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In wireless communications, eavesdropping is a threat due to the broadcast nature of the channel. Therefore, in addition to the rate and the error probability, the secrecy level should be considered in design and analysis of a system. In this study, by the error probability and the channel outage analysis, we derive the secret diversity-multiplexing tradeoff (DMT) for a multiuser multiple-input multiple-output (MIMO) fading channel. We consider two multiuser schemes, multiple-access channel and user-selection. Secret DMT characterizes the relation of the error probability, the secrecy and the rate of the system at high signal-to-noise ratio (SNR). We quantify how the number of users and antennas at all the nodes affects the secret DMT performance of the system. [ABSTRACT FROM AUTHOR]

Methods for improving the characteristics of the reliability message transmission in multiservice telecommunication networks in the provision of multimedia services are analyzed. The noise immunity reception, effective methods modulation, paths transmission systems, indicators of information, frequency and energy efficiency of the system, methods of processing and receiving messages are considered. The problems of optimizing signal-code constructions according to the criterion of energy efficiency of a telecommunications system are studied. A new approach to the construction of methods for calculating the indicators of noise immunity of receiving messages is proposed, taking into account signal-code structures. The developed calculation method takes into account effective types of modulation, demodulator synthesis algorithms, signal processing methods, bandwidth, signal-to-noise ratio and energy efficiency indicators. On the basis of the calculation method, important analytical expressions were obtained that evaluate the characteristics of the noise immunity reception, taking into account the indicators energy efficiency, throughput per sample, the conditions for the indicators of the signal-to-noise ratio and the probability erroneous reception discrete signals.

In this work, a noise-immune 16-QAM demodulator in a digital television system of the DVB-T2 standard is investigated and modeled using the Matlab/Simulink software environment. The requirements for normalized technical parameters that determine the quality and noise immunity of a 16-QAM demodulator in the DVB-T2 standard have been analyzed and investigated. Various communication channels are modeled and investigated, such as: the Gaussian, Rice and Rayleigh channel to determine and measure the signal-to-noise ratio, the theoretical and practical influence of communication channels on noise immunity without a filter and with a filter. The results of researches on the dependence of the bit error probability and the number of bits received with an error on Eb/N0, the spectrum of 16-QAM signals and constellation diagrams are presented. [ABSTRACT FROM AUTHOR]

We examine the effects of imperfect phase estimation of a reference signal on the bit error rate and mutual information over a communication channel influenced by fading and thermal noise. The Two-Wave Diffuse-Power (TWDP) model is utilized for statistical characterization of propagation environment where there are two dominant line-of-sight components together with diffuse ones. We derive novel analytical expression of the Fourier series for probability density function arising from the composite received signal phase. Further, the expression for the bit error rate is presented and numerically evaluated. We develop efficient analytical, numerical and simulation methods for estimating the value of the error floor and identifying the range of acceptable signal-to-noise ratio (SNR) values in cases when the floor is present during the detection of multilevel phase-shift keying (PSK) signals. In addition, we use Monte Carlo simulations in order to evaluate the mutual information for modulation orders two, four and eight, and identify its dependence on receiver hardware imperfections under the given channel conditions. Our results expose direct correspondence between bit error rate and mutual information value on one side, and the parameters of TWDP channel, SNR and phase noise standard deviation on the other side. The results illustrate that the error floor values are strongly influenced by the phase noise when signals propagate over a TWDP channel. In addition, the phase noise considerably affects the mutual information. [ABSTRACT FROM AUTHOR]

The paper discusses the operation of wireless sensor networks consisting of nodes based on the IEEE 802.15.4 ZigBee transceiver operating in the presence of Rayleigh or Nakagami-m fading, additive white Gaussian noise (AWGN) and interference. Analytical expressions for bit error rate (BER) for the IEEE 802.15.4 network were obtained when Rayleigh and Nakagami-m fading were processed with a selection-combining (SC) and maximum-ratio-combining (MRC) combiner and when AWGN and interference were present. Analytical results are presented graphically in the form of BER change, depending on the signal-to-noise ratio (SNR) for different values of network parameters: fading parameter (m), number of branches of MRC combiner (L), modulation parameter (M), and spreading sequence lengths (Lc). Graphical results are presented for the system when there are no combiners and when the SC and MRC combiners are included. Numerical results were confirmed by Monte Carlo simulation. Analysis of the SC and MRC combiner application impact on the performance improvement of the IEEE 802.15.4 network and the received signal was performed. [ABSTRACT FROM AUTHOR]

The secondary users can opportunistically utilize the spectrum holes left by the licensed users (also called primary users [PUs]) with the help of cognitive radio (CR) technology. The cooperative spectrum sensing (CSS) is crucial for the implementation of CR algorithms in the next‐generation wireless networks, for the specific identification of spectral gaps of PUs under any fading/shadowing channel. Accurate spectrum sensing reveals that the CUs only provide data when the PUs report being idle. Yet, there is always a possibility that CU transmission will cause interference with PU communications, leading to inefficient spectrum use. So, this work explores the performance of a proposed CSS by considering such factors with the key objective of enhancing spectrum utilisation efficiency. This paper evaluates the role of the proposed CSS with a variety of hard decision fusion rules (HDFR) schemes as well as soft data fusion schemes (SDFS) methods. Toward this end, for the proposed system, closed‐form expressions for the evaluation of various performance metrics such as the false alarm, miss‐detection probabilities, total error probability (TEP), and throughput/energy efficiency are derived by taking into consideration the Nakagami‐m fading environment using different hard and soft algorithms and are validated by means of numerical simulations. Furthermore, by taking into account various network specifications, such as channel error probability (q), fading severity parameter (m), number of samples (M), number of CR nodes (N), average sensing (S) channel signal‐to‐noise ratio, and sensing threshold (λ), a performance evaluation between the SDFS and HDFR schemes has been carried out. Furthermore, using HDFR/SDFS schemes, analytical models are formulated for determining an optimal number of CR nodes (Nopt$N_{opt}$) and optimal threshold (λopt$\lambda _{opt}$) values for achieving the lowest TEP and highest energy efficiency. [ABSTRACT FROM AUTHOR]

