[Tinyos-devel] CTP and LPL on tmote

[Geoffrey Werner-Allen]

Wow.  I've run reliable collection protocols on top of CTP and never saw the
packet loss get this bad.

Just as a sanity check: you are setting the per-packet duty cycle on the
sender side for each packet sent? It just seems like, given your delivery
ratios (which track *very* closely to the duty cycle), the sender is not
actually sending a packet train but only one packet, in which case the
reception probability should essentially be the duty cycle (i.e., what is
the probability the receiver happened to be listening at the precise moment
I sent the packet).

Also, how was LPL set up on the receiver side to achieve the DC numbers
listed? I'm just curious about the value used in the call to
LowPowerListening.setLocalSleepInterval() (or whatever call was used to
enable receive duty cycling).

Best,

-gwa-

geoffrey werner-allen :: 617.694.7261 :: www.eecs.harvard.edu/~werner


On Sat, Dec 6, 2008 at 3:28 AM, Omprakash Gnawali <gnawali at usc.edu> wrote:

> On Sat, Dec 6, 2008 at 12:03 AM, Andreas Köpke <koepke at tkn.tu-berlin.de>
> wrote:
> > Hi guys, looks like we isolated the problem.
> >
> > Using two nodes about 3m apart, one sender, one receiver, one message
> every
> > 1.5s on average we get the following delivery ratios:
> >
> > DC        mean    90% confidence interval
> > 5%        0.097   0.086   0.11
> > 10%      0.21     0.126   0.295
> > 20%      0.26     0.18   0.34
> > 50%      0.55     0.46   0.63
> > 100%    0.995   0.98    1.00
> >
> > Once we switch on LPL, the packets are hardly detected by the receiver.
>
> I don't remember things being this bad.
>
> Is your guess that if we used test programs with something like
> periodic packet transmission (lets say every 1s) and a base station,
> we will have similar problem? I would have a hard time believing that
> is the case but I haven't done this test in a while.
>
> - om_p
>
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