Average Channel Capacity Research Articles

Effect of Impulsive Noise on IRS-Aided Communication Systems

Recent studies have explored the potential benefits of the intelligent reflecting surface (IRS) in different wireless communication scenarios. However, no work has quantitatively analyzed the performance of IRS-aided communication systems impaired by non-Gaussian noise. In this article, motivated by this research gap, we study the effect of impulsive noise on IRS-aided communication systems. Specifically, the channel impairments are modeled by Middleton's class A noise (MCA) and Weibull fading. By leveraging the Laguerre series, accurate channel distributions are derived. Building upon these expressions, new closed-form expressions of average bit-error-rate (BER), average channel capacity (ACC), and outage probability (OP) are obtained. To gain further insight into the system performance at high signal-to-noise ratio (SNR) regime, the asymptotic expressions of BER, OP, and ACC are derived. In addition, a tight upper bound of ACC is obtained. The effect of the impulsive index <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ (A)$</tex-math></inline-formula> on the systems performance metrics is investigated for different parameter settings. Moreover, it is shown that IRS-assisted communication systems outperforms a multi-hop relaying network impaired by impulsive noise. The results reveal that the system performance impaired by impulsive noise can be significantly improved by increasing the reflecting elements (REs). The derived expressions are in excellent agreement with Monte-Carlo simulations.

A General Framework for UAV-aided THz Communications Subject to Generalized Geometric Loss

In this article, we develop a general framework for the performance analysis of unmanned aerial vehicle (UAV) aided terahertz (THz) communications under generalized geometric loss, which considers the fluctuations of the UAV's position and orientation alongside the non-orthogonality of the THz beam with respect to the detector plane. In particular, we derive general and novel analytical expressions for the probability density function and the cumulative distribution function of the instantaneous signal-to-noise ratio (SNR) under generalized fading channels subject to generalized geometric loss. Consequently, novel, general, and accurate analytical expressions for the outage probability, average symbol error rate, and average channel capacity are derived. Furthermore, approximate asymptotic expressions in the high SNR regime are also derived. Moreover, A very accurate approximate expression for the channel capacity is also provided in the low SNR regime. As an example, the system performance under the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> fading channel model is analyzed in terms of the above-mentioned performance metrics.

Performance analysis of flexible indoor and outdoor user distribution in urban multi-tier heterogeneous network

The next generation heterogeneous networks (hetnet) refer to a complex eco system of radio cells with varying coverage ranges and technologies that interoperate to deliver the required capacity and coverage. This paper addresses the impact of large scale transmissions and analyses the performance of a typical user distribution in an urban multi-tier hetnet. A Boolean scheme of building blockage has been used to abstract the urban environment, which affects the architecture of hetnet with millimetre wave (mmW) access. A distribution mechanism is proposed to enable the indoor users to operate in mmW band whereas the outdoor users to operate in microwave (μWave) band. An indoor user can be connected with mmW band if the line-of-sight (LOS) link exists. Otherwise, the exploitation is provided with μWave band to enhance the coverage. By employing tools from stochastic geometry, the mathematical expressions are derived for coverage probability, rate and spatial average channel capacity of a user in indoor and outdoor environments. The exact mathematical results show that an impact of small cell occupation ratio results in maximised spatial average channel capacity of an outdoor hetnet. The significant enhancement is provided with mmW small cell in terms of rate and coverage.

Stochastic modeling of q-Lognormal fading channels over Tsallis' entropy: Evaluation of channel capacity and higher order moments