This algorithm considers the tap delay channel model in 5G protocol, and does not consider the influence of SNR on the log-likelihood ratio of the received sequence for the segmented cyclic redundancy bit adaptive (SCADSCL) polarization decoding algorithm. This paper proposes the post-processing (PSCAD-SCL) decoding algorithm for SCAD-SCL. The algorithm determines the number of constant and unreliable log-likelihood ratio used to improve the reliability setting through simulation, and flips and appropriately enlarges the unreliable log-likelihood ratio to improve the bit error rate performance. The simulation results show that the bit error rate of PSCAD-SCL is better than the original SCAD-SCL decoding algorithm in the signal-to-noise ratio of 1～3dB. When the bit error rate is 10-4, the performance of PSCAD-SCL algorithm is about 0.3dB higher than that of SCAD-SCL algorithm. The proposed algorithm can improve 5G transmission performance. [ABSTRACT FROM AUTHOR]

We propose a downlink non-orthogonal multiple access (NOMA) architecture with a source, N one-way unmanned aerial vehicle (UAV) relays, and K destination users where the amplify-and-forward protocol is considered with the partial relay selection strategy. Then, we derive closed-form expressions for the bit error probability (BEP) of the NOMA users over the Rayleigh fading channel. This research investigated the selection of the nth best available UAV relay while presenting the bit error rate (BER) performance of a NOMA system. In addition, we analyze the diversity order and develop an asymptotic closed-form expression of the BEP in the high signal-to-noise ratio regime. To verify the accuracy of the analytical study of BER, numerical results are also provided taking into account the number of UAV relays, path loss exponent, power allocation coefficient, and channel gains. Finally, we validate that the simulation results precisely match our proposed theoretical analysis. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the performance of switch and stay combining (SSC) system operating over Fisher Snedecor (F) fading channels. Several statistical measures such as probability density function (PDF), cumulative distribution function (CDF), and moment generating function (MGF) are computed for independent identically distributed (i.i.d) dual branches. Correspondingly, the exact expressions of moments, amount of fading (AF), signal to noise ratio (SNR) output, outage probability (OP), and error probability for different detection schemes are derived. We also derive channel capacity expressions under four various adaptive transmission methods. In the next, we obtain the expressions of Nakagami-m and Rayleigh fading, as special case. Further, for deep analysis, we derive the asymptotic expressions at high SNR regime. Additionally, we calculate the optimum switching threshold of each performance measure. The results are presented and compared with the previous results. [ABSTRACT FROM AUTHOR]

The explosive growth of the Internet of Things (IoT) is putting higher requirements for the performance of co-time co-frequency full-duplex relaying (CCFD-R) due to small-size devices appearing in abundance. In this paper, we present a novel CCFD-R approach with very low complexity to deal with the issue above. Based on the orthogonality of its two components, a distributed usage mode of quadrature amplitude modulation (QAM) constellation is proposed to perform self-interference cancellation (SIC) without the complicated processing modules, as used widely in traditional full-duplex techniques. Instead of the conventional practice of assigning the entire QAM constellation to only one communication node, our scheme (termed as QAM-R) splits the constellation into two parts and further assigns them to different communication nodes, respectively. With the principle above, the mapping pattern and the frame format are carefully designed. Then, the corresponding signal model is established and the approximation of end-to-end bit error probability (BEP) is derived. Finally, numerical simulations validate the theoretical analysis and show that QAM-R can balance spectrum effectiveness and transmission reliability very well and, especially, performs even better in the low range of signal noise ratio (SNR) when adopting higher-order QAM constellations. [ABSTRACT FROM AUTHOR]

Promoted by the rapid development of information technology, 10kV overhead line has been widely used in the majority of cities, and it is of great significance to monitor the distribution network effectively, in order to ensure the normal operation of the system. Most of traditional distribution network monitoring methods are based on manual work, which causes inconvenience to the distribution network fault location, repair, maintenance and real-time monitoring, and reduces the efficiency of the distribution network emergency repair and the reliability of power supply. Aiming at the automatic monitoring problem of 10kV overhead network, this paper adopts an intelligent wireless monitoring technology, where a monitoring node is employed to monitor the network transmission status through wireless links. We evaluate the system monitoring performance by using the metric of outage probability, depending on the wireless data rate over wireless channels. For the considered system, we derive analytical outage probability, in order to measure the system performance in the whole range of signal-to-noise ratio (SNR). The simulation results are finally presented to verify the analytical expressions on the system monitoring outage probability in this paper. [ABSTRACT FROM AUTHOR]

Relay-assisted wireless communications, where both the relay and the final destiny employ diversity-combining techniques, represent a compelling strategy for improving the signal-to-noise ratio (SNR) for mobile terminals, mainly at millimeter-wave (mmWave) frequency bands. In this sense, this work considers a wireless network that employs a dual-hop decode-and-forward (DF) relaying protocol, in which the receivers at the relay and at the base station (BS) use an antenna array. Moreover, it is considered that the received signals are combined at reception using equal-gain-combining (EGC). Recent works have enthusiastically employed the Weibull distribution so as to emulate the small-scale fading behavior in mmWave frequencies, which also motivates its use in the present work. For this scenario, exact and asymptotic expressions for the system's outage probability (OP) and average bit error probability (ABEP) are derived in closed form. Useful insights are gained from these expressions. More precisely, they illustrate how the system and fading parameters affect the performance of the DF-EGC system. Monte Carlo simulations corroborate the accuracy and validity of the derived expressions. Furthermore, the mean achievable rate of the considered system is also evaluated via simulations. Useful insights regarding the system performance are obtained from these numerical results. [ABSTRACT FROM AUTHOR]

