1.3 System Communication

Communication happens over LoRa, facilitated by The Things Network. Messages to and from alarm devices go through a TTN Gateway, and are accessed by the server through The Things Network.

The Things Network limits the amount of messages per device per day, so an alternative solution may be explored in the future.

Two central alarm system communication scenarios. Image credit: baaabuuu

In the above diagram, the lightning rods denote communication by messages sent between alarm and server (through TTN) over LoRa. The messages between alarms and the server include information on the arming status, alarm (intruder detected) status and panic status, along with an optional hashed password. The three status-values are set to 1 when false and 2 when true, as leading zeroes are ignored.

Below are three sequence diagrams detailing the communication scenarios between the alarms and server.

General message from sensor node to server response sequence diagram

If an alarm stops sending messages, the server must warn users:

Alarm component AWOL sequence diagram

Control panels can send messages with a hashed password value, and this is processed right after the first alternate scenario in the top sequence diagram, so if the device and house are known.

Password sent from control panel sequence diagram, inject at second 'alt' scenario in general diagram