[Tinyos-help] [TinyOs 2.x] ACK Bug?

[Razvan Musaloiu-E.]

Hi!

On Tue, 23 Dec 2008, Pratibha S wrote:

> Hi All,
> We are running an algorithm in TOSSIM over 200-nodes and we are experiencing
> packet losses due to improper ACKs. i.e. The sender would receive the
> packet.wasAcked() signal, but the receiver wouldnt have got the message. Is
> this a bug? Any help on this issue would be appreciated.

The CpmModelC.nc contains the following lines:

   338       if (RandomUniform() < 0.001) {
   339         dbg("CpmModelC,SNRLoss", "Packet was technically lost, but TOSSIM introduces an ack false positive rate.\n");
   340         if (mine->ack && signal Model.shouldAck(mine->msg)) {
   341           dbg_clear("CpmModelC", " scheduling ack.\n");
   342           sim_gain_schedule_ack(mine->source, sim_time() + 1, mine);
   343         }
   344         else { // Otherwise free the receive_message_t*
   345           free_receive_message(mine);
   346 	    }

So it's normal to receive a small number (0.1%) of false acks. :-)

--
Razvan ME