-33-
v5.8
Radios
7.3. DigiMesh
XBee-802.15.4 and XBee-900 modules can use an optional firmware (DigiMesh) so that they are able to create mesh networks
instead of the usual point to point topology. This firmware has been developed by Digi aimed for allowing modules to sleep,
synchronize themselves and work on equal terms, avoiding the use of node routers or coordinators that have to be permanently
powered on. Characteristics of the implemented protocol:
•
Self Healing: any node can join or leave the network at any moment.
•
All nodes are equal. There are no father-son relationships.
•
Silent protocol: reduced routing heading due to using a reactive protocol similar to AODV (Ad hoc On-Demand Vector
Routing).
•
Route discovery: instead of keeping a route map, routes are discovered when they are needed.
•
Selective ACKs: only the recipient responds to route messages.
•
Reliability: the use of ACKs ensures data transmission reliability.
•
Sleep Modes: low energy consumption modes with synchronization to wake at the same time.
The classic topology of this type of network is mesh, as the nodes can establish point to point connections with brother nodes
through the use of parameters such as the MAC or network address or by making multi-jump connections.
Figure : Mesh topology
Module
Frequency
Tx Power
Sensitivity
Channels
Distance
PRO
2,40 – 2,48GHz
100mW
-100dBm
7
7km
XBee DigiMesh modules share hardware features with XBee-802.15.4 modules, being able to switch from one to the other by
changing the firmware.
XBee DigiMesh modules are based on the standard IEEE 802.15.4 that supports functionalities enabling mesh topology use.
All information about their programming and operation can be found in the DigiMesh Networking Guide available at
of Libelium website.
