LQI

LQI, or Link Quality Indicator, is a metric used in wireless network systems to quantify the perceived quality of a radio link between two nodes. It is commonly employed in low-power, short-range networks such as IEEE 802.15.4-based systems, including ZigBee and Thread, as well as 6LoWPAN deployments. LQI provides a coarse assessment of link health that supports network management tasks like neighbor discovery, routing decisions, and link maintenance.

LQI values are generated by the receiver hardware or software and are typically communicated to higher layers. In many implementations, the metric is represented on a scale from 0 to 255, where higher values indicate better link quality. However, the exact scale and interpretation can vary by chipset and software stack. LQI is often derived from a combination of physical layer indicators, such as received signal strength (RSSI) and error rates (bit error rate), rather than from a single, direct measurement of packet success probability. As a result, LQI is best understood as a heuristic or relative measure of link reliability rather than an exact predictor of throughput or delivery success.

In practice, LQI is used to determine preferred neighbors, influence routing decisions, and adjust network topology or power settings. It is commonly used alongside other metrics such as RSSI, BER, or ETX to provide a more robust view of link quality. Limitations include device-specific definitions, environmental variability, and potential non-comparability across different hardware platforms, underscoring the need for contextual assessment when using LQI for network management.