SARLink: Satellite Backscatter Connectivity using Synthetic Aperture Radar

2024-02-15

AI Summary

Conventional satellite-to-ground communication struggles with low-power, ultra-long-range connectivity in remote areas due to reliance on active ground transmitters and dedicated satellite resources. Method: This work proposes a passive backscatter communication paradigm leveraging existing spaceborne Synthetic Aperture Radar (SAR) satellites as receivers. It introduces—(i) the first use of SAR imaging satellites for communication reception; (ii) a multi-bit joint demodulation algorithm based on sub-aperture processing; and (iii) a mechanically modulated corner reflector enabling dynamic Radar Cross-Section (RCS) encoding via On-Off Keying (OOK). Contribution/Results: Field experiments using Sentinel-1A at 693 km altitude achieved successful transmission of 60 bits per pass with a 5.5 ft × 5.5 ft reflector; measured bit error rates align with theoretical predictions, confirming reliable state-switching detection. The approach eliminates dependence on ground-based active transmission and dedicated satellite infrastructure, establishing a viable technical pathway for large-scale, passive IoT deployment in remote and wide-area scenarios.

Technology Category

• Multiagent Systems: Agent Communication
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Cognitive Modeling & Cognitive Systems: Neural Spike Coding

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Search and Retrieval-Augmented AI: Assisted, interactive, and conversational search
• Security and Privacy: Large-scale security measurements

Abstract

SARLink is a passive satellite backscatter communication system that uses existing spaceborne synthetic aperture radar (SAR) imaging satellites to provide connectivity in remote regions. It achieves orders of magnitude more range than traditional backscatter systems, enabling communication between a passive ground node and a satellite in low earth orbit. The system is composed of a cooperative ground target, a SAR satellite, and a data processing algorithm. A mechanically modulating reflector was designed to apply amplitude modulation to ambient SAR backscatter signals by changing its radar cross section. These communication bits are extracted from the raw SAR data using an algorithm that leverages subaperture processing to detect multiple bits from a target in a single image dataset. A theoretical analysis of this communication system using on-off keying is presented, including the expected signal model, throughput, and bit error rate. The results suggest a 5.5 ft by 5.5 ft modulating corner reflector could send 60 bits every satellite pass, enough to support low bandwidth sensor data and messages. Using Sentinel-1A, a SAR satellite at an altitude of 693~km, we deployed static and modulating reflectors to evaluate the system. The results, successfully detecting the changing state of a modulating ground target, demonstrate our algorithm's effectiveness for extracting bits, paving the way for ultra-long-range, low-power satellite backscatter communication.

Problem

• Enables long-range communication in remote areas using SAR satellites.
• Develops a system for passive ground-to-satellite backscatter communication.
• Demonstrates algorithm effectiveness for extracting data from SAR signals.

Innovation

• Passive satellite backscatter communication system
• Mechanically modulating reflector for amplitude modulation
• Subaperture processing algorithm for bit extraction