Distributed deployment for integrated sensing and communication (ISAC) can improve the sensing accuracy by exploring spatial diversity for covering the target state. However, secure fusion and limited energy consumption are still challenges for wireless-transmission-based distributed ISAC. In this paper, a secure decision-fusion scheme under energy constraint is proposed. First, the local likelihood ratios (LRs) of the local observations at sensing nodes are quantified at multiple levels corresponding to a multiple phase-shift keying (MPSK) constellation, in order to retain more sensing information. Second, an antieavesdropping scheme, which randomly rotates the constellation based on the main channel information between the nodes and ally fusion center (AFC), is proposed to confuse the data fusion of the eavesdropping fusion center (EFC). In addition, the local quantization thresholds and the rotating threshold are optimized to realize the perfect security under energy constraint and maximum rotation angle of π. In addition, the optimized rotation angle is discussed under a relaxed security requirement of the EFC in exchange for reducing the AFC error. Performance evaluation results show that the AFC error probability of the proposed scheme with a two-bit quantization and soft fusion outperforms the single-bit case and three-bit case by above 3 dB and about 0.5 dB at the error probability of 10 − 2 , respectively. The former gain is just contributed by the more local information kept with two-bit against single-bit quantization. However, for the three-bit case, the advantage of more levels of quantization is eliminated by the worse transmission of denser constellation over a noisy channel. Moreover, the proposed scheme outperforms the conventional channel-aware encryption method under a stricter energy constraint and higher signal noise ratio (SNR). [ABSTRACT FROM AUTHOR]

Because of rain attenuation, the equivalent baseband transfer function of large bandwidth radio-links will not be ideal. We report the results concerning radio links to/from satellites orbiting in GeoSurf satellite constellations located at Spino d'Adda, Prague, Madrid, and Tampa, which are all sites in different climatic regions. By calculating rain attenuation and phase delay with the Synthetic Storm Technique, we have found that in a 10-GHz bandwidth centered at 80 GHz (W-Band)—to which we refer to as "ultra-wideband-, both direct and orthogonal channels will introduce significant amplitude and phase distortions, which increase with rain attenuation. Only "narrow-band" channels (100~200 MHz) will not be affected. The ratio between the probability of bit error with rain attenuation and the probability of bit error with no rain attenuation increases with rain attenuation. The estimated loss in the signal-to-noise ratio can reach 3~4 dB. All results depend on the site, Tampa being the worst. To confirm these findings, future work will need a full Monte Carlo digital simulation. [ABSTRACT FROM AUTHOR]

In this paper, cognitive technology is introduced into the integrated satellite terrestrial system to realize the dynamic spectrum sharing of the system and improve the utilization rate of spectrum resources. To overcome the effects of low signal-to-noise ratio (SNR) and noise uncertainty in the channel, a dual-threshold cooperative sensing strategy based on energy detection is introduced. Spectrum sensing is considered as a binary hypothesis problem, but the uncertainty of noise interference in the integrated satellite terrestrial cognitive system will cause the perception to appear ambiguous. Moreover, the noise power varies with time and relative position within a certain range. In the fuzzy state, the perception technology adopts the equal-gain merging algorithm, and derives the voting optimization algorithm to improve the accuracy of decision-making. In addition, taking the minimum error probability as the optimization goal, the optimal adjustment of the adaptive double threshold is realized based on the equal-gain combining algorithm. The simulation results show that the spectrum detection accuracy under low SNR is improved, and the opportunity for terrestrial networks to share spectrum resources is increased. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA) has been widely acclaimed as a promising solution to enhance spectral efficiency, increase user fairness, and scale up the number of users in wireless networks by enabling multiple users to share the symmetrical wireless resources. This work is concerned with the development and implementation of blind reconfigurable intelligent surface (RIS)-aided ordered NOMA (ONOMA) for smart reflector (SR) and access point (AP) configurations. For the RIS-SR-ONOMA and RIS-AP-ONOMA configurations, the closed-form probability of outage expressions is derived, and their performance is reported for distinct values of passive reflector elements. Through optimal power allocation, the downlink (DL) sum capacity is maximized. RIS-aided ONOMA reduces outage rates and increases sum capacity over the traditional ONOMA system. It is discovered that the RIS-aided ONOMA system increases the sum capacity by ≈33% at 20 dB signal-to-noise ratio (SNR) for 32 passive reflector elements. The addition of passive reflector elements and symmetrical allocation among users improves the performance of RIS-SR-ONOMA and RIS-AP-ONOMA in terms of outage probability, sum capacity, and probability of error. The proposed work can be employed in applications such as vehicular ad hoc networks, where obtaining precise channel information is difficult due to the rapid mobility of the vehicles. [ABSTRACT FROM AUTHOR]

In this paper, we consider a multi-source decode and forward cooperative network coding (NC) relay system based on single-carrier zero-padded (SC-ZP) transmission scheme. All channels are L-tap frequency selective with Rayleigh fading. The cooperative maximum ratio combining (C-MRC) and the selection relaying combiners are applied and investigated at the destination, separately. We analyze the performance of proposed method in terms of symbol error probability at high signal-to-noise ratio regime, by adopting maximum likelihood (ML) and zero forcing (ZF) detectors. We prove that the considered system using the C-MRC and the ML detector, successfully exploits maximum achievable multhipath and cooperative diversity gain of 2L. To reduce the ML decoding complexity which increases with the number of sources, linear low complexity detection methods are used even though they usually do not succeed in collecting the receive diversity gain. We analytically demonstrate that proposed SC-ZP based NC system using the linear ZF detector achieves full diversity gain as like as the ML for arbitrary modulation schemes and number of sources. Moreover, an optimal NC mapping coefficients has been designed to maximize the system coding gain. Also, we extend proposed single relay NC system to multi-relay cooperative network. Single relay selection protocol is implemented based on a proposed selection criterion. In addition, simulation results illustrate that the proposed NC system employing SC-ZP technique and without need of any channel coding outperforms its competitors about 1 dB, also the processing time is reduced up to 80 percent. [ABSTRACT FROM AUTHOR]

Covert communications is critical in many application scenarios for ensuring transmission security and privacy. Two-way protocols are widely adopted in intelligent reflecting surface (IRS) assisted relaying networks to enable covert communications and prevent wireless signals from being overheard. To quantify the performance of covert communications in this special scenario, we derive the closed-form expression of outage probability and its asymptote in this paper. Considering the worst-case of covert communications, the optimal normalized power threshold of warden's detector is analyzed under a complex Gaussian distribution approximation. To meet the requirement of the detection error probability, the ratio of the transmission power between the covert nodes is investigated. Simulation results are provided to validate the theoretical expressions as well as the asymptotic analysis with a small number of reflecting elements. [ABSTRACT FROM AUTHOR]

