CC1352R: Link Quality Indicator

Adam Kozlowski

Part Number: CC1352R
Other Parts Discussed in Thread: Z-STACK

Hi,

The radio unit provides two measures that can be used to derive LQI, which are RSSI and Correlation.

I found that OpenThread uses RSSI to derive LQI, but I also found many publications that claim the "symbol correlation value" is better suited to indicate link quality.

Questions:
Are there any application notes that relate to this subject?
I'm particularly interested in the correlation between these two measures and BER/PER.
What is the recommended formula (for CC1352R) to compute LQI (according to LQI given in IEEE 802.15.4)?
How exactly the correlation value is calculated by the radio unit?

Regards
Adam

over 4 years ago

0 YiKai Chen over 4 years ago

Guru 735685 points

Try to refer to https://sunmaysky.blogspot.com/2017/02/conversion-between-rssi-and-lqi-in-z.html for LQI/RSSI conversion in Z-Stack.

0 Adam Kozlowski over 4 years ago in reply to YiKai Chen

Expert 1805 points

Hi,

It is a basic formula, and LQI is derived from RSSI.
The same as in this thread https://e2e.ti.com/support/wireless-connectivity/sub-1-ghz-group/sub-1-ghz/f/sub-1-ghz-forum/856155/ccs-cc1352r-lqi-calculation

What about the other available measure (symbols correlation)?

In the predecessor's datasheet, we can find more detailed information regarding LQI
https://www.ti.com/lit/ds/symlink/cc2420.pdf
24 Link Quality Indication

Are there any formulas that combine two of them (RSSI and Corr) into LQI?

BR
Adam

0 TER over 4 years ago in reply to Adam Kozlowski

TI__Guru**** 317180 points

You have one option in this post: e2e.ti.com/.../cc1352p-how-to-get-lqi-value-working-on-ieee-802-15-4

0 Ryan Brown1 over 4 years ago

TI__Guru**** 216717 points

Hi Adam,

Here is another more recent E2E thread: https://e2e.ti.com/f/1/t/992257

Regards,
Ryan

0 Adam Kozlowski over 4 years ago in reply to Ryan Brown1

Expert 1805 points

LQI based on RSSI is straightforward, it can be narrowed down to the following rules
- RSSI_MIN - RX sensitivity (-100dBm) + 10dB
- RSSI_MAX - RX sensitivity (-100dBm) + RSSI dynamic range (95dB)

LQI based on Correlation is much more challenging.
Some information regarding min and max value are given in TER's thread.

Anyway, I wonder why there is no characterization with RSSI and CORR readings for various output power for a two-node setup in a non-echoing chamber for the constant distance between nodes (e.g. 1m).

BR
Adam

0 Siri over 4 years ago in reply to Adam Kozlowski

TI__Guru* 85791 points

I am sorry, but this kind of testing has not been done.

Siri

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CC1352R: Link Quality Indicator