Saiyan: Design and Implementation of a Low-power Demodulator for LoRa Backscatter Systems
Talkat 19th USENIX Symposium on Networked Systems Design and Implementation (NSDI '22) · 2022-04-04..04-06·
summary
Demodulator design claims 3.5–5x demodulation-range gain and a prototype two‑layer PCB that reaches up to 180 m while consuming about 370 μW (ASIC sim ~93.2 μW). It converts LoRa chirps to amplitude using a SAW filter, replaces ADCs with a comparator+counter to digitize peaks, and adds a low‑power cyclic frequency‑shifting block that yields ~11 dB SNR improvement. Enables downlink feedback, rate adaptation, channel hopping, and up to ~18 kbps throughput.
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chapters (20)
- 0:00Intro
- 0:36Backscatter Provides Ubiquitous Wireless Connectivity
- 1:07LoRa Backscatter Primer
- 1:31Challenge on Packet Delivery
- 3:28Existing Works for Downlink Demodulation
- 4:27How to demodulate LoRa Symbols?
- 5:14Saiyan: a Low-power Demodulator
- 5:40Key Observation
- 6:43Frequency-amplitude Transformation
- 7:14Surface Acoustic Wave (SAW) Filter
- 9:41Demodulation Sensitivity of Vanilla Saiyan
- 9:56Improving the Demodulation Sensitivity
- 10:23Cyclic-frequency Shifting
- 11:12High-level Circuit Schematic
- 11:36Implementation
- 11:53Demodulation Range
- 12:16Throughput
- 12:27Power Consumption & System Cost
- 12:48Take Away
- 13:58Conclusion
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