User's Guide

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The scheduled communication is being used to maintain the network in terms of
neighbour relations, and also to maintain routing information. As such, this
communication happens periodically regardless of payload data being send or not.
3.3.2 Network Initialization
The wireless mesh network is created automatically when the participating nodes are
powered up. Each node will go through the same sequence after power up: Initially it
will scan for an already active network to which it is allowed to join. If it detects an
operating network, it will join it. If no network is detected, the node will initiate the
network on its own, allowing other new nodes to detect it.
3.3.2.1 Beacon Transmissions
A node which is participating in the network, or is trying to initialize a new network, will
periodically transmit a beacon on a dedicated beacon channel.
Nodes not part of a network, or nodes already in a network, can detect new
neighbouring nodes through the reception of Beacons. Nodes who are part of the same
network will synchronize their Beacon timing such that the Beacon Event occurs at the
same time throughout the entire network.
Let us consider the situation where only two nodes are present, and they are in their
initial state where they are not yet synchronized to each other:
Node A transmits its beacon periodically. Node B does the same, but they are not
synchronized yet:
Figure 3 – Beacon timing, unsynchronized
To synchronize, the nodes performs a Full Beacon Scan. This is done periodically, and
entails that the scanning node listens at least for a full beacon period (“P
B
” in the figure
above).
When either Node A or Node B receives a beacon from its neighbouring node, it will -
based on certain rules, decide if it will follow the beacon timing of the other node, or if it
keeps its own timing. In the following illustration, Node B performs a Full Beacon Scan,
where it receives the beacon from Node A, and decides to follow the beacon timing of
Node A, after which the beacon transmissions of both Node A and Node B occurs at the
same time: