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The purpose of this work is to perform the generalized secrecy capacity (i.e., secrecy rate and secrecy outage capacity) analysis of the scheduled transmit antenna selection scheme over non-identical Nakagami fading channels. Especially, this work considers maximal ratio combining (MRC) and selection combining (SC) at the authorized receiver and eavesdropper. To derive the secrecy capacity, this work derives accurate and asymptotic distribution functions (i.e., probability density function and cumulative distribution function) of the received signal to noise ratio (SNR) of the proposed scheme using MRC and SC receivers over non-identical Nakagami fading channels. Using the accurate distribution functions, this work derives the accurate average secrecy rate and tight average secrecy outage capacity of the proposed scheme for various combining scenarios over non-identical Nakagami fading channels. Using the asymptotic distribution functions, this work derives the asymptotic average secrecy capacity and quantifies the high SNR slope and the high SNR power offset for the average secrecy capacity over non-identical Nakagami fading channels. From numerical results, this work shows that the high SNR slope for the average secrecy capacity is one regardless of combining type. It means that neither the authorized parameters nor the eavesdropper parameters affect the high SNR slope over non-identical Nakagami fading channels. On the contrary, the high SNR power offset improves proportionally to the authorized parameters and inversely proportional to the eavesdropper parameters over non-identical Nakagami fading channels. [ABSTRACT FROM AUTHOR]

This paper reports throughput maximization over various fading channels for cluster-based cooperative spectrum sensing in cognitive radio. For that purpose, the secondary users are grouped into clusters and effect of different fusion rules on throughput over Nakagami, Weibull, Rayleigh and Rician fading channels is investigated. Inside each cluster, i.e., for intra fusion, OR ( m = 1 ) and AND ( m = K ) fusion rules are considered. Further, a formula is proposed for optimal number of clusters which maximize throughput over fading channels. This expression is derived for two different inter-cluster fusion rules (fusion rule between cluster head and fusion centre) given as OR ( p = 1 ) and AND ( p = N ). Simulation results are carried out for OR-AND ( m = 1 , p = N ) and AND-OR ( m = K , p = 1 ) fusion rules for given cluster size (number of users inside a cluster), and number of clusters are optimized over Weibull and Nakagami fading channels. The proposed expressions for the optimal number of clusters are validated by the results. It is found that for given fixed parameters, the number of clusters at which throughput is maximum are N = 6 and N = 5 over Nakagami and Weibull fading channels respectively for AND-OR fusion rule. In case of OR-AND fusion rule, maximum throughput is achieved for N = 5 and N = 6 over Nakagami and Weibull fading channels respectively. [ABSTRACT FROM AUTHOR]

In cooperative spectrum sensing (CSS), in order to maximise the energy efficiency (EE) of cognitive radio (CR) users, users are divided into clusters. In this paper, the optimal inter-fusion rule threshold formula for different number of clusters and users is proposed for maximum EE in cluster-based CSS (CB-CSS). Different fusion rules are investigated for this purpose over Nakagami and Rician fading channel conditions. Simulations are conducted for different number of clusters and users using AND and OR intra-fusion rules and inter-fusion rule threshold is optimised in CB-CSS over the Nakagami-m fading channel and the Rician fading channel. The obtained mathematical expression for the inter-fusion rule threshold is verified by the results. It is investigated that when number of clusters are P = 4 and number of users in a cluster are K = 6 , OR-AND ( n = 1 , r = P) fusion rule achieves 2.46% more EE than AND-OR ( n = K , r = 1) fusion rule in case of Nakagami fading channel and 5.06% more EE than AND-OR fusion rule in case of Rician fading channel. Further, EE with respect to number of users is compared between additive white gaussian noise (AWGN) channel and Nakagami and Rician fading channels. [ABSTRACT FROM AUTHOR]

This paper analyzes the secrecy outage probability of amplify and forward (AF) relaying with triple selection over real valued Nakagami fading channels. This paper derives the new upper bound cumulative distribution function expressions of the proposed system for the received signal to noise ratio in which maximal ratio combining and selection combining receivers are considered. Further, this paper derives the lower bound and asymptotic expressions for the secrecy outage probability. An interesting numerical result is that the secrecy performance of the AF relaying with selection combining is superior to the AF relaying with maximal ratio combining over arbitrary Nakagami fading channels. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of a dual‐signal selection (i.e. selection of direct signal and relay signal) and multiple eavesdroppers on secrecy outage probability in cooperative‐relay systems over Nakagami fading channels. This work performs the derivation of the new exact and approximate distributions for the received signal to noise ratio of the dual‐signal selection in analytical forms where maximal‐ratio combining and selection combining are considered in the presence of multiple eavesdroppers. The lower bounds on the secrecy outage probability of the dual‐signal selection are derived for various receiver scenarios over Nakagami fading channels. This paper also quantifies the secrecy diversity order of the proposed scheme and shows that the dual‐signal selection provides a secrecy diversity order gain of λd=mdUMsMu compared to the conventional scheme by the dual‐signal selection. From the numerical results, this work observes that the sharpness of the dual‐signal selection for the secrecy performance curve is improved by the number of user nodes and fading index of the direct signal, while the number of eavesdroppers and fading index of the eavesdropper slightly affect the required signal to noise ratio of the proposed scheme to satisfy the secrecy outage probability. [ABSTRACT FROM AUTHOR]

