Spread Factor (SF)
Understanding Spreading Factor (SF)
Overview
Spreading Factor (SF) is a critical parameter in LoRaWAN communications that influences the range, reliability, data rate, and battery consumption of a LoRa device. This document provides technical insights into SF, its operational implications, and guidance for optimizing sensor performance within commercial environments such as cold rooms and kitchens.
What is Spreading Factor (SF)?
Spreading Factor defines the duration a LoRaWAN device takes to transmit data. It essentially determines how many chips are used per symbol in modulation. Higher SF values increase the transmission range and reliability of a signal, but at the cost of lower data rates and greater battery usage.
Key Range:
SF7 to SF12
Typical Use Cases:
SF7-SF9: Optimal performance, fast data rate, lower power consumption.
SF10-SF12: Used when signal penetration is difficult or range is extreme. Increases reliability but reduces battery life.
Ideal Operating Range
For most indoor commercial kitchen or cold storage deployments:
Recommended SF Range: SF7 to SF9
Ideal SF: SF7 (strong signal, efficient battery usage)
High SF (e.g., SF11-12) is generally indicative of signal degradation, which may be due to environmental interference or distance from the gateway.
Technical Explanation
Spreading Factor
Data Rate (bps)
Range
Power Consumption
SF7
High
Short
Low
SF8
Moderate
Medium
Moderate
SF9
Lower
Medium
Increased
SF10-SF12
Very Low
Long
High
Higher SF = Longer transmission time = Higher energy consumption
Lower SF = Quicker communication = Better battery efficiency
Visualizing in Didge
Refer to the following images for insights on SF:
Battery vs SF Scatter Plot:
Devices operating at SF11 (orange dots) show increased battery drain.
Clusters at SF7-SF8 indicate healthy deployments.
Device Table in DIGG:
Devices listed with SF11 are highlighted in red.
Typical voltages are around 2.7V. As SF increases, expect faster battery drop.
Causes of High Spreading Factor
Distance from the gateway
Thick walls or refrigeration barriers
Metal enclosures or RF interference
Sensor placement inside shielded zones (e.g., inside freezers)
Consequences of High SF
Battery drain: Higher SF leads to more frequent and longer transmission bursts.
Delayed updates: Lower data rate reduces message throughput.
Network congestion: Longer airtime increases collision risk.
Recommendations to Improve SF
Optimize Gateway Placement:
Place the gateway near the center of monitored zones.
Ensure line-of-sight where possible.
Use External Antennas:
Especially for freezers and enclosed units.
Avoid Obstacles:
Metal racks, refrigeration compressors, and walls can affect signal.
Monitor Regularly via DIGG:
Use the Battery & Signal tab to identify underperforming devices.
Replace or relocate any unit with persistent SF > 10.
Summary
Spreading Factor is a key performance metric for LoRaWAN sensor communication. Ensuring that sensors operate within the SF7 to SF9 range leads to:
Longer battery life
Reliable signal
Higher data throughput
Proper network planning and periodic review of DIGG dashboards can significantly improve operational stability in sensor-reliant environments.
Document Owner: MFC Safe Technical Team
Version: 1.0
Date: July 2, 2025
Last updated
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