joint transmit and receive antenna selection (JTRAS), and maximum ratio transmission/receive antenna selection (MRT/RAS). We present a unified outage probability (OP) performance analysis of AS techniques in UAV relay networks. We initially derive a closed-form expression for the OP under Nakagami-m fading channels. Subsequently, an asymptotic expression elucidating the array and diversity gain is derived to offer deeper insights into the performance of the studied system. Finally, Monte Carlo simulations are conducted to validate the theoretical results.

Performance analysis of multi-hop low earth orbit satellite network over mixed RF/FSO links

Low earth orbit satellite (LEOS) communication has emerged as a promising technology to achieve global coverage, while further reducing the end-to-end latency by establishing communication link between LEOSs. In this paper, we analyze the performance of multi-hop LEOS network in terms of bit error rate (BER) and outage probability over mixed radio frequency (RF)/free space optical (FSO) links where RF link is used for the link between ground terminal and LEOS and FSO link is used for establishing inter-satellite links (ISLs). The derived closed-form results are confirmed via Monte Carlo simulations and we show the effect of the number of satellite hops on outage probability and average BER performance by comparing scenarios both with and without ISLs.

ANALYSIS OF THE USER PAIRING NOMA SYSTEM OVER THE NAKAGAMI-M FADING CHANNEL CONDITIONS

The potential of non-orthogonal multiple access (NOMA) as a multiple access strategy for 5G and LTE upgrades has attracted much attention. In this study, we examine user pairing in NOMA strategy for multiple-input multiple-output (MIMO) users. The simulation results for near-near (N-N) and near-far (N-F) user pairing shames have been provided. The channel becomes time-selective after considering the node mobility situation. Furthermore, simulation curves demonstrate that adopting the user pairing approach reduces computing cost. The network's sum rate performance was further tested utilizing selection combining (SC) NOMA and time division for multiple access (TDMA). It is shown that when a user nearest to the base station is linked with the farthest user from the base station, the total sum rate dramatically increases. When the channel conditions between the two users are varied, the NOMA performs significantly better. The NOMA still surpasses TDMA in terms of sum rate when N-N and far-far (F-F) pairings are used, but the difference isn't significant. The SC-NOMA has a low performance when compared to TDMA. It was discovered that when the shape parameter is adjusted to two, the outage probability (OP) performance of three NOMA mobile users and a standard orthogonal multiple access (OMA) mobile user improved (multipath propagation scenario).

On the performance of outage probability in cognitive NOMA random networks with hardware impairments

ABSTRACT The performance of the cognitive non-orthogonal multiple access (NOMA) systems with random locations is examined in the present paper. More precisely, the positions of the secondary receivers (SRs) are randomly distributed inside a disk with the centre at the secondary transmitter (ST). The primary networks (PNs), on the other hand, are not necessarily inside the transmission range of the ST. Two user selection schemes namely, path-loss-based and channel-gain-based approaches, are adopted to serve two SRs according to the power domain NOMA technique. Additionally, the impact of the imperfect hardware impairments (HIs) on both transmitters and receivers is also taken into consideration. Furthermore, a recently proposed transmit power allocation at the ST is employed to concurrently maximize the system performance of the secondary networks (SNs) and to strictly protect the quality-of-service (QoS) of the PNs. The correctness of the developed mathematical frameworks is corroborated by simulation results based on the Monte Carlo method. Finally, we unveil that there is no scheme that always outperforms another. Thus, an adaptive scheme can be proposed to optimize the networks' performance. Our findings also reveal that the outage probability (OP) under the harmful effect of HI can be effectively mitigated by increasing the transmit power of the ST. Additionally, increasing the transmit power of the PT is also beneficial for the SNs with the adopted transmit power allocation at the ST.

