program ldpcsim174_74 ! End-to-end test of the (174,74)/crc24 encoder and decoders. use packjt77 parameter(N=174, K=74, M=N-K) character*8 arg character*37 msg0,msg character*77 c77 character*50 cmsg character*24 c24 integer*1 msgbits(74) integer*1 apmask(174) integer*1 cw(174) integer*1 codeword(N),message74(74) integer ncrc24 integer nerrtot(174),nerrdec(174),nmpcbad(74) real rxdata(N),llr(N) real dllr(174),llrd(174) logical first,unpk77_success data first/.true./ nerrtot=0 nerrdec=0 nmpcbad=0 ! Used to collect the number of errors in the message+crc part of the codeword nargs=iargc() if(nargs.ne.5 .and. nargs.ne.6) then print*,'Usage: ldpcsim niter ndeep #trials s K [msg]' print*,'e.g. ldpcsim174_74 20 5 1000 0.85 64 "K9AN EN50 37"' print*,'s : if negative, then value is ignored and sigma is calculated from SNR.' print*,'niter: is the number of BP iterations.' print*,'ndeep: -1 is BP only, ndeep>=0 is OSD order' print*,'K :is the number of message+CRC bits and must be in the range [50,74]' print*,'WSPR-format message is optional' return endif call getarg(1,arg) read(arg,*) max_iterations call getarg(2,arg) read(arg,*) ndeep call getarg(3,arg) read(arg,*) ntrials call getarg(4,arg) read(arg,*) s call getarg(5,arg) read(arg,*) Keff msg0='K9AN EN50 37 ' if(nargs.eq.6) call getarg(6,msg0) call pack77(msg0,i3,n3,c77) cmsg=c77(1:50) rate=real(Keff)/real(N) write(*,*) "code rate: ",rate write(*,*) "niter : ",max_iterations write(*,*) "ndeep : ",ndeep write(*,*) "s : ",s write(*,*) "K : ",Keff msgbits=0 read(cmsg,'(50i1)') msgbits(1:50) write(*,*) 'message' write(*,'(74i1)') msgbits call get_crc24(msgbits,74,ncrc24) write(c24,'(b24.24)') ncrc24 read(c24,'(24i1)') msgbits(51:74) call encode174_74(msgbits,codeword) call init_random_seed() call sgran() write(*,*) 'codeword' write(*,'(50i1,1x,24i1,1x,100i1)') codeword write(*,*) "Eb/N0 Es/N0 ngood nundetected sigma symbol error rate" do idb = 8,-3,-1 db=idb/2.0-1.0 sigma=1/sqrt( 2*rate*(10**(db/10.0)) ) ! to make db represent Eb/No ! sigma=1/sqrt( 2*(10**(db/10.0)) ) ! db represents Es/No ngood=0 nue=0 nberr=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 nberr=nberr+nerr 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) apmask=0 ! max_iterations is max number of belief propagation iterations call bpdecode174_74(llr,apmask,max_iterations,message74,cw,nharderror,niterations,nchecks) dmin=0.0 if( (nharderror .lt. 0) .and. (ndeep .ge. 0) ) then ! call osd174_74(llr, Keff, apmask, ndeep, message74, cw, nharderror, dmin) call decode174_74(llr,Keff,ndeep,apmask,max_iterations,message74,cw,nharderror,niterations,ncheck,dmin,isuper) endif if(nharderror.ge.0) then n2err=0 do i=1,N if( cw(i)*(2*codeword(i)-1.0) .lt. 0 ) n2err=n2err+1 enddo if(n2err.eq.0) then ngood=ngood+1 else nue=nue+1 endif endif enddo ! snr2500=db+10*log10(200.0/116.0/2500.0) esn0=db+10*log10(rate) pberr=real(nberr)/(real(ntrials*N)) write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,8x,f5.2,8x,e10.3)") db,esn0,ngood,nue,ss,pberr if(first) then write(c77,'(74i1)') message74 c77(51:77)='000000000000000000000110000' call unpack77(c77,0,msg,unpk77_success) if(unpk77_success) then write(*,1100) msg(1:14) 1100 format('Decoded message: ',a14) else print*,'Error unpacking message' endif first=.false. endif enddo open(unit=23,file='nerrhisto.dat',status='unknown') do i=1,120 write(23,'(i4,2x,i10,i10,f10.2)') i,nerrdec(i),nerrtot(i),real(nerrdec(i))/real(nerrtot(i)+1e-10) enddo close(23) open(unit=25,file='nmpcbad.dat',status='unknown') do i=1,68 write(25,'(i4,2x,i10)') i,nmpcbad(i) enddo close(25) end program ldpcsim174_74