2 - Sending Messages
Messages sent from an end device to a network server via one or more nearby gateways are referred to as uplinks.
In this book, you learn the rules and best practices to follow when sending uplinks from your end device using the LoRaWAN® 1.0.4 specification.
Composing the Packet
An uplink message is sent in a LoRaWAN® uplink packet. The LoRaWAN packet shown in Figure 1 contains a PHY Payload (PHYPayload) which contains three groups of fields:
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a MAC Header (MHDR) defining information about the type of message and its format version
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a MAC Payload (MACPayload) containing the information being transmitted
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a Message Integrity Code (MIC) used by the network server to verify that the message originated from the same end device registered with the network server
Figure 1: Fields contained in a LoRaWAN uplink packet
An explanation of how the end device sets each field in the MAC Header and MAC Payload follows in this chapter. Understanding how to set the Message Integrity Code is then explained in the chapter Calculating the Message Integrity Code.