how to select k antenna elements based on their gain

Hi. i am writing a code for 4x4 mimo channel using phased.ULA and scatteringchanmtx for setting properties for array and channel matrix i find out channel gain using [wp,wc,P,G,C] = diagbfweights(chmat). i want to select k antenna elements with largest gains and transmit data through the selected ones only.

i want to analyze the effect on BER after the selection.

i am getting the gains from all the antenna elements but i am not sure how to choose the k elements.

[Honglei Chen]

Could you provide a bit more info? I don't quite understand your question. If you only select a subset of antennas then the channel matrix is different than the case where all antennas are used. Did I miss anything? Is there a reference you can point me to? Thanks.

[Farah Mahmood]

actually i am trying to write a code for massive mimo antenna selection and i wanted to select channel subset matrix based on selecting channel matrix indices which which provide greater eigen values compared to a threshold. however this selection changes the matrix dimension and then a lot of errors appear. i want to compare BER with and without selection