This study deals with the performance analysis of adaptive combining‐based hybrid free‐space optics (FSO)/radio‐frequency (RF) system in a terrestrial communication scenario with and without pointing errors. Here, outage probability and average symbol error rate (SER) are used as the performance metrics. Adaptive combining is a switching scheme in which the FSO link is active throughout, whereas the RF link is activated based on the transmission reliability of the FSO link and maximal‐ratio‐combining (MRC) of RF and FSO links is performed at the destination. The small‐scale fading in RF and atmospheric turbulence induced fading in FSO links have been characterised by Nakagami‐m and Gamma–Gamma distributions, respectively. In addition, the radial displacement between the beam centre and detector centre, which induces pointing errors, is modelled using Rayleigh distribution. The exact closed form expressions for the outage and average SER have been derived along with their corresponding asymptotic expressions. Diversity gain of the system has also been determined using the asymptotic expressions. Further, the variation in the performance of the system has been analysed with respect to various parameters including link distance, fading severity parameter, average signal‐to‐noise of the RF link, and the pointing errors parameter. [ABSTRACT FROM AUTHOR]

Stochastic geometry is emerging as tractable solution and attractive approach to evaluate the performance of 5G heterogeneous network (5G‐Hetnet) such as coverage, outage and rate probability. The base stations (BSs) and fading distribution in 5G‐Hetnet are an almost ubiquitous assumption for analytical study, requiring flexible and scalable approaches. However, the β‐Ginibre point process (β‐GPP) has been proposed as a new method to model wireless network. This study provides a general framework to analyse downlink mmWave cellular network with Nakagami‐m fading and directional beamforming. First, cell association scheme in both line‐of‐site and non‐line‐of‐site is considered based on the strongest average received power. After deriving cell association probability between user equipment and BS, the computationally coverage probability expression is obtained depending on signal‐to‐interference‐plus‐noise ratio. Furthermore, the impact of biasing factor on rate coverage probability is investigated. Finally, considering inter‐cell‐interference coordination, most performances metrics will be re‐evaluated to determine their influence on the network. Recommended approaches produce satisfactory results when biasing factor and antenna beamforming are used. [ABSTRACT FROM AUTHOR]

In this work, the physical layer security performance of an underlay cognitive buffer‐aided relay network over the general Nakagami‐m fading channel model is addressed, where a primary source communicates with a destination via a decode‐and‐forward relay node in the presence of an eavesdropper and a secondary communication system. The relay is equipped with a finite‐size storage equipment or buffer which can store the sequence of received data packets from source and forward it immediately or subsequently in an adequate time‐slot. In this way, the buffer relay enables to adopt a link selection scheme in order to detect the best available link, (i.e. the one with higher secrecy rate) among the available data at source or at the relay buffer. The closed‐form expression for the secrecy outage probability (SOP), which is a widely adopted performance metric in the considered scenario, is also derived. Numerical results confirm the accuracy of the derived closed‐form analytic expression for SOP and indicates the interaction between secrecy performance and the Nakagami channel parameter m. In particular, it is shown that the SOP experiences a significant drop as the Nakagami channel parameter increases for a predefined target secrecy rate. [ABSTRACT FROM AUTHOR]

The paper derives the throughput, outage and packet error probabilities of cooperative non-orthogonal multiple access (NOMA) with energy harvesting. In the first time slot, relay node harvests energy using radio frequency (RF) signal received from the base station (BS). In the second time slot, BS transmits a combination of two symbols s f and s n dedicated for far and near users. This signal is received by the two users and a relay. In the third time slot, the relay node amplifies the received signal to the two users. Both users use the signal with the highest signal-to-interference plus noise ratio (SINR) among direct and relayed signals. The far user detects only its symbol. Near user first detects symbol s f of far user. After removing the contribution of far user, near user detects its own symbol s n . We propose the use of the gradient algorithm to optimize harvesting duration and the powers allocated to far and near users to maximize the total throughput. [ABSTRACT FROM AUTHOR]

This paper presents the secrecy outage probability of relay and user (RU) selection in the antenna selection (AS)-amplify and forward (AF) system over integer-valued m Nakagami fading channels for the physical layer security. This work derives the lower bound (LB) and asymptotic cumulative density functions (CDFs) of the signal to noise ratio (SNR) for the RU selection in the AS-AF system. This study also considers the impact of the two types of receivers, i.e., maximal ratio combining (MRC), selection combining (SC) for the authorized system and eavesdropper. Using the lower bound CDFs, the LB expressions of the secrecy outage probability are derived for various scenarios. Applying the asymptotic CDFs, the diversity order of the secrecy performance is also quantified for each case. From analysis results, we show that the diversity order of the secrecy outage probability in the proposed system is only affected by authorized system's parameters, not by eavesdropper's parameters. Further, the relay and user nodes with the MRC receiver provide the SNR gain compared to the SC receiver regardless of eavesdropper's receiver type. Finally, the secrecy outage probability of the proposed RU system with the SC eavesdropper has the SNR gain compared to the MRC eavesdropper, while the diversity order is identical to each other. [ABSTRACT FROM AUTHOR]

Stochastic geometry is emerging as tractable solution and attractive approach to evaluate the performance of 5G heterogeneous network (5G‐Hetnet) such as coverage, outage and rate probability. The base stations (BSs) and fading distribution in 5G‐Hetnet are an almost ubiquitous assumption for analytical study, requiring flexible and scalable approaches. However, the β‐Ginibre point process (β‐GPP) has been proposed as a new method to model wireless network. This study provides a general framework to analyse downlink mmWave cellular network with Nakagami‐m fading and directional beamforming. First, cell association scheme in both line‐of‐site and non‐line‐of‐site is considered based on the strongest average received power. After deriving cell association probability between user equipment and BS, the computationally coverage probability expression is obtained depending on signal‐to‐interference‐plus‐noise ratio. Furthermore, the impact of biasing factor on rate coverage probability is investigated. Finally, considering inter‐cell‐interference coordination, most performances metrics will be re‐evaluated to determine their influence on the network. Recommended approaches produce satisfactory results when biasing factor and antenna beamforming are used. [ABSTRACT FROM AUTHOR]

