CC2652P: Questions about rssi and linkquality relationship.

yingtao jia

Expert 1280 points

Part Number: CC2652P

Hi, Hi, I use CC2652P, simplelink_cc13x2_26x2_sdk_4_40_04_04, CCS10.2.

I found questions when I test 802.15.4 data tx.

In this site, https://e2e.ti.com/support/wireless-connectivity/zigbee-and-thread/f/158/t/953342

it says that RSSI = LQI * 0.38 - 87;

I test this in dataIndCb which support LQI and RSSI both.

And I get data as below:

RSSI : -73dBm, LQI : 51
RSSI : -72dBm, LQI : 54
RSSI : -71dBm, LQI : 57 
RSSI : -64dBm, LQI : 78
RSSI : -63dBm, LQI : 81

Do plot in MATLAB is below:

It's very linear. Using polyfit in MATLAB as below

It shows that RSSI = LQI * 0.33 - 90.

So, two results about relationship between RSSI and LQI, which one is correct?

Thanks.

over 4 years ago

+1 Ryan Brown1 over 4 years ago

TI__Guru**** 217867 points

Hey yingtao,

Thank you for providing the results of your investigation. I checked the MAC source and Hector's formula is still applicable. However, ED_RF_POWER_MAX_DBM has been modified to -5 dBm as well as ED_RF_POWER_MIN_DBM to -90 for this device family. With these values, I get the exact same formula you've deduced.

Regards,
Ryan

+1 dAVID over 4 years ago

Intellectual 790 points

Hi YingTao and Ryan,

Formula and (-5dBm and -90dBm) has been verified on ti154stack and zstack of simplelink_cc13x2_26x2_sdk_4_40_04_04.

LQI = (MAC_SPEC_ED_MAX * (RSSIdbm - ED_RF_POWER_MIN_DBM)) / (ED_RF_POWER_MAX_DBM - ED_RF_POWER_MIN_DBM);

where MAC_SPEC_ED_MAX = 255, ED_RF_POWER_MIN_DBM = -90,ED_RF_POWER_MAX_DBM = -5

Best regards,

David

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CC2652P: Questions about rssi and linkquality relationship.