Performance analysis and optimization of frequency division duplex based virtual full-duplex communication systems

Virtual full-duplex (VFD) communication systems have become smart alternative over residual self-interference (RSI) affected full-duplex (FD) systems and thus has drawn significant research attention in the recent years. However, in comparison to FD, the VFD system models studied in the literature are based on successive relaying (SR) that require an extra time phase and a double number of relays for each destination user. Thus, we propose a novel frequency division duplex (FDD) based VFD (FDD-VFD) system model that can not only match FD in terms of resource utilization but also outperform both SR-VFD and FD. We consider two practical scenarios of absence of inter relay interference (A-IRI) and presence of IRI (P-IRI). We analyze the outage probability and ergodic rate performance metrics and present their analytical expressions in closed-form over Nakagami-m fading channels. Next, to minimize the effect of inter-relay interference in P-IRI scenario, we investigate optimization problems of minimizing the system outage probability and maximizing the ergodic sum rate for jointly allocating transmit power of the relays. We utilize particle swarm optimization algorithm and deep learning architecture to solve the formulated problems. Extensive evaluations are carried out over different system parameters to prove the efficacy of proposed FDD scheme and obtain key inferences.

A Hybrid Millimeter-Wave and Free-Space-Optics Communication Architecture with Adaptive Diversity Combining and HARQ Techniques

We propose and demonstrate a hybrid communication architecture that combines millimeter-wave (MMW) in the radio frequency (RF) domain and free-space-optics (FSO) technologies using adaptive combining and hybrid automatic repeat request (HARQ) techniques. At the receiving end, we employed joint signal processing with an adaptive diversity combining technique (ADCT) based on a maximum ratio combining (MRC) algorithm. We derived closed-form expressions for the outage probability and throughput of the hybrid RF and FSO (RF/FSO) system, considering various characteristics of atmospheric turbulence in the FSO link. Experimental testing with 10-Gbaud quadrature phase shift keying (QPSK) data was conducted under different simulated atmospheric turbulence intensities, FSO and MMW speed-ratios, and forward error correction (FEC) overheads. Additionally, we validated improvements in terms of bit error ratio (BER), outage probability, and throughput performance.

Study on performance of a relay-assisted UWOC system based on adaptive optics

To improve the performance of underwater wireless optical communication (UWOC) systems, we propose a relay-assisted UWOC system model based on adaptive optics (AO). The closed expressions of the scintillation index, composite channel probability density function, and outage probability of the Gaussian beam before and after AO compensation are derived using the extended Rytov theory and Meijer G-function. The performance variation of an UWOC system with different parameters is analyzed by simulation. The results show that AO correction can compensate for the distorted wavefront and significantly reduce the intensity fluctuation at the receiving end. The proposed system can efficiently alleviate channel fading, improving the outage probability performance of the UWOC system.

IQ-Impaired Wireless-Powered Modify-and-Forward Relaying for IoT Networks: An In-Depth Physical-Layer Security Analysis

With the large-scale commercialization of 5G networks, the era of Internet-of-Things (IoT), which is oriented towards the internet-of-everything (IoE), is coming. Under the circumstance, reliable and secure communication are the great challenges for future wireless network because of the broadcasting characteristics of electromagnetic wave. Physical layer security (PLS) is an effective way to ensure secure communication by exploiting random nature of fading channels. Motivated by this, we investigate PLS of the wireless-powered cooperative multi-relaying for IoT networks in the presence of eavesdropper with the estimation errors of channel (EEC) and imbalance between in-phase and quadrature-phase (IIQ). Specifically, the relays can be charged by the source with the aid of energy harvesters, and a novel more secure modify-and-forward (MF) relay protocol is proposed. For further improving energy efficiency and reducing extra interference, the K-th superior relay selection scheme is proposed since some best ones are not available due to some scheduling or failure. Based on the system under study, we derive the analytical expressions for the outage probability (OP), intercept probability (IP) and secrecy outage probability (SOP) to evaluate the reliable and secure performance of this consideration system. Particularly, we then analyze the asymptotic behaviors of the OP, IP and SOP, respectively. Through computer simulation, we show that: i) With EEC, the error floors of the OP and SOP are of presence; ii) Multiple relays lead to better OP and SOP performance; and iii) IIQ improves the security and is detrimental to the system reliability.

