Harnessing Relay Selection and Fluid Antenna Systems (FAS) for Enhanced Cooperative Terahertz Networks

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.