[Tinyos-help] Sending Multiple Messages with SendMsg

Michael Schippling schip at santafe.edu
Sun Sep 11 23:19:56 PDT 2005

Sorta-right on the ACK in sendDone(). The TOSMsg->ack field will be
set !=0 in sendDone() if an ACK was received from the destination. Make
sure that the source and dest IDs are matched one-to-one, e.g., if the
TOSbase ID is not the acutal message source ID it won't get the ACK.
Also, not getting an ACK is no guarantee of message failure. In my
experience the ACKS are lost quite frequently. I have no stats for
this, but its around 20% ACK failure...


Vlasios Tsiatsis wrote:
> Now efficincy depends on what you want.
> If you want energy efficiency (as few transmissions as possible) then why
> don't you send the packet once (say with a Broadcast dest address) and
> have a list of intended
> recipients in the data portion of the packet? In that way you can do your
> filtering in the receive() function of your application.
> In that way you save N-1 message transmissions and receptions, where N is
> the number of neighbors.
> If you care about reliable delivery to each neighbor that might not get a
> packet due to a hidden terminal problem then you should use another scheme
> for the neigghbors to return the ACKs to the transmiting node. If you
> don't want to write your own ACK scheme you can enable the exisiting radio
> layer ACKs and use the send() and sendDone() command/event pair: every
> call to the send() command is followed by a sendDone() when the packet is
> transmitted (and I think after it is ACKed by I may be wrong). So you
> initiate a packet transfer with only one send() and you schedule the rest
> of the transmissions in the sendDone() event by posting a task to send the
> packet to the next neighbor.
> I hope this helps,
> vlassis
> On Sun, 11 Sep 2005, Brett Parsons wrote:
>>Hi All,
>>I have a situation where a node needs to unicast a message to multiple
>>neighbours.  In a simplistic view, it looks like:
>>for( i=0 ; i < num_neighbours ; i++)
>>   call  SendMsg.send(....) ;
>>I know there must be a better way of doing this (perhaps using something
>>provided by TinyOS).  Can anyone offer advice on the best way to unicast
>>messages to multple neighbours in an efficient manner?
>>Brett P
>>Tinyos-help mailing list
>>Tinyos-help at Millennium.Berkeley.EDU
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