R309 AT Commands
©2015 Telegesis (UK) Ltd - 116 - AT Command Manual (Rev 3.09)
7 Notes on Energy Levels and LQI
7.1 Interpreting LQI
On the EM250 as well as the EM35x, the LQI is closely related to the SNR (signal noise ratio) but
is calculated from the chip error rate. The graph below shows the relation between the SNR and
the LQI reading on the EM250, which is the basis of the ETRX2 series of modules.
Figure 1: LQI vs. SNR (source: Ember)
From the LQI the stack calculates the cost for a particular link based on the following table. The
cost is used by the stack to compare routes between nodes.
Table 10: LQI/Cost relationship
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