In wireless communication systems (WCSs), fading and shadowing of signals are the most frequently encountered phenomena which lead to degradation in the performance of communication channels. Several multipath distribution models like Weibull, Rayleigh, and Nakagami-m models have been extensively used for statistically capturing the fading signals in large-scale propagation scenarios. Several studies have emphasized on exploiting the log-normal model which efficiently characterizes the shadowing signals, or large-scale effects of the propagation channel. However, the conventional log-normal model suffers through some limitations, due to the lack of mathematical tractability in its analytical expression for characterizing shadowed multipath fading signals. In this perspective, the present work proposes a novel adaptive generalized stochastic differential equation (SDE) in context to Tsallis non-extensive sense, which leads to q-Lognormal distribution under a suitable initial condition corresponding to Fokker-Planck equation for effectively capturing the rapid fluctuations in composite signals. The closed form expressions corresponding to the probability density function (PDF) and cumulative distribution function (CDF) are obtained in terms of Gauss-Hypergeometric function F12[a,b,c;z] for the proposed distribution model. Finally, several performance measures like average channel capacity, higher order moments, and coefficient of variation (CV) are estimated for proposed q-Lognormal model by employing extensive Monte-Carlo simulations. The corresponding results obtained by using the above techniques are presented to understand the applicability of the proposed model for modeling WCS and multipath composite signals.

Mixed THz/FSO Relaying Systems: Statistical Analysis and Performance Evaluation

In this paper, the performance of a mixed Terahertz/free-space optical (THz/FSO) wireless transmission system is studied, where the joint effects of channel fading and pointing errors are considered for both THz and FSO links. Employing the semi-blind amplify-and-forward protocol, we derive the cumulative distribution function and probability density function of the end-to-end signal-to-noise ratio. By applying the derived statistics, exact expressions for the outage probability (OP), average bit error rate (BER), and average channel capacity are obtained. In order to attain useful physical insights, asymptotic OP and average BER expressions are also presented. Based on them, the diversity gain is determined, which is shown to depend on channel fading and pointing errors of both links. In addition, by taking into account the hardware impairments, the OP of the non-ideal hardware system is derived. Moreover, the analysis is extended to multi-antenna scenarios and the asymptotic OP is obtained. Finally, illustrative numerical results are plotted and it can be observed that the path loss, channel fading, pointing errors and hardware impairments lead to a considerable degradation in system performance.

Performance analysis of UAV-based mixed underwater PLC-RF systems

In this study, we analyzed the performance of an Unmanned Aerial Vehicle (UAV)-based mixed Underwater Power Line Communication-Radio Frequency (UPLC-RF) network. In this network, a buoy located at the sea is used as a relay to transmit signals from the underwater signal source to the UAV through the PLC link. We assume that the UPLC channel obeys a log-normal distribution and that the RF link follows the Rician distribution. Using this model, we obtained the closed-form expressions for the Outage Probability (OP), Average Bit-error-rate (ABER), and Average Channel Capacity (ACC). In addition, the asymptotic analysis of the OP and ABER was performed, and an upper bound for the average capacity was obtained. Finally, the analytical results were verified by Monte Carlo simulation thereby demonstrating the effect of impulse noise and the altitude of the UAV on network performance.

Make Smart Decisions Faster: Deciding D2D Resource Allocation via Stackelberg Game Guided Multi-Agent Deep Reinforcement Learning

Device-to-Device (D2D) communication enabling direct data transmission between two mobile users has emerged as a vital component for 5G cellular networks to improve spectrum utilization and enhance system capacity. A critical issue for realizing these benefits in D2D-enabled networks is to properly allocate radio resources while coordinating the co-channel interference in a time-varying communication environment. In this paper, we propose a Stackelberg game (SG) guided multi-agent deep reinforcement learning (MADRL) approach, which allows D2D users to make smart power control and channel allocation decisions in a distributed manner. In particular, we define a crucial Stackelberg Q-value (ST-Q) to guide the learning direction, which can be calculated based on the equilibrium achieved in the Stackelberg game. With the guidance of the Stackelberg equilibrium, our approach converges faster with fewer iterations than the general MADRL method and thereby exhibits better performance in handling the network dynamics. After the initial training, each agent can infer timely D2D resource allocation strategies with distributed execution. Extensive simulations are conducted to validate the efficacy of our proposed scheme in developing timely resource allocation strategies. The results also show that our method outperforms the general MADRL based approach in terms of the average utility, channel capacity, and training time.

