1146  Weightless Technical Implementation

1146.1 Introduction

⏱️ ~12 min | ⭐⭐ Intermediate | 📋 P09.C17B.U01

This chapter explores the technical aspects of Weightless LPWAN technology, including adaptive data rate calculations, TV White Space channel management, and cost analysis implementations. Through Python examples and interactive quizzes, you’ll gain hands-on understanding of Weightless protocol mechanics.

NoteLearning Objectives

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

  • Calculate adaptive data rate parameters for Weightless-P deployments
  • Understand TV White Space channel availability and spectrum management
  • Compare total cost of ownership across LPWAN technologies
  • Apply duty cycle and power consumption calculations

1146.2 Prerequisites

Before diving into this chapter, you should be familiar with:

1146.3 Weightless-P Adaptive Data Rate

Weightless-P uses Adaptive Data Rate (ADR) to optimize power consumption based on link quality. Devices close to the base station use higher data rates (faster transmission, lower energy), while distant devices use lower data rates (robust modulation, longer range).

1146.3.1 Modulation Options

Modulation Data Rate TX Time (37 bytes) Energy Range
GMSK_HIGH 100 kbps 13.8 ms 3,542 µJ 2 km
GMSK_MID 50 kbps 17.4 ms 3,392 µJ 3.5 km
DBPSK_LOW 12.5 kbps 39.6 ms 10,098 µJ 4.5 km
DBPSK_ULTRA 0.2 kbps 1,490 ms 536,400 µJ 6 km

Key Insight: Higher data rates save battery by reducing time-on-air, not by reducing range. ADR selects the highest data rate that maintains reliable connectivity.

1146.4 Python Implementation

1146.4.1 Implementation 1: Weightless-P Adaptive Data Rate Calculator

This implementation demonstrates how Weightless-P dynamically adjusts data rate based on link quality, optimizing for battery life and throughput.

Expected Output:

=== Weightless-P Adaptive Data Rate Analysis ===

Scenario: Agricultural sensor
Payload: 15 bytes
Frequency: 24 messages/day
Battery: 2400 mAh (2× AA)

Modulation Comparison:
----------------------------------------------------------------------------------------------------
Modulation      Data Rate    TX Time    Energy       Range    Battery Life
----------------------------------------------------------------------------------------------------
GMSK_HIGH          100.0 kbps   13.0 ms    1755.0 µJ   2.0 km          6.9 years
GMSK_MID            50.0 kbps   17.4 ms    3392.4 µJ   3.5 km          3.6 years
DBPSK_LOW           12.5 kbps   39.6 ms    10098.0 µJ  4.5 km          1.2 years
DBPSK_ULTRA          0.2 kbps 1490.0 ms  536400.0 µJ  6.0 km          0.0 years

====================================================================================================

Optimal Modulation Selection (ADR):
--------------------------------------------------------------------------------
Distance     Selected        Data Rate    Battery Life
--------------------------------------------------------------------------------
    1.5 km GMSK_HIGH           100.0 kbps          6.9 years
    3.0 km GMSK_MID             50.0 kbps          3.6 years
    4.0 km DBPSK_LOW            12.5 kbps          1.2 years
    5.5 km DBPSK_ULTRA           0.2 kbps          0.0 years

================================================================================

Key Insight: ADR uses highest data rate for given distance,
minimizing time-on-air and maximizing battery life.

Key Concepts Demonstrated: - Adaptive Data Rate (ADR): Automatically selects best modulation based on link quality - Time-on-Air Trade-off: Higher data rate = shorter TX time = lower energy - Range vs Battery: Longer range requires lower data rate, consuming more energy - GMSK vs DBPSK: GMSK offers higher rates for good links, DBPSK for challenging conditions

1146.4.2 Implementation 2: TV White Space Channel Availability Simulator

This implementation simulates TV White Space channel discovery for Weightless-W, demonstrating cognitive radio and dynamic spectrum access.

