[Tinyos-help] Acknowledgement

[Philip Levis]

On Dec 30, 2006, at 1:19 PM, Mayur Maheshwari wrote:

> Hi All
>
> I have been using TinyOS 2.0 for my experiments (TelosB) and I  
> tried implementing a scheme which makes sure that the data packets  
> are actually being received at the other end (one hop) with the  
> help of acknowledgements. This could be implemented using the same  
> interfaces and handling the acknowledegments.
>
> I was rather thinking what does the success message of  sendDone  
> event signify. Whether, it says that the packet has been handed  
> over to the Physical Layer(medium) or that packet has actually been  
> received at the other end (by confirming at the data link layer  
> with acknowledgements).
>
> I conducted an experiment with a mote programmed to send a packet  
> to a node addressed 3 and making it toggle the LED if the sendDone  
> event returns SUCCESS. Since, there was no other mote nearby so the  
> messages should not be acknowledged but still the LED toggled. This  
> confirmed that the success of sendDone event signifies that the  
> packets have been sent into the air but does not guarantee that  
> they have actually been caught by the addressed node.
>
> My question is that whether we we need to implement any scheme  
> which can handle the acknowledements and hence guarantee the data  
> has been received at the other end or there is any TinyOS interface  
> which can handle this.
>

Success in sendDone does not indicate whether or not the packet was  
acknowledged; it indicates whether the radio was able to send the  
packet successfully. If you want to see if it's acknowledged, you  
should use the PacketAcknowledgments interface.

Phil