ds-cdma.m

DS-CDMA仿真程序,有大量注释,很值得一看,全面的讲解了CDMA的原理.

% Program 5-6
%
% Simulation program to realize DS-CDMA system
%
% dscdma.m
%
% Programmed by yixiongshu,2006.8.9
clear all;
clc;

%----------------------preparation part -----------------------------
sr=256000.0;                            % symboll rate
ml=2;                                       % number of modulation levels
br=sr*ml;  % bit rate
nd=100;    % number of symbol
ebno=8;    % Ebno

%-----------------------------------------------Filter initialization-----------------
irfn=21;
IPOINT=8;
alfs=0.5;
[xh]=hrollfcoef(irfn,IPOINT,sr,alfs,1);       % Transmitting Filter
[xh2]=hrollfcoef(irfn,IPOINT,sr,alfs,0);      % Received Filter

%------------------------------ Spreading code initialization--------------------
user=1;   % number of users
seq=1;  % 1:m-sequence     2:Gold    3:orthogonal Gold
stage=3;
ptap1=[1 3];
ptap2=[2 3];
regi1=[1 1 1];
regi2=[1 1 1];

% ----------------------------- Generation of the spreading code --------
switch seq
    case 1
        code=mseq(stage,ptap1,regi1,user);
    case 2
        m1=mseq(stage,ptap1,regi1);
        m2=mseq(stage,ptap2,regi2);
        code=goldseq(m1,m2,user);
    case 3
        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);

% ---------------------------------- Fading initialization ---------------
rfade=0;   % Rayleigh fading  0:nothing  1:consider
itau=[0,8];   % delay time
dlvl1=[0.0,40.0];  % attenuation level
n0=[6,7];
th1=[0.0,0.0];
itnd1=[3001,4004];
now1=2;
tstp=1/sr/IPOINT/clen;  % time resolution
fd=160;
flat=1;
itnde1=nd*IPOINT*clen*30;

% ----------------------------- Start calculation -------------
nloop=1000;
noe=0;
nod=0;

for ii=1:nloop
    
    % -------------------------- Transmitter ---------------------
    data=rand(user,nd*ml)>0.5;
    [ich,qch]=qpskmod(data,user,nd,ml);
    
    [ich1,qch1]=spread(ich,qch,code);
    
    [ich2,qch2]=compoversamp2(ich1,qch1,IPOINT);
    [ich3,qch3]=compconv2(ich2,qch2,xh);
    
    if user==1
        ich4=ich3;
        qch4=qch3;
    else
        ich4=sum(ich3);
        qch4=sum(qch3);
    end

 % -------------------------- Fading channel -------------------
 if rfade==0
     ich5=ich4;
     qch5=qch4;
 else
     [ich5,qch5]=sefade(ich4,qch4,itau,dlvl1,th1,n0,itnd1,...
         now1,length(ich4),tstp,fd,flat);
     itnd1=itnd1+itnde1;
 end
 
 % ---------------------------------- Receiver  -----------------------------
 spow=sum(rot90(ich3.^2+qch3.^2))/nd;
 attn=sqrt(0.5*spow*sr/br*10^(-ebno/10));
 
 [ich6,qch6]=comb2(ich5,qch5,attn);
 
 [ich7,qch7]=compconv2(ich6,qch6,xh2); % filter
 
 samp1=irfn*IPOINT+1;
 ich8=ich7(:,samp1:IPOINT:IPOINT*nd*clen+samp1-1);
 qch8=qch7(:,samp1:IPOINT:IPOINT*nd*clen+samp1-1);
 
 [ich9 qch9]=despread(ich8,qch8,code);
 
 demodata=qpskdemod(ich9,qch9,user,nd,ml);   % QPSK demodulation
 
 %--------------------- BER -----------------------------
 noe2=sum(sum(abs(data-demodata)));
 nod2=user*nd*ml;
 noe=noe+noe2;
 nod=nod+nod2;
 
%  fprintf('%d\t%e\n',ii,noe2/nod2);
end

% ------------------------------Data file --------------------------

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

fid=fopen('BER.mat','a');
fprintf(fid,'%d\t%d\t%d\t%e\n',ebno,noe,nod,ber);

fclose(fid);

% --------------------------- end of file ----------------------

 

% Program 5-11
% comb2.m
% Function to add white gaussian noise.
% Programmed by yixiongshu.2006.8.9

function [iout,qout]=comb2(idata,qdata,attn)
%
% attn: attenuation level causedby ebno or C/N
%
v=length(idata);
h=length(attn);

iout=zeros(h,v);
qout=zeros(h,v);

for ii=1:h
    iout(ii,:)=idata+randn(1,v)*attn(ii);
    qout(ii,:)=qdata+randn(1,v)*attn(ii);
end 

% end of file.

