Sigfox Protocol Guide: Ultra-Narrowband IoT Network

Core Technical Specifications

center Freq 868.034–868.226 MHz (EU) / 902–904 MHz (US)

modulation D-BPSK (Ultra Narrowband)

data Encoding 100 bps uplink, 600 bps downlink

operating Range 3–50 km (rural), 1–10 km (urban)

antenna ¼ Wave Monopole

tx Power 14 dBm (EU) / 22 dBm (US)

bandwidth 100 Hz per channel

channel Spacing Random within 192 kHz macro-channel

Real-World Devices & Applications

IoT & Monitoring

Utility meters (water, gas)
Environmental sensors (air quality, temperature)
Asset trackers (low-update-rate)
Alarm systems (panic buttons, tamper alerts)
Smart agriculture (soil moisture, livestock)

Reference Circuits & Schematics

Sigfox Module — Wisol SFM10R1

Common Sigfox-certified module with integrated PA. UART AT command interface to host MCU.

Pin	Description
`VCC`	1.8–3.6V supply
`GND`	Ground
`UART TX`	AT command output to MCU RX
`UART RX`	AT command input from MCU TX
`ANT`	50Ω antenna

Circuit Walk-Through

MCU sends AT commands like 'AT$SF=AABBCCDD' to transmit a 12-byte payload. The module handles D-BPSK modulation, random frequency selection, and 3× frame repetition on different frequencies for redundancy.

Signal Structure & Waveform Analysis

Sigfox UNB Frame

Each uplink is transmitted 3 times on 3 different random frequencies for diversity.

Preamble

Variable

Bit sync sequence

Device ID

32 bits

Unique device identifier

Payload

0–96 bits

0–12 bytes application data

Auth + CRC

Variable

AES-128 auth and error check

Timing Notes: Max 140 uplinks/day, 12 bytes each. Max 4 downlinks/day, 8 bytes each. Each uplink takes ~2 seconds.

Analysis & Capture Tips

Check Sigfox backend portal for device registration and message history
Use SDR to verify UNB signal presence at 868 MHz
Monitor RSSI/SNR on Sigfox backend for coverage

Bench Troubleshooting & Repair Guide

1. Device Registration

Sigfox Backend portal

Every Sigfox device must be registered on the backend with its Device ID and PAC. Unregistered devices are silently dropped.

2. Message Quota

Sigfox Backend message counter

Max 140 uplinks/day. Optimise payload encoding to reduce message frequency.

3. Antenna Matching

NanoVNA

UNB signals (100 Hz) are extremely narrowband — antenna mismatch causes disproportionate signal loss. Verify with NanoVNA.

Sigfox