[Tinyos-help] CTP: ETX values vs. LPL wake-up interval

Manjunath Doddavenkatappa doddaven at comp.nus.edu.sg
Tue Nov 16 21:55:51 PST 2010


Dear Sir,

   The problem and its cause can be summarized as follows.

   In the case of CTP, I guess it is required to set LPL variables (local 
and remote sleep intervals) from the Makefile. Otherwise, I guess no 
preamble is sent before transmitting routing beacons thus resulting in 
unexpected behavior. Instead of defining LPL variables in the Makefile, I 
was using LowPowerListeniing interface to set LPL variables from the 
application. The interface allows to set local sleep interval, and remote 
wake-up interval for only the data packets that I send from the 
application and this does not have any effect on beacon transmission.

   As you suggested, I tested without CTP, program works without any 
problems in both the cases of on setting LPL variables from the Makefile 
and application. As no routing beacons are involved, behavior is 
independent of the location from where I set LPL variables.

Please correct me if my understanding is wrong.

Further, what is the reason for not having the LPL to use default preamble 
length for outgoing packets based on local sleep interval (that is set 
using the command setLocalWakeupInterval()). I understand that the command 
setRemoteWakeupInterval allows to handle different sleep intervals. But is 
is typical to have different schedules for different nodes ? and moreover, 
this requires every forwarder to know the sleep interval of its next hop.

Thanking you,
D. Manjunath

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On Mon, 15 Nov 2010, Philip Levis wrote:

>
> On Nov 7, 2010, at 3:40 AM, Manjunath Doddavenkatappa wrote:
>
>>
>> Dear Dr. Gnawali,
>>
>> Sorry to get back to you so late, we had a paper deadline.
>>
>> Everything works fine if I set LPL variables from the Makefile as in TestNetworkLpl. Problems arise only on trying to set LPL variables from the program using "setLocalWakeupInterval()". Just to verify in the later case, I retrived sleep interval value using "getLocalWakeupInterval()", the returned value is consistent with what I set it to.
>>
>> Manjunath D
>
> Here's a simpler question: outside of CTP, is there a relationship between the LPL interval and a link's packet reception ratio? I.e., if you send unicast LPL messages to a destination, do you see that increasing the LPL interval decreases the PRR? Note that CTP is often going to be using borderline links that are near the SNR/PRR threshold.
>
> Phil
>
>


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