 

% Program 5-10
% compconv2.m
% Function to perform convolution between signal and filter.
% Programmed by yixiongshu,2006.8.9

function [iout,qout]=compconv2(idata,qdata,filter)

% : filter tap coefficients.
iout=conv2(idata,filter);
qout=conv2(qdata,filter);

% end of file.

 

% Program 5-9
% compoversamp2.m
%
% Function to sample "sample"time
%
% programmed by yixiongshu.2006.8.9
function [iout,qout]=compoversamp2(iin,qin,sample)
%
% iin : input Ich sequence
% qin :input Qch sequence
% iout: ich output data sequence
% qout : qch output data sequence
% sample : Number of oversamples.

%--------------------------------------------------------------
[h,v]=size(iin);

iout=zeros(h,v*sample);
qout=zeros(h,v*sample);

iout(:,1:sample:1+sample*(v-1))=iin;
qout(:,1:sample:1+sample*(v-1))=qin;

% end of file.

 

% Program 5-1
% autocorr.m
% 
% Autocorrelation function of a sequence
%
% Programmed by yixoingshu,2007.8.9
%
function [out]=autocorr(indata,tn)
% indata: input sequence
% tn     :  number of period
% out   :  atuocorrelation data
%--------------------------------------------------------------------------
if nargin<2
    tn=1;
end
N=length(indata);
out=zeros(1,N*tn);

for ii=0:N*tn-1
    out(ii+1)=sum(indata.*shift(indata,ii,0));
end

% end of file

% Program 5-2
% crosscorr.m
%
% Crosscorrelation function of a sequence 
%
% Programmed by yixiongshu,2008.8.9
function [out]=crosscorr(indata1,indata2,tn)
%
% indata1: input sequence1
% indata2: input sequence2
% tn        : number of period 
% out      : crosscorrelation data
%----------------------------------------------------------------------
if nargin<3
    tn=1;
end 
N=length(indata1);
out=zeros(1,N*tn);

for ii=0:N*tn-1
    out(ii+1)=sum(indata1.*shift(indata2,ii,0));
end

% end of file.

 

% delay.m
% Gives delay to input signal
%
function [iout,qout]=delay(idata,qdata,nsamp,idel)

%*************************** variables ************************
iout=zeros(1,nsamp);
qout=zeros(1,nsamp);
if idel~=0
    iout(1:idel)=zeros(1,idel);
    qout(1:idel)=zeros(1,idel);
end
iout(idel+1:nsamp)=idata(1:nsamp-idel);
qout(idel+1:nsamp)=qdata(1:nsamp-idel);

 

% Program 5-8
% despread.m
%
% Data despread function.
% Programmed by yixiongshu.2006.8.9
function [iout,qout]=despread(idata,qdata,code1)
%
% idata : ich data sequence.
% qdata : qch data sequence.
% iout : ich output data sequence
% qout : qch output data sequence
% code1 : spread code sequence

%
switch nargin
    case{0,1}
        error('lack of input argument');
    case 2
        code1=qdata;
        qdata=idata;
end
[hn,vn]=size(idata);
[hc,vc]=size(code1);

vn=fix(vn/vc);
iout=zeros(hc,vn);
qout=zeros(hc,vn);

for ii=1:hc
    iout(ii,:)=rot90(flipud(rot90(reshape(idata...
        (ii,:),vc,vn)))*rot90(code1(ii,:),3));
    qout(ii,:)=rot90(flipud(rot90(reshape(qdata...
        (ii,:),vc,vn)))*rot90(code1(ii,:),3));
end

% end of file.

 

% fade.m
%
% Generate Rayleigh fading

function [iout,qout,ramp,rcos,rsin]=fade(idata,qdata,...
    nsamp,tstp,fd,no,counter,flat)