Expected Output:

=== TV White Space (TVWS) Availability Simulation ===

Location: London (Urban)
Coordinates: 51.5074°, -0.1278°
----------------------------------------------------------------------
Total UHF channels (21-60): 40
Active TV broadcasts: 16 (40.0%)
Protected channels: 2 (5.0%)
Available for Weightless-W: 22 (55.0%)
Total available bandwidth: 176 MHz
Spectrum utilization: 40.0%

Sample available channels:
  Channel 21: 474.0 MHz (8 MHz bandwidth)
  Channel 23: 490.0 MHz (8 MHz bandwidth)
  Channel 25: 506.0 MHz (8 MHz bandwidth)
  Channel 26: 514.0 MHz (8 MHz bandwidth)
  Channel 27: 522.0 MHz (8 MHz bandwidth)

======================================================================

Location: Cambridge (Suburban)
Coordinates: 52.2053°, 0.1218°
----------------------------------------------------------------------
Total UHF channels (21-60): 40
Active TV broadcasts: 10 (25.0%)
Protected channels: 2 (5.0%)
Available for Weightless-W: 28 (70.0%)
Total available bandwidth: 224 MHz
Spectrum utilization: 25.0%

Sample available channels:
  Channel 21: 474.0 MHz (8 MHz bandwidth)
  Channel 22: 482.0 MHz (8 MHz bandwidth)
  Channel 24: 498.0 MHz (8 MHz bandwidth)
  Channel 25: 506.0 MHz (8 MHz bandwidth)
  Channel 26: 514.0 MHz (8 MHz bandwidth)

======================================================================

Location: Rural Northumberland
Coordinates: 54.9783°, -1.6174°
----------------------------------------------------------------------
Total UHF channels (21-60): 40
Active TV broadcasts: 6 (15.0%)
Protected channels: 2 (5.0%)
Available for Weightless-W: 32 (80.0%)
Total available bandwidth: 256 MHz
Spectrum utilization: 15.0%

Sample available channels:
  Channel 21: 474.0 MHz (8 MHz bandwidth)
  Channel 22: 482.0 MHz (8 MHz bandwidth)
  Channel 23: 490.0 MHz (8 MHz bandwidth)
  Channel 24: 498.0 MHz (8 MHz bandwidth)
  Channel 25: 506.0 MHz (8 MHz bandwidth)

======================================================================

TVWS Availability Comparison:
----------------------------------------------------------------------
Location                       Available    Bandwidth       Utilization
----------------------------------------------------------------------
London (Urban)                   22 channels       176 MHz      40.0%
Cambridge (Suburban)             28 channels       224 MHz      25.0%
Rural Northumberland             32 channels       256 MHz      15.0%

======================================================================

Key Insight: Rural areas have more TVWS availability (less TV coverage),
making Weightless-W ideal for agricultural and rural IoT applications.

Key Concepts Demonstrated: - Cognitive Radio: Devices query database to avoid interference - Dynamic Spectrum Access: Use available channels without license - Geographic Variation: Urban areas have less TVWS than rural - Protected Channels: Must avoid wireless microphones and other licensed users

1146.4.3 Implementation 3: Weightless vs Competition Cost Analyzer

This implementation compares total cost of ownership (TCO) for Weightless-P, LoRaWAN, and NB-IoT across different deployment scales.

Expected Output:

=== LPWAN Technology Cost Comparison ===

Scenario 1: Small Smart Agriculture Deployment
  Devices: 100
  Area: 10 km²
  Lifetime: 7 years
  Messages: 24 per day

Cost Breakdown:
-----------------------------------------------------------------------------------------------
Technology      Infrastructure  Devices         Subscriptions   Total TCO       Rank
-----------------------------------------------------------------------------------------------
Weightless-P            €3,400        €1,900             €0        €5,300  1
LoRaWAN                €17,800        €1,600             €0       €19,400  2
NB-IoT                      €0        €2,000        €16,800      €18,800  3

===============================================================================================

Scenario 2: Large Smart City Deployment
  Devices: 5000
  Area: 100 km²
  Lifetime: 10 years
  Messages: 48 per day

Cost Breakdown:
-----------------------------------------------------------------------------------------------
Technology      Infrastructure  Devices         Subscriptions   Total TCO       Rank
-----------------------------------------------------------------------------------------------
Weightless-P           €30,500      €103,000             €0      €133,500  1
LoRaWAN                €38,000       €87,500             €0      €125,500  2
NB-IoT                      €0      €108,000    €1,200,000    €1,308,000  3

===============================================================================================

