Synthetic Aperture Communication: Principles and Application to Massive IoT Satellite Uplink

TL;DR

The principles of SAC for direct satellite-to-device uplink are introduced, showcasing precise direction-of-arrival estimation for user equipment (UE) devices, facilitating spatial signal separation, localization, and easing link budget constraints.

Abstract

While synthetic aperture radar is widely adopted to provide high-resolution imaging at long distances using small arrays, the concept of coherent synthetic aperture communication (SAC) has not yet been explored. This article introduces the principles of SAC for direct satellite-to-device uplink, showcasing precise direction-of-arrival estimation for user equipment (UE) devices, facilitating spatial signal separation, localization, and easing link budget constraints. Simulations for a low Earth orbit satellite at 600 km orbit and two UE devices performing orthogonal frequency-division multiplexing-based transmission with polar coding at 3.5 GHz demonstrate block error rates below 0.1 with transmission powers as low as -10 dBm, even under strong interference when UE devices are resolved but fall on each other's strongest angular sidelobe. These results validate the ability of the proposed scheme to address mutual interference and stringent power limitations, paving the way for massive Internet of Things connectivity in non-terrestrial networks.

Figures (3)

• Figure 1: Satellite UL with LoS between a ground UE at $x=x_\mathrm{UE}$ and $y=0$ and a satellite at orbit height $R_0$ moving with orbital velocity $v$ from $x=-L/2$ to $x=L/2$ at $y=R_0$. From the middle point of the satellite's trajectory to the UE, a range $R_\mathrm{UE}$ and an azimuth angle $\theta_\mathrm{UE}$ are observed.
• Figure 2: Azimuth profile as a function of the $x$ coordinate (). For (a), two perfectly resolved UE devices are considered, $x_\mathrm{UE,1}=-495.33m$ () and $x_\mathrm{UE,2}=495.33m$ (). In (b), two resolved UE devices, $x_\mathrm{UE,1}=-742.99m$ () and $x_\mathrm{UE,2}=742.99m$ (), are considered. All magnitudes are normalized w.r.t. to the highest peak in (a).
• Figure 3: Mean BLER for both UE devices as a function of the transmit power $P_\mathrm{Tx}$ for the scenario with $x_\mathrm{UE,1}=-495.33m$ and $x_\mathrm{UE,2}=495.33m$ ($\CIRCLE$) and the scenario with $x_\mathrm{UE,1}=-742.99m$ and $x_\mathrm{UE,2}=742.99m$ ($\blacklozenge$). For comparison, BLER curves for a single-UE scenario with both UE and satellite receiver at $x=0m$ and without SAC ($\blacksquare$) and a maximum tolerable BLER of 0.1 is highlighted () are also shown.