The standard simply says that LQI has to be between 0 and 255. It does not say how it is calculated. The raw value you get from CC2420 (CORR) is between 40 and 110. A simple thing to do might be to find 'a' and 'b' such that the final value is between 0 and 255.
To get a more meaningful value (such as the Packet Error Rate) from CORR, I did some experiments where I made many nodes send packets to others. From the collected data, I plotted average CORR and the PER for different links. Then I fitted a curve to this plot. I used this to map CORR to PER. Ofcourse, this is just an approximation as you don't get CORR for lost packets. You can refer to our paper titled "RSSI is Under Appreciated" published in EmNets 2006 for further details. Please note that we refer to raw CORR value as LQI in the paper. Kannan. ---------------------------------------------------------------- Quoting X Z <[EMAIL PROTECTED]>: > Hi, > > I have a question regarding the LQI value conversion. There is an > equation > in Chipcon CC2420 document as follows: > > LQI=(CORR-a)*b > > Where a and b are found empirically based on PER measurements as a > function > of correlation value. This equation refers to the 802.15.4 standard, but > I > couldn't find this equation from the standard. The CORR(correlation > value) > is the raw LQI value which can be obtained from the last byte of the > message. Does anyone know how to get the values of a and b or how to > convert the raw LQI reading to a meaningful value? > > Thanks > Xuan > > _______________________________________________ > Tinyos-help mailing list > Tinyos-help@Millennium.Berkeley.EDU > https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > _______________________________________________ Tinyos-help mailing list Tinyos-help@Millennium.Berkeley.EDU https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
