signal processing - What is theory behind AWGN channel command matlab -


kindly tell me theory behind 2 commands (marked ***) of awgn channel in below shown code.

code: 

n_all = [10^3*ones(1,6) 10^3*ones(1,5)]; eb_no = [0:2:20]; ii=1:length(eb_no)      n = n_all(ii);      b = (1/sqrt(2))*rand(1,n)>0.5;      ip = qpsk_new(b);      s = ip; ***  noise = 1/sqrt(2) * [randn(1,n/2)+j*randn(1,n/2)]; ***  y = s+10^(-eb_no(ii)/20)*noise; end

the randn function in first marked line generates complex, gaussian-distributed (1), independent (2) samples 0 mean , unit variance. second marked line scales samples according specified signal-to-noise ratio (eb/n0) , adds (3) them signal.

these operations stem definition of awgn:

  1. the "g" in "awgn" means "gaussian".
  2. the "w" means "white". term "white" applied stochastic process means samples statistically independent (or uncorrelated; in gaussian case equivalent conditions).
  3. the "a" "additive", add noise signal.

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