Relay event payload
The Relay event payload allows a Relay Gateway to broadcast data like a heartbeat, location information, battery status, ... The event payloads are encoded as TLV such that the event payload can contain data for known and unknown (proprietary) event types.
Bytes:
| 1 byte | 4 bytes | 4 bytes | n bytes | 4 bytes |
|---|---|---|---|---|
| Event MHDR | Timestamp | Relay ID | TLV payload (encrypted) | MIC |
Event MHDR
Bits:
| 7..5 | 4..3 | 2..0 |
|---|---|---|
| MType | Payload type | Hop count |
- MType =
111(= Proprietary LoRaWAN MType) - Payload type =
10(= Relay event) - Hop count =
000= 1, ...111= 8
Note: The hop count is incremented each time the event payload is relayed by an other Relay Gateway. The MIC must be re-calcalculated on each relay.
Timestamp
Unix timestamp (seconds).
Relay ID
The Relay ID of the Relay Gateway sending the event payload.
TLV payload
Bytes:
| 1 byte | 1 byte | n bytes |
|---|---|---|
| Type | Length | Payload |
Please see the TLV payloads page for the known payload types.
Encryption
The TLV payload is encrypted using the same encryption scheme as the LoRaWAN FrmPayload (see section 4.3.3 of the LoRaWAN 1.0.4 specs). For the encryption the block Ai is defined as follow:
Octets:
| 1 | 4 | 1 | 4 | 4 | 1 | 1 |
|---|---|---|---|---|---|---|
| 0x01 | 4 x 0x00 | 0x00 | Relay ID | Timestamp | 0x00 | i |
MIC
Message integrity code, used by other Relay and Border gateways to check the data integrity of the packet. This is obtained by calculating the CMAC over the event payload (- MIC bytes), and using the first 4 bytes of the calculated CMAC as MIC. Note: The MIC must be calculated after encrypting the TLV payload!