In recent years, reconfigurable intelligent surfaces (RIS) have emerged as a promising technology for enhancing link reliability in wireless communication systems. This paper introduces a novel RIS-assisted terahertz (THz) communication system utilizing the spatial modulation (SM) technique. We derive the closed-form expressions for the probability density function (PDF) and moment generating function (MGF) of the SM-based RIS-assisted THz system over α-μ fading. Leveraging these derived channel statistics, we obtain an upper bound on the average bit error rate (BER) and a lower bound on the ergodic capacity to evaluate the performance of the proposed system. The asymptotic BER is analyzed to determine the system’s diversity gain. The numerical results validate the theoretical findings and provide valuable insights into the system’s performance. The analysis shows that the SM-based RIS-assisted THz system outperforms the existing traditional systems. Lastly, a trade-off between average BER performance and spectral efficiency is observed.

In this paper, we investigate a full-duplex underlay device-to-device (D2D) communication system, where multiple D2D pairs exchange information with the assistance of a single reconfigurable intelligent surface (RIS). We begin by deriving analytical expressions for the outage probability of the users, and subsequently for ergodic rate. The analysis is carried out over a generalized Nakagami-m fading channel and incorporates several practical impairments, including residual self-interference (RSI), hardware imperfections (HI), and co-channel interference (CCI) from both cellular and D2D users. Assuming only statistical channel state information (CSI) is available for the CCI links, we formulate a joint optimization problem for D2D transmit power allocation and RIS partitioning, with the objective of maximizing the ergodic sum rate of the network. This optimization problem is efficiently solved using the particle swarm optimization (PSO) algorithm. Simulation results validate the effectiveness of the proposed system, demonstrating superior performance over conventional half-duplex systems and highlighting the advantages of the proposed optimization framework compared to benchmark schemes.

This paper explores a full-duplex underlay D2D communication system, where multiple D2D pairs exchange data with the help of a single RIS through RIS partitioning. Closed-form expressions for outage probability and ergodic rate are derived over generalized Nakagami-m fading, considering practical impairments such as residual self-interference, hardware imperfections, and co-channel interference (CCI). Assuming only statistical channel state information (CSI) availability for the CCI links, we formulate and solve a joint optimization problem for transmit power allocation and RIS partitioning using particle swarm optimization. Simulation results show significant performance gains over half-duplex systems and comparative benchmarks schemes.

Reconfigurable intelligent surfaces (RISs) hold great potential for addressing the challenges in terahertz (THz) communication. However, a single RIS cannot sufficiently overcome the high path loss of THz frequencies. This paper proposes a beam routing scheme for multi-RIS-assisted sixth-generation (6G) networks, employing a dynamic programming algorithm to optimize the propagation environment through multiple RISs for efficient multi-hop communication. A closed-form expression for ergodic capacity is derived. Simulation results demonstrate significant enhancements in throughput and reliability, highlighting the advantages of this approach over traditional methods and supporting the deployment of THz networks for future wireless applications.

This study explores a hybrid framework that merges terahertz (THz) and free space optics (FSO) technologies in a backhaul network. The combined FSO and THz systems leverage reconfigurable intelligent surfaces (RIS) and employ maximal ratio combining (MRC) at the receiver. Specifically, the closedform expressions for cumulative distribution function (CDF) of channel and signal-to-noise ratio (SNR) for RIS-assisted FSO and THz channels are derived by assuming the impediments such as atmospheric turbulence, fading, pointing errors, and pathloss. Using these statistics, outage probability, average symbol error rate (SER), and outage capacity are computed for the proposed RIS-assisted hybrid FSO/THz system. Numerical results compare the proposed hybrid FSO/THz system against various wireless systems, including RIS-assisted FSO, RIS-assisted THz, and hybrid FSO/THz systems without RIS.

Intelligent reflecting surface (IRS) technology is a promising solution for addressing the limitations of terahertz (THz) systems, including blockage effects and tremendous path loss. This paper investigates a novel IRS-assisted hybrid framework that seamlessly combines both THz and radio frequency (RF) technologies using a selection combining (SC) scheme, thereby enhancing system reliability. The study incorporates the deterministic and statistical properties of IRS in both RF and THz domains employing a sophisticated spatial scattering chan-nel model across generalized α - µ fading channels. Specifically, the exact closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the output signal-to-noise ratio (SNR) are derived for both THz and RF links. From this, the outage probability and average symbol error rate (SER) are derived. Furthermore, asymptotic expressions are evaluated for outage and average SER, offering insights into diversity gain of the system. Simulation results reveal a significant enhancement in system performance and power savings for the proposed IRS-aided hybrid THz/RF system. These findings provide valuable insights into the practical implementation of IRS-assisted hybrid networks, contributing to the ongoing efforts for future wireless networks.