This paper considers the downlink of an ultra-reliable low-latency communication (URLLC) system in which a base station (BS) serves multiple single-antenna users in the short (finite) blocklength (FBL) regime with the assistance of a reconfigurable intelligent surface (RIS). In the FBL regime, the users' achievable rates are complex functions of the beamforming vectors and of the RIS's programmable reflecting elements (PREs). We propose the joint design of the transmit beamformers and PREs to maximize the geometric mean (GM) of these rates (GM-rate) and show that this approach provides fair rate distribution and thus reliable links to all users. A novel computational algorithm is developed, which is based on closed forms to generate improved feasible points. Simulations show the merit of our solution. [ABSTRACT FROM AUTHOR]

The new Fifth generation (5G) of wireless communications and beyond 5G (B5G) networks are required to provide connectivity for massive number of devices at high speed and low latency. Within this context, non-orthogonal multiple access (NOMA) has been involved and emerged in recent research since it is considered as an enabling technology for 5G and B5G networks. NOMA allows several users to share the same resources of time and frequency, making it an excellent candidate to provide impressively large connectivity with high spectral efficiency. In this paper, we study the performance of NOMA systems assuming independent but not necessarily to be identical $N$ -Nakagami-m multipath fading channels. This channel model subsumes the double Nakagami-m, which was investigated in the context of intervehicular communications and keyhole multiple input multiple output systems, as special cases. To this end, we derive exact analytical and asymptotic expressions for the probability density function of the overall signal to noise ratio, system capacity, and the pairwise error probability (PEP) for each user. Numerical results are also provided herein to show the effects of fading parameters and number of users on the capacity and the PEP of each user. [ABSTRACT FROM AUTHOR]

We consider the joint constellation design problem for the noncoherent multiple-input multiple-output multiple-access channel (MAC). By analyzing the noncoherent maximum-likelihood detection error, we propose novel design criteria so as to minimize the error probability. As a baseline approach, we adapt several existing design criteria for the point-to-point channel to the MAC. Furthermore, we propose new design criteria. Our first proposed design metric is the dominating term in nonasymptotic lower and upper bounds on the pairwise error probability exponent. We give a geometric interpretation of the bound using Riemannian distance in the manifold of Hermitian positive definite matrices. From an analysis of this metric at high signal-to-noise ratio, we obtain further simplified metrics. For any given set of constellation sizes, the proposed metrics can be optimized over the set of constellation symbols. Motivated by the simplified metric, we propose a simple constellation construction consisting in partitioning a single-user constellation. We also provide a generalization of our previously proposed construction based on precoding individual constellations of lower dimensions. For a fixed joint constellation, the design metrics can be further optimized over the per-user transmit power, especially when the users transmit at different rates. Considering unitary space-time modulation, we investigate the option of building each individual constellation as a set of truncated unitary matrices scaled by the respective transmit power. Numerical results show that our proposed metrics are meaningful, and can be used as objectives to generate constellations through numerical optimization that perform better, for the same transmission rate and power constraint, than a common pilot-based scheme and the constellations optimized with existing metrics. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) have attracted a lot of research attention because of their high mobility and low cost in serving as temporary aerial base stations (BSs) and providing high data rates for next-generation communication networks. To protect user privacy while avoiding detection by a warden, we investigate a jammer-aided UAV covert communication system, which aims to maximize the user’s covert rate with optimized transmit and jamming power. The UAV is equipped with multi-antennas to serve multi-users simultaneously and enhance the Quality of Service. By considering the general composite fading and shadowing channel models, we derive the exact probability density (PDF) and cumulative distribution functions (CDF) of the signal-to-interference-plus-noise ratio (SINR). The obtained PDF and CDF are used to derive the closed-form expressions for detection error probability and covert rate. Furthermore, the covert rate maximization problem is formulated as a Nash bargaining game, and the Nash bargaining solution (NBS) is introduced to investigate the negotiation among users. To solve the NBS, we propose two algorithms, i.e., particle swarm optimization-based and joint two-stage power allocation algorithms, to achieve covertness and high data rates under the warden’s optimal detection threshold. All formulated problems are proven to be convex, and the complexity is analyzed. The numerical results are presented to verify the theoretical performance analysis and show the effectiveness and success of achieving the covert communication of our algorithms. [ABSTRACT FROM AUTHOR]

The design of a free-space optical (FSO) link between an unmanned aerial vehicle (UAV) and a high-altitude platform (HAP) in the practical scenario of generalized pointing errors (PE) and beam wandering (BWAN) is addressed. We propose to select appropriately the system parameters such as optical beamwidth at the UAV and its flight altitude so as to minimize the outage probability. First , we characterize the channel statistics by taking into account the joint influence of attenuation loss, weak atmospheric turbulence and generalized PE particularly impaired by BWAN. Second , we formulate the closed-form expressions for outage probability, where we also derive an asymptotic expression at high signal-to-noise ratios (SNR)s. Third , we derive the optimum beamwidth at the UAV leading to the instantaneous minimum outage probability under generalized PE and BWAN. Finally , we address the optimal flight altitude of the UAV to avoid strong turbulence in order to ensure efficient data transmission. Our simulation results validate both the effectiveness and the accuracy of the derived asymptotic outage probability and the adequate choice of beamwidth and flight altitude to minimize the average outage performance. For instance, our results show that at an SNR of 20 dBm, the link availability is increased from 20% (with nominal beamwidth) to more than 70% by adopting the proposed beamwidth optimization. [ABSTRACT FROM AUTHOR]

Due to poor (limited) scattering, a correlation among channels is inevitable, resulting in performance degradation of wireless communication systems. In this paper, we propose a hybrid selection combining (SC), also known as switched scaled – SC for correlated cooperative communication over κ - μ fading channel. By using paired error analysis, we derive the end-to-end symbol error probability of this system over bivariate κ - μ channel fading with M-ary phase shift keying (MPSK) modulation. In addition, we obtain significant parameters of hybrid SS-SC, such as the optimum scaling factor and optimum threshold by using the second derivative test. For every signal to noise ratio (SNR), we obtain different optimum thresholds and scaling factors. Our analytical results were found to overlap significantly with those of the simulation results. They were also compared with the variants of SC and switched diversity techniques. Our study demonstrates that the proposed hybrid technique performs better than the other SC and switched diversity schemes over correlated and uncorrelated fading channels. Furthermore, we derive an asymptotic symbol error probability for the proposed system, and the asymptotic results are in agreement with the analytical results at higher SNRs. Our study also shows that the diversity order of the system depends on the mutually exclusive events of the proposed technique. [ABSTRACT FROM AUTHOR]

