Hi Nathan, related to your results, one possible explanation is the "clipping effect" caused by the RF circuitry at the receiver. Therefore, the best way to realize experiment involving TX power level and RSSI is to define a strategic "reference distance". In the paper below, we have explanation about both topics when a section that explain how to use WSN sensors to realize RF measurements.
http://www.hindawi.com/journals/wcn/2010/620307.abs.html Try to repeat your experiments with a default distance of 5m. Regards, Agnelo Silva Cyber Physical Networking Laboratory University of Nebraska-Lincoln. 2010/4/19 wx li <[email protected]> > Sorry for forgetting a msg. I sample the RSSI value at the sending mote. > Besides, I wonder why the RSSI value varies if i move the receiving mote > further OR nearer. > > Thank you! > > Nathan > > > On Mon, Apr 19, 2010 at 5:28 PM, wx li <[email protected]> wrote: > >> hi, all. >> I have do some experiments using TinyOS2.x/Telosb. And the result makes me >> confused. >> >> I changed the level of RF power by modifying the Makefile. As below: >> COMPONENT = MyDemoAppC >> CFLAGS += "-DCC2420_DEF_RFPOWER=1" >> include $(MAKERULES) >> >> After that, I wrote a small program to test it. >> Having changed RF power to 1, it will loses almost half the packets with a >> communication distance of half meter. At the same time ,the RSSI value of >> the received packets is about 45 dbm. >> However, when i set the RF power level back to 31, it delivery almost all >> packets when the RSSI value is 45 dbm. >> I don't know why.. >> PS: I read the RSSI value using >> "CC2420ActiveMessageC.CC2420Packet.getRssi()" >> >> Thank you for your any help!! >> >> Nathan >> > > > _______________________________________________ > Tinyos-help mailing list > [email protected] > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help >
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