How to Generate zero-mean complex Gaussian random variables

[s.asad114]

Im Working on Cooperative communication.i want Generate zero-mean complex Gaussian random variables with variances δ2sd and δ2sr.
im using following Code for this

chan_sd = 1/sqrt(2)*( randn(1, length(Txsig) ) + j*randn(1, length(Txsig) ) );
chan_sr = 1/sqrt(2)*( randn(1, length(Txsig) ) + j*randn(1, length(Txsig) ) );

Txsig is the modulated signal (symbols)
im geting -Ve Mean with it
can any one help me out in this ????

 

[Ahmed Alaa]

Re: How to Generate zero-mean complex Gaussian random variab

I think your commands are right, how did you know that the mean is -ve?

 

[s.asad114]

Re: How to Generate zero-mean complex Gaussian random variab

I think your commands are right, how did you know that the mean is -ve?

Simply by Using Mean command ,
mean(chan_sd)
e.g. -0.003 + i 0.0049

Added after 32 minutes:

i wan to implement following equation
Y_sr = P * H_sr * X + N_sr

subscript _sr shows signal From Source to Relay.

y = O/p Signal
P = Power
H = Channel Response
X = Modulated Symbol
N = Additive Noise
* shows Multiplication not convolution (Single Tap environment )

i'm having problem in producing H & N .In a book im referring Author says
about H_sr "is model as zero-mean, complex Gaussian random variables with variances δsqr s,r
i need to know what is Sigma here .
now For Additive noise
"The noise terms ns,r is modeled as zero-mean complex Gaussian
random variables with variance N0."
i need to know what is N0 here .

im using following Command
Channel Response
chan_sr = 1/sqrt(2)*( randn(1, length(Txsig) ) + j*randn(1, length(Txsig) ) );

additive Noise
N_sr = ( randn( 1,NumBits / BPS ) + 1j * randn( 1,NumBits / BPS ) ) / sqrt( 2 ) *10.^(-SNR/20);

BPS=Bits per symbol. im scaling it with SNR also

PLease Help me Out in Understanding these term so that i can Work