This study deals with the performance analysis of adaptive combining‐based hybrid free‐space optics (FSO)/radio‐frequency (RF) system in a terrestrial communication scenario with and without pointing errors. Here, outage probability and average symbol error rate (SER) are used as the performance metrics. Adaptive combining is a switching scheme in which the FSO link is active throughout, whereas the RF link is activated based on the transmission reliability of the FSO link and maximal‐ratio‐combining (MRC) of RF and FSO links is performed at the destination. The small‐scale fading in RF and atmospheric turbulence induced fading in FSO links have been characterised by Nakagami‐m and Gamma–Gamma distributions, respectively. In addition, the radial displacement between the beam centre and detector centre, which induces pointing errors, is modelled using Rayleigh distribution. The exact closed form expressions for the outage and average SER have been derived along with their corresponding asymptotic expressions. Diversity gain of the system has also been determined using the asymptotic expressions. Further, the variation in the performance of the system has been analysed with respect to various parameters including link distance, fading severity parameter, average signal‐to‐noise of the RF link, and the pointing errors parameter. [ABSTRACT FROM AUTHOR]

As the first class of constructive channel codes achieving the symmetric capacity of the binary-input discrete memoryless channels, polar codes have been extended to the fading channel. But most constructions of polar codes in fading channel are only suitable for the Rayleigh fading and involve complex iterative-calculation. In this paper, we establish a systematic framework in term of the polar spectrum to analyze and construct polar codes in various fast fading channels, such as Rician, Rayleigh and Nakagami channels. In these three fading channels, by using the polar spectrum, we derive the upper bound of the error probability of the polarized channel and that of block error rate of polar codes. The analysis based on the polar spectrum explicitly reveals the relationship between the diversity order and the codeword weight. Furthermore, we propose two construction metrics, named logarithmic upper-bound weight (LUW) and minimum-weight LUW (MLUW) respectively, to design the polar codes in fast fading channels. These two constructions are simple with a linear complexity and explicit for the practical implementation. In addition, for various fading channels, they can construct polar codes with similar or better performance over those based on traditional methods. [ABSTRACT FROM AUTHOR]

In this paper, we suggest two adaptive cooperation protocols for millimeter wave communications. The first protocol chooses, between non cooperative and cooperative communications, the protocol that offers the highest instantaneous throughput. The second protocol chooses, between non cooperative and cooperative communications, the protocol maximizing the average throughput. Both protocols use adaptive modulation and coding to select the best modulation and coding scheme maximizing the average or instantaneous throughput. Our results are valid for interference limited millimeter wave communications in the presence of Nakagami fading channels. [ABSTRACT FROM AUTHOR]

In this study, the authors present an analytical approach to evaluate the performance of a two-way multi-relay system with direct link using a three-phase analogue network coding and opportunistic relay selection scheme. Herein, the imperfect channel state information is considered over independent and non-identically distributed Nakagami-m fading channels with integer-valued fading parameter. For analysis, initially, the closed-form expressions of cumulative distribution function and moment generating function (MGF) for the considered system are derived. Further, by using the MGF-based approach, generalised expressions of average symbol error rate (ASER) for higher-order quadrature amplitude modulation (QAM) schemes such as hexagonal QAM, rectangular QAM, and cross QAM are derived. They then analyse the asymptotic behaviour of ASER expression to evaluate the system's diversity order. Furthermore, a comparative analysis of the ASER performance for various QAM constellations is illustrated and impact of the number of relays, fading parameter, relay location, and channel estimation error are highlighted on the system's performance. Finally, all the analytical results are validated through Monte-Carlo simulations. [ABSTRACT FROM AUTHOR]

Summary: Future green technologies require the reduction of power consumptions, increasing energy efficiencies, and managing the electromagnetic interference footprints. In this paper, we investigate the use of randomized transmit power strategy in which the nodes transmit with random power in a single‐hop ad hoc wireless network. We assume Nakagami‐m channel with very slow feedback channel for power update commands. Hence, by using the characteristic function of the received power, we develop a new mathematical formulation for the outage probability. Further, we test the developed formulation on the known constant transmit power case and randomized uniform distribution with constant maximum case. We show that the performance in terms of outage probabilities and total power consumption of all nodes is generally poor. Therefore, we extend our results to the case of optimized constant power and propose the use of randomized uniform distribution with optimized maximum power. We show that the proposed power distribution outperforms the previous ones and reduces the overall power consumption by many orders of magnitude. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the throughput of cooperative communications with wireless energy harvesting. Relay nodes harvest energy from Radio Frequency (RF) signal transmitted by the source. We derive the packet error probability as well as the throughput for Nakagami fading channels. We also suggest to enhance the throughput by choosing the value of harvesting duration. Our results are valid for both Amplify and Forward (AF) and Decode and Forward (DF) relaying. [ABSTRACT FROM AUTHOR]

In this paper, we propose an asymmetric adaptive modulation scheme for a heterogeneous two-way relay network (TWRN). In this scheme, due to the heterogeneity of the TWRN, different modulation schemes with different bit rates are assigned to the source nodes. Due to the mismatch between the bit rates of the two opposite traffic flows, the conventional XOR-based network coding is not applicable to this scheme. To cope with this heterogeneity at the relay node, we propose a network coding scheme in which the two data streams are combined at the level of symbol. We optimize the pair of modulation schemes and bit rates such that the instantaneous transmission rate is maximized under the constraint that a quality-of-service requirement in terms of the end-to-end BER is satisfied. To find the solution of this multi-dimensional problem, we propose a simple procedure with very low computational complexity by reducing the problem dimension to one. We analyze the system performance in terms of the average end-to-end BER, the average transmission rate, and the outage probability over Nakagami fading channel. Our analysis shows that this scheme not only achieves high spectral efficiency but also mitigates error propagation from the relay to the transceivers. [ABSTRACT FROM AUTHOR]

