Every transaction in a Class A end-device starts with an uplink transmission, which is then followed by two downlink receive windows. The network server sends the downlink message after receiving the uplink. At the end of downlink message, the end-device enters into Sleep mode, thereby saving power. Therefore, Class A devices consume the least power and provide a long battery life. All LoRaWAN end-devices support Class A by default. The following figure shows the data transmission and reception sequence for a typical Class A end-device.
Figure 1. Class A Tx/Rx Sequence
