2 years ago.  This question has been closed. Reason: Duplicate question

Wrong calulation of RSSI in UBloxCellularBase ?

Hi

We are using the RSSI function in UbloxCellularBase to measure signal quality on our custom board with a Ublox SARA-U201 modem. The performance of the signal/antenna seems very poor and we have investigated the electronics and couldn't find anything.

I researched the Ublox AT manual and the UbloxCellularBase and I think there is a problem with the RSSI calculation.

According to the Ublox AT Manual the RSSI is calculated with this formula:

RSCP (dBm) = RSSI (dBm) - EC_NO_LEV (dB)

Looking into the library it seems the EC_NO_LEVEL is used. This is a level and not a value as specified by 3GPP. See the pictures below.

I have changed the conversion table in the library to use these interpolated values:

const int qualConvert3G[] = {21, 18, 15, 12, 9, 6, 3, 0};

and the RSSI result looks much better and what we expected. What is your take on this ?

3GPP EC_NO levels and values:

/media/uploads/jensoleg/sk-rmbillede_2018-06-29_kl._16.10.24.png

Table is from https://www.etsi.org/deliver/etsi_ts/125100_125199/125133/10.03.00_60/ts_125133v100300p.pdf