Understanding LoRa PHY Parameters: How SF, BW, CR, and LDRO Shape Range and Power Consumption

1. Why LoRa Can Communicate Over Long Distances

Unlike traditional wireless technologies, LoRa prioritizes sensitivity over throughput.
By trading data rate for processing gain, LoRa achieves exceptional link budgets suitable for low-power wide-area networks.

This capability is not driven by a single setting, but by the combined effect of multiple PHY parameters. Among them, SF, BW, CR, and LDRO play the most critical roles.

1. Spreading Factor (SF): The Primary Range Control

The Spreading Factor defines how many chips are used to encode each symbol. Typical LoRa configurations range from SF6 to SF12.

Key characteristics of SF include:

Higher SF values increase processing gain and communication range

Longer symbol duration results in lower data rates and longer time-on-air

In practice, SF represents a trade-off between distance and capacity.
Higher SF values are ideal for long-range, low-traffic devices, while lower SF values are preferred in dense networks.

1. Bandwidth (BW): Speed Versus Sensitivity

Bandwidth determines how wide the LoRa signal spreads across the frequency spectrum. Common options include 125 kHz, 250 kHz, and 500 kHz.

Increasing BW leads to:

Shorter symbol time and higher data rate

Reduced receiver sensitivity and shorter communication range

As a result, BW is inversely related to achievable distance.
Wider bandwidth is suitable for short-range or latency-sensitive transmissions, while narrower bandwidth improves robustness in weak-signal environments.

1. Coding Rate (CR): Enhancing Reliability Through Redundancy

Coding Rate reflects the proportion of forward error correction (FEC) bits added to the payload. Typical values range from 4/5 to 4/8.

A higher CR:

Improves resistance to interference and bit errors

Reduces effective payload throughput

In noisy or obstructed environments, a higher CR can significantly improve packet success rates. In clean radio conditions, lower CR values offer better efficiency.

1. Low Data Rate Optimization (LDRO): Stability for Long Symbols

LDRO is often overlooked but becomes critical when symbol duration exceeds approximately 16 ms.

Long symbol times can introduce:

Oscillator frequency drift

Accumulated phase errors during reception

Enabling LDRO optimizes demodulation for long symbols, improving robustness in low data rate scenarios. It is typically used with high SF and narrow BW configurations.

1. Parameter Trade-offs and Typical Use Cases

1. Conclusion

There is no universal “best” configuration for LoRa PHY parameters.
Optimal performance is always achieved by balancing communication range, payload size, power consumption, and radio conditions.

A solid understanding of SF, BW, CR, and LDRO is essential for designing reliable and efficient LoRa and LoRaWAN networks.