Open problems in 6G terahertz communications and networking

Investigate and resolve the primary unresolved questions in terahertz-band (0.1–10 THz) communications for 6G networks, including overcoming short-range propagation (“distance problem”) via ultra-massive MIMO and/or reconfigurable intelligent surfaces, developing accurate beamforming and practical initial access methods for THz ultra-massive MIMO, designing practical and cost-/energy-efficient electronic and photonic transceivers for THz signal generation and detection that are robust to severe hardware impairments (phase noise, non-linearity), creating flexible multi-waveform designs that mitigate hardware impairments at very high frequencies, establishing realistic THz channel and simulation models for link- and system-level evaluation in 6G scenarios, and integrating THz communication with high-accuracy localization and sensing.

Background

The paper identifies terahertz (THz) communication as a key enabler for extreme data rates in 6G owing to the massive spectrum available at 0.1–10 THz. However, THz links suffer from high propagation losses, easy blockages, and severe hardware impairments, which constrain coverage and practicality.

In the authors’ future directions, they enumerate several specific areas requiring further research to make THz viable for 6G: addressing the distance problem with ultra-massive MIMO and RISs, supporting close-proximity services and applications, selecting suitable THz bands, alleviating hardware impairments via multi-waveform designs, advancing practical transceiver design (electronic/photonic, signal generation/detection, RF/antenna), integrating THz communication and sensing, and developing realistic channel and simulation models for robust link- and system-level performance evaluations.

References

There are still many open problems to be addressed in future research toward efficient THz communications and networking in the 6G era.

— 6G: The Intelligent Network of Everything  (2407.09398 - Pennanen et al., 2024) in Section 6, Subsection 'Spectrum-Level Technologies for 6G' → Subsubsection 'THz Communications', Literature and Future Directions

At the time of writing, the channel dispersion of wireless THz channels has not been investigated in SQCC.

— Technical Report OFDM-Assisted Simultaneous Quantum and Classical THz Communications  (2609.20542 - Liu et al., 17 Sep 2026) in Section 1, Introduction

Secondly, THz beamforming has never been harnessed for compensating the severe path loss in THz SQCC applications.

— Technical Report OFDM-Assisted Simultaneous Quantum and Classical THz Communications  (2609.20542 - Liu et al., 17 Sep 2026) in Section 1, Introduction

The individual and joint effects of the other practical THz impairments are left for future investigation.

— Technical Report OFDM-Assisted Simultaneous Quantum and Classical THz Communications  (2609.20542 - Liu et al., 17 Sep 2026) in Section 1, Introduction, footnote following the discussion of unresolved THz SQCC problems