The correct answer to your first question is A, because a one-shot timer is used in the LPL layer. The use of a one-shot resets the timer after every wake-up, which allows you to change the period arbitrarily after the next timer fire.
Your second question concerns a synchronous low power listening implementation on top of an asynchronous implementation. And, rather than adjust when the receiver wakes up to expect a transmission, a possibly better method is to adjust when the transmitter begins transmitting its message to align with a specific receiver. By keeping the receive checks asynchronous, receivers will wake up at different times within the local geographical network and will be able to receive messages from transmitters targeting those individual receivers. This effectively shares the channel through more of a time division (TDMA). Your transmitters can also form a table of when its neighbors are awake based on when they receive acknowledgements from those receivers. Although a layer like this is not built into the radio stack now, it's just waiting for an implementation. Look up WiseMAC. -David _____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Murray, Ben Sent: Thursday, September 06, 2007 3:43 AM To: tinyos-help@Millennium.Berkeley.EDU Subject: [Tinyos-help] low power listening -- controlling when it wakes and confirming s leep period? I am using LowPowerListening with a MicaZ mote and am curious about a few more specifics. I am using the setLocalSleepInterval(X ms) command. My first question concerns the actual sleep period. Given the above command, will the mote: a) perform its low power listening period (taking approximately 5 ms) and having completed that go to sleep for X ms, for a total period of (X + 5) ms? /or/ b) would it wakeup every X ms, with the low power listening period basically taking up the first 5 ms of each X ms period? My second question concerns the timing of the wake period, and whether when this occurs is adjustable/controllable? For instance, if I have set my sleep interval to 5000 ms is there a way I can control when the wake period will occur. For the purpose of this example let us assume that my mote knows that a signal will be transmitted once every 5000 ms, and that it knows (magically) how many milliseconds its current waketime is shifted by with respect to this transmitted signal. E.g. (view with a mono-spaced font!) Tx:______|_________|_________|_________|____... Rx:__|___N_____X___A_________|_________|____... ... where N is the point where the receiver "magically knows" that it has missed the transmission and by how many milliseconds, so instead of activating its lpl receive period at X, it adjusts the low power listening period such that the new space lpl receive period is at A and subsequent receive period are now synchronised with the transmitter. Ignoring whether or not this is a good idea, is it possible to do something like this? Perhaps by altering the localsleepinterval value -- would this initiate a new listening period from the point at which it was called in the code? The other rough way to force this to happen I suppose might be to stop the radio altogether, and start it again with low power listening enabled -- is the wake period of low power listening active at the start immediately when setlocalsleepinterval is called / startDone is completed, or at the end, or somewhere in the middle? Apologies if this has been asked before! Thanks in advance Ben **************************************************************************** *** Please consider the environment before printing this email. **************************************************************************** *** This email and any files transmitted with it are intended solely for the use of the individual or entity to whom they are addressed and may not be divulged to any third party without the express permission of the originator. Any views expressed in this message are those of the individual sender, except where the sender specifically states them to be the views of Thales Research & Technology (UK) Limited. **************************************************************************** ***
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