Understanding Device Types
LoRaWAN defines three device classes (A, B, C) with distinct capabilities and power consumption profiles.
Class A (All Devices)
Most common and power-efficient
Characteristics
- Bi-directional communication
- Downlinks only after uplink transmission
- Two short receive windows after each uplink
- Lowest power consumption
How It Works
- Device sends an uplink message
- Opens RX1 window (1-2 seconds later)
- Opens RX2 window (1 second after RX1)
- Returns to sleep
Use Cases
- Battery-powered sensors
- Environmental monitoring
- Asset tracking
- Applications with infrequent downlinks
Power Profile
- Battery life of 5-10+ years
- Active only during transmission and receive windows
Class B (Beacon)
Scheduled receive windows
Characteristics
- Includes all Class A features
- Additional scheduled receive windows
- Synchronized with network beacon
- Moderate power consumption
How It Works
- Synchronizes with network beacon (every 128 seconds)
- Opens predictable receive windows
- Application can schedule downlinks
Use Cases
- Smart streetlights
- Irrigation control
- Applications requiring scheduled commands
Power Profile
- Moderate battery drain
- Battery life of months to years, depending on beacon frequency
Class C (Continuous)
Always listening
Characteristics
- Includes all Class A features
- Continuously listening (except when transmitting)
- Immediate downlink capability
- Highest power consumption
How It Works
- Receive windows open continuously
- Network can send downlinks at any time
- Closes briefly during uplink transmission
Use Cases
- Mains-powered devices
- Actuators requiring fast response
- Emergency systems
- Applications where latency is critical
Power Profile
- Requires mains power or frequent recharging
- Battery life of hours to days
Comparison Table
| Feature | Class A | Class B | Class C |
|---|---|---|---|
| Downlink latency | High (wait for uplink) | Medium (scheduled) | Low (immediate) |
| Power consumption | Lowest | Medium | Highest |
| Battery life | Years | Months-Years | Hours-Days |
| Downlink slots | 2 per uplink | Scheduled + uplink | Continuous |
| Best for | Sensors | Actuators (scheduled) | Actuators (immediate) |
Choosing the Right Class
Choose Class A if:
- Device is battery-powered
- Infrequent downlinks are acceptable
- Cost-sensitive application
- Maximum battery life is needed
Choose Class B if:
- Predictable downlink timing is required
- Cannot always wait for uplink
- Battery life is still important
- Scheduled operations are needed
Choose Class C if:
- Mains power is available
- Fast downlink response is critical
- Real-time control is required
- Battery life is not a concern
Switching Classes
Some devices support multiple classes:
- Start in Class A for lowest power consumption
- Switch to Class C when needed
- Return to Class A to conserve battery
Example: Smart valve
- Class A for periodic reporting
- Class C for maintenance/control
- Returns to Class A for normal operation
Implementation Notes
Class A Considerations
- Plan for delayed downlinks
- Implement retry logic
- Buffer commands on the server
Class B Considerations
- Ensure good gateway coverage for beacons
- Account for beacon synchronization time
- Handle missed beacon scenarios
Class C Considerations
- Design for higher power usage
- Implement power management
- Consider solar or large batteries