Understanding the shape of the csi array

[mamdouhJ]

Im collecting CSI based on the Atheros library. Im using csiread to parse the binary data and get the readings. The shape Im having is [40,56,2,2]. As far as I know 40 is the received packets, 56 is the number of subcarriers, one of the 2s is the number of antennas but I don't know what the other 2 refers. Thanks!

[citysu]

csidata.csi.shape is [packet_num, tones, nrxnum, ntxnum], but for each packet, [csidata.num_tones, csidata.nr, csidata.nc] is the real shape. csidata.csi is a container.