Performance Analysis of I/Q Imbalance With Hardware Impairments Over Hyper Fox’s H-Fading Channels

Impairments baseband model in-phase and quadrature-phase Imbalance (IQI) and Residual hardware impairments (RHI) are two key factors degrading the performance of wireless communication systems (WCSs), particularly when high-frequency bands are employed, as in 5G systems and beyond. The impact of either IQI or RHI on the performance of various WCSs has been investigated exclusively in a separate way. To fill this gap, in this paper, the joint effect of both IQI and RHI on the performance of a WCS subject to Hyper Fox’s H-fading (HFHF) channel, is investigated. Such a fading model generalizes most, if not all, of well-known fading and turbulence models. To this end, closed-form expressions for the outage probability (OP), Average channel capacity (ACC) under constant power with optimum rate adaptation (ORA) policy, and average symbol error probability (ASEP) for both coherent and non-coherent modulation schemes are derived. Specifically, all the analytical expressions are derived for three different scenarios: (i) ideal Tx and Rx impaired, (ii) Tx impaired and ideal Rx, and (iii) both Tx and Rx are impaired. Further, asymptotic expressions for OP, ACC under ORA policy, and ASEP are obtained, based on which, insightful discussions on the IQI and RHI impacts are made. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha -\mu $ </tex-math></inline-formula> and Málaga <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal {M}$ </tex-math></inline-formula> turbulence with pointing error distribution models have been considered as particular cases of the HFHF distribution. The analytical derivations, endorsed by simulation results, demonstrate that the RF impairments’ effects should be seriously taken into account in the design of next-generation wireless technologies.

Research on Performance of Cooperative FSO Communication System Based on Hierarchical Modulation and Physical Layer Network Code

To solve the problem that the channel conditions in asymmetric cooperative FSO communication systems are not fully utilized, and the data reliability deteriorates due to high-order modulation, we proposed a layered modulation, joint physical-layer network coding scheme. In this scheme, we first designate the data priority of the information to be transmitted at the source node. Then, the transmission power of different proportions is allocated to the data based on its priority. Then, the modulated data is sent to each node, and physical-layer network coding is performed on the received data at the relay node. Finally, the relay node sends the encoded information to the destination node, and the destination node recovers the original information using the physical-layer network coding scheme. The simulation results showed that when the average signal-to-noise ratio of the channel was 15 dB, the BER of the cooperative FSO communication system could be reduced to below . In the strong atmospheric turbulence channel, the cooperative FSO communication system can obtain a signal-to-noise ratio gain of about 1.5 dB. Under strong atmospheric turbulence, this scheme could also improve the average channel capacity performance of a cooperative FSO communication system.

User Grouping in Multiuser Satellite MIMO Downlink With Fairness Consideration

In this letter, a multi-user satellite MIMO downlink including a multi-beam GEO satellite and multiple user terminals (UTs) is considered. In order to make every UT get the service fairly, all UTs need to be divided into multiple groups so that UTs in the same group can be served simultaneously, and different groups can be served sequentially in different time slots. The user grouping problem is investigated in this letter with the objective of maximizing the average channel capacity per time slot, and a genetic based user grouping (GBUG) algorithm is proposed. Simulations show that the average channel capacity obtained by GBUG is larger than that of the existing algorithms in the ZF and MMSE precoding system.

Enhanced performance analysis with exact solutions for downlink-NOMA system in vehicular communications

This research presents an enhanced performance analysis process for the power domains of downlink-NOMA systems for vehicular communication over Rayleigh fading channels. We derived exact closed-form expressions of outage probability (OP), bit error rate (BER), outage capacity (OC), and average channel capacity (AVC) by using binary phase-shift keying (BPSK) modulation. All channel parameters required for downlink-NOMA system performance analysis were combined. The theoretical and simulation results perfectly confirmed one another. The obtained results were then compared with results from the literature, based on similar parameters. It was found that the proposed system increased the performance by 34 times for OP at SNR=15 dB, 92% and 22% for BER at SNR=24 dB, and 59% for AVC at SNR=30 dB. Finally, this study introduces exact solutions that will greatly accelerate NOMA system analysis by exploiting information in the existing database for analytical design processes based on communication theory.

