Hi!
On Mon, 24 Aug 2009, David Li wrote:
> Hi,
>
> Here are some questions on TEP105:
>
> 1. TEP 105 states: "the transmitter could send the same message over and
> over again for the duration of the receiver's receive check period. The
> receiver could wake up and see that another node is transmitting, receive a
> full message, and finally send back an acknowledgement for that message.".
>
> The questions is how the transmitter knows that the receiver is awake when
> he is transmitting? In other words how would receiver know it needs to wake
> up? I understand this is asynchronous so my guess is the transmitter has to
> repeat LONG enough to fall into the the receiver's wake up period to be
> captured. Is this correct?
Yes.
> 2. Is the transmitter repeating the real message or the preamble? Will the
> real message repeat actually consumes more power on the transmitter? The
> worse case would be when the transmitter starts to send right after the
> receiver went into sleep so the sender would have to stay on long enough
> till the receiver woke up. Is this correct?
Yes.
> 3. On interface: setRxSleepInterval(message_t *msg, uint16_t
> sleepIntervalMs). Is the purpose of this to let the receiver to "synch" up
> with duty cycle that the transmitter wanted?
Yes.
> 4. Duty cycle and sleep interval conversion: Is this always done using one
> second period? For example, if the sleep interval is 250 ms then the duty
> cycle would be 250/1000 = 40%? Or if the duty cycle is 0.1% then the sleep
> interval would be 1000x0.1% = 1ms?
The conversion is based on how long the checking for activity takes (and
not a one second period). This is tricky so the duty cycle functions were
removed in the next version of the LowPowerListening interface:
https://www.millennium.berkeley.edu/pipermail/tinyos-devel/2009-August/004020.html
Details about LPL implementation for CC2420 can be found in this paper:
http://sing.stanford.edu/pubs/sing-08-00.pdf
All the best!
Razvan ME
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