What is the Adaptative Data Rate (ADR)?

What is the ADR?

The LoRaWAN server employs an Adaptive Data Rate (ADR) mechanism, which is a crucial component of the LoRaWAN Stack, to dynamically adjust the spreading factor based on certain rules. According to Semtech documentation, the ADR mechanism simplifies the process of changing the data rate by following guidelines:

1. If the link budget, which represents the overall signal quality and strength, is high, the data rate can be increased by increasing the spreading factor (SF).
2. Conversely, if the link budget is low, the data rate can be lowered by reducing the spreading factor (SF).

By tailoring the data rate to the available link budget, the ADR mechanism ensures optimal performance for each end device within the LoRaWAN network. The network server utilizes the Received Signal Strength Indicator (RSSI) of the received messages from an end device to assess the proximity of the device to the nearest gateway(s).
This information enables the network server to select the most suitable settings for each specific end device.

The benefits of utilizing ADR are twofold: it helps preserve the battery life of end devices and reduces interference, thus increasing the communication performance for all devices within the network.

To fine-tune the data rate adjustments, our LoRaWAN server employs a strategy. It establishes an average using the data from the 10 most recent frames.
Additionally, it waits for 10 successive frames with stable sensor data rate before initiating any ADR requests.
For example: if the server observes 8 successive frames at SF8, and the sensor subsequently switches to SF10 for any reason, the server will reset the waiting period and require 10 successive frames at SF10 before sending an ADR request. This approach ensures stability and reliability in adjusting the data rate of the end devices.

Other benefits:

In addition, there are other notable advantages to consider having correct (low) SF:

1. Increased Sensor Capacity: The choice of spreading factor directly influences the number of sensors that can be connected to your Wattsense product. Opting for a lower spreading factor allows for a higher density of sensor connections within your project.

2. Reduced Uplink Time Delays: When the LoRaWAN server receives uplinks modulated with SF12, it needs to accommodate longer time delays compared to receiving uplinks in SF7. This consideration is important for optimizing the overall efficiency and responsiveness of the network.

By carefully managing the spreading factor and considering these benefits, you can effectively enhance the scalability and performance of your LoRaWAN project.

Here is a theoretical schematic:

We can easily see that using a better SF, the LoRaWAN server will be able to deal with more uplinks in the same period of time.