Performance Analysis of Dual-Hop THz Transmission Systems Over α-μ Fading Channels With Pointing Errors

In this article, the performance of a dual-hop relaying terahertz (THz) wireless communication system is investigated. In particular, the behaviors of the two THz hops are determined by three factors, such as the deterministic path loss, fading effects, and pointing errors. Assuming that both THz links are subject to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> fading with pointing errors, we derive exact expressions for the cumulative distribution function (CDF) and probability density function (PDF) of the end-to-end signal-to-noise ratio (SNR). With these statistical expressions, some important performance metrics are evaluated, such as the outage probability (OP), average bit error rate (BER), and average channel capacity (ACC). Moreover, the asymptotic analyses are presented to obtain more insights. The results show that the dual-hop relaying scheme has better performance than the single THz link. Furthermore, the system diversity order depends on the fading parameters and pointing errors of both THz links. In addition, we extend the analysis to a multirelay cooperative diversity system and derive the asymptotic symbol error rate (SER) expressions. Finally, the derived analytical expressions are verified by the Monte Carlo simulation.

Performance Analysis of Dual-Hop Mixed PLC/RF Communication Systems

In this article, we study a dual-hop mixed power line communication and radio-frequency communication (PLC/RF) system, where the connection between the PLC link and the RF link is made by a decode-and-forward or amplify-and-forward relay. It is assumed that the PLC channel is affected by both additive background noise and Poisson&#x2013;Gaussian impulsive noise which suffer from log-normal fading, while the RF link undergoes generalized Rician fading. Based on this model, analytical expressions for the outage probability (OP), average bit error rate (BER), and the average channel capacity (ACC) are derived. Furthermore, asymptotic analyses for the OP and average BER as well as an upper bound expression for the ACC are presented. Illustrative numerical results are presented along with insightful discussions.

A Novel System of Mixed RF/FSO UAV Communication Based on MRR and RIS by Adopting Hybrid Modulation

In this paper, we propose a mixed radio frequency (RF)/free space optical (FSO) unmanned aerial vehicle (UAV) communication system, based on modulating retro-reflector (MRR) and reconfigurable intelligent surface (RIS), which adopts the hybrid L-ary pulse position modulation-binary phase shift keying-subcarrier intensity modulation (L-PPM-BPSK-SIM). More specifically, the RF channel follows Rayleigh distribution, while the FSO channel obeys Gamma–Gamma distribution that considers atmospheric turbulence and pointing error. For decode-and-forward (DF) relay, the MRR is installed on the UAV to reduce its weight, size, and power consumption. In particular, the RIS is used as user terminal along with the RF signal generator to achieve signal enhancement. Based on this, closed expressions for the outage probability, average bit error rate (BER) and average channel capacity of the end-to-end uplink and downlink are derived. Numerical results confirm that while the relay limitation is solved by MRR, RIS significantly reduces the outage probability and average BER as well as obviously increases the average channel capacity. Furthermore, the hybrid L-PPM-BPSK-SIM with average symbol length greater than eight can effectively improve the average BER performance of the system.

On the Sum of α-μ/Inverse Gamma Variates with Applications to Diversity Receivers

How to model shadow fading by applying the inverse gamma (IGA) distribution has recently gained widespread attention in wireless transmissions. However, the sum of α-μ/IGA variates, and its applications under independent and/or correlated scenarios, have yet to be addressed in open research works. Hence, this paper provides a systematic investigation of the α-μ/IGA model. First, we derive the expressions of the fundamental statistics of the univariate and bivariate α-μ/IGA models including the probability density function, cumulative distribution function, and moment generating function, and propose a mixture α-μ model to approximate the α-μ/IGA model. Then, according to the above statistical expressions, the statistical properties of the sum of α-μ/IGA variates are obtained and employed in the maximal ratio combining receivers. Third, the novel exact and approximated expressions of some performance metrics of interest are also derived, for instance, the average bit/symbol error probability, the outage probability, the average channel capacity, and the effective rate. Moreover, to prove the asymptotic properties of the performance metrics at the high signal-to-noise regions, some examples are performed. Finally, we explore numerical analysis and simulations to demonstrate the accuracy of the theoretical expressions under the different channel and system parameters. These results provide some significant insights into the reliability design and deployment of some conventional and emerging wireless communication applications.

Average symbol error probability and channel capacity of the underwater wireless optical communication systems over oceanic turbulence with pointing error impairments.

