Implement a time synchronization protocol in non
ZigBee protocol is one of the most important protocols utilized by wireless sensor network (WSN). It
provides a standard platform which allows all the wireless devices to communicate with each other.
Moreover, by defining “application profiles”, ZigBee devices nowadays can be utilized in remote
monitoring, remote control, industry area, home atomization,
medication and even 3D data
synchronization. As a matter of fact, ZigBee are moving to more and more application area due to its
nature: low cost, low power and mesh network.
However, not all the devices in the ZigBee network consume the power which is low
guarantee a long battery life time. The ZigBee router which is working as message relay in the
network is not allowed to go to “sleep mode” even there is no task scheduled. If the ZigBee router is
powered by an AA lithium battery, the battery li
fe time maybe just around 15 to 20 days. In addition,
according to the statistic, the router is out of transition task almost 99% of operation time, especially
for wireless monitoring system.
The goal of this project is to solve this unsatisfactory by “f
orce” the ZigBee router into sleep mode
when it is not scheduled by any task. A time synchronization protocol is running in each device.
During the wake up time, the ZigBee network try to synchronize with each other until the next wake
up time is agreed be
fore go to “sleep mode”. During the communication period, the possible time
shift jitter could also be eliminated. Practically, there is no way to control the ZigBee router to go to
“sleep mode” from software. In this case, an external PCB board would be d
eveloped and processed
to control the router’s regulator. The external PCB is mounted with a low power CPU and
communicates with the ZigBee radio via serial communication. Once the ZigBee router is ready to
sleep, the external CPU will turn off the ZigBee
router’s regulator and go to “sleep mode”. When it is
time to wake up, the external CPU enables the ZigBee router regulator for scheduled tasks.
Once the synchronization protocol is implemented, its performance, availability, compatibility should
verified and compared with ZigBee protocol. Battery lifetime of the router should also be
calculated and compared with ZigBee standard router.