5G Toolbox example: "Downlink Control Processing and Procedures",

HI,

Data should be filled in pdcch REGs in time first fashion, that is, for example if we have 2 symbols then we will have REG0 in first ofdm symbol, REG1 in second ofdm symbol and REG2 again in 1st OFDM symbol and so on, but in each REG data will be inserted in frequency first fashion. My doubt here is that in, "Downlink Control Processing and Procedures" example, function "hPDCCHSpace" is generating a column vector for indexes for pdcch but these indexes are numbered entirely in frequency first fashion and then direct pdcch to REG mapping is performed which i think should not be the case. What i believe should be that the vector should have first 9 indexes of pdcch of REG0 should be created then 9 indexes of REG1(which is in 2nd symbol, so indexe should jump by NRB*12) and so on.

I am a little confused here, can you please explain on this?

Answer 1

[Simon]

Hello,

when looking at the "Downlink Control Processing and Procedures" example from 5G toolbox, i experienced the same confusion as you did. Even if the answer is more than 5 years later probably a little to late for you, i want to post it here to help others with the same problems as us.

The answer is that according to TS 38.211, Section 7.3.2.5, which defines the mapping of physical resources, the mapping is always done in a frequency-first manner, as you also observed in the Matlab example. The confusion comes from how the CCE-to REG mapping is done in a CORESET as described in Section 7.3.2.2 from TS 38.211, telling that the REGs within a CORESET are numbered in an increasing order in a time-first manner. However, this is only relevant for choosing the REGs used for a CORESET-transmission but after the REGs have been chosen, the real physical mapping of resources is done in a frequency-first manner for the chosen resources, as described above.

Hope this helps anyone!