After completing this chapter series, you should be able to:
Sigfox is an operator-managed LPWAN technology that uses Ultra-Narrow Band (UNB) modulation to send tiny 12-byte messages over distances of up to 50 km with extreme power efficiency. Unlike LoRaWAN, where you deploy your own network, Sigfox works like a cellular subscription – you pay an operator for connectivity across 75+ countries, with devices limited to 140 uplink messages per day. Choose Sigfox when you need simple, infrequent telemetry (e.g., asset tracking, environmental monitoring) with zero infrastructure investment.
Sigfox is both a proprietary LPWAN technology and the name of the French company that developed and operates it. Unlike other LPWAN technologies where you can deploy your own network, Sigfox operates as a network operator providing connectivity services globally. Sigfox pioneered the concept of ultra-narrow band (UNB) modulation for IoT, enabling billions of low-power devices to communicate with minimal infrastructure and energy consumption.
In one sentence: Sigfox is an ultra-low-power, operator-managed LPWAN that sends tiny messages (12 bytes) over extreme distances with no local infrastructure required.
Remember this rule: Choose Sigfox over LoRaWAN when you need global coverage without building infrastructure, only send small infrequent messages (<140/day), and can accept the operator’s coverage footprint; choose LoRaWAN when you need network control, larger payloads, or coverage in areas Sigfox doesn’t reach.
Lila had an idea: “What if our sensors could send postcards instead of letters?”
Sammy was confused: “Postcards? But they’re so small!”
“That’s the point!” said Lila. “Imagine you’re on vacation and you want to tell your family you’re fine. You don’t need a whole letter – just a postcard saying ‘Having fun! Weather is sunny, 25 degrees.’ That’s like Sigfox! Each sensor sends a tiny postcard (only 12 bytes!) that says something simple like ‘Temperature: 22, Battery: OK.’”
Max asked: “But who delivers the postcards?”
“The Sigfox company runs the postal service!” explained Lila. “You don’t need to build your own post office. You just buy a stamp (a subscription), and your sensor drops its postcard into the mailbox. The Sigfox towers pick it up and deliver it to the cloud. But remember – you can only send 140 postcards per day, so make each one count!”
Bella added: “It’s perfect for sensors that just need to whisper a tiny update once in a while – like a trash can saying ‘I’m full!’ or a parking sensor saying ‘Spot taken!’”
If you are new to LPWAN technologies, think of Sigfox as the budget airline of IoT connectivity:
When is Sigfox the right choice? When your devices send small, infrequent data, you want zero infrastructure cost, and Sigfox coverage exists in your deployment area.
The following diagram shows how data flows from a Sigfox device through the network to your application:
Key architectural points:
Understanding where Sigfox fits relative to other LPWAN options is essential for making the right technology choice:
This comprehensive guide to Sigfox fundamentals has been organized into four focused chapters for easier learning:
Start here if you’re new to Sigfox. This chapter covers:
Estimated time: ~10 minutes
Learn from real-world failures and avoid costly mistakes:
Estimated time: ~12 minutes
Understand the technical foundations:
Estimated time: ~12 minutes
Apply your knowledge with practical calculations:
Estimated time: ~15 minutes
| Property | Details |
|---|---|
| Modulation | Ultra Narrow Band (UNB), 100 Hz channels |
| Frequency | 868 MHz (Europe), 902 MHz (Americas), 923 MHz (Asia Pacific) |
| Range | 10-50 km (rural), 3-10 km (urban) |
| Data rate | 100 bps uplink, 600 bps downlink |
| Payload | 12 bytes uplink, 8 bytes downlink |
| Messages | 140 uplink + 4 downlink per day |
| Battery life | 10-20 years typical |
| Coverage | 75+ countries (operator-dependent) |
Use this calculator to check whether your IoT application fits within Sigfox’s daily message limits.
Test your understanding of Sigfox fundamentals before diving into the detailed chapters.
Assuming Sigfox coverage exists everywhere: Sigfox coverage is operator-dependent and varies significantly by country and region. Always verify coverage maps for your specific deployment locations before committing to Sigfox. Rural areas in countries with low Sigfox adoption may have no coverage at all.
Designing for frequent downlink: Sigfox allows only 4 downlink messages per day. If your application requires regular device configuration updates, firmware-over-the-air (FOTA), or command-and-control, Sigfox is the wrong choice. Plan for autonomous devices that rarely need instructions from the cloud.
Ignoring the operator dependency risk: Sigfox is a single-company network. If the operator in your region ceases operations (as happened in some markets), your devices become disconnected. Always have a fallback connectivity plan or choose LoRaWAN for mission-critical deployments where you need infrastructure control.
Encoding payloads as text instead of binary: With only 12 bytes, sending data as ASCII text (e.g., “T=22.5” = 6 bytes for one value) wastes precious payload space. Use binary encoding (e.g., temperature as a 2-byte integer with fixed-point scaling) to fit more sensor readings into each message.
Forgetting the duty cycle math: While Sigfox allows 140 messages/day, the actual transmission timing must comply with regional duty cycle regulations (e.g., 1% in EU 868 MHz). At ~2 seconds per transmission x 3 redundant copies = 6 seconds per message, the regulatory duty cycle ceiling is approximately 144 messages/day (864s available / 6s per message). The Sigfox subscription limit of 140 provides a small safety margin below this physical limit.
Sigfox message capacity analysis compares subscription limits vs. regulatory duty cycle. Daily airtime: \(T_{day} = n \times t_{TX}\)
Each 12-byte uplink frame (including preamble, device ID, authentication, and CRC) takes approximately 2 seconds at 100 bps. With 3 redundant transmissions: \[t_{TX} = 3 \times 2s = 6s \text{ per message}\]
(Note: payload-only calculation gives \(3 \times 0.96s = 2.88s\), but frame overhead roughly doubles the actual airtime.)
