Factorization of ppSNR(MMSE) by rankIdx for RI measurement in "5G NR Downlink CSI Reporting" example

In 5G example 5G NR Downlink CSI Reporting - MATLAB & Simulink (mathworks.com)

there is function: [RI,PMISet] = hRISelect(carrier,csirs,reportConfig,H,varargin) .

In short function should calculate post-processingSNR for each valid precode matrix of all valid ranks.

RI will be choosed based on zilion posible cost functions that related in some way to Channel Capacity maximization or weakest Eigan value maximization. In this case i think was used simple "Max-MMSE-PostCP Criterion Based RI Selection"[2].

My question is: What reason to multiply subbandSINRs, which have dimensions [subBand][iLayer], by factor rankIdx.

Line 351 and 353 of presented code

[1]Limited Feedback Unitary Precoding for Spatial Multiplexing Systems David J. Love, Member, IEEE, Robert W. Heath, Jr., Member, IEEE,

[2]Dynamic Transmission Mode Selection in LTE/LTE-Advanced System

Answer 1

[Max]

I would like to know if this is done to compensate for the normalization differences of codebooks with different numbers of ranks utilized in the calculation of SINR？