In the context of the fifth-generation new radio downlink scenario, we introduce an innovative approach for channel estimation in this paper that circumvents the requirement for the prior dataset. We incorporate anisotropic diffusion and bit-plane decomposition to remove the noise in channel estimates. We first pre-process wireless channel coefficients with bit-plane decomposition to partially reduce noise interference and maintain the granularity of the information. In the second stage, anisotropic diffusion is performed based on neighboring coefficients, and the gradient-based denoising takes place without prior training. We assess the mean square error (MSE) across varying noise levels compared to the state-of-the-art method and further explore the impact of key parameters governing anisotropic diffusion. The simulation results indicate that the proposed channel estimation technique achieves a 44.77% reduction in average MSE and a significant reduction in computational complexity compared to the baseline reference technique.

This work considers a three-dimensional mobile molecular communication (MC) via diffusion-based system. The communicating devices in the considered mobile MC system can move through Gaussian Brownian movement with emitted information-carrying molecules. We propose stochastic diffusivity models for both communicating devices and information-carrying molecules. Using the stochastic diffusivity model and considering initial distance as a reference, we derive the probability density function of the relative distance between the communicating devices. Through the proposed stochastic diffusivity model, we characterize the mobile MC channel by channel impulse response (CIR) and derive its statistical mean and the bit error rate expressions. Furthermore, we show the degree of accuracy of the mean of CIR through root mean square error using the Poisson and Gaussian distribution models.

In this work, we investigate an unmanned aerial vehicle (UAV)-assisted device-to-device (D2D) vehicular communication network that integrates the cellular link from a base station (BS). We minimize the system outage while ensuring reliability for individual vehicle-to-vehicle and vehicle-to-UAV links. To achieve this, we consider a generalized Nakagami-$m$fading distribution for the communication links in the network and utilize distinct fading parameters for various vehicle-to-everything links. We propose a novel selection and routing scheme to dynamically select between UAV and BS links for cellular vehicular communication. We explore redundancy strategies for data transmission and provide a comparative analysis that demonstrates that the single-copy multi-path (SCMP) routing strategy performs better than the single-copy single-path (SCSP) routing strategy, utilizing the UAV link judiciously in scenarios with poor signal-to-interference-plus-noise ratio in the vehicle-to-infrastructure network while maintaining a similar power requirement. We also observe that the multi-copy multi-path routing scheme performs better than SCMP and SCSP for scenarios without power constraints.

In this paper, we consider an amplify-and-forward (AF) relay-assisted two-way molecular communication via diffusion (MCvD) system with drift and propose three transmission schemes, where each scheme varies in the number of relay nodes and time slots required for transmitting a symbol. We propose a novel hybrid modulation scheme based on concentration-time and concentration-relay for transmitting a single molecule type to reduce the receiver complexity. We evaluate the error performance of each scheme and derive the expressions for the symbol error probability (SEP), and study the effects of various system parameters on the SEP, which are useful in system implementation and design. Furthermore, we extend the analytical framework for the performance analysis of the proposed schemes based on various constraints for the case of half-duplex and full-duplex AF relays. The numerical results show that the trade-off between complexity due to the number of relays and time slots required for transmission must be considered while designing the MC system for a specific application.

This work considers a three-dimensional mobile molecular communication (MC) via an anomalous-diffusion-based system. The communicating devices in the considered MC system are identical and can move anomalously with emitted information-carrying molecules. We propose a stochastic diffusivity-based anomalous diffusion model which considers the non-Gaussian Brownian displacement of the molecules using the subordination approach. The proposed stochastic diffusivity model for mobile MC channels is characterized by the channel impulse response (CIR), and its mean is derived. We consider a discrete-time statistical channel model at a high inter-symbol interference regime and derive the bit error rate expressions. We also derive the asymptotic expression and upper bound of the capacity for the subordination approach. Furthermore, we show the degree of accuracy through root mean square error for the Poisson and Gaussian distributions.

