Terahertz Ultra-Massive MIMO-Based Aeronautical Communications in Space-Air-Ground Integrated Networks

The emerging space-air-ground integrated network has attracted intensive research and necessitates reliable efficient aeronautical communications. This paper investigates terahertz Ultra-Massive (UM)-MIMO-based communications proposes an effective channel estimation tracking scheme, which can solve the performance degradation problem caused by unique triple delay-beam-Doppler squint effects of UM-MIMO channels. Specifically, based on rough angle estimates acquired from navigation information, initial link is established, where delay-beam at transceiver be significantly mitigated employing a Grouping True-Time Delay Unit (GTTDU) module (e.g., designed xmlns:xlink="http://www.w3.org/1999/xlink">Rotman lens -based GTTDU module). According to proposed prior-aided iterative algorithm, azimuth/elevation angles estimated, these are adopted achieve precise beam-alignment refine for further eliminating squint. Doppler shifts subsequently estimated using shift algorithm. On this basis, path delays gains accurately, effectively attenuated via compensation process. For data transmission, data-aided decision-directed algorithm developed track beam-aligned When invalid, will re-estimated pilot-aided stage with equivalent sparse digital array, ambiguity resolved previously angles. simulation results derived Cramér-Rao lower bounds verify effectiveness our solution.