nrDCIEncode versus physical layer subcomponents

Question

Alireza 2023-2-3

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https://ww2.mathworks.cn/matlabcentral/answers/1905896-nrdciencode-versus-physical-layer-subcomponents

回答： Saffan 2023-5-4

I expect the MATLAB function nrDCIEncode to return the same output as when the chain of nrCRCEncode, nrPolarEncode, and nrRateMatchPolar functions are used for encoding DCI. In other words, rate_matched_dci_bits in the following code is expected to be equal to dcicw. But it is not! Why?

A = 64;
poly = '24C';
rnti = 100;
E = 864;
L = 24;
n_max = 9;
iil = true;
ibil = false;
K = A + L;
dci_bits = randi([0 1] , A , 1 , 'int8');
crc_attached_dci_bits = nrCRCEncode(dci_bits , poly , rnti);
polar_encoded_dci_bits = nrPolarEncode(crc_attached_dci_bits , E , n_max , iil);
rate_matched_dci_bits = nrRateMatchPolar(polar_encoded_dci_bits , K , E , ibil);
dcicw = nrDCIEncode(dci_bits , rnti , E); 

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Answer 1

Saffan 2023-5-4

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https://ww2.mathworks.cn/matlabcentral/answers/1905896-nrdciencode-versus-physical-layer-subcomponents#answer_1229039

Hi Alireza,

The reason for the difference comes from the implementation of "nrDCIEncode" function. The implementation in this function is different from the way you are encoding in the following ways:

The “nrDCIEncode” function contains an additional step of prepending 24 ones to the input bits before calculating the CRC.
It then removes the ones after CRC is calculated before proceeding to channel coding and rate matching.

Additionally, it also includes a step for converting the 24 CRC bits to a MSB first decimal representation using a binary-to-decimal conversion formula.