A rotated quadrature phase-shift keying (QPSK) based semi-orthogonal multiple access (SOMA) data transmission is considered for a visible light communication (VLC) system with two users. The rotation of the QPSK constellation at the transmitter followed by a data pre-processing technique at the receiver of each user ensures the elimination of the successive interference cancellation unit. An optimal maximum likelihood receiver is proposed for the system under consideration using which, the closed-form expressions for the symbol error probability (SEP) for both the users in the VLC system are derived. The optimization problem to obtain the optimal angle of rotation of the QPSK constellation which minimizes the SEP of the users is formulated and solved. The dependency of the optimality of the QPSK rotation angle on various VLC system parameters is studied via numerical results which lead to the observation of a value of the signal-to-noise ratio of the system around 8.8 dB about which the dependency of the optimal rotation angle on the other VLC system parameters interchange, thus providing design aspects for a SOMA-VLC system.

Over recent years, reflective intelligent surface (RIS) and index modulation (IM) technologies have proven to be potential technologies for improving the performance of the fifth generation (5G) and beyond 5G wireless communication systems. In this paper, a space-shift keying (SSK) (an IM scheme)-based receive diversity and Nakagami-m faded wireless system is considered, which utilizes a RIS system in between the transmitter and the receiver. A greedy detector is proposed for the system, which chooses a target receiver antenna based on the maximum received energy at the diversity branches. An analytical framework is proposed based on a characteristic function approach to obtain a closed-form expression of the probability of erroneous detection of the target antenna. Asymptotic expressions at high and low average signal-to-noise ratios lead to the observation of a performance saturation, attributed to the structure of the greedy detector. Furthermore, numerical results are presented to show the dependency of the system’s performance on the various system parameters.

In this work, we present an outage analysis of an intelligent reflecting surface (IRS)-assisted wireless communications system considering direct and indirect communication links between the transmitter and the receiver. We derive the probability density function and cumulative distribution function for the combined communication link between the transmitter, IRS, and the receiver. Furthermore, we derive the closed-form expressions for the outage probability, considering the direct link between the transmitter and the receiver as Nakagami-m faded, and the indirect communication link via IRS is considered to be under Rician fading. The analytical results are verified by simulations and give insight into modeling and analysis of N element IRS-assisted wireless communications system. We observe that the performance of the considered IRS- assisted wireless communications system significantly improves with an increase in the number of reflecting elements.

A practical visible light communications (VLC) system accounting for the effect of the random orientation and the random location of the photo-detector receiver is considered in this paper. The characterizations of the random orientation of the receiver, modeled as the receiver employing wide field of view (FOV) for data detection, and the random location of the receiver are utilized to derive the statistics for the scenarios in which (i) only the orientation of the receiver is random, (ii) only the location of the receiver is random, and (iii) both the orientation and location of the receiver are random. Furthermore, the receiver structures for a fully coherent VLC system and a VLC system employing the least-squares technique for channel estimation are proposed. Employing the receiver structures, the closed/series-form expressions for the symbol error probabilities are derived for all three scenarios of practical VLC channel models. The numerical results particularly show the crucial role of the ratio of the distance of the location of the receiver from the center of the receiving plane to the distance from the light-emitting diode (LED) to the center of the receiving plane in the performance of all the considered VLC systems.

In this work, we consider a two-user receive diversity wireless communication system with a rotated M-ary phase-shift keying (M-PSK) modulation, also known as semi-orthogonal multiple access (SOMA), for data transmission at the transmitter. At the receiver of the considered wireless communication system, each user utilizes a maximum ratio combining (MRC) technique and an optimal maximum-likelihood (ML) rule for transmitted data detection. We provide an analytical framework for the error analysis of the receive diversity wireless communication system and derive the closed-form expressions of the symbol error probability (SEP) for the users. Further, we also obtain the asymptotic expressions of the SEP at a high signal-to-noise ratio (SNR). We provide a numerical solution for the problem of finding the optimal rotation angle for the M-PSK constellation minimizing the SEP. The effects of the system parameters, namely, the number of diversity branches, SNR, and M, on the optimal rotation angle are demonstrated via numerical results. Furthermore, the simulation results corroborate the presented analytical results.