Multipath fading is one of the most common distortions in wireless communications. The simulation of a fading channel typically requires drawing samples from a Rayleigh, Rice or Nakagami distribution. The Nakagami-m distribution is particularly important due to its good agreement with empirical channel measurements, as well as its ability to generalize the well-known Rayleigh and Rice distributions. In this paper, a simple and extremely efficient rejection sampling (RS) algorithm for generating independent samples from a Nakagami-m distribution is proposed. This RS approach is based on a novel proposal density composed of three pieces of well-known densities from which samples can be drawn easily and efficiently. The proposed method is valid for any combination of parameters of the Nakagami distribution, without any restriction in the domain and without requiring any adjustment from the final user. Simulations for several parameter combinations show that the proposed approach attains acceptance rates above 90% in all cases, outperforming all the RS techniques currently available in the literature. [ABSTRACT FROM AUTHOR]

Wireless energy harvesting has been recognized as a promising technique to prolong the lifetime of energy constrained relay nodes in wireless sensor networks. Its application and related performance study in three-step two-way decode-and-forward (DF) relay networks are of high interest but still lack sufficient study. In this paper, we propose a dynamic power-splitting (PS) scheme to minimize the system outage probability in a three-step two-way energy harvesting DF relay network and derive an analytical expression for the system outage probability with respect to the optimal dynamic PS ratios. In order to further improve the system outage performance, we propose an improved dynamic scheme where both the PS ratios and the power allocation ratio at the relay are dynamically adjusted according to instantaneous channel gains. The corresponding system performance with the improved dynamic scheme is also investigated. Simulation results show that our proposed schemes outperform the existing scheme in terms of the system outage performance and the improved dynamic scheme is superior to the dynamic PS scheme. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses articles in the issue on topics including 5G cellular network, wireless M2M devices, and Nakagami channels.

In this paper, the secrecy performance of cooperative heterogeneous networks with unreliable backhaul over Nakagami-m fading channels is investigated. To secure the proposed system, a friendly jammer is considered to confuse eavesdroppers. To transmit the signals from the source to the destination, a two-phase transmitter/relay selection scheme is proposed. The best transmitter is selected when the signal-to-noise ratio at the relays is maximized. In the second phase, the best relay is chosen when the jamming signal-to-interference-plus-noise ratio of the eavesdroppers is minimized. To investigate the system performance, closed -form expressions are derived for the secrecy outage probability, ergodic capacity and non-zero achievable secrecy rate. In order to gain an insight into the system, asymptotic analysis is also provided. The results show that the degree of cooperative transmission and backhaul reliability are key parameters in the system and these parameters determine the secrecy performance. [ABSTRACT FROM AUTHOR]

In this paper, two carrier index differential chaos shift keying (CI-DCSK) with simultaneous wireless information and power transfer schemes, which integrate CI-DCSK modulation with wireless power transfer, are proposed. In the proposed schemes, based on the transmission characteristics of index modulation, the inactive carriers of CI-DCSK are exploited to deliver energy by transmitting random noise-like signals subjected to normal distribution. By applying time switching (TS) at the receiver, each frame time of the proposed schemes is divided into two intervals. Unlike usual TS-based systems, two intervals of the proposed schemes are related, where energy harvesting and decoding of the modulated bits are both operated in the second interval. Analytical bit error rate (BER) expressions over additive white Gaussian noise and multipath Rayleigh fading channels of the two schemes are derived. The expression for the parameter $\xi$ is also derived that measures the probability of self-sufficiency of these schemes. The impact of the dividing point of two intervals on BER performance of systems is also analyzed and optimized. Since the energy on the inactive carriers is adjustable, the schemes are always self-sustainable in energy supply. To provide the best performance, the ratio of energy on the inactive carriers to that on the active carriers is optimized. Simulation results show that though performances of the proposed schemes are a little worse than CI-DCSK with the same spectral efficiency, the proposed schemes are all self-sustainable. [ABSTRACT FROM AUTHOR]

Using a distribution of a non-central chi-square random variable and selection combining, statistics of wireless systems employing decode-and-forward (DF) opportunistic relays (ORs) under outdated channel state information (CSI), and independent and identically distributed (i.i.d.) generalized-Rician fading environments are derived. By mathematically rewriting the Marcum $Q$ -function in its infinite-summation form, the distribution of non-central chi-square is mathematically simplified to its desirable form under different scenarios, which are then employed to compute average bit error rates for popular modulation schemes. Distributions of end-to-end system signal-to-noise ratio, useful for fifth-generation backhaul wireless communications, are also derived under integer and non-integer fading parameters. The new findings generalize existing findings employing DF ORs under i.i.d. Rayleigh fading environments. Mathematical predictions are shown to match simulation results. [ABSTRACT FROM AUTHOR]

In this paper, we consider a radio-frequency identification (RFID) backscatter system with two scenarios: single input multiple output (SIMO) and multiple input single output (MISO). We investigate the impact of channel correlation between the forward and backscatter links on the symbol error rate (SER), and we compare the performance of SIMO and MISO RFID systems with maximum ratio combining reception over arbitrarily correlated Nakagami- $m$ fading channels. In order to gain an insight for the system design, closed-form expressions for the asymptotic SER and an upper bound are derived for $M$ -ary phase-shift keying and quadrature amplitude modulation. The diversity order in the fully correlated cases, revealed from these expressions, is half of that in the partially correlated and uncorrelated cases. Finally, simulations are performed to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA) is currently considered as a promising technology for the next-generation wireless networks. In this paper, the error rate performance of NOMA systems is investigated over Nakagami- $m$ fading channels, while considering imperfect successive interference cancelation. In particular, this paper focuses on the pairwise error probability (PEP) analysis, where exact PEP expressions are derived to characterize the performance of all users under different fading conditions. The obtained PEP expressions are then used to derive an exact union bound on the bit error rate (BER). Through the derived PEP expressions, the asymptotic PEP analysis is presented to investigate the maximum achievable diversity gain of NOMA users. Moreover, using the derived BER bound, the power allocation problem for all users in NOMA systems is considered under average power and users BER constraints, which allows realizing the full potential of NOMA. Monte Carlo simulation and numerical results are presented to corroborate the derived analytical expressions and give valuable insights into the error rate performance of each user and the achievable diversity gain. [ABSTRACT FROM AUTHOR]