In this paper, the extended $\eta$ - ${\mathcal F}$ composite fading distribution is proposed. This new distribution is simple, characterized in terms of physical parameters, able to model environments where the multipath fading coexists with shadowing and takes into account the clustering imbalance between the in-phase and quadrature components. For the aforementioned distribution, new expressions are derived for the probability density function (PDF); cumulative distribution function, higher-order moments and moment generating function of the instantaneous signal-to-noise ratio; joint envelope-phase PDF and amount of fading. Subsequently, expressions are deduced for the outage probability, average symbol error probability and average channel capacity. An asymptotic analysis is also provided. Several curves are presented and the theoretical results are corroborated by Monte-Carlo simulations. Furthermore, an empirical validation is demonstrated in an underwater acoustic scenario, in which a better fit between the theoretical PDF and the empirical data is perceived for the extended $\eta$ - ${\mathcal F}$ model, when compared to the extended $\eta$ - $\mu$ and $\kappa$ - $\mu$ shadowed distributions. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surface (RIS) has been introduced as a promising emerging paradigm to design a smart radio environment for improving wireless capacity. It has the potential to reshape wave propagation via its tunable and low-cost reflecting elements. Therefore, it is regarded as a propitious solution that provides alternative paths for the propagation of high-frequency signals, which are vulnerable to blockages and suffer from penetration losses. Because of those features, RIS has been considered to be integrated into the wireless vehicular network (WVN), which is characterized by high mobility and high quality of service (QoS) requirements. Hence, similar to relaying systems, a vehicle needs to select the best available RIS that maximizes the signal-to-noise ratio (SNR) at the receiver. Inspired by that, in this paper, we introduce the partial RIS selection for enhancing capacity and reducing error rate. We derive closed-form expressions for the ergodic capacity, symbol error probability (SEP), and energy efficiency for a partial RIS selection design. Besides, we compare its performances to the partial relaying design while considering: decode-and-forward (DF) and amplify-and-forward fixed gain (AF). Moreover, we consider a wireless attack scenario, where an eavesdropper intends to overhear the transmitted signal at the receiver’s end. Then, we compare partial RIS to partial relay selection from this security perspective, where we derive closed-form expressions for the average secrecy capacity. Furthermore, we compare the partial RIS selection to a single RIS architecture scenario from the literature, where our solution outperforms the related existing work. [ABSTRACT FROM AUTHOR]

This study proposes and analyses the loop-interference based selection policy for the full-duplex relaying networks. A multiple full-duplex relay-assisted network model is considered for the investigation. Computer simulations are utilized to verify the analytical and asymptotic derivations. In reference to obtained results, the loop-interference based selection policy achieves cooperative diversity order, the total number of possible paths between source-destination terminals, in high signal-to-noise ratios. Proposed selection strategy's performance efficiency is measured by dint of outage probability, error probability, ergodic rate, and throughput. So as to provide more insight of the performance analysis, the asymptotic analysis is also provided. [ABSTRACT FROM AUTHOR]

The paper proposes a multiple-input multiple-output-based power line communication (PLC) system subject to Rayleigh fading and corrupted by additive cyclostationary Gaussian noise. The proposed coherent receiver structure employs a block reception rule at the reception unit for detecting the space-time block-coded transmitted data symbols. A closed-form expression for the pairwise error probability (PEP) is derived using a characteristic function approach. Exact and asymptotic expressions for the average PEP are obtained for the special case of Alamouti code transmission which show that the PLC system under consideration offers full diversity. Numerical results depict the improvement in the system performance with increase in the number of receive diversity branches and the average signal-to-noise ratio per branch and decrease in the correlation value between the noise samples. [ABSTRACT FROM AUTHOR]

In this paper, the role of feedback in two-way full-duplex Gaussian channel (TW-FD-GC) is revisited. First, we propose a practical coding scheme for the TW-FD-GC, which is based on the noisy type of the well-known Schalkwijk-Kailath (SK) feedback scheme. We show that though this scheme cannot achieve the capacity of the TW-FD-GC, the codeword length that achieves desired decoding error probability is extremely short. Then, we further prove that the proposed scheme is secure by itself, i.e., the achievable rate region of the proposed scheme is also an achievable secrecy rate region of the two-way full-duplex Gaussian wiretap channel (TW-FD-GWTC). In addition, for the TW-FD-GWTC, numerical result shows that the secrecy sum rate of our proposed scheme can be as large as those achieved by existing schemes in the literature for some cases. Next, we extend the proposed scheme to the TW-FD-GC with Gaussian state interference non-causally known by the corresponding transmitter. We show that the interference can be perfectly canceled by this extended scheme. Finally, we prove that this extended scheme is also secure by itself, and numerical result shows that this extended scheme may perform better than the existing ones in the literature. [ABSTRACT FROM AUTHOR]

A good wireless device in a system needs high spectral efficiency. Non-Orthogonal Multiple Access (NOMA) is a technique used to enhance spectral efficiency, thereby allowing users to share information at the same time and same frequency. The information of the user is super-positioned either in the power or code domain. However, interference cancellation in NOMA aided system is challenging as it determines the reliability of the system in terms of Bit Error Rate (BER). BER is an essential performance parameter for any wireless network. Intelligent Reflecting Surfaces (IRS) enhances the BER of the users by controlling the electromagnetic wave propagation of a given channel. IRS is able to boost the Signal to Noise Ratio (SNR) at the receiver by introducing a phase shift in the incoming signal utilizing cost-effective reflecting materials. This paper evaluates users' error rate performance by utilizing IRS in NOMA. The error probability expression of users is derived under Rayleigh and Rician fading channel. The accuracy of derived analytical expressions is then validated via simulations. Impact of power allocation factor, coherent and random phase shifting of IRS is evaluated for the proposed IRS-NOMA system. [ABSTRACT FROM AUTHOR]

