THzCondenser: A System Design for IRS-Aided Terahertz Wideband Communications

Abstract

With the access to tens of gigahertz of bandwidth, terahertz (THz) wideband communication emerges as a promising technology for the upcoming next generation mobile networks. To deal with the severe path loss and blockage of THz signals, massive multiple-input multiple-output and intelligent reflecting surface (IRS) can be jointly employed. Due to the extremely large signal bandwidth, the beams generated by the transmit hybrid beamforming may point to different directions around the target direction at different frequencies, which results in the beam splitting effect (BSE). In this paper, a new system design namely THzCondenser is introduced to mitigate the BSE, where the signals generated by each transmit radio frequency (RF) chain are reflected by one of the distributed IRSs in a one-to-one manner via the joint transmit and IRS beamforming design, thus creating adjustable multi-path components to achieve both high spatial multiplexing gain and array gain. Moreover, for practical scenarios when the number of transmit RF chains is more than that of IRSs, each IRS may need to reflect the signals generated by multiple RF chains in a one-to-many manner. For the above two cases, the joint beamforming design problems are efficiently solved to maximize the achievable rate. Simulations are conducted to verify the effectiveness of the proposed algorithms for mitigating the BSE and improving the achievable rate in IRS-aided THz wideband communications.