function  ch_out_signal=APSK_channel(ch_in_signal,p_noise)
len=length(ch_in_signal);
ch_in_R=real(ch_in_signal);
ch_in_I=imag(ch_in_signal);
randn('state',sum(100*clock));
ch_in_R=ch_in_R+randn(size(ch_in_R))*p_noise;
ch_in_I=ch_in_I+randn(size(ch_in_I))*p_noise;
for i=1:len
    ch_out_signal(i)=ch_in_R(i)+j*ch_in_I(i);
end