Hi.
I'm a student in Information Engeenering at University of Pisa.
I'm working on WSN and i'm using TinyOs 2.x on cygwin and TmoteSky motes.
In my application there is only one mote that sends messages in BROADCAST, (
so there is no collisions with other messages sent by other motes)
My problem is that in tossim simulation the average transmission time of a
packet is about 6,8 msec,
instead in tmotesky the average transmission time of a packet is about 10
msec.
In my makefile I have defined the preprocessor variable : PFLAGS +=
-DCC2420_NO_ACKNOWLEDGEMENTS
Im my applicationC file i use:
--------------- file StaticC.nc -------------------
components MainC, StaticP;
components ActiveMessageC;
components new AMSenderC(AM_APPLICATION);
components new AMReceiverC(AM_APPLICATION);
.......
StaticP.Receive -> AMReceiverC;
StaticP.AMSend -> AMSenderC;
StaticP.AMControl -> ActiveMessageC;
StaticP.Packet -> AMSenderC;
-------------------------------------------------------------------------
In my Python script i have defined :
mac = t.mac()
mac.setInitHigh(640)
mac.setInitLow(20)
mac.setHigh(160)
mac.setLow(20)
mac.setSymbolsPerSec(65536)
mac.setBitsBerSymbol(4)
in file "opt\tinyos-2.x\tos\chips\cc2420\CC2420.h" there ara values that
defines backoff times and delay for cc2420 radio stack:
enum cc2420_enums {
CC2420_TIME_ACK_TURNAROUND = 7, // jiffies
CC2420_TIME_VREN = 20, // jiffies
CC2420_TIME_SYMBOL = 2, // 2 symbols / jiffy
CC2420_BACKOFF_PERIOD = ( 20 / CC2420_TIME_SYMBOL ), // symbols
CC2420_MIN_BACKOFF = ( 20 / CC2420_TIME_SYMBOL ), // platform specific?
CC2420_ACK_WAIT_DELAY = 256, // jiffies
};
My questions are:
1) CC2420_TIME_SYMBOL = 2 ----> means that cc2420 works with 2 bits per
symbol ( 1 symbol = 1/32768 sec) ?
in this situation in my python script i must define mac.setBitsBerSymbol(2)
and define mac.setSymbolsPerSec(65536*2) to have a bit rate of
256kbit/sec?
2) CC2420_TIME_VREN = 20 is RxtxDelay?
3) what is CC2420_TIME_ACK_TURNAROUND?
4) I try to change value of CC2420_ACK_WAIT_DELAY, but this not influences
transmission time in motes---> so I can't find an explanation
for this difference of about 3msec between tossim simulation and Tmotesky
experimental tests....
Every idea is welcome, if you have an answer to one of my questions , please
answer me.
Best regards
Thanks for your attention and for your answers
Bye
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