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# BPSK BER in rayleigh IN MATLAB : why noise and channel is the same in matlab.

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#### mazdaspring

##### Advanced Member level 4
BPSK BER in rayleigh IN MATLAB : why noise and channel are the same in matlab.

I have a look on people's matlab on BPSK BER over rayleigh channel.

I don't understand why noise and channel are the same as shown below. so rayleigh channel is the same as noise then?
Can anyone explain it to me please.

noise=1/sqrt(2)*(randn(1,N)+1i*randn(1,N)); %AWGN noise with mean=0 var=1
h=1/sqrt(2)*(randn(1,N)+1i*randn(1,N)); %Rayleigh Flat Fading - single tap

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Re: BPSK BER in rayleigh IN MATLAB : why noise and channel are the same in matlab.

Hi mazdaspring,
I am also new to the fading channel.
Share my point of view with you,
if y = A*x + n,
where
y is the received signal; x is the transmitted signal;
n is complex AWGN with Re[n]=Im[n]=N(0,1);
A fading amplitude and p(A) is rayleigh distribution.

The generation of random variable "A" can be found by using A=\sqrt{a^{2}+b^{2}};
where a and b are i.i.d. and also Gaussian distributed with N(0,1).

So maybe you misunderstand the characteristic of noise and the channel.
They are different but can be generated by using the same i.i.d Gaussian random variable.

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Re: BPSK BER in rayleigh IN MATLAB : why noise and channel are the same in matlab.

In this case, if the average power of transmitted symbol is 1.
The SNR is 0 dB
You can scale the power of noise with some factor and this changes SNR.

I have a look on people's matlab on BPSK BER over rayleigh channel.

I don't understand why noise and channel are the same as shown below. so rayleigh channel is the same as noise then?
Can anyone explain it to me please.

noise=1/sqrt(2)*(randn(1,N)+1i*randn(1,N)); %AWGN noise with mean=0 var=1
h=1/sqrt(2)*(randn(1,N)+1i*randn(1,N)); %Rayleigh Flat Fading - single tap

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