Re: wireless sensors, and battery life: time synch

At 01:13 AM 6/1/2005, Ralph Hempel wrote:
>Like USB. USB is simple, reliable and rugged. And it's fast. All this
>talk about independent sensors talking via radio waves is interesting
>though. I still think that properly designing the system so that
>everything plays well together is a different story....

Yes -- and this is exactly Zigbee's target. BT was originally aimed at PC, 
PDA, peripheral communication, and it could have done well at that. Now I 
think it is eclipsed by the low cost and 10-100X better speed of 801.11b/g.

Zigbee has from the start been aimed at sensors and actuators 
communicating, with long battery life. So it stands a good chance of 
succeeding there. There's no other widely supported method which has 
Zigbee's intent.

Part of the battery life issue, as you allude, is not listening all the 
time. To make this happen, nodes have to share a common and precise time 
base. Then they just have to wake up at the allotted time. This is harder 
than it sounds, and is the subject of standards such as IEEE1588. We plan 
to experiment with this with our Zigbee nodes, since the power savings can 
be really significant.

Regards

Bruce


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