Intelligent reflecting surfaces (IRS) have emerged as a promising technology for addressing the inherent challenges associated with terahertz (THz) bands, thereby enhancing system performance and offering immense potential for future wireless systems. However, existing single and multi-IRS-aided wireless systems often overlook crucial IRS-related factors such as IRS unit-cell dimensions, IRS gain, and inter-IRS collaboration, potentially limiting system performance. To mitigate these limitations and to leverage the unique advantages of THz band, this study investigates a multi-IRS-empowered THz system, that incorporates design parameters such as, the transceiver antenna gains, operation frequency, link distances, molecular absorption losses, beam misalignment, transceiver hardware imperfections, and statistical characteristics of the THz channel. By utilizing a sophisticated channel model that integrates the joint effects of these parameters with IRS properties and inter-IRS collaboration, this study demonstrates a significant enhancement in system performance and power savings. Moreover, exact closed-form expression and asymptotic approximation for outage probability are derived to quantify the effects of the deterministic and statistical channel parameters. These findings provide valuable insights into the practical implementation of multi-IRS-assisted THz networks, contributing to the ongoing efforts to unlock the potential of THz band for future wireless applications.

This paper proposes an amplify-and-forward (AF)-based multihop THz backhaul communication integrated with an access THz link. The access link is assisted with an intel-ligent reflecting surfaces (IRS) with an aim to deal with the impediments in THz communication environment. The statistical analysis is presented by deriving the probability density function (PDF) and cumulative distribution function (CDF) of the in-stantaneous signal-to-noise ratio (SNR) for the proposed system. The combined effect of path loss, atmospheric attenuation, and generalized fading is considered for modelling the THz channel. Furthermore, with the aid of PDF and CDF statistics, we propose the exact expressions for outage probability and develop asymptotic analysis in high SNR regime. The simulations are presented to validate the exact analysis and to study various design aspects for the proposed system.

Terahertz (THz) wireless communication has emerged as a front-line technology for substantially improving the data rates for 6G networks. However, they suffer from tremendous path-attenuation that limits the communication distance. Intelligent reflecting surface (IRS) is an excellent cost-effective technology for enabling THz wireless systems. This article presents comprehensive analysis of an IRS-empowered THz system, incorporating a detailed channel model encompassing deterministic IRS channel gain, THz molecular absorption losses, and the characteristics of sum of double$\alpha -\mu $fading. The analysis considers IRS-specific parameters, such as unit-cell dimensions, gain, radiation pattern, and array factor, for accurate received signal power characterization. For statistical analysis, the probability density function, cumulative distribution function, and moments are characterized using programmable multivariate Fox’s H-functions. Using these derived statistical results, the exact closed-form solutions for outage probability, average bit error rate, and ergodic capacity are reported. Additionally, asymptotic approximations are presented for deeper insights. Finally, to validate the accuracy of analytical results, extensive Monte-Carlo simulations are conducted. Multiple results investigate various design aspects of the proposed system. The findings demonstrate that significant performance gains and power savings thereby making THz communication feasible and highly promising for future wireless networks.

This paper investigates a hybrid framework that combines free space optics (FSO) and terahertz (THz) technologies for a backhaul network. In this hybrid configuration, the FSO and THz systems are empowered by reconfigurable intelligent surface (RIS) and are combined at the receiver using either maximal ratio combining (MRC) or selection combining (SC). The performance of the RIS-assisted hybrid FSO/THz system is evaluated under multiple impairments for FSO and THz links. The exact closed-form expressions for probability density function (PDF), cumulative distribution function (CDF), and moment-generating function (MGF) of the output signal-to-noise ratio (SNR) of both RIS-assisted FSO and THz links are derived. Leveraging these SNR statistics, we compute the outage probability and the average symbol error rate (SER) of the proposed hybrid FSO/THz system with MRC and SC schemes. Additionally, this paper conducts an asymptotic analysis at high SNR levels, yielding asymptotic expressions for outage and average SER, which not only reduce computational complexity but also provide insights into the system’s diversity gain. In the numerical results, the performance of the proposed hybrid FSO/THz system is compared against other state-of-the-art wireless systems, including direct link FSO without RIS, RIS-aided FSO, and the hybrid FSO/THz systems without RIS using diversity combining techniques.

Intelligent reflecting surfaces (IRS), a new paradigm for controlling the wireless propagation environment, is an excellent cost-effective technology for terahertz (THz) systems. In this paper, the performance of an IRS-assisted THz system, with N reflective elements, is systematically analyzed over the deterministic IRS channel gain, the THz path loss model, and the sum of independent and non-identically distributed (i.ni.d.) cascaded α−µ fading channels. The probability density function (PDF) and the cumulative distribution function (CDF) of the proposed system are statistically characterized in terms of programmable multi-variate Fox’s H function. Using derived statistical results, the closed-form solution for outage probability of THz-IRS system is reported along with its simple asymptotic expansions. The analytical results are validated using Monte-Carlo simulations. Results show that, sufficient signal-to-noise ratio (SNR) can be achieved with enough number of IRS antenna elements, making THz communication feasible.