basetimcost.m

qam的matlab程序。m文件

% basetimcost.m: draw error surfaces for baseband signal cost functions
% in terms of chosen pulse shape
% crj jr, revised 4/22/03 

clear all

m=20;                        % evaluate at m+1 different points
unp=hamming(m);
cp=conv(unp,unp);            % receiver matched filter makes combo pulse
ps=sqrt(m)*cp/sqrt(sum(cp.^2));     %normalized combo pulse shape

cost1=zeros(1,m+1); cost2=zeros(1,m+1); cost3=zeros(1,m+1);
cost4=zeros(1,m+1); cost5=zeros(1,m+1);
n=1000; x=zeros(1,n);        % calculate cost via a "monte carlo" method

for i=1:m+1                  % for each offset                

% create +/-1 sequence
s1=sign(rand([1,n/m])-0.5);   
s2=sign(rand([1,n/m])-0.5); 
% zero pad T-spaced symbol sequence to create upsampled T/m-spaced
% sequence of scaled T-spaced pulses (with T = 1 time unit)
mup1=zeros(1,n); mup1(1:m:end)=s1; 
mup2=zeros(1,n); mup2(1:m:end)=s2; 
m1=filter(ps,1,mup1);        % convolve pulse shape with data
m2=filter(ps,1,mup2);        % convolve pulse shape with data

%sampled baseband data with timing offset iT/m
sm1=m1((length(ps)-1)/2+i:m:end);
sm2=m2((length(ps)-1)/2+i:m:end);
    
cost1(i)=sum(sqrt(sm1.^2+sm2.^2))/length(sm1);   % cost (abs value sum)
cost2(i)=sum(sm1.^2+sm2.^2)/length(sm1);         % cost (square)
cost3(i)=sum((sm1.^2+sm2.^2).^2)/length(sm1);    % cost (4th power sum)
cost4(i)=sum(abs(sm1)+abs(sm2))/length(sm1);     % cost (sum of abs)
cost5(i)=sum(sm1.^4+sm2.^4)/length(sm1);     % cost (sum of 4th power)
end

offset=(0:m)/m;
figure(1) 
plot(offset,cost1,'--'), hold on     % cost (absolute value)
plot(offset,cost2,':'),                 % cost (square)
plot(offset,cost3,'-'),                 % cost (4th power) 
plot(offset,cost4,'.'),
plot(offset,cost5,'-.'),
hold off, zoom on      
xlabel('timing offset \tau')
ylabel('value of cost functions')