Chapter 23: LEO Satellite Massive MIMO

Learning Objectives

• State the orbital classification LEO / MEO / GEO and compute the propagation delay budget for each from the altitude $h$ and the speed of light
• Derive the LEO one-way Doppler shift $f_D = (\mathbf{v}_{\text{sat}} \cdot \hat{\mathbf{u}}) \,f_0 / c$ as a function of elevation angle, and compute concrete numbers at S, Ku, and Ka bands
• Set up the free-space link budget for a Ka-band LEO link including rain fade, atmospheric absorption, and polarization loss, and relate the resulting SNR to the user terminal's $G/T$
• Explain the macro-diversity gain from joint reception across $M$ simultaneously visible LEOs, including the cell-free processing model and the feeder-link fronthaul requirement
• Compare OFDM and OTFS as waveforms for the LEO channel: ICI from Doppler, CP length vs differential delay spread across the footprint, and the delay-Doppler representation advantage
• Recognize how the CommIT contribution of Buzzi, Caire, and Colavolpe instantiates cell-free macro-diversity in LEO NTN, and how handover turns into user-centric cluster reselection