Link adaptation (LA) schemes maximize average spectral efficiency (ASE) using accurate channel state information (CSI) and knowledge of signal to noise ratio (SNR) distribution. In practical systems, partial CSI is available at the transmitter through feedback of modulation and coding scheme index, often known as channel quality indicator (CQI). However, parameters of SNR distribution (${\Theta }$) are not known or only assumed to be known. We propose two LA schemes, for execution at the receiver and transmitter, respectively, each without prior knowledge about ${\Theta }$. In the receiver centric schemes, parametric estimation of SNR distribution is performed using unquantized SNR samples. In the transmitter centric scheme, we estimate ${\Theta }$ from CQI samples using an iterative joint quantization-estimation algorithm. These parametric estimates form long-term SNR distribution, which is used to compute SNR switching thresholds. Using these thresholds, rate and power adaptation decisions are made based on instantaneous SNR. We have derived the maximum-likelihood estimator and Cramer–Rao lower bound for the proposed estimator using CQI feedback for Nakagami- $m$ fading channels and demonstrate that near optimal ASE can be achieved while using the proposed schemes as in an ideal scenario, where perfect knowledge about CSI and SNR distribution are available a priori. [ABSTRACT FROM AUTHOR]

This study presents a full‐duplex (FD) relaying non‐orthogonal multiple access (NOMA) scheme with self‐interference at relay taken into account, where a sender communicates with multiple terminals simultaneously with the help of an FD amplify‐and‐forward relay. The relay is equipped with two antennas, one for transmission and the other for reception. Moreover, with a direct link as a useful information transmission link, selection combining is applied to merge the information from the sender and the relay. General closed‐form expressions of the outage probability are deduced and the upper bound of the ergodic sum rate is derived, including half‐duplex (HD) mode relay as a special case. Compared with the HD relaying scheme, the authors can observe that the FD relaying scheme can achieve higher ergodic sum rate in the moderate‐ and high‐SNR regions and that the outage behaviour can be improved in most cases (if the self‐interference is not extremely severe). More importantly, the use of NOMA in FD relaying system is shown to outperform conventional orthogonal multiple access (OMA) network in terms of terminal fairness. Extensive simulation results are presented to confirm their conclusions and provide a significant reference for the system design. [ABSTRACT FROM AUTHOR]

In this study, the authors investigate the secrecy performance at the physical layer of wireless communication systems where the channels are modelled as cascaded fading channels, in which the fading effects are worse than those in the cellular communication channels like Rayleigh and Nakagami-m. Analytic results are derived for the cascaded Nakagami-m fading channel model comprising the cascaded Rayleigh, 2*Nakagami-m, the generalised-K, and the conventional cellular channel models as well. By evaluating the information-theoretic physical layer security performance, they obtain the closed-form expressions of the average secrecy capacity and probability of the positive secrecy capacity in case of that channel-stateinformation of the eavesdropper is known by the source. Then they obtain the exact closed-form secrecy outage probability (SOP) when the eavesdropper is passive. Analytic results are computed in terms of the bivariate and univariate Meijer's G functions and later on are successfully validated through Monte Carlo simulations. The simulation results show that the secrecy performance worsens with the increasing cascading degree of the fading channels. For example, in 2*Nakagami-m fading channels where the cascading degree is 2, extra 4 dB signal-to-noise ratio is required to achieve the same SOP value in comparison with the classical Nakagami-m fading channels. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we analyze the performance of the full-duplex relay system, wherein two terminal nodes operate in the half-duplex mode and the relay node with decode-and-forward scheme operates in the full-duplex mode. We consider the replenishes energy from radio frequency (RF) for the source and the relay nodes through the power beacon (PB) combine with the case of imperfect self-interference cancellation (SIC) at the full-duplex relay. To increase the collected energy for the source and the relay, on the other hand decreasing the complexity for the high power amplifier at the PB, we assume that the PB has multiple antennas. Using theoretical analysis, we obtain the closed-form of the exact outage probability of the system over Nakagami- m fading channels. Furthermore, the exact expression for the symbol error probability of the system is derived to evaluate the system performance with different modulation schemes. Based on this analysis, the impact of the antenna numbers, m parameters, the time duration for harvesting and the residual self-interference are considered. The Monte-Carlo simulations are used to demonstrate the correctness of numerical results. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the outage performance of cellular two-way amplify-and-forward (AF) cooperative spectrum sharing systems in the presence of primary user (PU) network and multiple secondary user (SU) destinations. A general Nakagami-m fading environment has been used, where distinct fading parameters, as well as unequal average fading powers between the interference and relaying links, are assumed. Focusing on the cooperation process among the SU nodes and making use of the underlay cognitive approach, an approximate closed-form expression for the overall outage probability (OOP) of the secondary network is derived. In this analysis, an opportunistic scheduling and transmit antenna selection (TAS) algorithm in the secondary network has been employed. Considering the interference constraints due to the presence of PU receiver, power allocation of secondary user is done. The effects of fading severity, secondary network relay placement, the number of PU & SU transmit antenna, and number of SUs on the end-to-end system performance are examined through some representative numerical plots. Moreover, to minimize the secondary network OOP, we investigate the optimization problems of relay position. Monte Carlo simulation results are presented to corroborate the proposed analysis. [ABSTRACT FROM AUTHOR]

