I meant a difference 20dBm in my previous email. Regards
On Mon, Aug 4, 2008 at 4:19 PM, Sarfraz Nawaz <[EMAIL PROTECTED]> wrote: > Hello everyone, > > I am trying to program an Iris mote to transmit all the packets with > maximum power but the observed received signal strength (RSSI) at a > receiver is causing me to doubt that the packets are being transmitted > at full power. Here is my setup. > > One transmitter mote transmits packets and a second mote connected to > a computer through the serial port displays the RSSI (taken from the > packet metadata) of the received packets. The motes are placed on a > desk and the distance between the motes is roughly 1.2m. While > programming the Iris motes I had used the flag -DRF230_DEF_RFPOWER = > 0x0. With this setup, the observed RSSI on the receiver side is around > -80dBm. I have used the following relation to convert from raw value > to dBm > > dBm = -91 + 1 * (raw - 1) > > When repeating the same experiment with two MicaZ motes, the observed > RSSI on the receiver side is around -60 dBm. For MicaZ motes I have > used the flag -DCC2420_TXPOWER=0x1F and the following relation to > convert from raw values to dBm. > > dBm = (raw > 127 ? raw - 256 : raw) - 45 > > The datasheets for ATRF230 and CC2420 state that the maximum > transmission power is +3dBm and 0dBm for ATRF230 and CC2420 > respectively. Given that the radio chip on Iris mote transmits at 3dBm > as compared to 0dBm of MicaZ, why is there a significant difference > between the received signal strengths when everything else has been > kept same. I know that the RSSI measurements in these chips are not > very accurate but a 30dBm difference is quite significant and the fact > that the chip that should transmit at higher power seems to be > performing poorly when compared to its weaker cousin. We have observed > similar behaviour in outdoor clear line of sight conditions. > > Any insight, comment or explanation would be much appreciated. I am > using a recent CVS check out of tinyos-2.x > > Regards > _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
