clear;?close?all;

%?Simulate?continuous?time
f_s?=?2000000;????%?400?kHz?（sampling?rate）
T=0.1;???????????%?0.1?second
samples=f_s*T;???%?total?number?of?samples?simulated
t=（0:（samples-1））/f_s;?%time?axis

%?Generate?bits
f_b=20000;???????%?bit_rate?=?20?kbps
bits=f_b*T;??????%?number?of?bits?simulated
rand（‘seed‘0）;??%?
b=round（rand（1bits））;?%?random?source?bits


%?Generate?Symbols:?QPSK?symbols
bits_per_symbol=2;
f_symbol?=?f_b/bits_per_symbol;????%?symbol?rate?=?20?ksym/s
symbols=?bits/bits_per_symbol;?????%?number?of?BPSK?symbols
samples_per_symbol=f_s/f_symbol;???%?number?of?samples?per?BPSK?symbol?（20）


b_mat=reshape（bbits_per_symbolsymbols）;
b_1=b_mat（1:）;
b_2=b_mat（2:）;
?
j=sqrt（-1）;
a??=??1/sqrt（2）;???????%?amplitude?????
xk=a*（（1-2*b_1）+j*（1-2*b_2））;?%?QPSK?symbols
%?figure;
%?subplot（211）
%?stem（0:1/f_symbol:（1/f_symbol）*49real（xk（1:50）））;
%?title（‘the?plot?of?real[xk]‘）;
%?xlabel（‘time（s）‘）;
%?ylabel（‘Amplitude‘）;
%?subplot（212）
%?stem（0:1/f_symbol:1/f_symbol*49imag（xk（1:50）））;
%?title（‘the?plot?of?imag[xk]‘）;
%?xlabel（‘time（s）‘）;
%?ylabel（‘Amplitude‘）;





%?Upsampling?to?simulate?impulses?in?continuous?time
x_up?=?upsample（xk?samples_per_symbol?samples_per_symbol/2）;

roll_off=0.5;????????????%?filter‘s?roll-off?factor
f_cut_off?=?f_symbol/2;??%?filter‘s?cut-off?frequency
filter_order=10;????????%?filter‘s?order/factor
????
%?Tx/Rx?filter
B_rrcos=sqrt（samples_per_symbol）*firrcos（filter_order*samples_per_symbolf_cut_offroll_offf_s‘rolloff‘‘sqrt‘）;

%?Tx?filter
xt=filter2（B_rrcosx_up）;
%?x（t）?=>?after?up_sampling?and?transmit?filter

%?Channel
c????=?[10.5];?????????????????????????????%?channel?profile
c_up?=?upsample（c?samples_per_symbol）;?%?upsampling?the?channel

%?convolution?of?x（t）?and?c（t）
xc?=?filter（c_up?1?xt）;

%?Rx?filter
xhat=filter2（B_rrcosxc）;

%?Eye?Diagram
repetition=?200;?????%?number?of?repetitions?for?the?drawing?of?the?eye?diagram
EYE?=?zeros（2*samples_per_symbol?repetition）;?%?Two?periods?draw?200（=repetition）?times
EYE（:）?=?xhat（samples_per_symbol*filter_order+1:（2*samples_per_symbol）*repetition+samples_per_symbol*filter_order）‘;??

%subplot（211）;
%plot（1:2*samples_per_symbolreal（EYE））;?grid;
%title（[‘Real?Eye?Diagram?（Received?QPSK?S