For (174,91) code, move CRC generation and testing into encode and decode routines. Make ldpcsim174_91.f90 work with the new encode/decode routines.

lib/encode128_90.f90

@@ -1,7 +1,6 @@
 subroutine encode128_90(message77,codeword)
-! Encode an 90-bit message and return a 128-bit codeword. 
+!
-! The generator matrix has dimensions (38,90). 
+! Add a 13-bit CRC to a 77-bit message and return a 128-bit codeword
-! The code is a (128,90) regular ldpc code with column weight 3.
 !
 use, intrinsic :: iso_c_binding
 use iso_c_binding, only: c_loc,c_size_t

lib/ft8/bpdecode174_91.f90

@@ -1,10 +1,14 @@
-subroutine bpdecode174_91(llr,apmask,maxiterations,decoded,cw,nharderror,iter)
+subroutine bpdecode174_91(llr,apmask,maxiterations,message77,cw,nharderror,iter)
 !
 ! A log-domain belief propagation decoder for the (174,91) code.
 !
+use iso_c_binding, only: c_loc,c_size_t
+use crc
 integer, parameter:: N=174, K=91, M=N-K
-integer*1 codeword(N),cw(N),apmask(N)
+integer*1 cw(N),apmask(N)
 integer*1 decoded(K)
+integer*1 message77(77)
+integer nrw(M),ncw
 integer Nm(7,M)   
 integer Mn(3,N)  ! 3 checks per bit
 integer synd(M)
@@ -14,7 +18,6 @@ real tanhtoc(7,M)
 real zn(N)
 real llr(N)
 real Tmn
-integer nrw(M),ncw
 
 include "ldpc_174_91_c_reordered_parity.f90"
 
@@ -52,15 +55,14 @@ do iter=0,maxiterations
 !   if( mod(synd(i),2) .ne. 0 ) write(*,*) 'check ',i,' unsatisfied'
   enddo
 ! write(*,*) 'number of unsatisfied parity checks ',ncheck
-  if( ncheck .eq. 0 ) then ! we have a codeword - reorder the columns and return it
+  if( ncheck .eq. 0 ) then ! we have a codeword - if crc is good, return it
-    codeword=cw
+    decoded=cw(1:K)
-    decoded=codeword(1:K)
+    call chkcrc14a(decoded,nbadcrc)
-    nerr=0
+    nharderror=count( (2*cw-1)*llr .lt. 0.0 )
-    do i=1,N
+    if(nbadcrc.eq.0) then
-      if( (2*cw(i)-1)*llr(i) .lt. 0.0 ) nerr=nerr+1
+      message77=decoded(1:77)
-    enddo
+      return
-    nharderror=nerr
+    endif
-    return
   endif
 
   if( iter.gt.0 ) then  ! this code block implements an early stopping criterion

lib/ft8/encode174_91.f90

@@ -1,15 +1,18 @@
-subroutine encode174_91(message,codeword)
+subroutine encode174_91(message77,codeword)
-! Encode an 91-bit message and return a 174-bit codeword. 
-! The generator matrix has dimensions (83,91). 
-! The code is a (174,91) regular ldpc code with column weight 3.
 !
+! Add a 14-bit CRC to a 77-bit message and return a 174-bit codeword
+!
+use, intrinsic :: iso_c_binding
+use iso_c_binding, only: c_loc,c_size_t
+use crc
 
 integer, parameter:: N=174, K=91, M=N-K
-
+character*91 tmpchar
 integer*1 codeword(N)
 integer*1 gen(M,K)
-integer*1 message(K)
+integer*1 message77(77),message(K)
 integer*1 pchecks(M)
+integer*1, target :: i1MsgBytes(12)
 include "ldpc_174_91_c_generator.f90"
 logical first
 data first/.true./
@@ -31,6 +34,15 @@ if( first ) then ! fill the generator matrix
 first=.false.
 endif
 
+! Add 14-bit CRC to form 91-bit message+CRC14
+write(tmpchar,'(77i1)') message77
+tmpchar(78:80)='000'
+i1MsgBytes=0
+read(tmpchar,'(10b8)') i1MsgBytes(1:10)
+ncrc14 = crc14 (c_loc (i1MsgBytes), 12)
+write(tmpchar(78:91),'(b14)') ncrc14
+read(tmpchar,'(91i1)') message
+
 do i=1,M
   nsum=0
   do j=1,K 

lib/ft8/ldpcsim174_91.f90

@@ -7,20 +7,18 @@ integer, parameter:: N=174, K=91, M=N-K
 character*22 msg,msgsent,msgreceived
 character*8 arg
 character*6 grid
+character*96 tmpchar
 integer*1, allocatable ::  codeword(:), decoded(:), message(:)
-integer*1, target:: i1Msg8BitBytes(12)
+integer*1 msgbits(77)
-integer*1 msgbits(K)
+integer*1 message77(77)
 integer*1 apmask(N), cw(N)
-integer*2 checksum
 integer*4 i4Msg6BitWords(13)
-integer nerrtot(N),nerrdec(N),nmpcbad(K)
+integer nerrtot(0:N),nerrdec(0:N)
-logical checksumok
 real*8, allocatable ::  rxdata(:)
 real, allocatable :: llr(:)
 