Investigation of the effect of topology on the communication efficiency of WSN nodes is carried out through simulation of 9 nodes in a 12 by 12 meters area. The obtained data and plots indicate that the grid topology is a more efficient and stable topology to use in comparison to the random uniform topology. The deduction is supported by probability of error as a function of error distribution values. Five different noise levels are used in the simulation (0dBm, −20 dBm, −40 dBm, −60 dBm, −80 dBm, and −100 dBm) with an output power of −10 dBm. The work shows that at −60 dBm redistribution of probability of error as a function of error values started to occur with higher level error values associated with the random uniform topology compared with the grid topology occurring at −60 dBm noise. The work also shows the relationship between received signal strength indicator (RSSI) and probability of error which decreases as RSSI increase in a similar manner as signal to noise ratio (SNR). Both RSSI and SNR are related through the mathematical model presented in the paper which is based on the path loss model. Common features between the error probability model and Gaussian interpolation function are also presented. A simplified 1-D design model is also presented to enable initial topology considerations. Criteria are also established to enable relating SNR, RSSI, topology, and WSN incremental position. [ABSTRACT FROM AUTHOR]

A non-multipath and a receive diversity power line communication (PLC) system subject to Rayleigh fading is considered in this paper with the transmitter employing non-orthogonal $M$ -ary frequency-shift keying ($M$ FSK) modulation scheme for data transmission. With the PLC systems corrupted by additive complex Nakagami- $m$ background noise, an optimal receiver for non-multipath PLC system and a Gauss-optimal receiver structure for the multipath PLC system are proposed using which, closed-form expressions for the symbol error probability (SEP) are derived using a characteristic function approach. The optimal correlation coefficients between the symbols of a binary FSK modulation scheme minimizing the SEP of the systems are obtained, which is further generalized by proposing a search-based algorithm to derive the optimal symbol correlation matrix for an $M$ FSK modulation leading to the minimal SEP values of the PLC systems. Numerical results show that the index value of the optimal correlation matrix depends on the system parameters namely the noise shape parameter and the average signal-to-noise ratio only for the case of the non-multipath PLC system, whereas there is no such dependency in the case of the multipath PLC system. [ABSTRACT FROM AUTHOR]

Symbol-level precoding (SLP) has recently emerged as a new paradigm for physical-layer transmit precoding in multiuser multi-input-multi-output (MIMO) channels. It exploits the underlying symbol constellation structure, which the conventional paradigm of linear precoding does not, to enhance symbol-level performance such as symbol error probability (SEP). This paper aims to better understand the relationships between SLP and linear precoding, subsequent design implications, and further connections beyond the existing SLP scope. Focused on the quadrature amplitude modulation (QAM) constellations, our study is built on a basic signal observation, namely, that SLP can be equivalently represented by a zero-forcing (ZF) linear precoding scheme augmented with some appropriately chosen symbol-dependent perturbation terms, and that some extended form of SLP is equivalent to a vector perturbation (VP) nonlinear precoding scheme augmented with the above-noted perturbation terms. We examine how insights arising from this perturbed ZF and VP interpretations can be leveraged to i) substantially simplify the optimization of certain SLP design criteria, namely, total or peak power minimization subject to SEP quality guarantees; and ii) draw connections with some existing SLP designs. We also touch on the analysis side by showing that, under total power minimization, the basic ZF scheme is a near-optimal SLP scheme when the QAM order is very high—which gives a vital implication that SLP is more useful for lower-order QAM cases. Numerical results further indicate the merits and limitations of the different SLP designs derived from the perturbed ZF and VP interpretations. [ABSTRACT FROM AUTHOR]

In this article, we consider a two-way communication system empowered by a reconfigurable intelligent surface (RIS), consisting of N passive reflective elements, in the presence of transceiver hardware impairments (HIs). To exploit the existence of a direct link between the end communication nodes, we utilize two time slots for their information exchange. We particularly analyze the instantaneous end-to-end signal-to-noise-plus-distortion-ratios (SNDRs) under HIs. The exact distribution of the magnitude of the end-to-end channel coefficients of the studied RIS-empowered communication system is derived under HIs and Nakagami- m fading channels. Using different settings for the level of HIs and the transmit powers at the end nodes, we also deduce novel exact and upper bound analytical expressions for the overall outage probability (OOP). For the high signal-to-noise ratio regime, an asymptotic OOP analysis is derived, which unveils the system's diversity order. The presented numerical and simulation results corroborate our derived analytical findings, and demonstrate the impact of different system and channel parameters on the system's OOP performance. [ABSTRACT FROM AUTHOR]

This paper proposes the novel space–time labeling diversity for the distributed Goppa-coded cooperation (STLD-DGCC) scheme over the Nakagami- q fading channel to improve the performance of the short-to-medium information block transmission. Two different Goppa codes with the same information length are deployed in the source and the relay, respectively, with the Goppa code at the relay providing additional redundancy. Meanwhile, two distinct labeling mappers of M -ary quadrature amplitude modulation (M -QAM) are used in the novel space–time labeling diversity (STLD) to achieve the extra diversity gain and decrease the error floor (EF) region in the Goppa coding scheme. To lower the computational complexity of the maximum likelihood (ML) detection, a near-ML reduced-complexity (RC) detection approach that compromises the system performance and the computation complexity is proposed. In addition, two novel joint decoding algorithms based on the critical signal-to-noise ratio (SNR) threshold are presented at the destination, namely the parallel algorithm and serial algorithm, to enhance the overall performance of the proposed STLD-DGCC scheme. In the case of the Nakagami- q fading model, the analytical union bound of the average bit error probability is provided, which tightly matches the Monte Carlo simulated results at high SNR. The simulation results further indicate that the proposed STLD-DGCC scheme significantly outperforms both the corresponding non-cooperative Goppa coding scheme and the DGCC scheme without the STLD technique under identical conditions. Furthermore, the performance of the STLD-DGCC scheme surpasses that of the existing transmission scheme, offering a promising candidate for further small information block communications. [ABSTRACT FROM AUTHOR]

