To calculate the network capacity of LoRaWAN, several technical factors must be considered, including channel bandwidth, spreading factor (SF), data rate, message size, duty cycle limitations, number of gateways, and the message transmission frequency of devices. Below is a detailed step-by-step guide to help estimate LoRaWAN network capacity:

1) Identify Key Parameters

• Bandwidth (BW): Typically 125 kHz.
• Spreading Factor (SF): LoRaWAN supports SF7 to SF12, where higher SF values mean lower data rates and longer transmission times.
• Data Rate (DR): Determined by the bandwidth and SF; different DR values result in different transmission times.
• Payload Size: Usually measured in bytes, assuming 12 bytes here.
• Message Transmission Frequency: Assume each device sends 10 messages per day.
• Duty Cycle Limitation: Assume 1% (a typical restriction in Europe).
• Number of Channels: Assume 8 channels.
• Number of Devices: This is the parameter we need to estimate.

2) Calculate the Transmission Time for a Single Message

Use the following formula to calculate the airtime of a single LoRa message:
[T_msg = Symbol Time × (Payload Symbols +Preamble Length)]
Where Symbol Time depends on SF and BW, and Payload Symbols are related to the payload size and coding rate (CR).

• Symbol Time = (2^SF/BW)
• Payload Symbols depend on CR and the payload size.

For example, with a 125 kHz bandwidth and SF12, sending a 12-byte message may take about 1.5 seconds (this is an approximation, and specific values can be calculated using specialized tools).

A simple way to calculate this number is to use the tool below.

https://www.semtech.com/design-support/lora-calculator

3) Calculate the Maximum Number of Messages Per Channel

Assuming the channel is working at the maximum duty cycle:

[N_{max per channel} =T_available/T_msg]

Where is the total available time in a day (typically 24 hours multiplied by 3600 seconds) and the duty cycle limit (e.g., 1%).

4) Calculate the Maximum Number of Messages Per Gateway

If there are 8 channels:

[N_{max per gateway} = N_{max per channel} × 8]

5) Estimate the Maximum Number of Devices

Assuming each device sends 10 messages per day:

[N_devices = N_{max per gateway}/Daily Messages per Device]

6) Final Network Capacity Estimation

By following the steps above, you can estimate the theoretical maximum capacity of a LoRaWAN network. However, the actual capacity is typically lower due to real-world factors such as device distribution, signal interference, package confliction and transmission failure rates. In practice, the actual capacity of an 8-channel gateway might range from several thousand to tens of thousands of devices.

Example:

• If the transmission time (T_”msg” ) for a single message is 1.5 seconds and the duty cycle is 1%, then one channel can handle approximately 576 messages per day.
• Across 8 channels, this totals around 4608 messages per day.
• If each device sends 10 messages per day, the gateway can support approximately 460 devices. We recommend to use ~15% of the total capacity of a gateway to avoid repeatedly package conflicts and lost.

This calculation method can be applied to various LoRaWAN deployment scenarios, with specific values varying based on network configuration and environmental conditions. Please ติดต่อเรา to get the “8 Channel LoRaWAN Network Capacity Evaluation Tool”