program ldpcsim174_91 ! End to end test of the (174,91)/crc14 encoder and decoder. use crc use packjt77 integer, parameter:: N=174, K=91, M=N-K character*37 msg,msgsent,msgreceived character*77 c77 character*8 arg character*6 grid character*96 tmpchar integer*1, allocatable :: codeword(:), decoded(:), message(:) integer*1 msgbits(77) integer*1 message77(77) integer*1 apmask(N), cw(N) integer nerrtot(0:N),nerrdec(0:N) real*8, allocatable :: rxdata(:) real, allocatable :: llr(:) nerrtot=0 nerrdec=0 nargs=iargc() if(nargs.ne.4) then print*,'Usage: ldpcsim niter ndepth #trials s ' print*,'eg: ldpcsim 10 2 1000 0.84' print*,'belief propagation iterations: niter, ordered-statistics depth: ndepth' print*,'If s is negative, then value is ignored and sigma is calculated from SNR.' return endif call getarg(1,arg) read(arg,*) max_iterations call getarg(2,arg) read(arg,*) ndepth call getarg(3,arg) read(arg,*) ntrials call getarg(4,arg) read(arg,*) s ! scale Eb/No for a (174,91) code rate=real(K)/real(N) write(*,*) "rate: ",rate write(*,*) "niter= ",max_iterations," s= ",s allocate ( codeword(N), decoded(K), message(K) ) allocate ( rxdata(N), llr(N) ) ! msg="K1JT K9AN EN50" msg="G4WJS K9AN EN50" i3=0 n3=1 call pack77(msg,i3,n3,c77) !Pack into 12 6-bit bytes call unpack77(c77,msgsent) !Unpack to get msgsent write(*,*) "message sent ",msgsent read(c77,'(77i1)') msgbits(1:77) write(*,*) 'message' write(*,'(a71,1x,a3,1x,a3)') c77(1:71),c77(72:74),c77(75:77) call encode174_91(msgbits,codeword) call init_random_seed() write(*,*) 'codeword' write(*,'(22(8i1,1x))') codeword write(*,*) "Eb/N0 SNR2500 ngood nundetected sigma psymerr" do idb = 20,-10,-1 !do idb = 0,0,-1 db=idb/2.0-1.0 sigma=1/sqrt( 2*rate*(10**(db/10.0)) ) ngood=0 nue=0 nsumerr=0 do itrial=1, ntrials ! Create a realization of a noisy received word do i=1,N rxdata(i) = 2.0*codeword(i)-1.0 + sigma*gran() enddo nerr=0 do i=1,N if( rxdata(i)*(2*codeword(i)-1.0) .lt. 0 ) nerr=nerr+1 enddo if(nerr.ge.1) nerrtot(nerr)=nerrtot(nerr)+1 rxav=sum(rxdata)/N rx2av=sum(rxdata*rxdata)/N rxsig=sqrt(rx2av-rxav*rxav) rxdata=rxdata/rxsig if( s .lt. 0 ) then ss=sigma else ss=s endif llr=2.0*rxdata/(ss*ss) nap=0 ! number of AP bits llr(1:nap)=5*(2.0*msgbits(1:nap)-1.0) apmask=0 apmask(1:nap)=1 ! max_iterations is max number of belief propagation iterations call bpdecode174_91(llr, apmask, max_iterations, message77, cw, nharderrors,niterations) if( ndepth .ge. 0 .and. nharderrors .lt. 0 ) call osd174_91(llr, apmask, ndepth, message77, cw, nharderrors, dmin) ! If the decoder finds a valid codeword, nharderrors will be .ge. 0. if( nharderrors .ge. 0 ) then call extractmessage77(message77,msgreceived) nhw=count(cw.ne.codeword) if(nhw.eq.0) then ! this is a good decode ngood=ngood+1 nerrdec(nerr)=nerrdec(nerr)+1 else nue=nue+1 endif endif nsumerr=nsumerr+nerr enddo baud=12000/1920 snr2500=db+10.0*log10((baud/2500.0)) pberr=real(nsumerr)/(real(ntrials*N)) write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,8x,f5.2,8x,e10.3)") db,SNR2500,ngood,nue,ss,pberr enddo open(unit=23,file='nerrhisto.dat',status='unknown') do i=1,174 write(23,'(i4,2x,i10,i10,f10.2)') i,nerrdec(i),nerrtot(i),real(nerrdec(i))/real(nerrtot(i)+1e-10) enddo close(23) end program ldpcsim174_91