MSK.rar_MATLAB msk_msk_msk matlab_msk receiver

%implementation of MSK transmitter and Receiver clc; clear all; close all; N=10000; fac=8; L=1; b=rand(1,N); % dec(b>=0.5)=-1; % dec(b<0.5)=1; dec = randsrc(1,N); theta=0; for x=1:N A = dec(1,x) + theta; bn(1,x) = exp(j*pi*A/2); theta = theta + dec(1,x); end d(1:8:N*fac)=bn; d = [d zeros(1,fac-1)]; t=0:1/fac:2-1/fac; h=sin(pi*t/2); e_h = h*h'; ene =sum(h.*h); h1=h./sqrt(ene); s1=conv(d,h1); s1=s1(9:end-7); %---------------------------------------------------------------- %MSK demodulation-viterbi algorithm %---------------------------------------------------------------- mem_elem=1; blk_size=N; no_state=2^mem_elem; load past_state_tab.mat; load next_state.mat; load metind.mat; path_table=zeros(no_state,blk_size); metric_table=zeros(no_state,blk_size); metrics=zeros(no_state,1); k1= 1; % SNRdiff = 10*log10(2); SNRa = 5; SNRb = 15; for SNRdB = SNRa : 1: SNRb SNRdB noise_var = 0.5*10^(-SNRdB/10); noise = sqrt(noise_var)*complex(randn(1,length(s1)),randn(1,length(s1))); bits_noise = s1 + noise; %implementation of matched filter at receiver r_0=conv(bits_noise,h1); r0_=r_0(9:end-7); r0 = r0_(1:fac:end); r1 = [0 r0]; state=0; metric1=0; for m=1:mem_elem ind=next_state(state+1,:); ind=reshape(ind',2^m,1); path_table(ind+1,m)=reshape(repmat(state',2,1),2^m,1); a1=repmat(r0(1,m),2^m,1); d1=repmat(r1(1,m),2^m,1); [value] = metric_msk(state,a1,d1,m); metric1=reshape((repmat(metric1,1,2))',2^m,1); metric1=metric1+value; metrics(ind+1)=metric1; state=ind; end state = [0 1]; for ind_bit=mem_elem+1:blk_size a1=repmat(r0(1,ind_bit),4,1); d1=repmat(r1(1,ind_bit),4,1); [value] = metric_msk(state,a1,d1,ind_bit); metrics=repmat(metrics,1,2); metrics=reshape(metrics',2*no_state,1); metrics=metrics+value; m1=metrics(metind+1); path_table(:,ind_bit)=past_state_tab(:,1).*(m1(:,1)>=m1(:,2)) + past_state_tab(:,2).*(m1(:,1)<m1(:,2)); metric_table(:,ind_bit)=m1(:,1).*(m1(:,1)>=m1(:,2)) + m1(:,2).*(m1(:,1)<m1(:,2)); metrics=m1(:,1).*(m1(:,1)>=m1(:,2)) + m1(:,2).*(m1(:,1)<m1(:,2)); end [val index]=max(metrics); start_init=index-1; traceback_state(blk_size+1)=start_init; for m=length(path_table):-1:1 start_init=path_table(start_init+1,m); traceback_state(m)=start_init; end state_next=next_state(traceback_state+1,:); for m=1:blk_size bits_rx(m)=(traceback_state(m+1)==state_next(m,2)); end bits_rx=1-2*bits_rx; ber(k1) = length(find(bits_rx-dec))/(N) tbpsk(k1) =(1/2)* erfc(sqrt(10^(SNRdB/10))); k1 = k1+1; end % figure; semilogy(SNRa:1:SNRb, ber,'b'); hold on; semilogy(SNRa:1:SNRb,tbpsk,'r'); title('BER curve'); grid on;