1109  Sigfox Worked Examples and Assessment

1109.1 Introduction

⏱️ ~15 min | ⭐⭐ Intermediate | πŸ“‹ P09.C10.U04

This chapter provides detailed worked examples for Sigfox deployment calculations and comprehensive assessment questions to test your understanding of Sigfox fundamentals.

NoteLearning Objectives

By the end of this chapter, you will be able to:

  • Calculate message budgets for Sigfox applications
  • Perform total cost of ownership (TCO) comparisons between Sigfox and LoRaWAN
  • Calculate link budgets for long-range Sigfox deployments
  • Design duty cycle compliant tracking schedules
  • Apply Sigfox knowledge to real-world deployment decisions

1109.2 Worked Examples

NoteWorked Example: Sigfox Message Budget for Asset Tracking

Scenario: A logistics company wants to track 1,000 shipping containers using Sigfox. Each container needs to report its location and status during ocean transit (typically 30 days). Can Sigfox meet the tracking requirements within its message limits?

Given:

  • Number of containers: 1,000
  • Transit duration: 30 days average
  • Sigfox uplink limit: 140 messages per day per device
  • Sigfox downlink limit: 4 messages per day per device
  • Payload size: 12 bytes maximum
  • Required tracking data: GPS (8 bytes), temperature (1 byte), shock alert (1 byte), battery (1 byte), status (1 byte) = 12 bytes total

Step 1: Define tracking requirements

Location updates needed:
- Port departure: 1 message
- Ocean transit: Position every 4 hours = 6 per day Γ— 30 days = 180 messages
- Port arrival: 1 message
- Total location: 182 messages over 30 days

Event alerts:
- Temperature excursion: Up to 5 events
- Shock/impact: Up to 10 events
- Door open/close: Up to 4 events
- Total events: ~19 messages

Grand total: 182 + 19 = 201 messages per transit

Step 2: Check against Sigfox daily limits

Sigfox limit: 140 messages per day
Required per day (transit): 6 location + ~0.6 events = 6.6 messages/day

6.6 messages/day << 140 messages/day limit

VERDICT: Well within daily limit (using only 4.7% of quota)

Step 3: Optimize message payload (12-byte constraint)

Standard GPS: Latitude (4 bytes) + Longitude (4 bytes) = 8 bytes
Temperature: Signed integer (-40 to +85C) = 1 byte
Shock level: 0-255 scale = 1 byte
Battery: 0-100% = 1 byte
Status flags: Door, motion, alarm = 1 byte

Total: 8 + 1 + 1 + 1 + 1 = 12 bytes (exactly fits!)

Example encoded message:
41.8902N, -87.6245W, 23C, no shock, 87%, door closed
Hex: 41 B9 45 C8 A7 B9 0A 17 00 57 00 00

Step 4: Calculate 5-year cost comparison

Sigfox Solution:
- Hardware (Sigfox module): 1,000 Γ— $15 = $15,000
- Subscription: 1,000 Γ— $2/year Γ— 5 = $10,000
- Total 5-year: $25,000 ($25/container)

Cellular (NB-IoT) Solution:
- Hardware: 1,000 Γ— $25 = $25,000
- SIM + data: 1,000 Γ— $60/year Γ— 5 = $300,000
- Total 5-year: $325,000 ($325/container)

Sigfox savings: $300,000 (92% cost reduction)

Result: Sigfox is ideal for this use case - the container tracking requirements use only 4.7% of the daily message quota, the 12-byte payload fits perfectly, and the 5-year cost is 92% lower than cellular alternatives.

Key insight: Sigfox excels when you can design your data to fit the 12-byte payload constraint. GPS coordinates can be encoded efficiently (8 bytes covers global positioning to ~1 meter accuracy). The 140 messages/day limit is rarely a constraint for asset tracking applications that update hourly or less frequently. Calculate your actual message needs - many applications use less than 10% of the Sigfox quota.