In this paper, an energy harvesting relay network over Nakagami-m fading is investigated. In the considered system, the power beacon can provide wireless energy for the source and relays which deploy time-switching-based radio frequency energy harvesting technique. Two relay selection schemes, namely partial relay selection and optimal relay selection, are proposed in order to enhance the system performance. In the former, the source only has the channel state information of the first hop, while in the latter it has the full knowledge of the channel state information. The eavesdropper is able to wiretap to the signal transmitted from the source and the relays. The exact closed-form expressions of secrecy outage probability are derived. The results show that optimal relay selection performs better than partial relay selection. With increasing number of relays, the considered system shows better performance. In addition, the energy harvesting duration has a significant effect on the secrecy outage probability. [ABSTRACT FROM AUTHOR]

To enhance the spectrum scarcity of cooperative heterogeneous networks (HetNets) with unreliable backhaul connections, we examine the impact of cognitive spectrum sharing over multiple small-cell transmitters in Nakagami-m fading channels. In this system, the secondary transmitters are connected to macro-cell via wireless backhaul links and communicate with the secondary receiver by sharing the same spectrum with the primary user. Integrating cognitive radio (CR) network into the system, we address the combined power constraints: 1) the peak interference power at the primary user and 2) the maximal transmit power at the secondary transmitters. In addition, to exclude the signaling overhead for exchanging channel-state-information (CSI) at the transmitters, the selection combining (SC) protocol is assumed to employ at the receivers. To evaluate the performance, we first derive the closed-form statistics of the end-to-end signal-to-noise (SNR) ratio, from which the exact outage probability, ergodic capacity and symbol error rate expressions are derived. To reveal further insights into the effective unreliable backhaul links and the diversity of fading parameters, the asymptotic expressions are also attained. The two interesting non-cooperative and Rayleigh fading scenarios are also investigated. Numerical results are conducted to verify the performance of the considered system via Monte-Carlo simulations. [ABSTRACT FROM AUTHOR]

We propose a power-and rate-adaptation scheme for cloud radio access networks (C-RANs), where each radio remote head (RRH) is connected to the baseband unit pool through optical links. The RRHs jointly support the users by efficiently exploiting the enhanced spatial degrees of freedom. Our proposed scheme aims at maximizing the effective capacity (EC) of the user subject to both per-RRH average- and peak-power constraints, where the EC is defined as the maximum arrival rate that can be supported by the C-RAN under the statistical delay requirement. We first transform the EC maximization problem into an equivalent convex optimization problem. By using the Lagrange dual decomposition method and solving the Karush–Kuhn–Tucker equations, the optimal transmission power of each RRH can be obtained in the closed form. Furthermore, an online tracking method is provided for approximating the average power of each RRH. For the special case of two RRHs, the expression of the average power of each RRH can be calculated in the explicit form. Hence, the Lagrange dual variables can be computed in advance in this special case. Furthermore, we derive the power allocation for two important extreme cases: first, no delay constraint and, second, extremely stringent delay requirements. Our simulation results show that the proposed scheme significantly outperforms the conventional algorithm without considering the delay requirements. Furthermore, when appropriately tuning the value of the delay exponent, our proposed algorithm is capable of guaranteeing a delay outage probability below $10^{-9}$ when the maximum tolerable delay is 1 ms. This is suitable for the future ultra-reliable low-latency communications. [ABSTRACT FROM AUTHOR]

Using a well-known wire-tap model, novel wireless secrecy analyses under dual correlated Nakagami- $m$ fading with a real fading parameter $m$ are reported. Infinite summations for incomplete gamma functions are employed to derive compact expressions for secrecy capacity and secrecy outage probability (SOP) under noninteger $m$. Independently, using finite summations, corresponding closed-form findings for integer $m$ are also derived. In the current literature, finite summations for the incomplete gamma functions, whose first arguments and hence $m$ must be an integer, are employed to obtain closed-form expressions for, first, the SOP (with an unknown passive wire-tapper's channel state information), and second, ergodic secrecy capacity (with partially known active wire-tapper's channel state information under slow fading). The new secrecy results for noninteger $m$ generalize the proposed findings for integer $m$ , and existing findings under dual correlated Rayleigh fading for $m=1$. The new findings can thus be comprehensively employed for wireless secrecy computation under dual correlated Nakagami- $m$ fading for real $m$. Infinite-summation convergence and cross verification are also obtained for a finite number of terms, which shows the practicality and consistency of the new findings. For the first time, secrecy analyses employing an adaptive encoder with on/off transmission are performed under dual correlated Nakagami- $m$ fading for real $m$ to not only improve wireless secrecy, but also achieve the eventual successful transmission from a source to a destination. The new SOP results for real $m$ can be employed as lower bounds and complete theoretical secrecy analyses, for SOP under dual correlated Nakagami- $m$ fading with integer $m$. Simulation results are employed to show matching between the proposed findings and existing findings. [ABSTRACT FROM AUTHOR]

Summary: This paper investigates the secrecy outage probability (SOP) and intercept behavior for the amplify‐and‐forward network over Nakagami‐m fading channels. Relay selection schemes are evaluated. The optimal and suboptimal criterions require the instantaneous and statistical channel state information of the eavesdroppers' channels, respectively. The enhanced 2‐hop criterion needs the additional information of the target secrecy rate for relay selection. Theoretical analysis reveals that the diversity order of the SOP is dominated by the minimum fading figures of the source‐relay and relay‐destination channels, while that of the intercept probability depends on the fading figure of the relay‐destination channel. In the multirelay scenario, the optimal, suboptimal, and enhanced 2‐hop scheme achieve the same diversity orders of the SOP. For the intercept probability, the optimal and second‐hop relay selection schemes provide the same diversity order, while the diversity orders of the suboptimal and enhanced 2‐hop schemes are the same. Simulation results finally substantiate the accuracy of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a high data rate bidirectional relay network is proposed by combining the merits of spatial modulation (SM) and physical layer network coding. All nodes in the network are equipped with multiple antennas. Spatial modulation technique is used to reduce hardware complexity and interchannel interference by activating only one antenna at any time during transmission. In the proposed bidirectional relay network, transmit antennas are selected at the source nodes and relay node on the basis of the order statistics of channel power. It increases received signal power and provides a significant improvement in the outage performance. Also, the data rate of the proposed network is improved by physical layer network coding at the relay node. A closed form analytical expression for the outage probability of the network over Nakagami‐m fading channel is derived and validated by Monte Carlo simulations. In addition, asymptotic analysis is investigated at high signal‐to‐noise ratio region.The outage performance of the proposed network is compared with SM and physical layer network coding bidirectional relay network without transmit antenna selection and point‐to‐point SM. With approximate SNR≈1 dB difference between the two networks, the same data rate is achieved. [ABSTRACT FROM AUTHOR]

