clc
clear?all
close?all
%?DPSK?system
%?assuming?to?have?ideal?channel?H（z）=1
%?AWGN
%?initiate?variances

symbol_num0=14;
symbol_num=symbol_num0+1;
b_d=zeros（1symbol_num0）;?%?relative?code
Rs=1200;??????????????????%?symbol?rate
T=10;???%?oversampling?7?points?per?symbol
s_t=zeros（1symbol_num*T）;
f_C=1800;?%?the?carrier?frequence?is?1800?Hz
fs=Rs*T;
ts=1/fs;
Eb=1;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%?Tx??%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%?carrier?generate?
t=0:1/fs:（symbol_num*T-1）/fs;
carrier_sig=?sin（2*pi*f_C*t）;

%?code?exchanger?（absolute?to?differential）
b_org=unifrnd（-111symbol_num0）>0;?%?the?absolute?sequence?b_n
%b_org=[1?0?0?1?0?0?1?1];
b_d（1）=1;???????????????????????????%?initiate?the?d_（n-1）‘s?d（1）=1
for?i=2:1:symbol_num????????????????%?get?the?d_（n-1）
????b_d（i）=xor（b_org（i-1）b_d（i-1））;
end

%?generate?the?square?series?with?message
for?n=1:symbol_num*T
????n_temp=ceil（n/T）;
????s_t（n）=b_d（n_temp）;
end

%?another?way?to?generate?the?dpsk?
s1=s_t.*carrier_sig;
s2=（ones（1symbol_num*T）-s_t）.*（-carrier_sig）;
%（-carrier?means?phase?shift?in?pi）
s_t=s1+s2;?%?transmition?signal?is?s_t



EbN0=20;
%%%%%%%%%%%%%%%%%%%?creating?the?AWGN?%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
mu=0;
N0=Eb/（10^（EbN0/10））;
sigma=sqrt（N0*2）;
gs_noise=normrnd（musigma[1?symbol_num*T]）;
%another?way:?awgn（xsnr）
%gs_noise=zeros（1symbol_num*T）;
%gs_noise=awgn（gs_noiseEbN0）;
s_t1=s_t+gs_noise;
%s_t1=awgn（s_tEbN0‘measured‘）;


%%%%%%%%%%%%%%%%%%%%?Rx?DPSK?demodulation?%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%?pass?a?bandpass?filter?to?get?R_temp
lowpassband=f_C-Rs;
highpassband=f_C+Rs;
order=40;?????????%?expecially?the?time?of?T
wn=[lowpassband?highpassband]/（fs/2）;
Filter_coefficient=fir1（orderwn）;
R_temp=filter（Filter_coeffi