THz Precoding for 6G: Applications, Challenges, Solutions, and Opportunities

TL;DR

This paper reviews THz precoding techniques for 6G, discussing challenges like path loss and beam split, and evaluates solutions such as analog, hybrid, and delay-phase precoding through simulations and future research insights.

Contribution

It systematically analyzes key THz precoding methods for 6G, highlighting their designs, advantages, limitations, and potential research directions including RIS integration.

Findings

Hybrid precoding offers a good balance between performance and complexity.

Simulation results compare spectrum and energy efficiencies of different schemes.

Reconfigurable intelligent surfaces can mitigate THz blockage issues.

Abstract

Benefiting from the ultra-wide bandwidth, terahertz (THz) communication is becoming a promising technology for future 6G networks. For THz communication, precoding is an essential technique to overcome the severe path loss of THz signals in order to support the desired coverage. In this article, we systematically investigate the dominant THz precoding techniques for future 6G networks, with the highlight on its key challenges and opportunities. Specifically, we first illustrate three typical THz application scenarios including indoor, mobile, and satellite communications. Then, the major differences between millimeter-wave and THz channels are explicitly clarified, based on which we reveal the key challenges of THz precoding, such as the distance-dependent path loss, the beam split effect, and the high power consumption. To address these challenges, three representative THz precoding techniques, i.e., analog beamforming, hybrid precoding, and delay-phase precoding, are extensively investigated in terms of their different structures, designs, most recent results, pros and cons. We also provide simulation results of spectrum and energy efficiencies to compare these typical THz precoding schemes to draw some insights for their applications in future 6G networks. Finally, several important open issues and the potential research opportunities, such as the use of reconfigurable intelligent surface (RIS) to solve the THz blockage problem, are pointed out and discussed.