Hi,
Anyone has empirical results to adjust tranmission power of CC2420 based on
LQI -- like some linear equation? I have tried adjustLQI() in
MultihopLQI.nc, the return value is not stable and oscillate in a large
range. Actually, I wonder why not use the original LQI in TOS_Msg header?
Since CC2420 datasheet said: "A correlation value of ~110 indicates a
maximum quality frame while a value of ~50 is typically the lowest quality
frames detectable by CC2420."
Anyone successfully get a linear relation between the LQI value and actual
link quality?
====================================
//From CC2420 Data sheet
As described in the Frame check
sequence section on page 38, the average
correlation value for the 8 first symbols is
appended to each received frame together
with the RSSI and CRC OK/not OK when
MDMCTRL0.AUTOCRC is set. A correlation
value of ~110 indicates a maximum quality
frame while a value of ~50 is typically the
lowest quality frames detectable by
CC2420.
Software must convert the correlation
value to the range 0-255 defined by [1],
e.g. by calculating:
LQI = (CORR - a) . b
limited to the range 0-255, where a and b
are found empirically based on PER
measurements as a function of the
correlation value.
A combination of RSSI and correlation
values may also be used to generate the
LQI value.
======================================
// A function got from MultihopLQI.nc
uint16_t adjustLQI(uint8_t val) {
uint16_t result = (80 - (val - 50));
result = (((result * result) >> 3) * result) >> 3;
return result;
}
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