NoteWorked Example: Sigfox vs LoRaWAN TCO for Smart Parking

Scenario: A city is deploying 5,000 parking sensors across downtown. Each sensor detects vehicle presence and sends status updates. The city needs to choose between Sigfox and LoRaWAN based on 5-year total cost of ownership.

Given:

  • Number of sensors: 5,000
  • Message frequency: Event-driven (car arrives/departs) + hourly heartbeat
  • Average messages per sensor per day: 20 (10 car events + 14 heartbeats, within 140 limit)
  • Payload: 5 bytes (sensor ID, status, battery, timestamp)
  • Deployment area: 15 kmΒ² downtown area
  • Sigfox coverage: Available from regional operator
  • LoRaWAN: Would require private gateway deployment

Step 1: Calculate Sigfox costs

Hardware:
- Sigfox sensor modules: 5,000 Γ— $18 = $90,000
- Installation: 5,000 Γ— $25 = $125,000

Subscription (5 years):
- Annual fee: 5,000 Γ— $2/year = $10,000/year
- 5-year total: $10,000 Γ— 5 = $50,000

Infrastructure: $0 (uses operator network)

Sigfox Total 5-Year: $90,000 + $125,000 + $50,000 = $265,000
Per sensor: $53

Step 2: Calculate LoRaWAN costs

Hardware:
- LoRaWAN sensor modules: 5,000 Γ— $22 = $110,000
- Installation: 5,000 Γ— $25 = $125,000

Gateway infrastructure:
- Gateways needed (15 kmΒ² / 2 kmΒ² coverage each): 8 gateways
- Gateway cost: 8 Γ— $1,200 = $9,600
- Gateway installation (rooftop): 8 Γ— $500 = $4,000
- Gateway internet backhaul: 8 Γ— $50/month Γ— 60 = $24,000

Network server:
- Cloud LoRaWAN service: $200/month Γ— 60 = $12,000
  OR
- Self-hosted: $5,000 initial + $2,000/year maintenance = $15,000

Operations:
- Gateway maintenance: $1,000/year Γ— 5 = $5,000

LoRaWAN Total 5-Year: $110,000 + $125,000 + $9,600 + $4,000 + $24,000 + $12,000 + $5,000 = $289,600
Per sensor: $57.92

Step 3: Compare and analyze

Cost Summary:
- Sigfox 5-year: $265,000
- LoRaWAN 5-year: $289,600
- Difference: $24,600 (LoRaWAN costs 9.3% more)

Operational Comparison:
                    Sigfox          LoRaWAN
Infrastructure      None            8 gateways to maintain
Deployment time     2 weeks         2 months (gateway install)
Coverage guarantee  Operator SLA    Self-managed
Scalability         Unlimited       May need more gateways
Network control     None            Full control

Step 4: Break-even analysis

At what scale does LoRaWAN become cheaper?

LoRaWAN fixed costs: $9,600 + $4,000 + $24,000 + $12,000 + $5,000 = $54,600
LoRaWAN per-sensor: $22 + $25 = $47 (no subscription)

Sigfox per-sensor: $18 + $25 + ($2 Γ— 5) = $53

LoRaWAN becomes cheaper when:
N Γ— $53 > $54,600 + N Γ— $47
N Γ— $6 > $54,600
N > 9,100 sensors

CROSSOVER: ~9,100 sensors

Result: For this 5,000-sensor deployment, Sigfox is $24,600 cheaper with zero infrastructure management. However, if the city expands to 10,000+ sensors, LoRaWAN would become more economical due to its zero per-device recurring fees.

Key insight: The Sigfox vs LoRaWAN decision depends heavily on scale. Below ~9,000 devices, Sigfox’s operator model eliminates infrastructure complexity and reduces TCO. Above that threshold, LoRaWAN’s gateway investment becomes amortized across enough devices to beat Sigfox’s subscription fees. Always calculate the crossover point for your specific deployment - it varies based on gateway costs, coverage area, and local Sigfox subscription rates.

NoteWorked Example: Sigfox UNB Link Budget for Remote Agricultural Monitoring

Scenario: A vineyard deploys soil moisture sensors across 50 km of hilly terrain in rural France. The nearest Sigfox base station is 25 km away. Will the UNB (Ultra-Narrow Band) technology provide reliable connectivity at this extreme range?