%****************************** varibles *********************
% idata: input Ich data
% qdata: input Qch data
% iout:  output Ich data
% qout:  output Qch data
% ramp:  Amplitude contaminated by fading
% rcos:  Cosine value contaminated by fading
% rsin:  Sine value contaminated by fading
% nsamp: Number of samples to be simulated
% tstp:  Minimum time resolution
% fd:    maximum doppler frequency
% no:    number of waves in order to generate fading
% counter : fading counter
% flat:     flat fading or not
% (1-flat (only amplitude is fluctuated),0-normal(phase and amplitude are
% fluctutated))
%****************************************************************
if fd~=0.0
    ac0=sqrt(1.0./(2.0.*(no+1)));
    as0=sqrt(1.0./(2.0.*no));
    ic0=counter;
    pai=3.14159265;
    wm=2.0.*pai.*fd;
    n=4.0*no+2;
    ts=tstp;
    wmts=wm.*ts;
    paino=pai./no;
    
    xc=zeros(1,nsamp);
    xs=zeros(1,nsamp);
    ic=[1:nsamp]+ic0;
    
    for nn=1:no
        cwn=cos(cos(2.0.*pai.*nn./no).*ic.*wmts);
        xc=xc+cos(paino.*nn).*cwn;
        xs=xs+sin(paino.*nn).*cwn;
    end
    cwmt=sqrt(2.0).*cos(ic.*wmts);
    xc=(2.0.*xc+cwmt).*ac0;
    xs=2.0.*xs.*as0;
    ramp=sqrt(xc.^2+xs.^2);
    rcos=xc./ramp;
    rsin=xs./ramp;
    if flat==1
        iout=sqrt(xc.^2+xs.^2).*idata(1:nsamp);
        qout=sqrt(xc.^2+xs.^2).*qdata(1:nsamp);
    else
        iout=xc.*idata(1:nsamp)-xs.*qdata(1:nsamp);
        qout=xs.*idata(1:nsamp)+xc.*qdata(1:nsamp);
    end
else
    iout=idata;
    qout=qdata;
end

 

% Program 5-5
% goldseq.m
%
% The generation function of Gold sequence
%
% Programmed by yixiongshu,2006.8.9
function [gout]=goldseq(m1,m2,n)
%
% m1 : m-sequence 1
% m2:  m-sequence 2
% n   : Number of output sequence (It can be omitted)
% gout :output Gold sequence
%
if nargin<3
    n=1;
end 
gout=zeros(n,length(m1));
for ii=1:n
    gout(ii,:)=xor(m1,m2);
    m2=shift(m2,1,0);
end

% end of file.

 

% hrollfcoef.m
%
%  Generate coefficients of Nyquist filter

function [xh]=hrollfcoef(irfn,ipoint,sr,alfs,ncc)

xi=zeros(1,irfn*ipoint+1);
xq=zeros(1,irfn*ipoint+1);
point=ipoint;
tr=sr;
tstp=1.0./tr./ipoint;
n=ipoint.*irfn;
mid=(n./2)+1;
sub1=4.0.*alfs.*tr;

for i=1:n
    icon=i-mid;
    ym=icon;
    if icon==0.0
        xt=(1.0-alfs+4.0.*alfs./pi).*tr;
    else
        sub2=16.0.*alfs.*alfs.*ym.*ym./ipoint./ipoint;
        if sub2~=1.0
            x1=sin(pi*(1.0-alfs)/ipoint*ym)./pi./...
                (1.0-sub2)./ym./tstp;
            x2=cos(pi*(1.0+alfs)/ipoint*ym)./pi.*sub1./(1.0-sub2);
            xt=x1+x2;
        else
            xt=alfs.*tr.*((1.0-2.0/pi).*cos(pi/4.0/alfs)+(1.0+2.0./pi).*...
                sin(pi/4.0/alfs))./sqrt(2.0);
        end
    end
    if ncc==0
        xh(i)=xt./ipoint./tr;
    elseif ncc==1
        xh(i)=xt./tr;
    else
        error('ncc error');
    end
end

 

% Program 5-4
% mseq.m
%
% The generation function of m-sequence
%
% An example
% stg=3
% taps=[1,3]
% inidata=[1,1,1]
% n=2
%
% Programmed by yixiongshu,2006.8.9
function [mout]=mseq(stg,taps,inidata,n)
% stg : Number of stages
% taps: Position of register feedback
% inidata : Initial sequence
% n : Number of output sequence (it can be omitted)
% mout : output m-sequence
%
if nargin<4
    n=1;
end

mout=zeros(n,2^stg-1);
fpos=zeros(stg,1);
fpos(taps)=1;

for ii=1:2^stg-1
    mout(1,ii)=inidata(stg);
    num=mod(inidata*fpos,2);
    
    inidata(2:stg)=inidata(1:stg-1);
    
    inidata(1)=num;
    
end
if n>1
    for ii=2:n
        mout(ii,:)=shift(mout(ii-1,:),1,0);
    end
end

% end of file.