The theory of weighted distributions introduced and unified by Fisher (1934) and Rao (1965) gives a consolidated approach of dealing with model specification and data interpretation problems. In this manuscript, we estimate the scale parameter of weighted Nakagami distribution (WND) through classical and Bayesian methods of estimation. The posterior distributions are derived by considering different types of priors. Also the posterior risks and posterior estimates are calculated under the combination of different priors and loss functions. For analysis, we use R-software. [ABSTRACT FROM AUTHOR]

For buffer-aided tandem networks consisting of relay nodes and multiple channels per hop, we consider two traffic allocation schemes, namely local allocation and global allocation, and investigate the end-to-end latency of a file transfer. We formulate the problem for generic multi-hop queuing systems and subsequently derive closed-form expressions of the end-to-end latency. We quantify the advantages of the global allocation scheme relative to its local allocation counterpart, and we conduct an asymptotic analysis on the performance gain when the number of channels in each hops increases to infinity. The traffic allocations and the analytical delay performance are validated through simulations. Furthermore, taking a specific two-hop network with millimeter-wave (mm-wave) as an example, we derive lower bounds on the average end-to-end latency, where Nakagami- $m$ fading is considered. Numerical results demonstrate that, compared with the local allocation scheme, the advantage of global allocation grows as the number of relay nodes increases, at the expense of higher complexity that linearly increases with the number of relay nodes. It is also demonstrated that a proper deployment of relay nodes in a linear mm-wave network plays an important role in reducing the average end-to-end latency, and the average latency decays as the mm-wave channels become more deterministic. These findings provide insights for designing multi-hop mm-wave networks with low end-to-end latency. [ABSTRACT FROM AUTHOR]

Millimeter-wave (mm-wave) device-to-device (D2D) communication is considered one of the most promising enabling technologies to meet the demanding requirements of future networks. Previous works on mm-wave D2D network analysis mostly considered the case that all devices were equipped with exactly the same number of antennas, whereas real networks are more complicated due to the coexistence of diverse devices. In this paper, we present a comprehensive investigation on the interference characteristics and link performance in mm-wave D2D networks where the concurrent transmission beams are varying in width. First, we establish a general and tractable framework for the target network with Nakagami fading and directional beamforming. To fully characterize the interference, we derive the mean and variance of the interference and then provide an approximation of the interference distribution by a mixture of the inverse gamma and the log-normal distributions. More importantly, the coexistence of varied beamwidths renders their interactions and thus the interference quite complicated and sensitive to the antenna pattern, highlighting the significance of adopting an accurate model for the antenna pattern. Second, to show the impact of heterogeneous antenna arrays on the link performance, we derive the signal-to-interference-plus-noise ratio and rate distributions of the typical receiver as well as their asymptotics, bounds, and approximations to get deep insights on the performance of the network. [ABSTRACT FROM AUTHOR]

In this paper, we provide a global framework analysis of a dual-hop mixed radio frequency (RF)/free space optical (FSO) system with multiple branches/relays wherein the first and second hops, respectively, consist of RF and FSO channels. To cover various cases of fading, we propose generalized channels’ models for RF and FSO links that follow the Nakagami-m and the double generalized gamma distributions, respectively. Moreover, we suggest channel state information (CSI)-assisted relaying or variable relaying gain based amplifiy-and-forward amplification. Partial relay selection with outdated CSI is assumed as a relay selection protocol based on the knowledge of the RF CSI. In order to derive the end-to-end signal-to-interference-plus-noise ratio statistics, such as the cumulative distribution function, the probability density function, the higher order moments, the amount of fading and the moment generating function, the numerical values of the fading severity parameters are only valid for integer values. Based on these statistics, we derive closed-forms of the outage probability, the bit error probability, the ergodic capacity, and the outage capacity in terms of Meijer-G, univariate, bivariate, and trivariate Fox-H functions. Capitalizing on these expressions, we derive the asymptotic high SNR to unpack valuable engineering insights of the system performance. Monte Carlo simulation is used to confirm the analytical expressions. [ABSTRACT FROM AUTHOR]

In this Letter, performance of multiple users in downlink of non-orthogonal multiple access (NOMA) network considering the general α − κ − μ shadowed fading model which was proposed in recent years is studied. In particular, main metrics including the outage probability, ergodic rate related to ordered channels are derived in novel and exact expressions for arbitrary values of the fading parameters. Moreover, numerical simulations are carried out in order to exhibit further insights on how the system performance is affected by the fading parameters. [ABSTRACT FROM AUTHOR]

In this paper, we introduce the length biased form of the Nakagami distribution known as length biased Nakagami distribution (LBND). Some properties of the model were studied such as moments, reliability function, and the hazard rate function. Maximum likelihood and Bayes estimators of the scale parameter are derived. Also, the Posterior risk under different loss functions is obtained. A real life data set is used and the results are compared through R-software. [ABSTRACT FROM AUTHOR]

