A Generalized Statistical Model for THz wireless Channel with Random Atmospheric Absorption

Current statistical channel models for Terahertz (THz) wireless communication primarily concentrate on the sub-THz band, mostly with $\alpha$-$\mu$ and Gaussian mixture fading distributions for short-term fading and deterministic modeling for atmospheric absorption. In this paper, we develop a generalized statistical model for signal propagation at THz frequencies considering random path-loss employing Gamma distribution for the molecular absorption coefficient, short-term fading characterized by the $\alpha$-$\eta$-$\kappa$-$\mu$ distribution, antenna misalignment errors, and transceiver hardware impairments. The proposed model can handle various propagation scenarios, including indoor and outdoor environments, backhaul/fronthaul situations, and complex urban settings. Using Fox's H-functions, we present the probability density function (PDF) and cumulative distribution function (CDF) that capture the combined statistical effects of channel impairments. We analyze the outage probability of a THz link to demonstrate the analytical tractability of the proposed generalized model. We present computer simulations to demonstrate the efficacy of the proposed model for performance assessment with the statistical effect of atmospheric absorption.Comment: This work has been submitted to IEEE for possible publcatio

Statistical Results of Multivariate Fox-H Function for Exact Performance Analysis of RIS-Assisted Wireless Communication

Existing research provides statistical results on the sum of single-variate Fox-H functions to analyze the performance of diversity receivers and reconfigurable intelligent surfaces (RIS) based wireless systems. There is a research gap in exact performance analysis when more than a single-variate Fox-H function represents the statistical characterization of wireless systems. In this paper, we propose a novel approach to obtain the distribution of the sum of independent and non-identically distributed (i.ni.d) random variables characterized by the multivariate Fox-H function. Further, we develop a general framework for an exact analysis of the ergodic capacity when the multivariate Fox-H function characterizes the statistics of signal-to-noise ratio (SNR). We apply the derived results to conduct an exact performance analysis of outage probability and ergodic capacity, taking an example of RIS-assisted communication over Rician fading channels with phase errors. We conduct computer simulations to validate the exact analysis and demonstrate performance of the RIS-assisted system under various practically relevant scenarios for a better performance assessment

Random Access Protocols for Cell-Free Wireless Network Exploiting Statistical Behavior of THz Signal Propagation

The current body of research on terahertz (THz) wireless communications predominantly focuses on its application for single-user backhaul/fronthaul connectivity at sub-THz frequencies. First, we develop a generalized statistical model for signal propagation at THz frequencies encompassing physical layer impairments, including random path-loss with Gamma distribution for the molecular absorption coefficient, short-term fading characterized by the $\alpha$-$\eta$-$\kappa$-$\mu$ distribution, antenna misalignment errors, and transceiver hardware impairments. Next, we propose random access protocols for a cell-free wireless network, ensuring successful transmission for multiple users with limited delay and energy loss, exploiting the combined effect of random atmospheric absorption, non-linearity of fading, hardware impairments, and antenna misalignment errors. We consider two schemes: a fixed transmission probability (FTP) scheme where the transmission probability (TP) of each user is updated at the beginning of the data transmission and an adaptive transmission probability (ATP) scheme where the TP is updated with each successful reception of the data. We analyze the performance of both protocols using delay, energy consumption, and outage probability with scaling laws for the transmission of a data frame consisting of a single packet from users at a predefined quality of service (QoS).Comment: This work has been submitted to IEEE for possible publcation. arXiv admin note: substantial text overlap with arXiv:2310.1861