QoS indicators are only visible for LoRaWAN devices, even if they come through other networks that provide the necessary parameters for QoS calculation. QoS values are determined based on the frame count sent by the device. Every payload that a device transmits to the server contains a frame count number (FC), which the device increments for each payload. This information allows us to determine if any payloads are missing or duplicated.
For instance, if a payload is missing, it might mean that the device sent out payload number 1 and the next one received by the server was number 3. This prompts the question: where is number 2? This could indicate a potential connection error between the gateway and the device, resulting in the payload not reaching the gateway.
On the other hand, if there are duplicated payloads with the same frame-count, it's problematic because the device's battery life depletes more rapidly than if it were sending only one payload. This suggests that the device might be using an incorrect LoRaWAN Profile. A LoRaWAN Profile can comprise various MAC Versions and other parameters that influence how payloads are transmitted to the device. In most cases, if payloads are duplicated, it signifies that the NbRep is not being read by the server. The device might prefer a different profile that reduces the NbRep value.
QoS is always calculated based on the last 100 payloads, or fewer if there are fewer than 100 payloads available. If the device has sent 100 or more payloads, we refer to it as a full dataset.
First, we determine the calculation parameters:
The reset indicator starts at number one because many devices do not initiate their frame-counts from zero.
Next, we begin the QoS calculation, which is categorized into three main approaches:
Within the calculation mode, the QoS computation is split into two subcategories:
LM : difference between the latest FC and the minimum value of FC
FM : difference between the first FC and the maximum value of FC
ΣLMFM = ΔLM + ΔFM (simplified to LMFM)