The influence of oceanic turbulence and pointing error impairments on the underwater wireless optical communication (UWOC) systems is considered in this study. We propose a generalized fading model, which comprises the path loss due to the absorption and scattering, the oceanic turbulence (modeled by Málaga distribution), and the pointing error impairments resulting from ocean movements. Thereafter, closed-form expressions of the average symbol error probability (SEP) and average channel capacity are proposed for optical waves propagate in oceanic turbulence with the M-ary pulse position modulation (PPM) and under the constraints of the limited average-power and peak-power. The Monte Carlo simulations are conducted to validate the analytical results and demonstrate that the fading parameters, including the mean-squared temperature, the salinity-temperature contribution factor, jitters, and water conditions, significantly affect the system performance. Moreover, the thermal noise and quantum noise in ocean environment have more serious impact than the background noise. Finally, we prove that the UWOC systems with the pure peak-power constraint performs better than that limited by average-power and peak-power.

Average Channel Capacity Evaluation for Selection Combining Diversity Schemes over Nakagami-0.5 fading Channels.

This paper provides Closed-form expressions for the average channel capacity and probability of outage of dual-branch Selection Combining (SC) over uncorrelated Nakagami-0.5 fading channels. This channel capacity and probability of outage are evaluated under Optimum Power with Rate Adaptation (OPRA) and Truncated channel Inversion with Fixed Rate transmission (TIFR) schemes. Since, the channel capacity and probability of outage expressions contain an infinite series, the series are truncated and bounds on the truncated errors are presented. The corresponding expressions for Nakagami-0.5 fading are called expressions under worst fading condition with severe fading. Finally, numerical results are presented, which are then compared to the channel capacity and probability of outage results for no diversity case, which has been previously published under OPRA and TIFR schemes. It has been observed that OPRA provides improved average channel capacity and probability of outage, as compared to TIFR under worst case of fading.

Capacity Estimation for a DS-CDMA System in Nakagami-m Fading

Ιn this paper, a novel closed-form expression of the Shannon average channel capacity per user for direct- sequence code-division multiple access (DS-CDMA) systems, operating in Nakagami-m fading, with optimum RAKE reception, is obtained. Numerical results are also presented to illustrate the proposed mathematical analysis and to point out the effect of the fading severity on the user’s average channel capacity.

Average spectral efficiency of multi-pulse position with adaptive transmissions and aperture averaging over atmospheric turbulence

Abstract The analysis of average spectral efficiency (ASE) of multi-pulse position modulation (MPPM) scheme with optimal rate adaptation (ORA) and channel inversion with fixed rate (CIFR) adaptation schemes over the gamma–gamma free space optical (FSO) channel has been carried out in this paper. The performance of the adaptation schemes has been analyzed in terms of the average channel capacity and has been further scrutinized under the aperture averaging effects in moderate and strong atmospheric turbulence. For the first time, closed form expressions for MPPM with ORA and CIFR transmitter adaptation schemes have been derived in terms of Meijer’s G functions. Using the derived expressions, the performance of the two adaptation policies have been compared for different transmitter power and varying FSO length, MPPM modulation order and aperture averaging. The analysis results revealed that generally, ORA performs better than CIFR under the considered turbulence strength, modulation order and aperture averaging. However, aperture averaging offers more gain in ASE in strong turbulence than moderate turbulence for both ORA and CIFR. Furthermore, the results revealed that aperture averaging effects offers much more gain in ASE when used with CIFR than ORA.

Throughput Analysis of α-κ-µ Extreme/Gamma Composite Fading Channel

In this paper, we consider α-κ-µ-Extreme/gamma composite fading channel model, which is used to characterize non-linear severe fading and shadowing impairments in enclosed wireless propagation scenarios. For this model, we first obtain the probability density function (PDF) expression for the received signal-to-noise ratio(SNR). Using the derived PDF, throughput analysis is provided by deriving expressions for the average channel capacity(ACC) and effective capacity(EC) in closed-form. The derived expressions are evaluated for several values of fading and shadowing indexes to study their effect on the ACC and EC. Furthermore, asymptotic analysis of ACC and EC are carried out to show better approximation under the high and low SNR regimes.