XBee®/XBee‐PRO® ZB SMT RF Modules
Routing Approach Description
When to Use
Ad hoc On-demand
Routing paths are created between source and Use in networks that will not scale beyond about
Distance Vector (AODV) destination, possibly traversing multiple nodes 40 destination devices.
Mesh Routing
(“hops”). Each device knows who to send data
to next to eventually reach the destination
Many-to-One Routing
A single broadcast transmission configures
Useful when many remote devices must send
reverse routes on all devices into the device that data to a single gateway or collector device.
sends the broadcast
Source Routing
Data packets include the entire route the packet Improves routing efficiency in large networks
should traverse to get from source to
destination
(over 40 remote devices)
Note – End devices do not make use of these routing protocols. Rather, an end device sends a unicast transmission to its
parent and allows the parent to route the data packet in its behalf.
Note - A network cannot revert from Many-to-One routing to AODV routing without first doing a network reset (NR).
Link Status Transmission
Before discussing the various routing protocols, it is worth understanding the primary mechanism in ZigBee for
establishing reliable bi-directional links. This mechanism is especially useful in networks that may have a
mixture of devices with varying output power and/or receiver sensitivity levels.
Each coordinator or router device periodically sends a link status message. This message is sent as a 1-hop
broadcast transmission, received only by one-hop neighbors. The link status message contains a list of
neighboring devices and incoming and outgoing link qualities for each neighbor. Using these messages,
neighboring devices can determine the quality of a bi-directional link with each neighbor and use that
information to select a route that works well in both directions.
For example, consider a network of two neighboring devices that send periodic link status messages. Suppose
that the output power of device A is +18dBm, and the output power of device B is +3dBm (considerably less
than the output power of device A). The link status messages might indicate the following:
© 2010 Digi International, Inc.
54
DCD [ DIGITAL CORE DESIGN ]