Given: - Distance to base station: 25 km - Frequency: 868 MHz (RC1 Europe) - Sigfox TX power: 14 dBm (25 mW, EU limit) - Device antenna gain: 0 dBi (simple wire antenna) - Base station antenna gain: 6 dBi (omnidirectional tower) - Base station height: 30 meters - Terrain: Hilly rural with vineyard rows - Sigfox receiver sensitivity: -142 dBm (UNB advantage) - Required link margin: 15 dB (for weather, seasonal foliage)

Step 1: Calculate free-space path loss

\[FSPL = 20 \log_{10}(d_{km}) + 20 \log_{10}(f_{MHz}) + 32.45\]

For 25 km at 868 MHz:

FSPL = 20 Γ— log10(25) + 20 Γ— log10(868) + 32.45
FSPL = 28.0 + 58.8 + 32.45 = 119.25 dB

Step 2: Add terrain and environmental losses

Hilly terrain (non-line-of-sight): +12 dB
Vegetation (vineyard canopy): +4 dB
Weather margin (rain fade at 868 MHz): +2 dB
Total additional losses: +18 dB

Total path loss = 119.25 + 18 = 137.25 dB

Step 3: Calculate link budget

Uplink Link Budget:
────────────────────────────────────
TX power (sensor):           +14 dBm
TX antenna gain:             +0 dBi
Path loss:                   -137.25 dB
RX antenna gain (base):      +6 dBi
────────────────────────────────────
Signal at receiver:          -117.25 dBm

Sigfox sensitivity:          -142 dBm
Link margin available:       24.75 dB
Required margin:             15 dB
Excess margin:               9.75 dB

Step 4: Compare with LoRaWAN at same distance

LoRaWAN SF12 sensitivity: -137 dBm (best case)
Signal at receiver: -117.25 dBm
LoRaWAN margin: 19.75 dB

Sigfox margin: 24.75 dB
Sigfox advantage: +5 dB (1.8x better range)

Step 5: Validate with Sigfox triple-redundancy

Sigfox transmits each message 3 times on different frequencies:
- If 1 transmission fails (interference), 2 others likely succeed
- Effective reliability at 24.75 dB margin: >99.9%

Per-transmission success probability at 24.75 dB margin: ~99%
3 independent transmissions: 1 - (0.01)Β³ = 99.9999%

Result: The vineyard sensors will work reliably at 25 km range with 24.75 dB link margin (9.75 dB excess). Sigfox’s -142 dBm sensitivity provides 5 dB advantage over LoRaWAN SF12, enabling this extreme-range rural deployment.

Key Insight: Sigfox’s ultra-narrow band (100 Hz) modulation concentrates transmission energy, achieving -142 dBm sensitivity versus LoRa’s -137 dBm at SF12. This 5 dB advantage translates to ~1.8x range extension, making Sigfox ideal for sparse rural deployments where base stations are far apart. The triple-redundancy transmission pattern further improves reliability in challenging RF environments.

NoteWorked Example: Sigfox Duty Cycle and Message Timing Compliance

Scenario: A cold chain logistics company tracks 500 refrigerated containers. Each container has sensors for temperature, door status, and GPS location. The company wants to maximize tracking frequency while staying within Sigfox’s 140 messages/day limit and EU duty cycle regulations.

Given: - Sigfox payload: 12 bytes maximum - Sigfox uplink limit: 140 messages per day per device - EU868 duty cycle: 1% (36 seconds per hour TX time) - Sigfox message duration: ~2 seconds (100 bps Γ— 12 bytes Γ— 3 transmissions) - Required data: GPS (6 bytes), temperature (2 bytes), door status (1 byte), battery (1 byte), timestamp (2 bytes) = 12 bytes

Step 1: Calculate maximum message rate under duty cycle

EU868 duty cycle limit: 1% = 36 seconds/hour TX time
Sigfox message duration: ~6 seconds (including 3Γ— redundancy)
Max messages/hour (duty cycle): 36 Γ· 6 = 6 messages/hour
Max messages/day (duty cycle): 6 Γ— 24 = 144 messages/day