This research paper presents the Physical (PHY) layer analysis of multiple input multiple output (MIMO) systems in line-of-sight environments between a user equipment (UE) and a base station when an information data is transmitted. The data transmission in wireless networks often takes place in non-line-of-sight in urban environments and Line-of-Sight (LoS) in rural environments depending on the bandwidth, power constraints. Using MIMO technology, the data transmission takes place with increased number of transmit and receive antennas which results in reduced signal to noise ratio (SNR) requirement. In this research work, simulation for PHY layer metric of probability of error, mean square error (MSE) for data transmission in MIMO wireless networks is obtained Matrix Laboratory (MATLAB) for LoS environment which follows Rician distribution. Probability of error reduces to a significant extent when the Rician factor increases as the line-of-sight component prevails which also takes lesser power in the lower SNR limits. Further, in MIMO systems also the probability of error and MSE reduces in concatenation with single antenna terminals thereby exploring power control a significant possibility for implementation in massive MIMO and millimeter wave communication systems for 5G and 6G systems. [ABSTRACT FROM AUTHOR]

Ultra-Reliable and Low-Latency Communications (URLLC) has attracted considerable attention because of its potential applications in factory automation, automated driving, and telesurgery anticipated for the era of the sixth-Generation (6G) networks. In URLLC with random channel gains and a hard delay constraint, the scheduling of backlogged queues and finite blocklength coding in the physical layer will make it very challenging to specify its performance limits. In this paper, we focus our attention on the asymptotic cross-layer analysis of URLLC when the Signal-to-Noise Ratio (SNR) is sufficiently high. More specifically, we find that a fundamental tradeoff exists among the service capability, latency, and error probability in the high SNR regime, which is characterized by a gain conservation equation. The main result of this work reveals that the sum of our defined service rate gain, real-time gain, and reliability gain is equal to one under the optimal policy. Numerical simulations are also exploited to validate that the derived gain conservation equation holds even with bounded random arrival. [ABSTRACT FROM AUTHOR]

This work tackles the joint optimization of a unmanned aerial vehicle's (UAV's) three-dimensional (3D) placement and transmit power for covert communications with the objective to maximize the communication covertness subject to a constraint on communication quality. We analytically prove that the optimal horizontal location of the UAV must be on the straight line connecting the legitimate receiver and the warden, while its optimal height is the minimum allowable flying altitude. Subsequently, we derive closed-form expressions to characterize the UAV's optimal 3D location and its optimal transmit power, taking into account the impact of finite blocklength coding. Our numerical results show that the developed optimal design can achieve a better covertness performance compared with an optimal two-dimensional (2D) UAV deployment, especially when the warden is close to the receiver. Besides, we show that, for a given requirement on the communication quality, communication covertness does not always improve as the number of channel uses increases. [ABSTRACT FROM AUTHOR]

We consider multi-input convolutional codes with unequal error protection (UEP) among the inputs. Using conventional metrics including the free input distance and free input sum weight as a measure for UEP degree, we design efficient and optimal algorithms to evaluate these metrics for any number of inputs. Next, we discuss several ambiguities arisen from using these metrics to estimate convolutional code UEP property and propose two new metrics, the average weight per path and the ant colony system UEP (ACS-UEP) index. The ACS-UEP index can accurately and consistently capture UEP properties over all ranges of SNR. Using these metrics, we propose an algorithmic process for designing convolutional codes with bounded external degree complexity to minimize a weighted sum of input error probabilities. We analyze the effectiveness of the design approach and show significant improvements over existing UEP convolutional code designing approach in terms of both the absolute and UEP input error protections. Our proposed algorithms for designing multi-input convolutional codes with UEP are flexible, adaptable, and provide high performance codes within the specified complexity. [ABSTRACT FROM AUTHOR]

Owing to the ever increasing of information privacy requirement, covert communication has gained more and more attention, whose effective range is limited by the trade-off between the covertness and the transmit power. Benefiting from the high mobility and easy deployment, unmanned aerial vehicles (UAVs) can be utilized to expand the range of covert networks. Thus, we propose a UAV-relayed covert communication scheme with finite blocklength to maximize the effective transmission bits from the transmitter to the legitimate receiver against a flying warden. The transmitter adopts the maximum ratio transmission and the relay performs Gaussian signalling transmission to cause uncertainty at the warden. First, the optimal detection thresholds are derived at the warden towards the transmitter and the relay, respectively. Then, the hovering location of the warden is optimized to maximize the summation of relative entropies from the transmitter and the relay, which can greatly threaten the covertness. With this worst covert situation, the blocklength and transmit power at the transmitter and the relay are jointly optimized under the constraint of the end-to-end error detection probability to maximize the effective transmission rate from the transmitter to the legitimate receiver. Numerical results are provided to demonstrate the effectiveness of the proposed UAV-relayed covert communication scheme. [ABSTRACT FROM AUTHOR]

Free-space optical (FSO) communications will play an important role in the backhaul of future generation of wireless networks in order to support high data rates. Because of narrow beamwidth inherent to an optical signal, acquisition and tracking form an important component of any FSO communication system. In this study, we have analyzed the optimization of received power allocation between tracking and data channels in an FSO receiver. In this regard, we have carried out a detailed analysis of the error statistics of the centroid estimator that is used for tracking the beam with the help of an array. The objective function that is optimized (minimized) are the probability of error and the probability of outage, and the optimization of power allocation is carried out as a function of parameters such as noise power, pointing error variance, pointing error correlation coefficient, and the threshold of outage. We have analyzed the optimization concerning the lognormal and exponentiated Weibull fading scenarios as well. We learn that the optimal power allocation is a function of the received signal-to-noise ratio: a lower signal-to-noise ratio dictates that a higher fraction of received power should be diverted to the tracking channel and vice versa. [ABSTRACT FROM AUTHOR]

In this paper, the average achievable rate and error probability of a reconfigurable intelligent surface (RIS) aided systems is investigated for the finite blocklength (FBL) regime. The performance loss due to the presence of phase errors arising from limited quantization levels as well as hardware impairments at the RIS elements is also discussed. First, the composite channel containing the direct path plus the product of reflected channels through the RIS is characterized. Then, the distribution of the received signal-to-noise ratio (SNR) is matched to a Gamma random variable whose parameters depend on the total number of RIS elements, phase errors and the channels’ path loss. Next, by considering the FBL regime, the achievable rate expression and error probability are identified and the corresponding average rate and average error probability are elaborated based on the proposed SNR distribution. Furthermore, the impact of the presence of phase error due to either limited quantization levels or hardware impairments on the average rate and error probability is discussed. The numerical results show that Monte Carlo simulations conform to matched Gamma distribution to received SNR for sufficiently large number of RIS elements. In addition, the system reliability indicated by the tightness of the SNR distribution increases when RIS is leveraged particularly when only the reflected channel exists. This highlights the advantages of RIS-aided communications for ultra-reliable and low-latency systems. The difference between Shannon capacity and achievable rate in FBL regime is also discussed. Additionally, the required number of RIS elements to achieve a desired error probability in the FBL regime will be significantly reduced when the phase shifts are performed without error. [ABSTRACT FROM AUTHOR]

