On the performance of dual-hop mixed THz-RF cooperative relay networks

The 0.1–10 terahertz (THz) band theoretically offers the potential to provide high data rates for 6G and beyond infrastructure. Consequently, THz band communication can be utilized in wireless fiber extenders and backhaul networks. Nonetheless, THz band communication suffers significantly from losses due to molecular attenuation and pointing errors, which result from antenna misalignment caused by small antenna apertures. However, cooperative communication strategies exhibit considerable potential in enhancing the THz link. Additionally, to address THz link limitations, a blend of technologies is necessary. Therefore, in this paper, we consider a decode-and-forward (DF)-based mixed THz-radio frequency (RF) cooperative system model. Furthermore, an in-depth exploration of coherent quadrature amplitude modulation and non-coherent modulation schemes is undertaken. Exact expressions for end-to-end (e2e) outage probability (OP), moment generating function (MGF), and channel capacity (CC) are derived, along with exact average symbol error rate (ASER) expressions for both coherent and non-coherent modulation schemes. We also perform asymptotic analysis to determine the system’s diversity gain and coding gain. Moreover, we conduct a thorough performance analysis to examine the impact of various parameters on e2e performance. Finally, validation through Monte-Carlo simulations ensures system accuracy, facilitating the extraction of practical design principles for optimizing THz-RF cooperative systems.