Step 2: Compare with Sigfox network limit

Sigfox network limit: 140 messages/day
EU duty cycle limit: 144 messages/day
Binding constraint: Sigfox network (140/day)

Step 3: Design optimal tracking schedule

Container states and tracking needs:
────────────────────────────────────
1. Stationary at warehouse: Low priority
   - 1 message every 4 hours = 6 messages/day

2. In transit (truck/ship): High priority
   - 1 message every 10 minutes during active hours
   - Active period: 12 hours/day
   - Messages: 72 messages/day

3. Temperature alarm: Critical
   - Immediate transmission on threshold breach
   - Reserve: 20 messages/day for alarms

4. Door open/close events: Important
   - Max 10 events/day typical
   - Reserve: 15 messages/day

Total allocation:
- Stationary: 6
- Transit tracking: 72
- Temperature alarms: 20
- Door events: 15
- Buffer: 27 (for retries, unexpected events)
────────────────────────────────────
Total: 140 messages/day (exactly at limit)

Step 4: Optimize payload encoding

%% fig-alt: Sigfox 12-byte payload structure diagram showing byte allocation for GPS coordinates, temperature, status flags, battery, and timestamp
%%{init: {'theme': 'base', 'themeVariables': {'primaryColor': '#2C3E50', 'primaryTextColor': '#fff', 'primaryBorderColor': '#16A085', 'lineColor': '#16A085', 'secondaryColor': '#E67E22', 'tertiaryColor': '#7F8C8D'}}}%%
flowchart LR
    subgraph PAYLOAD["12-Byte Payload Structure"]
        direction TB
        B0["Byte 0-2<br/>Latitude<br/>(scaled integer, 0.0001Β° res)"]
        B3["Byte 3-5<br/>Longitude<br/>(scaled integer)"]
        B6["Byte 6<br/>Temperature<br/>(signed, -40 to +85Β°C)"]
        B7["Byte 7<br/>Temp decimal +<br/>alarm flags"]
        B8["Byte 8<br/>Door status +<br/>motion + shock flags"]
        B9["Byte 9<br/>Battery %<br/>(0-100)"]
        B10["Byte 10-11<br/>Timestamp<br/>(minutes since midnight)"]
    end

    style B0 fill:#2C3E50,color:#fff
    style B3 fill:#2C3E50,color:#fff
    style B6 fill:#16A085,color:#fff
    style B7 fill:#16A085,color:#fff
    style B8 fill:#E67E22,color:#fff
    style B9 fill:#7F8C8D,color:#fff
    style B10 fill:#7F8C8D,color:#fff

GPS encoding example:

  • Latitude 48.8566N = 488566 = 0x07 0x74 0x26 (3 bytes)
  • Longitude 2.3522E = 23522 = 0x00 0x5B 0xE2 (3 bytes)
  • Resolution: 0.0001 degrees = approximately 11 meters (sufficient for container tracking)

Step 5: Calculate battery impact of message rate

Energy per Sigfox transmission:
- TX current: 50 mA
- TX duration: 6 seconds (3Γ— redundancy)
- Energy: 50 mA Γ— 6s = 300 mAs = 0.083 mAh

Daily consumption at 140 messages:
- TX energy: 140 Γ— 0.083 = 11.62 mAh
- Sleep (3 Β΅A Γ— 24h): 0.072 mAh
- Total daily: 11.69 mAh

Battery life with 5000 mAh battery:
- Theoretical: 5000 Γ· 11.69 = 427 days = 1.2 years
- With 70% usable capacity: 299 days β‰ˆ 10 months

For 5-year operation, reduce to:
- Messages/day: 140 Γ· 5 = 28 messages/day
- Update every 51 minutes (acceptable for stationary containers)

Result: The cold chain system can achieve 10-minute tracking intervals during transit (72 messages) plus temperature alarms and door events, staying within the 140 messages/day limit. However, this aggressive rate limits battery life to ~10 months. For 5-year battery life, reduce to 28 messages/day (every 51 minutes).

