Hey,

There are many time-synchronization protocols both deployed and in the
literature. In a manner similar to honeybees finding their new nest, i
think we'll just have to scout about.

Small errors in timing may be considered an additional noise source in
the overall noise budget.

  S/N = 3/(sigma_t^2 * 4 pi^2 * BW^2)

Where (S/N) is the signal to noise ratio due exclusively to the effect
of jitter, (sigma_t) is the RMS jitter in seconds, and (BW) is the
signal bandwidth. This assumes a broad band signal occupying the full
spectrum from zero to (BW).
See
  http://www.analog.com/static/imported-files/application_notes/AN-741.pdf

The desired noise level can be used to guide the required timing
accuracy.

(2011.05.18) ja...@minilop.net:
> On Wed, May 18, 2011 at 02:31:17AM -0700, Chris Crase wrote:
> > Quick question....   Is there a common time stamp between all the
> > sensor data? Or does each sensor keep track of its own Hz rate and own
> > time stamp? Also if it is common, what is the time time stamp?
> 
> Hi Chris!
> 
> That's actually an open question. We haven't decided yet how to handle
> timestamping. Since we have the sensors scattered across several
> microcontrollers, maintaining a common timebase is kind of a pain. We've
> considered some possibilities though:
> 
> 1. As long as all the sensors are attached using USB, the host will
>    broadcast a start-of-frame packet to them all once per millisecond.
>    We can use that as a semi-precise common time source.
> 
> 2. If we have a working GPS receiver: many receivers can produce a 1MHz
>    clock pulse that's synchronized to GPS time. Andrew has talked about
>    routing that signal to all the sensor nodes as a high-precision,
>    high-accuracy common time source.
> 
> 3. I think Theo had found an NTP-like protocol we could use in this
>    setting, but I don't remember the details.
> 
> I assume you're asking because both Kalman and Bayesian Particle Filters
> need to know how far forward to run the physics/dynamics model before
> checking a new sensor measurement?

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