Performance Analysis for mmWave Cell-Free Access Network Based on Terahertz Backhaul

This letter proposes a downlink cell-free massive multiple-input multiple-output (CF-mMIMO) network architecture integrating terahertz (THz) backhaul and millimeter wave (mmWave) access, where a source server transmits signals to the central processing unit (CPU) via THz links, then enabling adaptive decode-and-forward transmission to multiple fiber-connected mmWave access points (APs). A novel fluctuating two-ray (FTR) fading model is adopted to characterize mmWave links for accurate performance analysis. Closed-form expressions for outage probability and ergodic capacity are derived for maximum ratio combining (MRC) receivers, complemented by asymptotic analysis in high signal-to-noise ratio (SNR) regimes. Extensive simulations validate the analytical results and demonstrate a critical trade-off: while increasing the number of APs yields marginal outage probability improvement due to THz backhaul limitations, it substantially enhances ergodic capacity through effective spatial multiplexing.