The sixth-generation (6G) communication networks being highly data-intensive and enabled by the Internet of Everything (IoE) are envisaged to find applications in various domains including smart healthcare, smart industry, and gaming. In this article, a novel hybrid 6G-based cybertwin cooperative architecture is studied and an analytical framework for the secrecy outage analysis is presented. The base station (BS) considered utilizes nonorthogonal-multiple-access for content request transmission to the cybertwin host and the server with a direct communication link present between the BS and the server. A wireless link experiencing Nakagami-$m$fading is considered which is further assisted in the communication network by a wired link which is a power line communication link and experiences Rayleigh fading, for the communication between the cybertwin host and the server. Secrecy error probability expressions are derived for the cybertwin host and the server for the scenario when both the wireless and the wired links are available for communication and only the wireless link is available for communication. Furthermore, the presented analytical results are corroborated with simulation results which demonstrate the optimality of operating the wireless links at lower signal-to-noise ratio (SNR) values. It is observed that for the lower values of Nakagami fading parameter, better secrecy performance is observed with the usage of wired link along with the wireless link, and also the secrecy performance of the cybertwin host and the server is dependent on the system parameters like the fading parameter and the average SNR.

Due to the exponential increase in the number of users, the next-generation cellular networks are resource-constrained in power and bandwidth. Power consumption is one of the critical consideration for the next-generation wireless networks, therefore, management of available resources is essential to achieve power efficiency. With the growing incentive to ‘go green’ and to reduce the carbon footprint, the fifth generation (5G) and beyond wireless networks will derive power from renewable sources to solve the energy efficiency problems. This work focuses on integrated regulation of the traditional, i.e., the grid-based and the renewable, i.e., the solar-based power supplies for the 5G and beyond 5G green base stations (BSs) in a smart city scenario. We propose a pricing model for suppliers to charge the BSs for electricity consumption when the renewable power supply cannot meet their total energy requirements. We propose a game-theoretic analysis for cost optimization by proposing two games, i.e., the power control game and the best supplier game. Each BS acts as a game player and has some actions like power reduction and supplier selection to reduce the total energy costs. We also provide the game transition profiles for the BSs. Furthermore, the Nash Equilibrium’s existence is verified for each of these games and an optimal cost solution is proposed for the green BSs.

We study a practical simulation set-up of indoor device-to-device (D2D) communications scenario for fifth generation (5G) applications to analyse the effects of power level variations, path-loss, and the impact of transmission through direct and indirect communication links. We provide a simulation based analysis considering a generalized indoor office building for the context of D2D indoor communication with line-of-sight and non-line-of-sight communication links. We show the effect of power level on the transmission, variation of the connectivity probability with the change in the number of receivers, and also consider the impact on connectivity of modeling the network as a mesh where the users act as relays. The simulation is performed at different operating frequencies including the 5G frequency range and for different path loss functions. We present the coverage analysis by taking actual measurements for an office setup, validating it through simulations, and show that the network coverage extends with the D2D communications. Furthermore, we observe that, as the number of users increases, the number of users able to access the network also increases, but with D2D communication included, that number approaches between 80% and 100% at 2.4 GHz, or around 50% to 90% at 5.8 GHz, in the presented scenario.

This paper considers a device-to-device (D2D) cellular communication network with the wireless communication link among the devices and the base station (BS) modeled by the Rician fading and the wireless communication link between the devices modeled by Nakagami-m fading distribution. The devices and the BSs are assumed to be placed randomly as independent Poisson point processes with the devices experiencing interference from both D2D users and the cellular users. Using the techniques of stochastic geometry, series form expressions of the coverage probability of the cellular users are derived for the underlying interference-limited D2D cellular network. Furthermore, the optimal coverage values that maximize the energy efficiency of the network are also obtained analytically. The effect of the Rician factor and other system parameters on the performance of the system is studied by numerical results. The study of the variations of the optimal coverage analysis with the system parameters presented in this paper gives an insight into the design of cellular D2D communication networks.