EU duty cycle (1%): \(T_{max} = 0.01 \times 86{,}400s = 864s\)
Maximum messages under duty cycle: \[n_{max} = \frac{864s}{6s} \approx 144 \text{ messages/day}\]
Subscription limit: 140 messages/day
Binding constraint: subscription (140 < 144)
This shows Sigfox’s 140-message subscription limit closely tracks the physical duty cycle ceiling of ~144 messages/day. The subscription limit provides a small safety margin (2.8%) to ensure regulatory compliance even with timing variations.
Use this framework to choose the right LPWAN technology for your deployment:
STEP 1: Message Frequency Check
How often do devices transmit?
├─ Once per hour or less → All LPWAN options viable, continue to Step 2
├─ Every 10-15 minutes → Sigfox marginal (133-144 msgs/day), favor LoRaWAN
└─ Every minute or more → LoRaWAN or NB-IoT only (Sigfox impossible)STEP 2: Payload Size Check
What is the message size?
├─ ≤12 bytes → Sigfox works, continue to Step 3
├─ 13-51 bytes → LoRaWAN SF12, continue to Step 3
├─ 52-242 bytes → LoRaWAN SF7-11 only
└─ >242 bytes → NB-IoT onlySTEP 3: Coverage Availability
Does Sigfox operator coverage exist in deployment area?
├─ YES (verified via pilot test) → Sigfox viable, continue to Step 4
└─ NO → Choose between LoRaWAN (deploy own gateways) or NB-IoT (cellular)STEP 4: Deployment Scale & Cost
How many devices will you deploy?
├─ <1,000 devices → Sigfox likely cheapest ($1-2/device/year)
├─ 1,000-10,000 devices → Calculate TCO (crossover ~9,000 devices)
└─ >10,000 devices → LoRaWAN likely cheapest (gateway cost amortized)STEP 5: Infrastructure Control Requirement
Do you need to control network infrastructure?
├─ NO (acceptable to rely on operator) → Sigfox remains viable
└─ YES (critical infrastructure, data privacy) → LoRaWAN or NB-IoTSTEP 6: Bidirectional Communication
How many downlink messages needed per day?
├─ 0-4 downlinks/day → Sigfox adequate
├─ 5-100 downlinks/day → LoRaWAN Class A
└─ >100 downlinks or immediate response → LoRaWAN Class C or NB-IoTDecision Matrix Example:
| Use Case | Msg Freq | Payload | Scale | Coverage | Recommendation |
|---|---|---|---|---|---|
| Parking sensors | 50/day | 5 bytes | 5,000 | Yes | Sigfox (simple, cheap) |
| Soil moisture | 24/day | 8 bytes | 500 | Yes | Sigfox (lowest cost) |
| Asset tracking | 96/day | 12 bytes | 10,000 | Partial | LoRaWAN (scale + coverage gaps) |
| Smart meters | 1/day | 20 bytes | 50,000 | No | LoRaWAN (no Sigfox, scale) |
| Industrial control | 1/min | 50 bytes | 100 | Yes | LoRaWAN (frequency + payload) |
| Fleet tracking | 20/day | 100 bytes | 1,000 | Global | NB-IoT (mobility + payload) |
Quick Rules of Thumb:
Cost Comparison (5-year TCO, 1,000 devices):
| Technology | Device | Infrastructure | Subscription | Total |
|---|---|---|---|---|
| Sigfox | $12K | $0 | $10K | $22K |
| LoRaWAN | $15K | $10K | $0 | $25K |
| NB-IoT | $20K | $0 | $300K | $320K |
Sigfox wins at this scale. At 50,000 devices, LoRaWAN becomes cheapest.
| Core Concept | Builds On | Leads To | Contrasts With | Prerequisites |
|---|---|---|---|---|
| Operator-Managed LPWAN | Cellular network model, ISM band | Zero infrastructure deployment, global roaming | LoRaWAN user-deployable gateways | Network architecture basics |
| Ultra-Narrow Band (UNB) | Shannon-Hartley theorem, narrow-band modulation | 100 Hz channels, -142 dBm sensitivity, 30-50 km range | LoRa spread spectrum (125 kHz channels) | RF fundamentals, modulation |
| Message Constraints | Regulatory duty cycle, network design | 140 uplink/4 downlink daily limits | LoRaWAN unlimited messages (duty cycle only) | LPWAN positioning |
| Payload Encoding | Binary encoding, fixed-point arithmetic | 12-byte uplink, 8-byte downlink max | ASCII text encoding (wasteful) | Data representation |
| Cost Model | Subscription economics, infrastructure TCO | $6-10/year subscription vs. gateway CapEx | LoRaWAN gateway investment model | LPWAN economics |
Sigfox occupies a unique position in the LPWAN landscape as an operator-managed, ultra-low-power network optimized for simple, infrequent sensor telemetry. Its key differentiators are:
The chapters that follow explore each of these aspects in detail, from the radio physics of UNB modulation to real-world deployment case studies and cost comparisons.
| Topic | Link | Description |
|---|---|---|
| Sigfox Advanced Topics | sigfox.html | Deep dive into UNB modulation, message flow, and deployment models |
| LoRaWAN Architecture | lorawan-architecture.html | Compare Sigfox with user-deployable LoRaWAN gateway networks |
| NB-IoT Fundamentals | nb-iot-fundamentals.html | Cellular LPWAN alternative operating in licensed spectrum |
| LPWAN Comparison | lpwan-comparison-and-review.html | Comprehensive side-by-side comparison of all LPWAN technologies |