On Thu, Sep 11, 2008 at 9:02 AM, Gaurav Chandwani <[EMAIL PROTECTED]> wrote: > Hi All, > > I am facing a strange packet loss behaviour in my network which is affecting > my final > project. I would like to ask a few questions for the same. > > TestBed: 15 motes running the simple apps/RadioCountToLeds application > which sends periodic(5 sec) brodcast > messages, the additions are that I switch Off the Radio(to improve liftime > of the mote) after SendDone and start it when the timer fires, also I have > removed the receive interface. > I am running the apps/BaseStation code for receiving all these messages and > then check the packet loss through > java. The nodes are kept close to each other. I am using tinyos-2.1. > > So, 15 motes sending a packet every 5 seconds and a BaseStation receiving. > > Result: Packet loss in high numbers and the more troubling statistics was > that I lost upto 15 consecutive packets > from a particular node. My application is based on calculating the presence > of the motes in a particular period, > lets say 30 sec(6 times the frequency), so 15 packets result into a lost > mote which is not true. > > Acknowledgements: Are there ACK's for broadcast packets ? So, would my > application wait for ack's and if it doesnt > arrive retransmit ? If not, can i enable it somehow ? I read many replies on > the mailing list but cudnt arrive to a conclusion. > I have tried putting the following two methods(similar to TestPacketLink) > but according to this I never lose any ack and packets are always ACKed. > call PacketAcknowledgements.requestAck(&packet); > call PacketAcknowledgements.wasAcked(bufPtr). > Also, I had commented CFLAGS += -DCC2420_NO_ACKNOWLEDGEMENTS in MakeFile for > the BaseStation. > > BaseStation Queue: This sounds absurd, but is it possible that BaseStation's > receive queue cannot handle packets that arrive at more or less the same > time, so the Radio receives the packet and sends ACK(if it does) but the > Queue somehow looses some packets. > I presume that cc2420 is fast enough to handle such slow rate here but can > anybody prvovide the statistics for reception of colliding packets ? how > close can they be ? > > Tweak - If I add a delay of 100ms in SendDone before switching Off the > Radio, the packet loss is much much less and max number of > consecutive packet loss from one node is 6. Further if I add a delay of > 200/300 ms, there is a drastic decrease in packet loss and I dont loose more > than 1-2 consecutive packets from a particular node. I cant understand > whatcan be the reason behind the dramatic change ???? > ACK's ? but 100/200/300 ms is a very big time. > > Channel: This test is done in a regular office environment where ofcourse > there is wireless and other regular interferences, but nothing > that can be pinpointed as 'the' problem. Will changing the default channel > on which the motes are sending packets have any positive effect ? What > amount of packet loss rate should be expected from the motes in such a > simple environment and what can be the reasons ? > > Bigger Picture: Putting 200ms delay leads to an acceptable packet loss rate > but decreases the lifetime of the nodes and also when I make the network a > bit more complex e.g adding some nodes with MultiHopOscilloscope app which > can also accept the broadcast messages from these RadioCountToLeds motes, > the packet loss re-emerges. So understanding some of the above Questions is > necessary for the bigger picture. > > Waiting for some hints, > Gaurav > >
Is there any reason you don't want to use LPL? LPL does what you are trying to do and more to minimize energy use. - om_p _______________________________________________ Tinyos-help mailing list Tinyos-help@millennium.berkeley.edu https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