 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.4) then
@@ -54,73 +52,31 @@ allocate ( rxdata(N), llr(N) )
   call unpackmsg(i4Msg6BitWords,msgsent,.false.,grid) !Unpack to get msgsent
   write(*,*) "message sent ",msgsent
 
-  i4=0
+  tmpchar=' '
-  ik=0
+  write(tmpchar,'(12b6.6)') i4Msg6BitWords(1:12)
-  im=0
+  tmpchar(73:77)='00000'   !i5bit
-  do i=1,12
+  read(tmpchar,'(77i1)') msgbits(1:77)
-    nn=i4Msg6BitWords(i)
-    do j=1, 6
-      ik=ik+1
-      i4=i4+i4+iand(1,ishft(nn,j-6))
-      i4=iand(i4,255)
-      if(ik.eq.8) then
-        im=im+1
-!           if(i4.gt.127) i4=i4-256
-        i1Msg8BitBytes(im)=i4
-        ik=0
-      endif
-    enddo
-  enddo
-
-  i1Msg8BitBytes(10:12)=0
-  checksum = crc14 (c_loc (i1Msg8BitBytes), 12)
-! For reference, the next 3 lines show how to check the CRC
-  i1Msg8BitBytes(11)=checksum/256
-  i1Msg8BitBytes(12)=iand (checksum,255)
-  checksumok = crc14_check(c_loc (i1Msg8BitBytes), 12)
-  if( checksumok ) write(*,*) 'Good checksum'
-
-! K=91, For now: 
-! msgbits(1:72) JT message bits
-! msgbits(73:77) 5 free message bits (set to 0) 
-! msgbits(78:91) CRC14
-  mbit=0
-  do i=1, 9 
-    i1=i1Msg8BitBytes(i)
-    do ibit=1,8
-      mbit=mbit+1
-      msgbits(mbit)=iand(1,ishft(i1,ibit-8))
-    enddo
-  enddo
-  msgbits(73:77)=0  ! the five extra message bits go here
-  i1=i1Msg8BitBytes(11) ! First 6 bits of crc12 are LSB of this byte
-  do ibit=1,6
-    msgbits(77+ibit)=iand(1,ishft(i1,ibit-6))
-  enddo
-  i1=i1Msg8BitBytes(12) ! Now shift in last 8 bits of the CRC
-  do ibit=1,8
-    msgbits(83+ibit)=iand(1,ishft(i1,ibit-8))
-  enddo
 
   write(*,*) 'message'
-  write(*,'(12(8i1,1x))') msgbits
+  write(*,'(28i1,1x,28i1,1x,16i1,1x,5i1)') msgbits
 
+! msgbits is the 77-bit message, codeword is 174 bits
   call encode174_91(msgbits,codeword)
+
   call init_random_seed()
-!  call sgran()
 
   write(*,*) 'codeword' 
   write(*,'(22(8i1,1x))') codeword
 
-write(*,*) "Eb/N0   SNR2500   ngood  nundetected nbadcrc   sigma"
+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
-  nbadcrc=0
+  nsumerr=0
-  nberr=0
+
   do itrial=1, ntrials
 ! Create a realization of a noisy received word
     do i=1,N
@@ -131,7 +87,6 @@ do idb = 20,-10,-1
       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
@@ -150,38 +105,26 @@ do idb = 20,-10,-1
     apmask(1:nap)=1
 
