% Simulation program to realize DS-CDMA system
%
% dscdmabpsk.m
%
%

%******************** Preparation part **********************

sr=256000.0; % Symbol rate
ml=1;        % Number of modulation levels
br=sr.*ml;   % Bit rate (=symbol rate in this case)
nd = 2;
N=nd;% Number of symbols that simulates in each loop
snr_in_dB=3;
ebn0=10^(snr_in_dB/10);     % Eb/N0
IPOINT=8;    % Number of oversamples

%******************* Filter initialization ********************

irfn=21;     % Number of filter taps          
alfs=0.5;    % Rolloff factor
[xh] = hrollfcoef(irfn,IPOINT,sr,alfs,1);   %Transmitter filter coefficients 
[xh2] = hrollfcoef(irfn,IPOINT,sr,alfs,0);  %Receiver filter coefficients 

m=8;    %擴頻碼的碼片數目


%********************** Spreading code initialization **********************

user  = 2;                                                          % number of users
seq   = 3;                                                          % 1:M-sequence  2:Gold  3:Orthogonal Gold
stage = 3;                                                          % number of stages
ptap1 = [1 3];                                                      % position of taps for 1st
ptap2 = [2 3];                                                      % position of taps for 2nd
regi1 = [1 1 1];                                                    % initial value of register for 1st
regi2 = [1 1 1];                                                    % initial value of register for 2nd

%******************** Generation of the spreading code *********************

switch seq
case 1                                                              % M-sequence
    code = mseq(stage,ptap1,regi1,user);
case 2                                                              % Gold sequence
    m1   = mseq(stage,ptap1,regi1);
    m2   = mseq(stage,ptap2,regi2);
    code = goldseq(m1,m2,user);
case 3                                                              % Orthogonal Gold sequence
    m1   = mseq(stage,ptap1,regi1);
    m2   = mseq(stage,ptap2,regi2);
    code = [goldseq(m1,m2,user),zeros(user,1)];
end
code = code * 2 - 1
clen = length(code);

%**************************** START CALCULATION ****************************

nloop = 1000;                                                       % simulation number of times
noe   = 0;
nod   = 0;

%for iii=1:nloop
    
%****************************** Transmitter ********************************
    data = rand(1,nd*ml) > 0.5;
    
%******************** 第一路 BPSK 調制 ***********************  

      data1=data.*2-1 %————————測試點————————

%********************擴展原始碼元以實現擴頻序列*************
%for i=1:N
    %for j=(m*(i-1)+1):m*i
      % data1((m*(i-1)+1):m*i)=data1(i)*code(1,:)      %第一路天線需要發射的信號————————測試點
%end
data1=spread(data1,code(1,:))    %第一路天線需要發射的信號————————測試點16  nd=2
%data8=despread(data1,code)%-------可以用于檢測
[data2] = oversamp( data1, N*m , IPOINT)                 %128  -1,0,1
[data3] = conv(data2,xh) % conv: built in function--------測試點  295

%******************** 第二路 BPSK 調制 ***********************  

      data_1=data.*2-1;   %————————測試點————————

%********************擴展原始碼元以實現擴頻序列*************

data_1=spread(data_1,code(2,:)) %第二路天線需要發射的信號————————測試點16
[data_2] = oversamp( data_1, N*m , IPOINT)                 %128  -1,0,1
[data_3] = conv(data_2,xh) % conv: built in function--------測試點  295


%******************產生空間路徑衰落系數矩陣*******************
Nr=1;
Nt=2;
t=1;
h=mimo_channel(Nr,Nt,t)  %********2 x 1 天線********
receiver1=1/sqrt(2)*(h(1,1)*data3+h(1,2)*data_3)  %------295 復數

%****************** Attenuation Calculation *****************
	
    spow=sum(data3.*data3)/nd;%————————————————————————？？？？
	attn=0.5*spow*sr/br*10.^(-ebn0/10);
	attn=sqrt(attn);
  

%************ Add White Gaussian Noise (AWGN) ***************
	
    inoise=randn(1,length(data3)).*attn;  % randn: built in function
	data4=receiver1+inoise  %-------295復數
	data5=conv(data4,xh2)  % conv: built in function  ---------462復數

	sampl=irfn*IPOINT+1;
	data6 = data5(sampl:8:8*nd+sampl-1)  %-------2個復數 
    
    
 %****************************解擴信號************************
           
   data7=code(1,:)'*data6       
 %data7=despread(data6,code(1,:))
           data8=despread(data6,code(2,:));
           data9=conj(h(1,1))*data7+conj(h(1,2))*data8;
    
   
%******************** BPSK Demodulation *********************

                 demodata=data9 > 0;
    
%******************** Bit Error Rate (BER) ******************
	
    % count number of instantaneous errors
    noe2=sum(abs(data-demodata));  % sum: built in function
	
    % count number of instantaneous transmitted data
    nod2=length(data);  % length: built in function
	
    noe=noe+noe2;
	nod=nod+nod2;

	fprintf('%d\t%e\n',iii,noe2/nod2);
%end % for iii=1:nloop    

%********************** Output result ***************************

dscdma_open_ber = noe/nod;
fprintf('%d\t%d\t%d\t%e\n',snr_in_dB,noe,nod,noe/nod);


%******************** end of file ***************************