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While reading 3gpp 38.211, Chapter 6.3.1.5 I noticed

For non-codebook-based transmission, the precoding matrix equals the identity matrix.

So, I guess, non-codebook-based precoding shall be implemented somewhere else but I couldn’t find where. No page in the 3gpp spec has information about this. Where could I find implementation details?

Marcus Müller
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Dmitriy
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  • ok, it means bypass mode. Where precoding by a non-codebook matrix shall take place? – Dmitriy Nov 22 '21 at 16:47
  • The values of such matric are arbitrary numeric values. There is no sense using identity matrix. Sorry, I don't understand your point. – Dmitriy Nov 22 '21 at 16:51
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    The idea behind non-codebook precoding is that precoding matrix is not selected from a set (codebook) but is evaluated using DL/UL channel reciprocity. The 3GPP implicitly defines the place where codebook precoding takes place, but says nothing about non-codebook. – Dmitriy Nov 22 '21 at 16:58
  • Read 38.214 6.1.1.2 and see https://youtu.be/lI0TSXb9sq0?t=602 – AlexTP Nov 22 '21 at 17:24
  • I still don't get the idea where the multiplication by non-codebook matrix takes place. What I got is that SRS should be affected by it, so it happens after SRS multiplexing. – Dmitriy Nov 23 '21 at 14:16

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