模拟噪声的程序，可以根据需要改写，主要功能是实现噪声模型-Additive Noise Channel/Additive Guassian Noise Channel is the simplest of all channels. File usage details:

op_channel = additivenoise(input_signal)

mathematical Model:

s(t) input signal to channel (=sig_ip)

n(t)additive random noise process added by channel (=noise_mat)

a(t) attenutation factor , here it is taken as random(=att_fact)

out put signal r(t) = a .* s(t)+ n(t)

an additional file named through_anc is there which shows 2 figures, 1. input signal 2. output signal