RSSI is Under Appreciated

There is a general belief in the Wireless Sensor Network (WSN) community that the received signal strength indicator (RSSI) is a bad estimator of the link quality. This belief is due to the existence of many asymmetry links in older radios such as CC1000 and TR1000. Newer radios that are based on IEEE 802.15.4 standard such as CC2420 implement another parameter called link quality indicator (LQI) which is believed to be a better indicator than RSSI. There is so far no extensive evaluation of CC2420 to validate this claim. We have conducted such an evaluation and our preliminary results indicate that RSSI for a given link has very small variation over time for a link. Our results also indicate that when the RSSI is above the sensitivity threshold (about -87 dBm), the packet reception rate (PRR) is atleast 85%. Around this sensitivity threshold, however, the PRR is not correlated possibly due to variations in local phenomena such as noise. LQI, on the other hand, varies over a wider range over time for a given link. However, the mean LQI computed over many packets has a better correlation with PRR.