Evaluation of antenna and relay scheme for cooperative non‐orthogonal multiple access

AbstractAn antenna selection followed by a relay selection scheme (ASRS) is proposed for cooperative non‐orthogonal multiple access (NOMA)‐based network. The proposed work selects an antenna to maximise the instantaneous rate of poor channel condition users while providing good quality of services (QoS). The outage probability performance of the proposed scheme is plotted for different antenna configuration while varying the SNR and distance with variable number of antennas and available relays. The fairness factor of the proposed work is also discussed, considering three different density areas. The proposed scheme is compared with novel schemes in literature for average sum rate and average energy efficiency to show its superiority.

Performance analysis of ambient backscatter communication empowered IoV networks

This paper investigates the performance of Internet-of-Vehicles networks supporting vehicular communication applications empowered by ambient backscatter communication technology. Specifically, we consider that the tag and reader are mounted on the vehicles while the ambient radio frequency source is a fixed infrastructure, allowing for both vehicle-to-vehicle and vehicle-to-infrastructure modes of communication in the network under consideration. We evaluate the exact outage probability expression for the AmBC-enabled Internet-of-Vehicles systems by characterizing the fading associated with vehicle-to-infrastructure and vehicle-to-vehicle transmissions as Rayleigh distributed and cascaded (double) Rayleigh distributed, respectively. Also, asymptotic outage probability expression is derived under high signal-to-noise ratio regime, from which a meaningful discussion on the system’s diversity order is carried out. Moreover, we deduce the tight ergodic capacity expression over mixed Rayleigh and double-Rayleigh fading channels. Finally, the simulation studies verify the proposed theoretical framework and show the impact of various channel and system parameters on the outage probability and ergodic capacity performance.

Bi‐directional LSTM based channel estimation in 5G massive MIMO OFDM systems over TDL‐C model with Rayleigh fading distribution

SummaryIn this work, a deep learning (DL)‐based massive multiple‐input multiple‐output (mMIMO) orthogonal frequency division multiplexing (OFDM) system is investigated over the tapped delay line type C (TDL‐C) model with a Rayleigh fading distribution at frequencies ranging from 0.5 to 100 GHz. The proposed bi‐directional long short‐term memory (Bi‐LSTM) channel state information (CSI) estimator uses online learning during training and offline learning during the practical implementation phase. The design of the estimator takes into account situations in which prior knowledge of channel statistics is limited and targets excellent performance, even with limited pilot symbols (PS). Three separate loss functions (mean square logarithmic error [MSLE], Huber, and Kullback–Leibler Distance [KLD]) are assessed in three classification layers. The symbol error rate (SER) and outage probability performance of the proposed estimator are evaluated using a number of optimization techniques, such as stochastic gradient descent (SGD), momentum, and the adaptive gradient (AdaGrad) algorithm. The Bi‐LSTM‐based CSI estimator is trained considering a specific number of PS. It can be readily seen that by incorporating a cyclic prefix (CP), the system becomes more resilient to channel impairments, resulting in a lower SER. Simulations show that the SGD optimization approach and Huber loss function‐trained Bi‐LSTM‐based CSI estimator have the lowest SER and very high estimation accuracy. By using deep neural networks (DNNs), the Bi‐LSTM method for CSI estimation achieves a superior channel capacity (in bps/Hz) at 10 dB than long short‐term memory (LSTM) and other conventional CSI estimators, such as minimum mean square error (MMSE) and least squares (LS). The simulation results validate the analytical results in the study.

