bpskqpsk_matlat.m

Consider a BPSK and a QPSK system for the following two cases: 1) The probability that the symbol 1

clear;
N1 = 10^6 % select bit size
rand('state',100); % initialize rand() function
randn('state',200); % initialize randn() function
 
% BPSK Case1
case1 = rand(1,N1)>0.5; % 0,1阑 阿阿 0.5 犬伏肺 积己
s1 = 2*case1-1; % 0 -> -1, 1 -> 0  函炼
n1 = 1/sqrt(2)*[randn(1,N1) + j*randn(1,N1)]; % white gaussian noise, 0dB variance 

Eb_N0 = [-3:10];
 
for a = 1:length(Eb_N0)
   % Noise addition
   y1 = s1 + 10^(-Eb_N0(a)/20)*n1; % additive white gaussian noise
    % receiver - hard decision decoding
   case1Hat = real(y1)>0;
 % error啊 抄 term阑 技绢辰促.
   E1(a) = size(find([case1- case1Hat]),2);
end

case1ber = E1/N1; % simulated ber
 
% BPSK Case2
case2 = rand(1,N1)>(1/3); % 0,1阑 阿阿 1/3,2/3 犬伏肺 积己
s2 = 2*case2-1;  % 0 -> -1, 1 -> 0  函炼
n2 = 1/sqrt(2)*[randn(1,N1) + j*randn(1,N1)]; % white gaussian noise, 0dB variance 
Eb_N0 = [-3:10]; 
 
for b = 1:length(Eb_N0)
   % Noise addition
   y2 = s2 + 10^(-Eb_N0(b)/20)*n2; % additive white gaussian noise
    % receiver - hard decision decoding
   case2Hat = real(y2)>0;
 % error啊 抄 term阑 技绢辰促.
   E2(b) = size(find([case2- case2Hat]),2);
 end
    case2ber = E2/N1; % simulated ber
	 
	% QPSK Case1
	N2 = 10^5; % symbols 荐
	Es_N0 = [-3:20]; 
	case3Hat = zeros(1,N2);
	for c = 1:length(Es_N0)
	case3 = (2*(rand(1,N2)>0.5)-1) + j*(2*(rand(1,N2)>0.5)-1); % 0.5狼 悼老茄 犬伏肺 0,1 积己
	s3 = (1/sqrt(2))*case3; % signal 积己
	n3 = 1/sqrt(2)*[randn(1,N2) + j*randn(1,N2)]; % white guassian noise, 0dB variance 
	y3 = s3 + 10^(-Es_N0(c)/20)*n3; % additive white gaussian noise
	 
	% demodulation
	y3_re = real(y3); % real part
	y3_im = imag(y3); % imaginary part
	ipHat(find(y3_re < 0 & y3_im < 0)) = -1 + -1*j; % real, imaginary甫 唱穿绢 demodulation 荐青
	ipHat(find(y3_re >= 0 & y3_im > 0)) = 1 + 1*j;
	ipHat(find(y3_re < 0 & y3_im >= 0)) = -1 + 1*j;
	ipHat(find(y3_re >= 0 & y3_im < 0)) = 1 - 1*j;
	% error啊 抄 term阑 技绢辰促 
	E3(c) = size(find([case3- case3Hat]),2); .
	end
	case3ber = E3/N2;
	 
	% QPSK Case2
	case4Hat = zeros(1,N2);
	for d = 1:length(Es_N0)
	case4 = (2*(rand(1,N2)>1/3)-1) + j*(2*(rand(1,N2)>1/3)-1); % 1/3, 2/3 狼 犬伏肺 0,1 积己
	s4 = (1/sqrt(2))*case4; % 俊呈瘤甫 1肺 沥痹拳 窍咯 signal 积己
	n4 = 1/sqrt(2)*[randn(1,N2) + j*randn(1,N2)]; % white guassian noise, 0dB variance
	y4 = s4 + 10^(-Es_N0(d)/20)*n4; % additive white gaussian noise
	 
	% demodulation
	y4_re = real(y4); % real part
	y4_im = imag(y4); % imaginary part
	% 4啊瘤 level肺 盒幅窍咯 demodulation
    ipHat(find(y4_re < 0 & y4_im < 0)) = -1 + -1*j;
	ipHat(find(y4_re >= 0 & y4_im > 0)) = 1 + 1*j;
	ipHat(find(y4_re < 0 & y4_im >= 0)) = -1 + 1*j;
	ipHat(find(y4_re >= 0 & y4_im < 0)) = 1 - 1*j;
	% error啊 抄 term阑 技绢辰促. 
	E4(d) = size(find([case4- case4Hat]),2); 
	end
	 
    case4ber = E4/N2;
	 
	%plot
	close all
	figure
	semilogy(Eb_N0,case1ber,'s-');
	hold on
	semilogy(Eb_N0,case2ber,'+-');
	hold on
	semilogy(Es_N0,case3ber,'o-');
	hold on
	semilogy(Es_N0,case4ber,'p-');
	axis([-3 10 10^-5 0.5])
	grid on
	legend( 'BPSK case1','BPSK case2','QPSK case1','QPSK case2');
	xlabel('Eb/No, dB');
	ylabel('Bit Error Rate');
	title('Bit error probability curve for BPSK & QPSK modulation');
	scatterplot(y1);
	grid on
	title('Constellation of BPSK case1');
	scatterplot(y2);
	grid on
	title('Constellation of BPSK case2');
	scatterplot(y3);
	grid on
	title('Constellation of QPSK case1');
	scatterplot(y4);
	grid on
	title('Constellation of QPSK case2');