Software-Defined Radio and LoRa Analysis

Learning Objectives

1. Explain what SDR is and how it differs from traditional radio
2. Use an SDR to observe the 915 MHz ISM band
3. Identify LoRa transmissions on a waterfall display
4. Understand FCC Part 15 rules for 915 MHz
5. Set up GNU Radio with gr-lora_sdr for LoRa analysis
6. Build a LoRa protocol analysis flowgraph

Session 1: SDR Fundamentals (3 hours)

Part 1: SDR Fundamentals (30 min)

Sampling, Nyquist theorem, quadrature (I/Q), dynamic range. Traditional radio uses fixed hardware filters; SDR does filtering in software.

Part 2: FCC Part 15.247 (20 min)

Part 3: Live Spectrum Observation (45 min)

RTL-SDR waterfall of 915 MHz band. Identify LoRa chirps, WiFi, and other ISM traffic.

Part 4: LoRa Signal Anatomy (30 min)

Chirp structure, preamble, spreading factors (SF7-SF12), bandwidth, coding rate, time-on-air calculations.

Part 5: GNU Radio + gr-lora_sdr (45 min)

Build a receive flowgraph: RTL-SDR Source -> Channel Filter -> gr-lora Demodulator -> Message Debug.

Part 6: RF Troubleshooting (30 min)

Link budget: TX power + TX antenna gain - path loss + RX antenna gain = received power. Compare against receiver sensitivity.

Session 2: Advanced Topics (3 hours)

Part 7: LoRa Protocol Analysis with GNURadio (45 min)

Exercise: Build a receive flowgraph, capture packets from a known Meshtastic transmission, and observe why encrypted payloads look random (AES-256 working correctly).

TEMPEST and Emanation Security

Electromagnetic side-channel analysis is covered in a dedicated workshop: TEMPEST and Emanation Security.