Enhancement of outage probability for down link cooperative non-orthogonal multiple access in fifth-generation network

<span lang="EN-US">Future wireless networks are expected to face several issues, but cooperative non-orthogonal multiple access (C-NOMA) is a promising technology that could help solve them by providing unprecedented levels of connection and system capacity. In this regard, the influence of the power location coefficient (PLC) for remote users adopting multiple-input-multiple-output (MIMO) and massive MIMO has been explored to provide effective performance. The goal of this study is to design fifth-generation (5G) downlink (DL) NOMA power domain (PD) networks with a variety of distances and PLCs for remote users and then to compare their outage probability (OP) performance versus signal to noise ratio (SNR). As a novel approach to improving OP performance rate and mitigating the influence of the PLC for remote users, DL C-NOMA is combined with 16×16, 32×23, and 64×64 MIMO and 128×128, 256×256, and 512×512 massive MIMO. The results were obtained that the 64×64 MIMO improves the OP for the remote user by 65.0E-03, while the 512×512 massive MIMO achieved an improvement that reaches 1.0E-06 for the PLC of 0.8 at SNR of 14 dB. The Rayleigh fading channels and MATLAB simulation tools were utilized to carry out the study work.</span>

Outage Probability Oriented Secrecy Rate Optimization for Finite-Alphabet Inputs

This paper aims at investigating the secrecy outage probability (SOP) performance and formulating an associated precoder optimization problem to maximize the achievable secrecy rate (SR) for finite-alphabet inputs. As a passive eavesdropper is taken into account, we derive that: 1) the phase of the optimal precoder is orthogonal to that of the channel spanning from the transmitter to the intended receiver; 2) the modulus of the optimal precoder vector also has a linear correlation to that of the mentioned channel. Benefited from these findings, the original optimization problem is simplified to one only related to a pair of scalars, which thus dramatically reduces the computational complexity. Our simulation results finally verify the effectiveness of the proposed precoder design scheme.

Performance Analysis of Full Duplex Bidirectional Machine Type Communication System Using IRS with Discrete Phase Shifter

In this paper, passive Intelligent Reflecting Surface (IRS) is used to enhance the performance of a Full Duplex (FD) bidirectional Machine Type Communication (MTC) system with two source nodes. Each node is equipped with two antennas to operate in FD mode. In reality, self-interference and discrete phase shifting are two major impairments in FD and IRS-assisted communication, respectively. The self-interference at source nodes operating in FD mode is mitigated by increasing the number of meta-surface elements at the IRS. Bit Error Rate (BER) and outage performances are analyzed with continuous phase shifting and discrete phase shifting in IRS. Closed-form analytical expressions are derived for the outage probability and BER performances of the IRS-assisted bidirectional FD-MTC system with a continuous phase shifter. The outage and BER performances of the IRS-assisted bidirectional MTC system in the FD mode have Signal-to-Noise Ratio (SNR) improvement compared with the IRS-assisted bidirectional MTC system in Half Duplex (HD) mode, as the number of reflecting elements in IRS is doubled in the FD mode. The outage and BER performances are degraded by a discrete phase shifter. Hence, performance degradation of the proposed IRS-assisted bidirectional FD-MTC is examined for 1-bit shifter (0, π), 2-bit shifter (0, π/2, π, 3π/2), and for 3-bit shifter (0, π/4, π/2, 3π/4, π, 5π/4, 3π/2, 7π/4). The performance degradation when a discrete phase shifter is employed in IRS is compared with the ideal continuous phase shifter in IRS. Further, achievable rate analysis is carried out for finding the best location of the IRS in a bidirectional FD-MTC system.

