Hello,everyone. Recently I am working on a project of simulating a whole OFDM system.
I have made some progress. Now I want to change me (2,1,7) convolutional code – hard decode to soft-decision decode in order to get a better performance. I have learned from the matlab example how to implement soft-decision decode in an AWGN channel. But now I also want to apply it to a fast and multi-path fading channel. As a result of that, I am not sure about the value of noise power when calculate LLR.
I first pass my signal to a fading channel by using comm.RayleighChannel() , then I add noise by using awgn() block. This will give a noise power value.
[y_re,noise_var]=awgn(x_tr,SNR_dB(i),’measured’);

Then I do LS channel estimation and equalization at the receiver. This will change the value of the signal, so as the value of the noise. So I also calculate the noise power at this time.
noise_var_1= 10^(-SNR_dB(i)/10)* mean(Y_equalized.*conj(Y_equalized));
The two power values will be totally different since one is computed with the channel effect and one is not (with channel equalization). So wich value should I use to calculate LLR?
Thanks for your reading and hope you have some ideas about this question.Hello,everyone. Recently I am working on a project of simulating a whole OFDM system.
I have made some progress. Now I want to change me (2,1,7) convolutional code – hard decode to soft-decision decode in order to get a better performance. I have learned from the matlab example how to implement soft-decision decode in an AWGN channel. But now I also want to apply it to a fast and multi-path fading channel. As a result of that, I am not sure about the value of noise power when calculate LLR.
I first pass my signal to a fading channel by using comm.RayleighChannel() , then I add noise by using awgn() block. This will give a noise power value.
[y_re,noise_var]=awgn(x_tr,SNR_dB(i),’measured’);

Then I do LS channel estimation and equalization at the receiver. This will change the value of the signal, so as the value of the noise. So I also calculate the noise power at this time.
noise_var_1= 10^(-SNR_dB(i)/10)* mean(Y_equalized.*conj(Y_equalized));
The two power values will be totally different since one is computed with the channel effect and one is not (with channel equalization). So wich value should I use to calculate LLR?
Thanks for your reading and hope you have some ideas about this question. Hello,everyone. Recently I am working on a project of simulating a whole OFDM system.
I have made some progress. Now I want to change me (2,1,7) convolutional code – hard decode to soft-decision decode in order to get a better performance. I have learned from the matlab example how to implement soft-decision decode in an AWGN channel. But now I also want to apply it to a fast and multi-path fading channel. As a result of that, I am not sure about the value of noise power when calculate LLR.
I first pass my signal to a fading channel by using comm.RayleighChannel() , then I add noise by using awgn() block. This will give a noise power value.
[y_re,noise_var]=awgn(x_tr,SNR_dB(i),’measured’);

Then I do LS channel estimation and equalization at the receiver. This will change the value of the signal, so as the value of the noise. So I also calculate the noise power at this time.
noise_var_1= 10^(-SNR_dB(i)/10)* mean(Y_equalized.*conj(Y_equalized));
The two power values will be totally different since one is computed with the channel effect and one is not (with channel equalization). So wich value should I use to calculate LLR?
Thanks for your reading and hope you have some ideas about this question. ofdm, soft-decison decode MATLAB Answers — New Questions

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