In this study, the secrecy performance of the classic Wyner's wiretap model over k-μ shadowed fading channels is studied. More specifically, the authors derive two analytical expressions for the lower bound of secure outage probability at high signal-to-noise ratio regime and the probability of strictly positive secrecy capacity over k-μ shadowed fading channels, respectively. As there exist infinite series in the two derived expressions, they further obtain two simple and explicit approximate expressions for the lower bound of secure outage probability and the probability of strictly positive secrecy capacity with the aid of the moment matching method. It is shown that the match between the analytical results and simulations is very excellent for all parameters under considerations. [ABSTRACT FROM AUTHOR]

In this study, the authors first propose two protocols, namely the opportunistic relay (OR) priority and the direct retransmission (DR) priority, based on the reactive and proactive OR selection schemes, respectively. Then, they investigate the outage performance of these protocols with outdated channel state information (CSI) and derive the exact closed-form expressions of the outage probabilities of all the considered scenarios based on the decode-and-forward (DF) protocol. In the high signal-to-noise ratio regime, the authors analyse the asymptotic outage behaviour. In addition, based on the asymptotic analysis, the diversity orders of all the schemes mentioned above are derived. Theoretical analysis and simulation results show that (i) the outage performance of the DR priority is better than that of the OR priority; (ii) the outage performance of the reactive OR selection is better than that of the proactive OR selection in the same scenario; (iii) the diversity orders of all the considered schemes will be reduced to 2 when the CSI is outdated; (iv) the outage performance will be decreased substantially in the case that the channel correlation coefficient has only a little reduction. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the ergodic capacity (EC) of a downlink multiuser hybrid satellite-terrestrial amplify-and-forward relay network (HSTAFRN) using a fixed-gain relaying protocol in the presence of co-channel interference. Herein, we employ opportunistic scheduling of terrestrial users by considering outdated channel state information over Nakagami-m fading channels of pertinent links. By deploying multiple antennas at the satellite, we derive a novel and accurate analytical expression of the achievable EC by making use of the complementary moment generating function transform. More importantly, we carry out the EC analysis under both uncorrelated and correlated shadowed-Rician fading channels of satellite links. Our numerical and simulation results attest the accuracy of the proposed analysis and reveal the impact of various system/channel parameters on EC of the considered HSTAFRN. [ABSTRACT FROM PUBLISHER]

We here introduce an extension and natural generalization of both the $\kappa$-$\mu$ shadowed and the classical Beckmann fading models: the Fluctuating Beckmann (FB) fading model. This new model considers the clustering of multipath waves on which the line-of-sight (LoS) components randomly fluctuate, together with the effect of in-phase/quadrature power imbalance in the LoS and non-LoS components. Thus, it unifies a variety of important fading distributions as the one-sided Gaussian, Rayleigh, Nakagami- $m$, Rician, $\kappa$ -$\mu$, $\eta$- $\mu$, $\eta$ -$\kappa$, Beckmann, Rician shadowed, and the $\kappa$- $\mu$ shadowed distribution. The chief probability functions of the FB fading model, namely probability density function, cumulative distribution function, and moment generating function are derived. The second-order statistics such as the level crossing rate and the average fade duration are also analyzed. These results can be used to derive some performance metrics of interest of wireless communication systems operating over FB fading channels [ABSTRACT FROM PUBLISHER]

Abstract: Radio wave propagation through wireless channels is characterized by 4 main physical phenomena: reflection, diffraction, scattering, and absorption. Considerable efforts have been devoted to develop precise mathematical description of signal fluctuations which is very helpful in designing and evaluating the performance of wireless communication systems. A space diversity reception technique presents effective method for increasing channel capacity and upgrading transmission reliability at relatively low cost. In this paper, wireless communication system with maximal‐ratio combining (MRC) microdiversity and selection combining (SC) macrodiversity reception operating over correlated gamma shadowed Nakagami‐m fading channels is studied. Average bit error probability (ABEP), outage probability and average channel capacity, being significant and generally adopted performance measures, are employed to investigate how system performance is affected by the number of base stations and the number of antennas per base station. [ABSTRACT FROM AUTHOR]

In this paper, we study a cooperative vehicle-to-vehicle (V2V) interference-limited communication system with decode-and-forward relaying operating over double-Nakagami (DN) fading channels. This distribution has been proposed as a fading model for scenarios where both the transmitter and the receiver are in motion, as is the case in V2V communications. For the purposes of our analysis, we introduce the bivariate DN distribution and derive statistical metrics for this distribution, such as the probability density function, the cumulative distribution function, and the moments. The new expressions have been employed to model the outdated channel state information (CSI) that is due to the fast time-varying nature of the wireless medium and the delay naturally existing between relay selection and data transmission instances. The analysis considers two relay selection schemes, according to the relay-destination channel quality, namely the well-known best relay selection (BRS) and a new one termed as threshold-based relay selection, which offers lower complexity than BRS. Using our analytical framework, exact and asymptotic performance results are obtained for the outage and the average symbol error probabilities, while the diversity order has been also evaluated. The numerical and simulation results corroborate our theoretical ones and quantify the impact of the outdated CSI, level of interference, and varying distances between the relay nodes and the final destination on the system's performance. [ABSTRACT FROM PUBLISHER]

In this work, signal space diversity (SSD) is incorporated into a multiple-input multiple-output system with maximal ratio combining and transmit antenna selection. The performance of the proposed system with phase-shift keying (PSK) modulation is studied under a slow flat Rayleigh fading channel scenario with the correlated receive antennas. By adopting the realistic exponential correlation model, an exact closed-form expression is derived for pairwise error probability. The optimal rotation angles are obtained for binary and quadrature PSK signal constellations. The theoretical analysis is verified by the numerical simulations. It is shown that the error performance of the system can be improved with almost no extra complexity or cost. It is also demonstrated that the proposed scheme with SSD is more resistant against the studied correlation model as compared to the original scheme without SSD. [ABSTRACT FROM AUTHOR]