Terahertz (THz) communication with a Tbps transmission rate requires novel channel propagation models and designs for antennas and RF components to address the challenges in THz bands, including molecular absorption effects, high penetration loss, and frequent blockages. An extreme data rate, ultra-low latency, and cm-level localization in the THz band will accelerate a massive deployment of IoT devices, where device nodes may re-transmit other users’ messages. In this work, we study a THz cooperative network with an N-relay decode-and-forward relay selection scheme, where users are equipped with a fluid antenna system (FAS) receiver technology. FAS offers paramount flexibility and numerous advantages, especially for biomedical applications. Moreover, the proposed system considers non-ideal transceiver hardware that emits residual transceiver hardware impairments (RTHI) noise that notably deteriorates the performance of high-rate networks. Existing research often focuses on ideal transceiver hardware, overlooking the impact of RTHI noise. As a result, we introduce a rapidly converging semi-infinite expression for the coverage probability (CP), validated through extensive Monte Carlo simulations. The results highlight a substantial degradation in the CP performance with each distance meter. Thus, deploying devices for relaying messages and employing FAS receivers significantly enhance the CP performance.

Reconfigurability and innovative design approaches to radio frequency components and network infrastructure are critical for the development of future communication networks, particularly beyond 5G (B5G), which aim to support the proliferation of Internet of Things (IoT) devices. Leveraging its favorable performance characteristics and potentially low cost, the fluid antenna system (FAS) has emerged as a compelling solution, garnering significant interest due to its reconfigurability, small form factor, flexibility, and transparency. This paper presents a comprehensive analysis of FAS in the context of B5G networks, with a focus on its theoretical performance and practical implementations. By deriving formulas for the semi-infinite outage probability and ergodic capacity of FAS receivers in equally correlated Nakagami-m channels, we showcase the remarkable diversity performance exhibited by FAS receivers, even with a half-wavelength antenna size. Monte Carlo simulations are employed to validate our theoretical findings in terms of the number of antenna ports and transmission power.

Millimeter-wave networks have already been successfully rolled out in many countries and now the research direction heads toward new technologies and standards to enable Tbps rates for future sixth-generation (6G) wireless communication systems. This work studies a point-to-point terahertz (THz) communication network exploiting the concept of a fluid antenna system (FAS) over correlated alpha-mu fading channels, nicely fitting the THz communication. Furthermore, the considered system is expanded to the selection-combining-FAS (SC-FAS) and maximum-gain-combining-FAS (MGC-FAS) diversity variates at the receiver side. The proposed FAS and its diversity configuration techniques are aimed to combat the high path loss, blockages, and molecular absorption effect related to the THz band. Our contribution includes comprehensive outage probability (OP) performance analysis for the THz band given the non-diversity and diversity FAS receivers. Moreover, the derived outage probability formulas are verified via Monte Carlo simulations. Numerical results have confirmed the superior performance of the MGC-FAS scheme in terms of OP. Finally, this work justifies that a higher number of antenna ports dramatically improves the system performance, even in the presence of correlation.

Fluid antenna systems (FAS) enable mechanically flexible antennas that offer adaptability and flexibility for modern communication devices. In this work, we present a conceptual model for a single-antenna N-port (SANP) FAS over spatially correlated Nakagami-m fading channels and compare it with the traditional diversity schemes in terms of outage probability. The proposed FAS model switches to the best antenna port and resembles the operation of a selection combining (SC) diversity. FAS improves the quality of service (QoS) of the network through antenna port selection. The advantage of FAS is the ability to fit hundreds of antenna ports into a half-wavelength antenna size at the cost of spatial channel correlation. Simulation results demonstrate the superior outage probability performance of FAS at several tens of antenna ports compared to the traditional diversity schemes such as maximum ratio combining, equal gain combining, and SC. Moreover, the novel probability and cumulative density functions for the land mobile correlated Nakagami-m random variates are evaluated in this paper.

This paper investigates RF power leakage in millimeter wave (mmWave) networks operating on hybrid beamforming (HB) system where a base station with massive MIMO antennas communicates with user equipment (UE) nodes equipped with a single antenna. RF power leaks between spatially divided transmissions to different users, due to back/side lobes of antennas. A maximum sub-array transmission diversity technique implemented on HB is proposed to improve the system performance under RF power leakage and residual transceiver distortion noise. In this work, we emphasize how RF power leakage and residual transceiver distortion noise constraints degrade the quality of communication performance in terms of outage probability (OP) and ergodic capacity. An analytic model of mmWave connectivity is used, resulting in closed-form expressions for the OP and ergodic capacity. These are corroborated through Monte-Carlo simulations. Simulation results demonstrate that the effect of transceiver distortion noise is more severe at high signal power due to the proportionality of transceiver distortion noise to signal power.