Outage probability analysis of multiple intelligent reflecting surface‐assisted single‐input single‐output system with switched diversity

SummaryIn this paper, we have presented the outage probability analysis of multiple intelligent reflecting surface (IRS)‐assisted single‐input‐single‐output (SISO) system with switched diversity schemes. The switched diversity is simpler than the selection combining diversity technique, which can help in reducing the channel estimation overhead. There are two main types of switch diversity schemes, namely, switch and stay combining (SSC) and switch and examine combining (SEC). We consider a SISO wireless scenario in which a single transmitting antenna is sending its message to the receiving antenna with the aid of multiple IRS panels. This communication scenario will arise as a typical application of uplink scenario for future 6G wireless systems. The outage probability (OP) expressions for dual‐IRS‐panel‐aided SSC system and multiple‐IRS‐panel‐aided SEC system are analyzed, respectively, over Rician fading channels. We derive tight approximate OP expressions in closed form for a large number of IRS elements. Further, we derive a simple asymptotic OP for studying diversity order and coding gain. The OP performance with respect to each system parameter is thoroughly explored. Several numerical OP results are presented with corresponding simulated OP results to validate the accuracy of the presented analytical analysis.

Performance analysis of MRT/RAS scheme in dual-hop NOMA energy harvesting relay networks

This paper investigates the outage probability (OP) performance of multiple-input multiple-output non-orthogonal multiple access (MIMO-NOMA) relaying networks. In the investigated network, a source simultaneously communicates multiple NOMA users with the assistance of an amplify-and-forward energy harvesting relay. We derive each user’s OP expression in closed form over the generic channel model Nakagami-m fading. Moreover, we carry out asymptotic analysis to have clear insights into the OP behavior in the high signal-to-noise ratio region. The theoretical analysis’s correctness is finally verified via Monte Carlo simulations. The results show that the OP performance improves with the increased number of antennas and enhancement in the channel conditions. Furthermore, the relay has to be near the source in order to have better OP performance. Moreover, each user has a different optimum power division ratio.

Outage probability of multiple-IRS-assisted SISO wireless communications over Rician fading

Outage probability (OP) performance of multiple-intelligent reflecting surface (IRS)-assisted is presented for a practically important single-input-single-output (SISO) wireless communication system over Rician fading channels where the IRS panel selection is considered. We investigate the SISO wireless communication scenario in which a single antenna transmitting node is sending its message to the receiving node with the aid of the best IRS panel selection. This wireless communication scenario model is a typical application of the uplink scenarios for future cellular wireless systems. We derive approximate OP expressions in the closed form using both the central limit theorem and the Laguerre series expansion. Further, we also derive a simple asymptotic OP to get diversity order and coding gain. The influence of each system parameter on OP performance is thoroughly investigated. In addition, the analytical OP results are corroborated with simulated OP results to confirm the accuracy of our presented analytical results.

Performance Analysis and Research of Knowledge Sharing System for Power Grid Networks

Knowledge sharing is a critical aspect of machine learning and knowledge management, which also plays an important role in regulating the power grid networks. Hence, it is important to investigate the performance of knowledge sharing in the power grid networks. Motivated by this, we firstly investigate a typical power grid network with a knowledge sharing node, where the transmit power of users is constrained by the knowledge sharing node. We then measure the system performance by evaluating the system outage probability (OP), where the analytical expression of OP is derived in detail. Finally, we present some simulation and numerical results on the OP for the considered power grid networks with knowledge sharing, in order to verify the proposed studies on the OP. In particular, these results show that the knowledge sharing can help enhance the system OP performance efficiently.

Outage probability of NOMA systems with receive antenna selection in [formula omitted]-[formula omitted] fading channels

This article considers power-domain non-orthogonal multiple access (NOMA) for downlink communication systems that involve multiple users. The base station, equipped with a single transmit antenna, communicates simultaneously with multiple users, each equipped with a single receive antenna. The article examines the system’s outage probability (OP) performance in α−μ generalized fading channels. The article first derives the instantaneous signal-to-interference-and-noise ratio (SINR) and then obtains the OP expression for each user in a closed form. The derived expression for OP is general and includes special cases such as Nakagami-m, Weibull, Gamma, Rayleigh, and Exponential distributions. This α−μ expression helps quantify the improvement of the OP performance. In order to improve the OP performance, multiple antennas are included for the users, and then receive antenna selection (RAS) scheme is employed. Finally, the theoretical OP expressions are verified via Monte Carlo simulations.