OFDMA + Beamforming

[Felix-willaumez]

Hi Sionna team,

We are trying to implement a multiuser system with with 1 base station combining OFDMA and beamforming techniques. Doing so we ran into the following issue:

In the OFDM ZF precoder, the number of streams at TX should be equal to the number of users (times the the amount of antenna they have). We did not find any mention of this constrain anywhere in the doc (we might have miss it) but in the source code it appears pretty clearly in the comments and in the dimensions of the channel and data. Indeed note in the attached screenshot coming from ofdm/precoding.py source code (line 155-162) the renaming of num_streams_per_tx into num_rx_per_tx * num_rx_ant .

We want to overcome this constrain because on top of differentiating the users in space we would like to separate them in the frequency domain is it possible in the Sionna framework or should we implement it ourselves.