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Add code needed to unpack decoded message.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6645 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke
parent
e68674214c
commit
45ba25f6ed
@ -7,8 +7,8 @@ use, intrinsic :: iso_c_binding
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use hashing
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use packjt
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character*22 msg,msgsent
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integer*4 i4Msg6BitWords(12)
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character*22 msg,msgsent,msgreceived
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integer*4 i4Msg6BitWords(12),i4Dec6BitWords(12)
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integer*1, target:: i1Msg8BitBytes(10) ! 72 bit msg + 8 bit hash
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integer*1, target:: i1Dec8BitBytes(10) ! 72 bit msg + 8 bit hash
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integer*1 i1hashdec
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@ -22,8 +22,8 @@ equivalence (ihash,i1hash)
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nargs=iargc()
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if(nargs.ne.7) then
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print*,'Usage: ldpcsim pchk/gen file prefix N K niter ndither #trials s '
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print*,'eg: ldpcsim "128-80-peg-reg3" 128 80 10 1 1000 0.75'
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print*,'Usage: ldpcsim <pchk file prefix > N K niter ndither #trials s '
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print*,'eg: ldpcsim "/pathto/128-80-peg-reg3" 128 80 10 1 1000 0.75'
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return
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endif
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call getarg(1,prefix)
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@ -43,7 +43,7 @@ read(arg,*) s
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pchk_file=trim(prefix)//".pchk"
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gen_file=trim(prefix)//".gen"
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!rate=real(K)/real(N)
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! rate=real(K)/real(N)
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! don't count hash bits as data bits
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rate=72.0/real(N)
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@ -54,7 +54,7 @@ allocate ( codeword(N), decoded(K), message(K) )
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allocate ( lratio(N), rxdata(N) )
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call init_ldpc(trim(pchk_file)//char(0),trim(gen_file)//char(0))
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msg="K1JT K9AN EN50"
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msg="123"
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call fmtmsg(msg,iz)
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call packmsg(msg,i4Msg6BitWords,itype)
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call unpackmsg(i4Msg6BitWords,msgsent)
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@ -104,19 +104,19 @@ do idb = 0, 11
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do itrial=1, ntrials
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! create a realization of a noisy received word
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! Create a realization of a noisy received word
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do i=1,N
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rxdata(i) = 2.0*(codeword(i)-0.5) + sigma*gran()
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enddo
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! correct signal normalization is important for this decoder.
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! Correct signal normalization is important for this decoder.
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rxav=sum(rxdata)/N
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rx2av=sum(rxdata*rxdata)/N
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rxsig=sqrt(rx2av-rxav*rxav)
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rxdata=rxdata/rxsig
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! To match the metric to the channel, s should be set to the noise standard deviation.
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! For now we just set s to the value that optimizes decode probability near threshold.
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! For now, set s to the value that optimizes decode probability near threshold.
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! The s parameter can be tuned to trade a few tenth's dB of threshold for an order of
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! magnitude in UER
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do i=1,N
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@ -128,18 +128,16 @@ do idb = 0, 11
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lratio(i)=exp(2.0*rxdata(i)/(ss*ss))
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enddo
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! call interface to Radford Neal implementation of binary belief propagation.
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! max_iterations is max number of belief propagation iterations
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! max_dither is the number of tries - try number 2 and beyond start with dithered likelihood ratios.
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call ldpc_decode(lratio, decoded, max_iterations, niterations, max_dither, ndither)
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! if the decoder finds a valid codeword, niterations will be .ge. 0
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! If the decoder finds a valid codeword, niterations will be .ge. 0.
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if( niterations .ge. 0 ) then
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nueflag=0
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nhashflag=0
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! the decoder produced a codeword --- compare hash part of message (byte 10) with computed hash
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! first collapse 80 decoded bits to 10 bytes
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! the first 9 bytes are the message, 10'th byte is the hash.
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! The decoder found a codeword. Compare received hash (byte 10) with computed hash.
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! Collapse 80 decoded bits to 10 bytes. Bytes 1-9 are the message, byte 10 is the hash.
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do ibyte=1,10
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itmp=0
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do ibit=1,8
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@ -147,17 +145,19 @@ do idb = 0, 11
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enddo
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i1Dec8BitBytes(ibyte)=itmp
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enddo
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! calculate the hash using the first 9 bytes
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! Calculate the hash using the first 9 bytes.
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ihashdec=nhash(c_loc(i1Dec8BitBytes),int(9,c_size_t),146)
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ihashdec=2*iand(ihashdec,255)
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! compare calculated hash with received byte 10 - if they agree, keep the message
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! Compare calculated hash with received byte 10 - if they agree, keep the message.
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i1hashdec=ihashdec
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if( i1hashdec .ne. i1Dec8BitBytes(10) ) then
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nbadhash=nbadhash+1
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nhashflag=1
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endif
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! check the message plus hash against what was sent
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! Check the message plus hash against what was sent.
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do i=1,K
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if( message(i) .ne. decoded(i) ) then
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nueflag=1
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@ -166,11 +166,25 @@ do idb = 0, 11
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if( nhashflag .eq. 0 .and. nueflag .eq. 0 ) then
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ngood=ngood+1
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! don't bother to unpack while testing
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if( .false. ) then
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! unpack 72-bit message
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do ibyte=1,12
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itmp=0
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do ibit=1,6
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itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*6+ibit))
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enddo
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i4Dec6BitWords(ibyte)=itmp
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enddo
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call unpackmsg(i4Dec6BitWords,msgreceived)
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print*,"Received ",msgreceived
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endif
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else if( nhashflag .eq. 0 .and. nueflag .eq. 1 ) then
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nue=nue+1;
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endif
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endif
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enddo
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write(*,"(f4.1,1x,i8,1x,i8,1x,i8)") db,ngood,nue,nbadhash
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