 

% qpskdemod.m
function [demodata]=qpskdemod(idata,qdata,para,nd,ml)

demodata=zeros(para,ml*nd);
demodata((1:para),(1:ml:ml*nd-1))=idata((1:para),(1:nd))>=0;
demodata((1:para),(2:ml:ml*nd))=qdata((1:para),(1:nd))>=0;

 

% qpskmod.m
function [iout,qout]=qpskmod(paradata,para,nd,ml)
m2=ml./2;
paradata2=paradata.*2-1;
count2=0;

for jj=1:nd
    isi=zeros(para,1);
    isq=zeros(para,1);
    for ii=1:m2
        isi=isi+2.^(m2-ii).*paradata2((1:para),ii+count2);
        isq=isq+2.^(m2-ii).*paradata2((1:para),m2+ii+count2);
    end
    iout((1:para),jj)=isi;
    qout((1:para),jj)=isq;
    count2=count2+ml;
end

 

% sefade.m
%
% This function generates frequency selecting fading
%
function [iout,qout,ramp,rcos,rsin]=sefade(idata,qdata,itau,...
    dlvl,th,n0,itn,n1,nsamp,tstp,fd,flat)

%************************ variables *****************************
% idata input Ich data
% qdata input  Qch data
% iout output Ich data
% qout output Qch data
% ramp : Amplitude contaminated by fading
% rcos : Cosine value contaminated by fading
% rsin : Sine value contaminated by fading
% itau : Delay time for each multipath fading
% dlvl : Attenuation level for each multipath fading
% th   : Initialized phase for each multipath fading
% n0   : Number of waves in order to generate each multipath fading
% itn  : Fading counter for each multipath fading
% n1   : Number of summation for direct and delayed waves
% nsamp: Total number of symbols 
% tstp : Minimum time resolution
% fd   : Maximum doppler frequency
% flat : flat fading or not

iout=zeros(1,nsamp);
qout=zeros(1,nsamp);

total_attn=sum(10.^(-1.0.*dlvl./10.0));
for k=1:n1
    atts=10.^(-0.05.*dlvl(k));
    if dlvl(k)==40.0
        atts=0.0;
    end
    theta=th(k).*pi./180.0;
    [itmp,qtmp]=delay(idata,qdata,nsamp,itau(k));
    [itmp3,qtmp3,ramp,rcos,rsin]=fade(itmp,qtmp,...
        nsamp,tstp,fd,n0(k),itn(k),flat);
    iout=iout+atts.*itmp3./sqrt(total_attn);
    qout=qout+atts.*qtmp3./sqrt(total_attn);
end

 

% Program 5-3
% shift.m
%
% Shift the contents of the register
%
% Programmed by yixiongshu,2006.8.9
function [outregi]=shift(inregi,shiftr,shiftu)
%
% inregi : Vector or matrix
% shiftr :  The amount of shift to the right.
% shiftu : The amount of shift to the top.
% outregi: Register output 

% ----------------------------------------------------
[h,v]=size(inregi);
outregi=inregi;
shiftr=rem(shiftr,v);
shiftu=rem(shiftu,h);
if shiftr>0
    outregi(:,1:shiftr)=inregi(:,v-shiftr+1:v);
    outregi(:,1+shiftr:v)=inregi(:,1:v-shiftr);
elseif shiftr<0
    outregi(:,1:v+shiftr)=inregi(:,1-shiftr:v);
    outregi(:,v+shiftr+1:v)=inregi(:,1:-shiftr);
end

inregi=outregi;

if shiftu>0
    outregi(1:h-shiftu,:)=inregi(1+shiftu:h,:);
    outregi(h-shiftu+1:h,:)=inregi(1:shiftu,:);
elseif shiftu<0
    outregi(1:-shiftu,:)=inregi(h+shiftu+1:h,:);
    outregi(1-shiftu:h,:)=inregi(1:h+shiftu,:);
end

% end of file.

 

% Program 5-7
% spread.m
%
% Data spread function
%
% programmed by yixongshu,2006.8.9
function [iout,qout]=spread(idata,qdata,code1);
%
% code1: spread code sequence
%
switch nargin
    case{0,1}
        error('lack of input argument');
    case 2
        code1=qdata;
        qdata=idata;
end
[hn,vn]=size(idata);
[hc,vc]=size(code1);

if hn>hc
    error('lack of spread code sequences');
end

iout=zeros(hn,vn*vc);
qout=zeros(hn,vn*vc);

for ii=1:hn                       % spread the information correctly.
    iout(ii,:)=reshape(rot90(code1(ii,:),3)...
        *idata(ii,:),1,vn*vc);
    qout(ii,:)=reshape(rot90(code1(ii,:),3)...
        *qdata(ii,:),1,vn*vc);
end

% end of file.