1056  LPWAN Fundamentals: Knowledge Checks

1056.1 Knowledge Check

Test your understanding of LPWAN concepts with these scenario-based questions.

Question 1: A logistics company tracks 50,000 shipping containers globally using Sigfox. After 3 years, Sigfox operator coverage disappears in a key region due to bankruptcy. What is their BEST mitigation strategy going forward?

💡 Explanation: Option C (NB-IoT/LTE-M) is the most pragmatic solution for global shipping logistics:

Analysis of each option:

Option A - LoRaWAN private network: - Pros: Full control, zero recurring costs after deployment - Cons: - Infeasible global coverage: 50,000 containers move globally - cannot deploy gateways at every port, warehouse, rail yard, and transit route worldwide - Mobility challenge: Containers move between ocean, rail, truck - LoRaWAN is designed for stationary sensors, not high mobility - Deployment complexity: Installing gateways in foreign countries involves permits, power, backhaul, maintenance - Cost: 1,000+ gateways × $1,500 = $1.5M upfront + ongoing maintenance - Verdict: ❌ Impractical for global mobile asset tracking

Option B - Alternative Sigfox operators: - Pros: Minimal device changes (same hardware/firmware) - Cons: - Same risk: Dependence on Sigfox ecosystem; if one operator failed, others may follow - Coverage gaps: Sigfox is unavailable or unreliable in many countries (e.g., China, Russia) - No global roaming: Sigfox roaming is limited; containers crossing regions may lose connectivity - Technology lock-in: Sigfox ecosystem is declining; betting on recovery is risky - Verdict: ⚠️ Short-term fix but doesn’t address fundamental risk

Option C - NB-IoT/LTE-M cellular: - Pros: - Global coverage: Cellular networks in 190+ countries; containers stay connected worldwide - Carrier redundancy: Multi-IMSI SIMs connect to multiple carriers; if one fails, others provide coverage - Mobility support: LTE-M designed for mobile assets with full handover at vehicular speeds - No infrastructure: Leverages existing carrier networks; no gateway deployment needed - Future-proof: 4G/5G cellular is long-term bet; carriers won’t disappear like LPWAN startups - Cons: - Higher cost: $24-120/device/year subscription (50,000 devices × $50/year = $2.5M/year) - Device replacement: Must replace 50,000 Sigfox devices with cellular modules ($20 each = $1M hardware) - Higher power: Cellular consumes more power than Sigfox (but containers have rechargeable batteries/solar) - Total cost (10 years): $1M hardware + $25M subscriptions = $26M - Verdict: ✓ Most reliable solution for global logistics

Option D - Hybrid LoRaWAN + Satellite: - Pros: - LoRaWAN for controlled environments (ports/warehouses) - Satellite IoT (Iridium, Swarm) for oceanic/remote transit - Cons: - Complexity: Managing 3 technologies (LoRaWAN, satellite, transitional) - Satellite cost: $10-50/device/month = $500,000-$2.5M/month for 50,000 devices! - Power: Satellite transmission consumes 10× cellular (drains batteries on weeks-long ocean voyages) - Latency: Satellite IoT has minutes-to-hours latency - Verdict: ⚠️ Niche use case but very expensive and complex

Decision Matrix:

Option Coverage Reliability Cost (10yr) Complexity Mobility
LoRaWAN Regional Medium $2-5M High Poor
Alt. Sigfox Spotty Low $10M Low Poor
NB-IoT/LTE-M Global High $26M Low Excellent
Hybrid Global High $50M+ Very High Excellent

Recommended strategy: 1. Immediate: Activate NB-IoT/LTE-M fallback for affected regions (if devices have dual-mode radios) 2. 6-12 months: Gradual device replacement to NB-IoT/LTE-M modules 3. Risk mitigation: Use multi-IMSI SIMs to prevent single-carrier dependency 4. Cost optimization: Negotiate fleet discount with carrier (50,000 devices = bulk pricing power)

Real-world parallel: Maersk, CMA CGM, and other shipping giants use cellular IoT (NB-IoT/LTE-M) for global container tracking because reliable global coverage is non-negotiable. The higher cost ($50/year/device) is offset by operational efficiency (reduces lost containers worth $5,000-50,000 each).

Key lesson: For mission-critical global deployments, cellular IoT’s reliability and ubiquity justify higher cost versus private LPWAN’s deployment complexity or operator LPWAN’s bankruptcy risk.

Question 2: An agricultural IoT company must choose between LoRaWAN and Sigfox for soil moisture sensors deployed across a 100 km² farming region. The sensors send 20-byte readings every hour. The region has no existing LPWAN infrastructure. What is the PRIMARY factor favoring LoRaWAN?

