Hi Omprakash,
Are you suggesting me to put LPL in the RadioCountToLeds code and not use Radio On/Off ? Does LPL save more battery than switching off the radio while its not transmitting ? can you give some statistics if available. I was of the impression that with LPL, there is more probability of loosing packets, which is more important to me ..I read abt CTP + LPL which probably is totally another thing .. but I have not read much LPL yet, would go thru it .. Meanwhile, can you just point out a bit more clearly in which ways it could help :) Thanks for the reply, Regards, Gaurav On Thu, Sep 11, 2008 at 9:53 PM, Omprakash Gnawali <[EMAIL PROTECTED]> wrote: > 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 > -- --------------------------------------------------------------------------------------------------------------------- To accomplish great things, we must not only act, but also dream; not only plan, but also believe. - Anatole France
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