AssertionError: num_effective_subcarriers must be an integer multiple of num_tx*num_streams_per_tx.

[marxwolf]

Hi, I am testing the tutorial, https://nvlabs.github.io/sionna/examples/Realistic_Multiuser_MIMO_Simulations.html
When I set num_ut=100 in cell 3, the execution of cell 6 throws an error out. I search the num_effective_subcarriers, it is self._mask.shape[3]. But in this tutorial, we don't explicitly set the PilotPattern, or mask.

I didn't change other parameters, What am I supposed to do to solve this problem?

[jhoydis]

You are implicitly setting the KroneckerPilotPattern in this example.

rg = ResourceGrid(num_ofdm_symbols=14,
                  fft_size=128,
                  subcarrier_spacing=30e3,
                  num_tx=num_ut,
                  num_streams_per_tx=num_streams_per_tx,
                  cyclic_prefix_length=20,
                  pilot_pattern="kronecker",
                  pilot_ofdm_symbol_indices=[2,11])
rg.show();

The problem with 100 UTs is that this number is not compatible with the FFT size and this pilot pattern. You can try with any fft_size that is a multiple of 100. However, even if you do it, the performance won't be great because each UT sends a pilot on every 100th subcarrier. This is not sufficient for channel estimation in most cases.