Transmission, addressing, and routing RF packet routing
XBee/XBee-PRO ZigBee RF Modules User Guide 61
When a router or coordinator device powers on, it sends link status messages every couple seconds to attempt to
discover link qualities with its neighbors quickly. After being powered on for some time, the link status messages
are sent at a much slower rate (about every three to four times per minute).
AODV mesh routing
ZigBee employs mesh routing to establish a route between the source device and the destination. Mesh routing
allows data packets to traverse multiple nodes (hops) in a network to route data from a source to a destination.
Routers and coordinators can participate in establishing routes between source and destination devices using a
process called route discovery. The Route discovery process is based on the AODV protocol.
Sample transmission through a mesh network
AODV routing algorithm
Routing under the AODV protocol is accomplished using tables in each node that store the next hop
(intermediary node between source and destination nodes) for a destination node. If a next hop is not known,
route discovery must take place in order to find a path. Since only a limited number of routes can be stored on a
Router, route discovery will take place more often on a large network with communication between many
different nodes.
When a source node must discover a route to a destination node, it sends a broadcast route request command.
The route request command contains the source network address, the destination network address and a path
cost field (a metric for measuring route quality). As the route request command is propagated through the
network (refer to the Broadcast Transmission), each node that re-broadcasts the message updates the path cost
field and creates a temporary entry in its route discovery table.
Node Destination Address Next Hop Address
R3 Router 6 Coordinator
C Router 6 Router 5
R5 Router 6 Router 6
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