C07W as a LoRaWAN base station

LoRa is a protocol to transmit data packets over long distance (LOng RAnge). This is mainly used for packets with little information or low frequency. This is roughly on the order of 10-15 data points every 5 to 10 minutes. In ideal conditions, such as an open space, good antennas and direct "line of sight" the bridgeable distance goes up to several kilometers. Obstacles between the sensor and gateway however, negatively affect these signals. Especially metal structures can cause poor reception.

The use of LoRa sensors always requires a base station, in our solutions this is a Calculus C07W with built-in LoRa concentrator. This is best placed as centrally as possible to ensure good coverage. The height of the antenna is also important here. The higher the antenna is placed, the better. Obstacles in the vicinity of the antenna are best avoided. If possible, do not place it close against a metal wall, but try to stay away from it.

Pour les installations, vous pouvez également optimiser le placement en utilisant certaines valeurs du portail.

With LoRa, you also have the risk of packet loss. Up to 10% of packets can be lost. For crucial messages, a confirmation can also requested, but it is not recommended to do this continuously. You get more radio traffic making it more difficult for other sensors to send their messages. If their confirmations then fail, they are sent again, causing more and more radio traffic.

RSSI, or Received Signal Strength Indication is the received strength of the signal. Briefly, it means how loudly you hear a signal from the transmitter. This number is always negative and is usually between -120dBm and -30dBm. -120dBm is very weak reception, -30dBm is very strong reception. A sensor sending messages at -120dBm also means that more packets may be lost in poorer conditions.

SNR, or Signal-to-Noise ratio, is the ratio of background noise to the transmitted signal.

This value fluctuates between -20dBm and +10dBm. Again again, the higher the value the better.

SF or Spreading Factor is a value specific to LoRa as opposed to RSSI and SNR, which are both values common in radio communications. Spreading Factor is a value between 7 & 12.

This is a setting that automatically adjusts itself based on conditions and reception. As a comparison, you can think of it as a value that tells you how fast you are speaking. The better the reception, the faster you can communicate and still be clearly understood. If the reception and distance is somewhat greater you had best do this more clearly and more slowly. If a predefined number of messages is not acknowledged by the gateway, the sensor goes up a value, it does this by itself. SF12 is clearer here than SF7. However, longer sending also means more battery consumption.

With Elsys sensors, for example, this provides the following consumption:

As you can see, consumption goes up exponentially, and so it is important to keep the Spreading Factor as low as possible. This can be done by finding a better location or improving the placement of sensors and/or antenna.

A LoRa antenna is not a directional antenna. These antennas work best by mounting it perpendicularly.

The ideal scenario, of course, is direct "line of sight", but this is rarely possible in practice. Also with direct line of sight, but being just above the ground, because of the "fresnel zone" you also have interference from the ground. This is approximately an ellipsoid around the line of sight. The exact size you can possibly calculate, but the important thing is to realize that objects that are near the line of sight can also have influence, and that when placed close to the ground you may experience interference from the earth as well.