Why does nrSSBMeasurements use UE generated reference signal when measuring SS-RSRP?

3GPP describes SS-RSRP as the linear average over the power contributions of the resource elements that carry secondary synchronization signals (TS 38.215 5.1.1).

The corresponding code in nrSSBMeasurements from 5G Toolbox is

refSSS=nrSSS(nCellID);

% RSRP - Use reference symbols to get most accurate power readings
meas.RSRPPerAntenna(rxAntIdx) = abs(mean(ssblock(sssInd).*conj(refSSS))).^2;

It is not clear to me why they used reference symbols at all as it has nothing to do with the power of the received sequence. I was expecting implementation to be something more like

sss = ssblock(sssInd);
ssrsrp = (sss'*sss)/numel(sss);

Am I missing something?

Answer 1

[Harsh]

Hi Utku,

As per the 3GPP definition, reference signal received power (RSRP) is defined as the linear average over the power contributions (in [W]) of the resource elements that carry cell-specific reference signals within the considered measurement frequency bandwidth.

Therefore, SS-RSRP is nothing but the measure of RSRP for synchronization signals.

In 3GPP (TS 38.215 5.1.1), it is further mentioned that SS-RSRP shall be measured only among the reference signals corresponding to SS/PBCH blocks with the same SS/PBCH block index and the same physical-layer cell identity. It can be observed that this definition corresponds to the code implementation in the 5G toolbox.

Additionally, the RSRP measure is used to rank different candidate cells as per their signal strength. Therefore, the reference signals are important for generating the RSRP measures.

I hope this helps.