Per-Device Annual Cost:
----------------------------------------------------------------------
Technology      Small (100 dev)      Large (5000 dev)
----------------------------------------------------------------------
Weightless-P              €7.57/year            €2.67/year
LoRaWAN                  €27.71/year            €2.51/year
NB-IoT                   €26.86/year           €26.16/year

======================================================================

Key Insights:
- Small deployments: Weightless-P/LoRaWAN cheaper (no subscriptions)
- Large deployments: Private networks dominate due to economies of scale
- NB-IoT subscription costs scale linearly with device count

Key Concepts Demonstrated: - Total Cost of Ownership (TCO): Infrastructure + devices + subscriptions + maintenance - Scale Economics: Private networks become more cost-effective at larger scales - Subscription Impact: NB-IoT’s per-device fees dominate at scale - Decision Criteria: Small deployments favor simplest solution, large deployments favor private networks

1146.5 Knowledge Check: Performance Calculations

Question 1: A company evaluates Weightless-P vs LoRaWAN for 500 sensors over 10 years. Weightless-P: €18 devices, €2,500 base stations, 0 subscription. LoRaWAN: €15 devices, public network €2/device/year. Which has lower TCO?

💡 Explanation: Weightless-P TCO: 500 × €18 = €9,000 (devices) + 5 × €2,500 = €12,500 (base stations) + €0 (subscriptions) = €21,500 for 10 years. LoRaWAN TCO: 500 × €15 = €7,500 (devices) + €0 (public network) + 500 × €2 × 10 years = €10,000 (subscriptions) = €17,500 for 10 years. However, Weightless-P advantages include: no dependency on third-party network availability/reliability, data sovereignty (own infrastructure), no vendor lock-in, and no risk of subscription price increases. For critical applications or locations without LoRaWAN coverage, Weightless-P’s private network justifies the higher upfront cost. The break-even point is around 4 years.

Question 2: A Weightless-P sensor is 2 km from base station in rural farm. Using Adaptive Data Rate (ADR), which modulation does ADR select, and what battery life results?

💡 Explanation: ADR selects GMSK_HIGH (100 kbps) because 2 km is well within its reliable range (up to 5 km rural). Key principle: battery life is dominated by transmission time, not data rate. GMSK_HIGH transmits 37 bytes in 13.8 ms (7× faster than DBPSK’s 93 ms), consuming 3,542 µJ vs 21,390 µJ per message—saving 83% energy! Over 5 years this yields 6.9 years battery life. ADR only steps down to lower rates if link quality degrades (packet loss, low RSSI). The counter-intuitive insight: higher data rates save battery by reducing time-on-air, not by reducing range. This is why modern IoT protocols optimize for speed when signal allows.

Question 3: A Weightless-P sensor must transmit a 37-byte packet every hour. If it uses GMSK 100 kbps (13.8 ms transmission, 100 mW TX power, 1 µW sleep), what is the average power consumption?

💡 Explanation: Duty cycle calculation for infrequent transmissions: (1) Transmit time: 13.8 ms per hour = 13.8 ms / 3,600,000 ms = 0.00000383 duty cycle (0.00038%). (2) Sleep time: 3,600,000 ms - 13.8 ms ≈ 3,599,986 ms (99.99962% of time). (3) Average power: P_avg = (P_tx × T_tx + P_sleep × T_sleep) / T_total = (100 mW × 13.8 ms + 0.001 mW × 3,599,986 ms) / 3,600,000 ms = (1,380 mW·ms + 3,599.986 mW·ms) / 3,600,000 ms = 4,979.986 mW·ms / 3,600,000 ms = 1.38 µW. Key insight: Sleep power DOMINATES average consumption because sensor spends 99.99%+ time sleeping. Transmit power (100 mW) is 100,000× higher than sleep (1 µW), but occurs 0.00038% of time, contributing equally: 1,380 µW·ms (TX) + 3,600 µW·ms (sleep) = 5,000 µW·ms total. Battery life: 1.38 µW average = 1.38 µA @ 1V. With 2000 mAh battery: 2000 mAh / 0.00138 mA = 1,449,275 hours = 165 years (theoretical). Practical: ~5-10 years accounting for self-discharge, leakage, voltage drop. Comparison: This demonstrates why LPWAN protocols optimize sleep current (1 µW → 0.1 µW saves 50% battery) and transmission time (13.8 ms → 6.9 ms saves 50% energy), not transmit power (100 mW → 50 mW saves only 25% battery due to low duty cycle).

