Error in resource grid 624 subcarriers and 8 streams

[alejandroBlancoPizarro]

Dear Sionna community,

I am trying to simulate a 5G link using 10MHz (624 subcarriers) and 8 streams.

However, I got an error when calling the ResourceGrid function. This error applies only to 8 streams, for 2 and 4 streams works fine.

The Sionna version is 0.16.

Below is a screenshot of the error. I understand from the error that the size of the calculated pilots is not the same as the allocated positions of the pilots, but I am not sure how to handle it.

[jhoydis]

Hi @alejandroBlancoPizarro,

Thanks for reporting this issue. We'll look into it. In the meantime, you could just create a custom pilot pattern yourself. It should not be too difficult. Just allocate random QAM symbols for every stream on non-overlapping elements of the OFDM symbols dedicated to pilots. Just look at the patterns for 2 and 4 streams as examples.

[alejandroBlancoPizarro]

Hello Jakob,

Ok, I will try your solution, it looks feasible to me.

Thanks and best regards,
Alejandro

[SebastianCa]

Hi @alejandroBlancoPizarro,

The issue with your code is that num_effective_subcarriers=612 is not a multiple of num_streams=8. Sionna should raise an assertion in such cases. This will be fixed in the next release of Sionna.

As a workaround, you can either remove the guard carriers (including DC nulling) or adjust the fft_size accordingly.

[alejandroBlancoPizarro]

Hello @SebastianCa,

Thanks for the clarification. I removed the guard carriers and the error is gone.

We can close this issue.

Best,
Alejandro