Comprehensive Guide to the Sigfox Protocol: A Fierce Competitor to LoRa in IoT (LPWAN)
The Internet of Things (IoT) is expanding daily, and selecting the appropriate wireless communication protocol is one of the primary challenges for designers. In previous articles, we became familiar with one of the most important LPWAN protocols, LoRaWAN. In this article, we intend to explore another major competitor in this arena: the Sigfox protocol, examining its features and how it operates.
What is the Sigfox Protocol, and Where Did It Originate?
Sigfox is the name of a French company founded in 2009. The company took a serious step in 2012 by introducing a dedicated IoT protocol focused on low power consumption. This protocol operates in the unlicensed ISM bands, specifically within the 868 MHz frequency range in Europe and 902 MHz in the US.
To date, Sigfox has successfully rolled out network coverage across dozens of countries.
How Does the Sigfox Protocol Work?
Since Sigfox falls under the LPWAN (Low-Power Wide-Area Network) category, its operational model shares similarities with other protocols in this sector. However, it is specifically designed for ultra-low-power applications that only need to transmit very small amounts of data over long distances.
Technical Specifications:
- Maximum Messages per Day: 140 (per device)
- Maximum Payload per Message: 12 bytes (equivalent to 96 bits)
- Data Transmission Speed: 100 bits per second (bps) using a technique called Ultra-Narrow Band (UNB).
Data Transmission Process in the Sigfox Network:
- Uplink (Device to Cloud): IoT devices (sensors) transmit their data via the Sigfox network to a Sigfox Gateway (Base Station).
- Processing (Gateway to Cloud): The Gateway detects the signals and forwards the messages to the Sigfox Cloud.
- Delivery (Cloud to Client): Finally, the Sigfox Cloud processes the data and makes it available to the end-user Client via an API or callback integration.
While the general flow resembles LoRa, technically, the modulation techniques and electrical instructions controlling data rate and transmission duration are distinct.
Data Transmission Method in Sigfox
The Sigfox network architecture consists of three main components:
- Devices (Sensors): Objects such as temperature, humidity, or parking sensors located within range of a base station (up to 10–50 km in rural areas, 1–5 km in urban areas).
- Base Stations (Gateway): Equipped with large antennas to receive low-power signals.
- Sigfox Cloud (Internet): The central core responsible for processing, validation, and data management.
Sigfox primarily utilizes Uplink communication (sensor to cloud). While Downlink (cloud to sensor) capability exists (max 4 messages per day, 8 bytes each), it requires the device to initiate contact first to “open” a receive window.
Furthermore, gateways use a method called DPSK (Differential Phase Shift Keying) to handle signal modulation and demodulation before transferring data to the cloud.
Layered Model of the Sigfox Protocol
The Sigfox protocol follows a simplified protocol stack compared to standard networking models:
- Physical Layer (PHY): Handles radio transmission using DBPSK (Differential Binary Phase Shift Keying) for Uplink and GFSK (Gaussian Frequency Shift Keying) for Downlink. It operates on the Ultra-Narrow Band.
- MAC Layer: Responsible for device identification (HMAC), message authentication, and error control (CRC).
- Frame Layer: Structures the application data into radio frames and systematically adds a sequence number.
- Application Layer: The interface for end-user applications to receive and manage data.
Conclusion
With its ultra-lightweight structure, extremely low power consumption, and global network infrastructure, the Sigfox protocol is one of the best options for industrial and smart city IoT applications (such as smart metering, asset tracking, and alarms) that require transmitting small packets of data over vast distances.
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