Question 4: Why does Weightless-P use adaptive modulation (switching between DBPSK 12.5 kbps and GMSK 100 kbps) rather than fixed modulation like Sigfox?

💡 Explanation: Adaptive modulation in Weightless-P optimizes the link budget vs energy trade-off: Devices close to base station (high RSSI, good SNR) use GMSK 100 kbps - transmits 37-byte packet in 13.8 ms, consuming 3,542 µJ (100 mW × 13.8 ms). Fast transmission = low time-on-air = low energy. Devices far from base station (low RSSI, marginal link) use DBPSK 12.5 kbps - transmits same packet in 93 ms, consuming 21,390 µJ, but achieves 10-15 dB better link margin (DBPSK more robust to noise). Benefit: Network optimizes per-device: urban sensors (100m from BS) use GMSK (6.9 year battery), rural sensors (5 km from BS) use DBPSK (2.6 year battery but maintain connectivity). Without adaptation, fixed DBPSK wastes energy for nearby devices, fixed GMSK loses coverage for distant devices. Comparison to Sigfox: Sigfox uses fixed DBPSK 100 Hz (no adaptation) for simplicity and maximum range, but sacrifices efficiency - nearby devices transmit unnecessarily slowly. Implementation: Base station measures RSSI/SNR per device, sends modulation control command; device adjusts PHY. This is Adaptive Data Rate (ADR) - common in LoRaWAN (SF7-12), Weightless-P, cellular LTE (MCS 0-28), but absent in Sigfox (fixed UNB). Why not others? (A) No regulatory requirement for adaptation - fixed modulation allowed. (C) Spectrum efficiency not primary goal (still one device per channel at a time). (D) No backward compatibility - N and P are separate standards.

Question 5: Weightless-N uses narrowband channels (100 Hz - 2 kHz bandwidth) compared to Weightless-P’s 12.5-100 kHz channels. What is the primary benefit of narrowband operation?

💡 Explanation: Narrowband improves link budget via noise reduction: (1) Noise power formula: P_noise = k × T × B, where k = Boltzmann constant (1.38×10^-23 J/K), T = temperature (290 K), B = bandwidth (Hz). At 290K: P_noise_dBm = -174 dBm + 10×log10(B). (2) Narrowband (100 Hz): P_noise = -174 + 10×log10(100) = -174 + 20 = -154 dBm. (3) Wideband (100 kHz): P_noise = -174 + 10×log10(100,000) = -174 + 50 = -124 dBm. (4) SNR improvement: 30 dB lower noise power with narrowband! If transmit power is same (e.g., 20 dBm), narrowband achieves 30 dB better SNR, translating to 10× longer range (path loss ∝ distance²; 30 dB = 1000× power = √1000 ≈ 31× range improvement in free space, ~10× in real environments with fading). Trade-off: Narrowband sacrifices data rate - 100 Hz channel can only carry ~100 bps (Shannon limit: C = B × log2(1+SNR)), vs 100 kbps for wideband. But LPWAN applications transmit small payloads infrequently (37 bytes every hour), so ultra-low data rate acceptable. Why not others? (B) Spectrum efficiency not primary benefit (LPWAN has plenty of sub-GHz spectrum, ~26 MHz in 868/915 bands). (C) Narrowband doesn’t directly reduce TX power - same power needed to reach base station, but link budget improvement means weaker signal still decoded (sensitivity improvement). (D) Narrowband NOT exempt from duty cycle (ISM regulations apply to all users regardless of bandwidth).

1146.6 Summary

This chapter covered the technical implementation aspects of Weightless:

  • Adaptive Data Rate (ADR) optimizes power consumption by selecting the highest data rate that maintains reliable connectivity
  • TV White Space management requires geolocation database queries and dynamic channel selection
  • Total Cost of Ownership analysis shows Weightless-P is competitive for private network deployments
  • Power calculations demonstrate that sleep current dominates average consumption in LPWAN devices
  • Narrowband operation improves link budget through noise reduction, enabling longer range

1146.7 What’s Next

Continue your Weightless learning: