Accurate Channel Model for Near Field Terahertz Communications beyond 6G

Future 6G and beyond-6G cellular systems are expected to operate in the sub-terahertz (0.1-0.3 THz) and terahertz (THz, 0.3-3 THz) frequency bands. However, the small wavelength coupled with large antenna apertures force a part of the (sub-)THz access points coverage to be in the near field. There, conventional far-field propagation models (e.g., free space path loss, FSPL) are not applicable, as their use leads to substantial errors in the analysis. At the same time, existing exact near-field models following the electromagnetic principles are relatively complex and require additional efforts when using them for simple link budget predictions. In this paper, we fill this gap by developing an accurate yet easy-to-use propagation model for near-field THz communications. The proposed model has a simple algebraic structure, is applicable to both near field and far field, and requires no fine-tuning for different sets of input parameters. We analyze the key dependencies in the THz near field channel with the developed model and also contrast the results with those by FSPL, noticing up to 20 dB difference.