Multi-Hop Relaying Distribution Strategies for Terahertz-Band Communication Networks: A Cross-Layer Analysis
Qing Xia, Josep Miquel Jornet
Abstract
Terahertz (THz) band (0.1-10 THz) communication is envisioned as a key wireless technology to satisfy the need for wireless Terabit-per-second (Tbps) links in 6G systems. The THz band supports very large channel bandwidths with the cost of very high propagation losses. On the one hand, the absorption by water vapor molecules manifests itself in the form of absorption lines that broaden in frequency with distance, resulting into a highly distance-dependent channel bandwidth. On the other hand, the very high spreading or free-space losses require the use of highly directional antennas (DAs) simultaneously in transmission and reception at all times. As with the bandwidth, the beamwidth of such DAs is also related with the transmission distance, and introduces severe synchronization and, correspondingly, delay challenges. These issues become even worse when the system needs to support up to Tbps peak data-rates. The end-to-end (E2E) delay and, correspondingly, effective throughput in multi-hop THz communication networks can drastically suffer if all these peculiarities are not taken into account. In this paper, multi-hop relaying distribution strategies are developed for THz-band communication to minimize the multi-hop E2E delay by considering cross-layer effects between the THz channel, highly DAs, nodes’ buffer and the physical, link and network layers.