Key Insight: Sigfox’s 140 messages/day limit is the primary constraint for high-frequency tracking, not EU duty cycle (which allows 144/day). Design your tracking schedule around message budget, not just RF regulations. For cold chain, prioritize temperature alarms (immediate) over regular position updates (can be less frequent). The 12-byte payload constraint requires careful data encoding - GPS coordinates fit in 6 bytes using scaled integers with 11-meter resolution.

1109.3 Quiz 1: Sigfox Fundamentals

Question 1: A fleet management company operates in 30 countries worldwide. They choose Sigfox for vehicle trackers but discover coverage gaps in 8 countries. What factor did they MOST likely underestimate?

Explanation: Option B is correct - Sigfox operator coverage is fragmented globally:

Sigfox Coverage Reality:

Operator-Dependent Model: - Sigfox is NOT a single global network like cellular - Each country has licensed Sigfox Network Operator (SNO) - Coverage quality varies DRAMATICALLY by operator

Geographic Coverage Analysis (as of 2024):

Strong Coverage (Western Europe): - France: Excellent (95% population coverage) - Sigfox birthplace - Spain, Portugal, Germany, UK, Netherlands: Good (85-90%) - Operator: UnaBiz (after Sigfox SA bankruptcy acquisition)

Moderate Coverage (Eastern Europe, Americas): - US: Moderate (60-70% population, concentrated in cities) - Latin America: Spotty (major cities only: SΓ£o Paulo, Mexico City) - Eastern Europe: Limited (Poland, Czech Republic OK; others minimal)

Poor/No Coverage (Asia, Africa, Middle East): - China: NO Sigfox coverage (government restrictions on unlicensed IoT networks) - Russia: NO coverage (geopolitical restrictions) - India: Minimal coverage (3-4 cities only) - Africa: Very limited (South Africa only, major cities) - Middle East: Dubai, Qatar only

Why Other Options Are Wrong:

A - GPS payload fits easily: - GPS coordinates: 6-8 bytes (latitude + longitude as integers) - Sigfox payload: 12 bytes maximum - Easily fits: GPS (6 bytes) + vehicle ID (2 bytes) + speed (1 byte) + battery (1 byte) + flags (2 bytes) = 12 bytes - Not the limiting factor

C - 140 messages/day sufficient for fleet tracking: - Typical fleet tracking: Location update every 5-15 minutes - 15-minute interval: 96 messages/day << 140 limit - Even 10-minute interval: 144 messages/day (slightly over, but close) - Message limit is NOT the primary issue for normal vehicle tracking

D - Sigfox supports mobile assets: - Sigfox does NOT require handover (star topology, not cellular) - As long as vehicle within base station range (10-40 km), it works - Mobility is actually a Sigfox strength (no handover = simpler than cellular)

Summary: Operator-dependent coverage is Sigfox’s Achilles heel for global applications. The company underestimated geographic fragmentation of Sigfox network operators.

Question 2: A water utility monitors 5000 smart meters, each sending one reading per day using Sigfox. The utility operates across a region with 70% Sigfox coverage. What is the MOST CRITICAL deployment consideration they must address?

Explanation: Option C is correct - Pre-deployment coverage verification is CRITICAL:

The Critical Issue:

Total meters: 5,000
Sigfox coverage: 70%
Meters in coverage: 5,000 Γ— 0.70 = 3,500 βœ“
Meters without coverage: 5,000 Γ— 0.30 = 1,500 ❌

Problem:
- 1,500 meters (30%) cannot send data
- Utility lacks readings from 1,500 customers
- Billing impact: 30% of customers
- Regulatory compliance issues

Why Other Options Are Wrong:

A - Cannot deploy Sigfox base stations: - Sigfox is a CLOSED network - Customers cannot purchase or deploy base stations - Only Sigfox operators can expand coverage

B - More messages don’t solve coverage gaps: - If meter is outside coverage, 0 messages reach the network - Sending 10Γ— more messages into the void wastes battery

D - Downlink limit (4/day) cannot confirm 5,000 meters: - Would take 1,250 days to confirm all meters once - Also doesn’t fix the coverage problem

Cost of Coverage Failure:

If deploying without verification:
- 1,500 Γ— $10 = $15,000 (wasted hardware)
- 1,500 Γ— $6/year = $9,000/year (wasted subscription)

Cost of pre-verification:
- 100 test devices Γ— $10 = $1,000
- 1 month testing labor: $5,000
- Total: $6,000

ROI: Saves $44,000-$94,000!

