nrPolarDecode - Transmit and Decode Polar Encoded Data example

In that example, the output of the decoder was zero. When I run that example, I get some errors and some zero bit errors. If I comment out the modulation/demodulation and AWGN channel (the encoder and decoder only), then I should get zero every time. But that is still not the case. Can anyone explain why that is not zero bit error everytime?

Answer 1

[Adeline]

I understand that you are trying to execute the “nrPolarDecode” example in https://www.mathworks.com/help/5g/ref/nrpolardecode.html. The code will result in zero if you use a default AWGN channel as follows:

chan = comm.AWGNChannel;

instead of

chan = comm.AWGNChannel('NoiseMethod','Variance','Variance',nVar); 

Regarding the scenario where your system only had the encoder and decoder: The input “rxLLR” represents the log-likelihood ratios per bit with a negative bipolar mapping. Here, a 0 should be mapped to 1, and a 1 should be mapped to -1. Therefore, a zero error can be obtained by defining the input to the decoder as mentioned below:

rxLLR = 1.0 - 2.0*double(enc);