Hi Sudha, Try using lower power levels for taking measurements. My understanding is that you are using maximum power 0dbM in CC2420 for taking measurements, and the distances being small comparatively, not much variation can be observed in RSSI values. Also, placing the motes above ground is also not helping the cause. Try, averaging RSSI values over a large number of runs. -- Regards Manoj
Sudha wrote --------------------------------- Hi, We are doing some localization expts for which we are collecting RSSI values using the Xbow micaz motes. We use a transmitter and receiver, with their power level set to 31 (0dBm) using the TinyOS makefile (CC2420_DEF_RFPOWER=31). We are ?essentially using the RssiDemo code with an additional field in the beacon message. I have attached a plot that displays the RSSI values (y-axis, in dBm) taken at different distances (X-axis in feet) in a free space outside environment. The distances are [6,9,12,15,12,18,21,24,30,36]ft. We subtract -45 from the raw RSSI values output by the RSSIdemo code to get the value in dBm. ?Both the motes are in line of sight and placed well above ground level and there is no other known source of interference. Generally the RSSI values are supposed to decrease with distance and follow a log-linear path loss model. Strangely, as you can see from the plot after some distance the RSSI values are higher. We are unable to explain this behaviour, especially given that the multipath effect is minimal in free space. We are not sure if this an artifact of the micaz mote hardware or the CC2420 radio or something else we have overlooked in the software. Has anyone else observed this behaviour with micaz motes? ?If someone has an idea why this may be occurring and how to fix this problem, we would be interested in knowing. thanks sudha
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