R308 AT Command Manual - wless.ru
R308 AT Command Manual - wless.ru
R308 AT Command Manual - wless.ru
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<strong>R308</strong> <strong>AT</strong> <strong>Command</strong>s<br />
8 Notes on Energy Levels and LQI<br />
8.1 Interpreting LQI<br />
On the EM250 as well as the EM35x, the LQI is closely related to the SNR (signal noise ratio) but<br />
is calculated from the chip error rate. The graph below shows the relation between the SNR and<br />
the LQI reading on the EM250, which is the basis of the ETRX2 series of modules.<br />
EM250 SNR vs LQI<br />
0.<br />
Figure 1: LQI vs. SNR (source: Ember)<br />
From the LQI the stack calculates the cost for a particular link based on the following table. The<br />
cost is used by the stack to compare routes between nodes.<br />
Cost LQI<br />
1 254 - 255<br />
3 247 - 253<br />
5 200 - 246<br />
7 0 - 199<br />
Table 12: LQI/Cost relationship<br />
©2012 Telegesis (UK) Ltd - 104 - <strong>AT</strong> <strong>Command</strong> <strong>Manual</strong> (Rev 3.08)
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