The cooperative device‐to‐device (D2D) network employing non‐orthogonal multiple access (NOMA) is expected to play an important role in the next‐generation wireless networks. In this work, the authors derive outage probability expressions of a cooperative NOMA D2D network which employs decode‐and‐forward relaying. A wireless link experiencing Nakagami‐ m fading is considered which is further assisted in the communication network by a wired link which is a powerline communication link and experiences Rayleigh fading. The outage analysis, shown for both the strong user and the weak user, is derived assuming that at the receiver there is perfect successive interference cancellation. Employing power division NOMA, optimum value for the coefficient of power allocation is obtained corresponding to the minimum probability of outage of the strong user. Furthermore, a range of the NOMA power allocation coefficient is provided for the communication link at the weak user which is between the wireless and the powerline link. Symbol error probability expressions are also derived for the strong and the weak users for the scenario when: i) both the wireless and the wired links are available for communication and ii) only the wireless link is available for communication.

Cooperative device-to-device communication with non- orthogonal multiple access (NOMA) employing additional power line communication technology is an effective way to increase the coverage and spectral efficiency of the next generation hybrid networks. In this paper, we present the outage analysis of a cooperative network with NOMA and decode-and-forward relaying assuming a direct link between the base station and the users. We consider a relaying network consisting of a wireless link for the strong user and the weak user having both wireless and a wired link which is assumed as a power line link. The wireless links are subjected to Nakagami-m fading and the power line link experiences Rayleigh fading. The outage probability expressions for both the strong and the weak users are derived assuming power division NOMA and perfect successive interference cancellation at the receivers. We also derive the optimal value of the NOMA power allocation coefficient minimizing the outage probability at the strong user and obtain the range of the power allocation coefficient between the power line and the wireless link at the weak user. Furthermore, numerical results validate the derived analytical results.

Cooperative non-orthogonal multiple access (NOMA) scheme is emerging as an important part of the next generation wireless systems. Recently, device-to-device (D2D) networks with NOMA have received considerable attention by the researchers due to the advantages offered by them. D2D communication involves direct contact between the devices in proximity and the devices can also be used as relays for cooperative communication. In this paper, we present the performance analysis of a downlink cooperative D2D network with NOMA and amplify-and-forward (AF) relaying with fixed gain assuming that the D2D communication links experience independent Nakagami-m fading. We derive closed-form expressions for the outage probability of strong and weak D2D users with the assumption that there exists a direct communication link between the base station and the D2D users. Further, we also present the system throughput and the asymptotic outage analysis for both strong D2D user and weak D2D user. As a special case, we also provide the outage expressions for both strong D2D user and weak D2D user when the D2D communication links experience Rayleigh fading. Furthermore, numerical results are in agreement with the derived analytical expressions.

Device‐to‐device (D2D) communication, unlike conventional cellular communication, is described as the direct communication between devices bypassing the network infrastructure. This mode of direct communication, due to its advantages, is being proposed as an integral part of the next generation cellular networks with the additional interference between the users being a challenge. In this study, the authors develop an analytical framework for a D2D‐enabled downlink cellular network with Nakagami‐ m fading between the D2D communication links. The authors derive tractable expressions for the coverage probability of D2D links and cellular users, considering different propagation conditions experienced by D2D and cellular links. Using stochastic geometry, the authors provide the coverage probability analysis for the dedicated network, having orthogonal frequency resource allocation, and for the shared network, where the frequency resources are reused. Furthermore, the authors extend the coverage probability analysis to include interference‐limited dedicated and shared networks. Numerical results corroborate their analysis. The authors also derive the expressions for ergodic spectral efficiency of D2D links for both dedicated and shared networks. The results obtained are helpful in understanding the system behaviour and show the dependence of network performance on the system parameters.