Near-field propagation models for system-level research of 6G+ cellular systems
Farooqui, Huda (2026)
2026
Master's Programme in Computing Sciences and Electrical Engineering
Informaatioteknologian ja viestinnän tiedekunta - Faculty of Information Technology and Communication Sciences
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Hyväksymispäivämäärä
2026-01-20
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202601201660
https://urn.fi/URN:NBN:fi:tuni-202601201660
Tiivistelmä
Future beyond-6G wireless networks are expected to operate in the terahertz (THz) band (0.3–3 THz), where many users will be located in the near-field region of the base station (BS) antenna. Unlike conventional 5G systems in the millimeter-wave (mmWave) band (30–100 GHz), where received power mainly depends on distance, near-field THz propagation is highly sensitive to the precise position of the user equipment (UE). Even very small movements, on the order of a wavelength, can cause rapid changes in signal strength. This makes near-field modeling significantly more complex and challenging as compared to the far field.
To conceal the impact of rapid variations in received signal strength, different wavefront formation techniques have been proposed, including beam focusing and non-diffractive beams, in addition to the conventional beamforming technique. However, their ultimate performance on system-level metrics of interest, such as spectral efficiency and system capacity, has not been addressed so far, due to the lack of tractable near-field propagation models. This highlights the need for computationally efficient and analytically simple near-field propagation models that capture key physical effects without the high computational cost of full-wave Hertzian formulations.
Thus, this thesis provides a comprehensive review of near-field propagation models. Among the candidate models, the spherical-wave model (SWM) delivers the most accurate representation of near-field effects. Although it is more computationally efficient than full-wave methods, SWM still requires summations over all antenna elements, which can be intensive for large arrays.
To address this limitation, a polynomial-corrected Friis model is proposed, applying a closed-form polynomial correction to the classical Friis far-field formula. MAT-LAB simulations demonstrate that this model closely matches the SWM reference across different distances, azimuth and elevation angles, and operating frequencies, including sub-THz and THz bands. By accurately capturing near-field effects while remaining computationally simple, the proposed approach enables efficient, precise system-level evaluation of THz channels, providing a practical, scalable solution for the design and analysis of future beyond-6G networks.
To conceal the impact of rapid variations in received signal strength, different wavefront formation techniques have been proposed, including beam focusing and non-diffractive beams, in addition to the conventional beamforming technique. However, their ultimate performance on system-level metrics of interest, such as spectral efficiency and system capacity, has not been addressed so far, due to the lack of tractable near-field propagation models. This highlights the need for computationally efficient and analytically simple near-field propagation models that capture key physical effects without the high computational cost of full-wave Hertzian formulations.
Thus, this thesis provides a comprehensive review of near-field propagation models. Among the candidate models, the spherical-wave model (SWM) delivers the most accurate representation of near-field effects. Although it is more computationally efficient than full-wave methods, SWM still requires summations over all antenna elements, which can be intensive for large arrays.
To address this limitation, a polynomial-corrected Friis model is proposed, applying a closed-form polynomial correction to the classical Friis far-field formula. MAT-LAB simulations demonstrate that this model closely matches the SWM reference across different distances, azimuth and elevation angles, and operating frequencies, including sub-THz and THz bands. By accurately capturing near-field effects while remaining computationally simple, the proposed approach enables efficient, precise system-level evaluation of THz channels, providing a practical, scalable solution for the design and analysis of future beyond-6G networks.