💡 Explanation: Option B is correct - Private infrastructure is LoRaWAN’s key differentiator:

LoRaWAN vs Sigfox Architecture:

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graph TB
    subgraph lorawan_model[" LoRaWAN - Private Network Model "]
        LD[Farm Sensors<br/>1000 devices]
        LG1[Your Gateway 1<br/>€500]
        LG2[Your Gateway 2<br/>€500]
        LNS[Your Network Server<br/>ChirpStack FREE]
        LAPP[Your Application<br/>Full Control]

        LD -->|LoRa RF| LG1
        LD -->|LoRa RF| LG2
        LG1 -->|IP Backhaul| LNS
        LG2 -->|IP Backhaul| LNS
        LNS -->|Application Data| LAPP
    end

    subgraph sigfox_model[" Sigfox - Operator Network Model "]
        SD[Farm Sensors<br/>1000 devices]
        SBS[Sigfox Base Stations<br/>Operator-Owned]
        SBE[Sigfox Backend<br/>Operator-Managed]
        SCALLBACK[Your Callback Server<br/>Limited Control]

        SD -->|UNB RF| SBS
        SBS -->|Proprietary| SBE
        SBE -->|HTTP Webhook<br/>€1.50/device/year| SCALLBACK
    end

    style lorawan_model fill:#f0f0f0,stroke:#16A085,stroke-width:3px
    style sigfox_model fill:#f0f0f0,stroke:#E67E22,stroke-width:3px
    style LD fill:#2C3E50,stroke:#16A085,color:#fff
    style LG1 fill:#16A085,stroke:#2C3E50,color:#fff
    style LG2 fill:#16A085,stroke:#2C3E50,color:#fff
    style LNS fill:#16A085,stroke:#2C3E50,color:#fff
    style LAPP fill:#16A085,stroke:#2C3E50,color:#fff
    style SD fill:#2C3E50,stroke:#E67E22,color:#fff
    style SBS fill:#E67E22,stroke:#2C3E50,color:#fff
    style SBE fill:#E67E22,stroke:#2C3E50,color:#fff
    style SCALLBACK fill:#E67E22,stroke:#2C3E50,color:#fff

Figure 1056.1: LoRaWAN private network vs Sigfox operator model comparison

{fig-alt=“Comparison of LoRaWAN private network model (you own gateways and network server, full control, no subscription fees) versus Sigfox operator model (operator-owned base stations and backend, subscription-based, limited control via HTTP callbacks). Highlights infrastructure ownership and cost structure differences for agricultural IoT deployment.”}

Why Private Network Matters for Agriculture:

Cost Comparison (1,000 sensors, 10 years):

LoRaWAN (Private):
- Sensors: 1,000 × €15 = €15,000
- Gateways: 5 × €500 = €2,500
- Network server: €0 (ChirpStack free)
- 10-year cost: €17,500 (€1.75/sensor/year)

Sigfox:
- Sensors: 1,000 × €10 = €10,000
- Subscription: 1,000 × €1.50 × 10 = €15,000
- 10-year cost: €25,000 (€2.50/sensor/year)

LoRaWAN becomes cheaper after year 3!

Additional LoRaWAN Advantages for Agriculture:

1. No coverage dependency:
   - Rural farms often have no Sigfox coverage
   - Deploy your own gateways where needed

2. Control and privacy:
   - Soil data stays on your servers
   - No third-party access to farm data

3. Flexibility:
   - Adjust SF/BW for range vs battery
   - Add gateways as farm expands

Why Other Options Are Wrong:

A - Signal penetration: - Both use sub-GHz frequencies with similar penetration - LoRa CSS and Sigfox UNB have comparable link budgets (~150 dB) - Not a differentiator

C - Data rates: - LoRaWAN: 0.3-50 kbps (varies by SF) - Sigfox: 100-600 bps - LoRaWAN is faster, but 20-byte hourly readings work on either - FUOTA is possible but rarely used in agriculture

D - Licensed spectrum: - BOTH use unlicensed ISM bands (868 MHz EU, 915 MHz US) - Neither uses licensed spectrum - This statement is factually incorrect

Question 3: A smart city deploys LPWAN-connected parking sensors. Sensors must detect car presence (1 bit) and report immediately when a spot becomes vacant. The city requires 99.9% message delivery reliability. Which LPWAN technology is MOST suitable?