1109.4 Knowledge Check

Test your understanding of fundamental concepts with these questions.

Question 1: An IoT startup needs to send 50-byte sensor readings every 15 minutes from environmental monitors. Why is Sigfox NOT suitable for this application?

Explanation: Sigfox has strict message limitations:

Constraint Sigfox Limit Required
Payload size 12 bytes max 50 bytes
Uplink messages 140/day 96/day (every 15 min)
Average interval ~10 minutes 15 minutes

The 50-byte payload is the killer issue - Sigfox cannot transmit it in a single message. You’d need 5 messages (5Γ—12=60 bytes) per reading, requiring 480 messages/day - far exceeding the 140 limit.

Better alternatives: LoRaWAN (up to 242 bytes) or NB-IoT (up to 1600 bytes).

Question 2: What makes Sigfox’s Ultra-Narrow Band (UNB) technology unique compared to other LPWAN technologies?

Explanation: Sigfox’s UNB approach uses extremely narrow 100 Hz channels:

Bandwidth comparison:
 LoRa:      125,000 Hz (125 kHz)
 NB-IoT:    180,000 Hz (180 kHz)
 Sigfox:        100 Hz (0.1 kHz) ← 1250Γ— narrower than LoRa!

Benefits of Ultra-Narrow Band: - Exceptional receiver sensitivity (-126 to -142 dBm) - Strong interference rejection - Long range in sub-GHz ISM bands (868 MHz EU, 902 MHz US) - Simple, cheap radio design

Trade-off: Very low data rate (~100 bps) and small payloads (12 bytes).

Question 3: A smart city deploys 50,000 parking sensors. Why might LoRaWAN be more cost-effective than Sigfox at this scale?

Explanation: Cost comparison at scale:

50,000 parking sensors over 5 years:

SIGFOX:
- Subscription: 50,000 Γ— $9/year Γ— 5 = $2,250,000
- Gateway: $0 (network provided)
- Total: ~$2.25M

LoRaWAN (private network):
- Gateway infrastructure: 50 gateways Γ— $500 = $25,000
- Network server: $5,000/year Γ— 5 = $25,000
- Subscription: $0
- Total: ~$50,000

Savings with LoRaWAN: $2.2M over 5 years!

Crossover point: ~1,000-2,000 devices. Below this, Sigfox is simpler and cheaper. Above this, private LoRaWAN becomes economical.

1109.6 Summary

This chapter provided practical application of Sigfox concepts through worked examples:

  • Message budget calculations show Sigfox typically uses <10% of daily quota for asset tracking
  • TCO comparisons reveal crossover points around 9,000 devices where LoRaWAN becomes cheaper
  • Link budget analysis demonstrates Sigfox’s 5 dB sensitivity advantage over LoRaWAN for extreme range
  • Duty cycle design balances tracking frequency with battery life and message limits
  • Payload encoding requires efficient data representation to fit 12 bytes

1109.7 What’s Next

Now that you understand Sigfox fundamentals, explore related LPWAN technologies and compare deployment options:

  • Next Chapter: Sigfox Advanced Topics - Deep dive into architecture, protocols, and implementation details
  • Compare with LoRaWAN: LoRaWAN Fundamentals - Understand user-deployable alternative with higher data rates and no message limits
  • Compare with Cellular: NB-IoT & LTE-M - Explore cellular LPWAN with global coverage and mobility support
  • Broader Context: LPWAN Overview - Compare all LPWAN technologies including Weightless and other alternatives