A Near-Field Extension of the 3GPP Geometry-Based Stochastic Channel Model for Sub-THz Communications

Many conventional radio channel models, such as 3GPP TR 38.901, assume far-field conditions and rely on the plane wave approximation. However, as antenna arrays grow in size and link distances decrease, near-field propagation effects become significant, particularly at sub-terahertz (THz) frequencies. This letter proposes an initial extension to the 3GPP channel model to incorporate near-field characteristics at these frequencies. The approach models both line-of-sight and non-line-of-sight paths using exact geometric distances. An image-theory-based method is introduced to model specular reflections. The extended model maintains consistency with the existing 3GPP framework while enhancing modeling accuracy in the near field. © 2026 IEEE.