Unsourced random-access (U-RA) is a type of grant-free random access with a virtually unlimited number of users, of which only a certain number $K_{a}$ are active on the same time slot. Users employ exactly the same codebook, and the task of the receiver is to decode the list of transmitted messages. We present a concatenated coding construction for U-RA on the AWGN channel, in which a sparse regression code (SPARC) is used as an inner code to create an effective outer OR-channel. Then an outer code is used to resolve the multiple-access interference in the OR-MAC. We propose a modified version of the approximate message passing (AMP) algorithm as an inner decoder and give a precise asymptotic analysis of the error probabilities of the AMP decoder and of a hypothetical optimal inner MAP decoder. This analysis shows that the concatenated construction under optimal decoding can achieve a vanishing per-user error probability in the limit of large blocklength and a large number of active users at sum-rates up to the symmetric Shannon capacity, i.e. as long as $K_{a}R < 0.5\log _{2}(1+K_{a} { \mathsf {SNR}})$. This extends previous point-to-point optimality results about SPARCs to the unsourced multiuser scenario. Furthermore, we give an optimization algorithm to find the power allocation for the inner SPARC code that minimizes the ${\mathsf {SNR}}$ required to achieve a given target per-user error probability with the AMP decoder. [ABSTRACT FROM AUTHOR]

The noise immunity of receiving signals with pseudorandom tuning of the operating frequency in low-speed radio communication systems under the influence of jamming in a part of the band is considered. The dependences of the error probability of signal reception on the signal-to-noise ratio and on the frequency parameters of the interference for various algorithms for receiving signals of frequency shift keying with intrasymbol pseudorandom tuning of the operating frequency are obtained. The effectiveness of the considered reception methods is estimated. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surfaces (RIS) allow significant throughput enhancement as all reflections have the same phase at the receiver. In this paper, we suggest to optimize packet length for wireless communications using RIS. Two techniques are suggested in order to maximize average or instantaneous throughput. Average throughput maximization requires only the average signal to noise ratio to determine the optimal packet length. The Gradient algorithm is used to maximize the average throughput. Instantaneous throughput maximization requires the instantaneous SNR in order to adapt packet length to channel conditions. We derive in closed form the expression of optimal packet length, maximizing the instantaneous throughput. Our results are valid for any number of reflecting meta-surfaces N of the RIS. [ABSTRACT FROM AUTHOR]

The traditional channel encryption method is interfered by noise signal, which leads to long encryption time and poor security. This paper proposes a communication channel security encryption method based on cloud computing technology. In order to obtain the minimum benefits of the same channel and orthogonal channel in the frequency conversion receiver, the dual input and dual output model is constructed; the influence of time domain and frequency domain on the transmission signal is analyzed, and the nonlinear transmission characteristics of the channel signal are obtained. Through cloud computing technology, the channel transmission characteristics are divided into dynamic parameters and static parameters to realize the key distribution of communication channel under cloud computing technology; the balance factor is used to provide the key for the sorted generators to realize the secure encryption of communication channel. The results show that the average error probability of the proposed method is about 0.275, and the signal-to-noise ratio is between 115 and 118 SNR. [ABSTRACT FROM AUTHOR]

A receive diversity power line communication (PLC) system subject to correlated multipath channel fading and corrupted by additive Nakagami- $m$ background noise is considered. The optimal receiver employing a 4-ary imbalanced-phase-amplitude modulation (I-PAM) scheme for data transmission is obtained, using which closed form expressions for the symbol error probability (SEP) in the union bound sense and the SEP in the asymptotic sense at high signal-to-noise ratio (SNR) are derived. The diversity order of the system is found to be independent of the shape parameter of the additive noise. Furthermore, the optimal 4-ary I-PAM constellation minimizing the SEP at lower SNR values is computed numerically. The optimal 4-ary I-PAM constellation is found to be elliptical in shape as opposed to the traditional circular QPSK constellation generally employed in wireless communication systems. The effects of the correlation among the multipath channel gains and the shape parameter of the noise on the optimality of the considered constellation are also presented via numerical studies. [ABSTRACT FROM AUTHOR]

This work presents a performance analysis for downlink non-orthogonal multiple accesses (DL-NOMA) systems where the channel gains follow the $\alpha$ - $\mu$ fading distribution. Specifically, closed-form expressions are derived for DL-NOMA in terms of the outage probability (OP), bit error rate (BER), and ergodic capacity (EC). The OP analysis considers two main scenarios, the first is when the individual user's rate is required to satisfy a certain quality of service (QoS), while the second is when the individual user's NOMA rate is less than that of the conventional orthogonal multiple access (OMA) rate. Moreover, the derived BER performance is generalized for the case of $M$ -ary quadrature amplitude modulation (MQAM). The results demonstrate the interplay between the system performance, the power allocation coefficients, target data rates, and the channel fading parameters. Moreover, the OP results reveal that NOMA users with OMA data rate experience higher outage compared to NOMA with fixed target data rate. The accuracy of the derived expressions is validated using extensive Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

In this paper, a mixture Gamma shadowed (MGS) model is proposed as a unified composite distribution via representing the shadowing impact by an inverse Nakagami- $m$. The exact expression and the asymptotic behaviour at high average signal-to-noise ratio (SNR) regime of the fundamental statistics of a MGS distribution are derived first. These statistics are then applied to analyze the performance of the wireless communication systems over double shadowed $\kappa$ - $\mu$ fading channels. In particular, the outage probability (OP), average bit error probability (ABEP), average channel capacity (ACC), effective capacity (EC) and average area under the receiver operating characteristics curve (AUC) of energy detection (ED) are provided. The numerical and simulation results as well as a comparison with previous exact works are presented to verify the validation of our analysis. [ABSTRACT FROM AUTHOR]