 ! max_iterations is max number of belief propagation iterations
-    call bpdecode174_91(llr, apmask, max_iterations, decoded, cw, nharderrors,niterations)
+    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, decoded, cw,  nharderrors, dmin)
+    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 extractmessage174_91(decoded,msgreceived,ncrcflag)
+      call extractmessage77(message77,msgreceived)
-      if( ncrcflag .ne. 1 ) then
+      nhw=count(cw.ne.codeword)
-        nbadcrc=nbadcrc+1
+      if(nhw.eq.0) then ! this is a good decode
-      endif
+         ngood=ngood+1
-
+         nerrdec(nerr)=nerrdec(nerr)+1
-      nueflag=0
+      else
-      nerrmpc=0
+         nue=nue+1
-      do i=1,K   ! find number of errors in message+crc part of codeword
-        if( msgbits(i) .ne. decoded(i) ) then
-          nueflag=1
-          nerrmpc=nerrmpc+1 
-        endif
-      enddo
-      if(nerrmpc.ge.1) nmpcbad(nerrmpc)=nmpcbad(nerrmpc)+1
-      if( ncrcflag .eq. 1 ) then
-        if( nueflag .eq. 0 ) then
-          ngood=ngood+1
-          if(nerr.ge.1) nerrdec(nerr)=nerrdec(nerr)+1
-        else if( nueflag .eq. 1 ) then
-          nue=nue+1;
-        endif
       endif
     endif
+    nsumerr=nsumerr+nerr
   enddo
+
   baud=12000/1920
   snr2500=db+10.0*log10((baud/2500.0))
-  pberr=real(nberr)/(real(ntrials*N))
+  pberr=real(nsumerr)/(real(ntrials*N))
-  write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,1x,i8,8x,f5.2,8x,e10.3)") db,SNR2500,ngood,nue,nbadcrc,ss,pberr
+  write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,8x,f5.2,8x,e10.3)") db,SNR2500,ngood,nue,ss,pberr
 
 enddo
 
@@ -190,10 +133,5 @@ 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)
-open(unit=25,file='nmpcbad.dat',status='unknown')
-do i=1,87
-  write(25,'(i4,2x,i10)') i,nmpcbad(i)
-enddo
-close(25)
 
 end program ldpcsim174_91

lib/ft8/osd174_91.f90

@@ -1,4 +1,4 @@
-subroutine osd174_91(llr,apmask,ndeep,decoded,cw,nhardmin,dmin)
+subroutine osd174_91(llr,apmask,ndeep,message77,cw,nhardmin,dmin)
 !
 ! An ordered-statistics decoder for the (174,91) code.
 ! 
@@ -11,6 +11,7 @@ integer*1 r2pat(N-K)
 integer indices(N),nxor(N)
 integer*1 cw(N),ce(N),c0(N),hdec(N)
 integer*1 decoded(K)
+integer*1 message77(77)
 integer indx(N)
 real llr(N),rx(N),absrx(N)
 
@@ -247,6 +248,10 @@ endif
 cw(indices)=cw
 hdec(indices)=hdec
 decoded=cw(1:K) 
+call chkcrc14a(decoded,nbadcrc)
+message77=decoded(1:77)
+if(nbadcrc.eq.1) nhardmin=-nhardmin
+
 return
 end subroutine osd174_91
 

lib/ldpcsim128_90.f90

@@ -9,9 +9,8 @@ character*8 arg
 integer*1 codeword(N), message77(77)
 integer*1 apmask(N),cw(N)
 integer*1 msgbits(77)
-integer*2 ncrc13 
 integer*4 i4Msg6BitWords(13)
-integer nerrtot(0:N),nerrdec(0:N),nmpcbad(0:K),nbadwt(0:N)
+integer nerrtot(0:N),nerrdec(0:N)
 real*8 rxdata(N), rxavgd(N)
 real llr(N)
 
@@ -20,8 +19,6 @@ do i=1,NRECENT
 enddo
 nerrtot=0
 nerrdec=0
-nmpcbad=0
-nbadwt=0
 
 nargs=iargc()
 if(nargs.ne.4) then
@@ -55,7 +52,7 @@ msg="G4WJS K1JT FN20"
   read(tmpchar,'(77i1)') msgbits(1:77)
 
   write(*,*) 'msgbits'
-  write(*,'(28i1,1x,28i1,1x,16i1,1x,5i1,1x,13i1)') msgbits
+  write(*,'(28i1,1x,28i1,1x,16i1,1x,5i1)') msgbits
 
 ! msgbits is the 77-bit message, codeword is 128 bits
   call encode128_90(msgbits,codeword)
@@ -109,7 +106,7 @@ do idb = 14,-6,-1
 ! If the decoder finds a valid codeword, nharderrors will be .ge. 0.
     if( nharderrors .ge. 0 ) then
        call extractmessage77(message77,msgreceived)
-       nhw=count(message77.ne.codeword(1:77))
+       nhw=count(cw.ne.codeword)
        if(nhw.eq.0) then ! this is a good decode
           ngood=ngood+1
           nerrdec(nerr)=nerrdec(nerr)+1 
@@ -132,10 +129,4 @@ do i=0,N
 enddo
 close(23)
 
-open(unit=25,file='badcrc_hamming_weight.dat',status='unknown')
-do i=0,N
-  write(25,'(i4,2x,i10)') i,nbadwt(i)
-enddo
-close(25)
-
 end program ldpcsim