💡 Explanation: Option A is correct - NB-IoT provides cellular-grade reliability:

Reliability Comparison:

Technology          Typical PER    Achievable Reliability
─────────────────────────────────────────────────────────
NB-IoT              0.01-0.1%      99.9-99.99%   ← Best
LoRaWAN Confirmed   1-3%           97-99%
LoRaWAN Unconfirmed 5-15%          85-95%
Sigfox (3× repeat)  2-5%           95-98%

Why NB-IoT Achieves 99.9%:

NB-IoT Reliability Features:
1. Licensed spectrum (no interference from other devices)
2. TCP/IP-like acknowledgments at RLC layer
3. Automatic retransmission (HARQ)
4. Carrier-managed QoS and coverage optimization
5. Redundant cell coverage in cities

Parking sensor NB-IoT behavior:
1. Car leaves → Sensor detects vacancy
2. Wake from PSM → Connect to network (~2 seconds)
3. Send 1-byte payload with RLC ACK
4. If ACK received → Success (99.9% cases)
5. If no ACK → Automatic retransmit (catches remaining 0.1%)
6. Return to PSM → 10 µA sleep current

Why Other Options Fall Short:

B - LoRaWAN Confirmed:

LoRaWAN Confirmed Message Problem:
1. Send uplink
2. Open RX1 window (1 second)
3. Server must ACK during narrow window
4. If ACK missed → retransmit (but how many times?)

Issues:
- Limited downlink capacity (1% duty cycle for gateway)
- With 10,000 sensors, 100 ACKs/second needed
- Gateway can only send ~10-20 downlinks/second
- Result: ACKs queue up → perceived failures

Achieved reliability: 97-99% (not 99.9%)

C - Sigfox 3× Repetition:

Sigfox Redundancy Strategy:
- Each message sent 3 times on different frequencies
- Receiver uses best copy

Problem:
- Still single-direction (no ACK from network)
- If all 3 copies fail (interference, fading): lost
- Deep urban canyon: all 3 may fail together
- No retry mechanism

Achieved reliability: 95-98% (not 99.9%)

D - LoRaWAN Class C:

Class C Feature:
- Continuous receive window (always listening)
- Instant downlink capability

Why it doesn't help:
1. Doesn't improve UPLINK reliability
2. Still same 1-5% PER on uplinks
3. Continuous listening drains battery fast
4. Parking sensors are uplink-dominant

Class C is for downlink-heavy devices (street lights, displays)
Not for parking sensors that only need uplink

Smart City Parking Reality:

Cities like Barcelona, San Francisco use NB-IoT parking:
- Require 99.9% reliability for payment/enforcement
- NB-IoT provides carrier SLA
- Higher cost ($1-3/device/month) justified by reliability
- Alternative: LoRaWAN with app-level retries (~99%)

Question 1: A city wants to deploy 5,000 smart streetlight controllers that need to receive on/off commands in near real-time (within 10 seconds). The lights are mains-powered. Which LPWAN technology is LEAST suitable?

💡 Explanation: Sigfox’s extreme downlink limitation makes it unsuitable:

Downlink capability comparison:

Technology Downlink limit Streetlight control suitability
Sigfox 4 messages/day ❌ Only 4 commands per day
LoRaWAN (C) Unlimited ✓ Commands at any time
NB-IoT Unlimited ✓ Commands at any time
LTE-M Unlimited ✓ Commands at any time

Sigfox was designed for uplink-dominant sensors, not actuator control. LoRaWAN Class C, NB-IoT, and LTE-M all support real-time downlink commands.

Question 2: Which characteristic distinguishes LPWAN from Wi-Fi and cellular networks?

💡 Explanation: LPWAN’s fundamental trade-off is speed for range and power:

Technology comparison:

Technology Typical range Data rate Battery life Monthly connectivity cost
Wi-Fi ~100 m ≈ 1 Gbps Days $0
Bluetooth ~50 m ≈ 3 Mbps Months $0
4G/LTE ~10 km ≈ 100 Mbps Hours $10–50
LoRaWAN up to 15 km up to 50 kbps ~10 years $0–1
Sigfox up to 40 km ≈ 100 bps ~15 years ≈ $1
NB-IoT up to 15 km up to 250 kbps ~10 years $1–5

LPWAN sacrifices 1000-10000× data rate to achieve 100× better range and 1000× better battery life.

Question 3: A logistics company needs to track shipping containers globally, including on ocean vessels. Which LPWAN technology can meet this requirement?

💡 Explanation: Global tracking requires cellular + satellite:

Coverage analysis for ocean shipping:

Option Coverage at sea Notes
LoRaWAN ❌ No direct ocean coverage (needs gateways) Good for ports or private coastal networks
Sigfox ❌ Land‑based towers only No mid‑ocean connectivity
NB‑IoT alone ❌ Limited to coastal cellular coverage Drops out quickly offshore
NB‑IoT + sat ✓ Cellular near ports, satellite at sea Hybrid LPWAN + satellite trackers
LTE‑M + sat ✓ Similar hybrid approach Often used in high‑value logistics

Solution: use dual‑mode trackers that: - Prefer NB‑IoT/LTE‑M when in cellular coverage (ports and coastal waters). - Fall back to satellite (e.g., Iridium, Starlink) on the open ocean. - Cost more per device, but they are the only realistic option for true global coverage.