program ldpcsim use, intrinsic :: iso_c_binding use hashing use packjt character*22 msg,msgsent,msgreceived character*8 arg integer*1, allocatable :: codeword(:), decoded(:), message(:) real*8, allocatable :: lratio(:), rxdata(:) real, allocatable :: llr(:) integer ihash integer*1 hardbits(32) nargs=iargc() if(nargs.ne.4) then print*,'Usage: ldpcsim niter ndither #trials s ' print*,'eg: ldpcsim 10 1 1000 0.75' return endif call getarg(1,arg) read(arg,*) max_iterations call getarg(2,arg) read(arg,*) max_dither call getarg(3,arg) read(arg,*) ntrials call getarg(4,arg) read(arg,*) s n=32 !rate=real(K)/real(N) ! don't count hash bits as data bits rate=4.0/real(N) write(*,*) "rate: ",rate write(*,*) "niter= ",max_iterations," ndither= ",max_dither," s= ",s allocate ( codeword(N), decoded(K), message(K) ) allocate ( lratio(N), rxdata(N), llr(N) ) msg="K1JT K9AN" irpt=14 call hash(msg,22,ihash) ihash=iand(ihash,4095) !12-bit hash ig=16*ihash + irpt !4-bit report write(*,*) irpt,ihash,ig do i=1,16 message(i)=iand(1,ishft(ig,1-i)) enddo write(*,'(16i1)') message call encode_msk40(message,codeword) write(*,'(32i1)') codeword call init_random_seed() write(*,*) "Eb/N0 SNR2500 ngood nundetected nbadhash" do idb = 0, 30 db=idb/2.0 sigma=1/sqrt( 2*rate*(10**(db/10.0)) ) ngood=0 nue=0 nbadhash=0 itsum=0 do itrial=1, ntrials call sgran() ! Create a realization of a noisy received word do i=1,N rxdata(i) = 2.0*codeword(i)-1.0 + sigma*gran() enddo ! Correct signal normalization is important for this decoder. rxav=sum(rxdata)/N rx2av=sum(rxdata*rxdata)/N rxsig=sqrt(rx2av-rxav*rxav) rxdata=rxdata/rxsig if( s .le. 0 ) then ss=sigma else ss=s endif llr=2.0*rxdata/(ss*ss) lratio=exp(llr) call bpdecode40(llr, max_iterations, decoded, niterations) ! If the decoder finds a valid codeword, niterations will be .ge. 0. if( niterations .ge. 0 ) then nueflag=0 nhashflag=0 imsg=0 do i=1,16 imsg=ishft(imsg,1)+iand(1,decoded(17-i)) enddo nrxrpt=iand(imsg,15) nrxhash=(imsg-nrxrpt)/16 if( nrxhash .ne. ihash ) then nbadhash=nbadhash+1 nhashflag=1 endif ! Check the message plus hash against what was sent. do i=1,K if( message(i) .ne. decoded(i) ) then nueflag=1 endif enddo if( nhashflag .eq. 0 .and. nueflag .eq. 0 ) then ngood=ngood+1 itsum=itsum+niterations else if( nhashflag .eq. 0 .and. nueflag .eq. 1 ) then nue=nue+1; endif else hardbits=0 where(llr .gt. 0) hardbits=1 ! write(*,'(32i1)') hardbits ! write(*,'(32i1)') codeword isum=0 do i=1,32 if( hardbits(i) .ne. codeword(i) ) isum=isum+1 enddo ! write(*,*) 'number of errors ',isum endif enddo avits=real(itsum)/real(ngood+0.1) snr2500=db-10.0 write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,1x,i8,1x,f8.2,1x,f8.1)") db,snr2500,ngood,nue,nbadhash,ss,avits enddo end program ldpcsim