WSJT-X/lib/genmsk32.f90
Steven Franke cbc0eb0114 First-cut at decoder for (32,16) msk32. Needs more work.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6954 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2016-07-27 14:40:38 +00:00

80 lines
1.8 KiB
Fortran

subroutine genmsk32(msg,msgsent,ichk,itone,itype)
use hashing
character*22 msg,msgsent,hashmsg
character*4 crpt,rpt(0:63)
logical first
integer itone(144)
integer ig32(0:65536-1) !Codewords for Golay (24,12) code
integer*1 codeword(32),bitseq(32)
integer*1 s8r(8)
data s8r/1,0,1,1,0,0,0,1/
data first/.true./
save first,rpt,ig32
if(first) then
call ldpc32_table(ig32) !Define the Golay(24,12) codewords
do i=0,30
if( i.lt.5 ) then
write(rpt(i),'(a1,i2.2,a1)') '-',abs(i-5)
write(rpt(i+31),'(a2,i2.2,a1)') 'R-',abs(i-5)
else
write(rpt(i),'(a1,i2.2,a1)') '+',i-5
write(rpt(i+31),'(a2,i2.2,a1)') 'R+',i-5
endif
enddo
rpt(62)='RRR '
rpt(63)='73 '
first=.false.
endif
itype=-1
msgsent='*** bad message ***'
itone=0
i1=index(msg,'>')
if(i1.lt.9) go to 900
call fmtmsg(msg,iz)
crpt=msg(i1+2:i1+5)
do i=0,63
if(crpt.eq.rpt(i)) go to 10
enddo
go to 900
10 irpt=i !Report index, 0-31
if(ichk.lt.10000) then
hashmsg=msg(2:i1-1)//' '//crpt
call hash(hashmsg,22,ihash)
ihash=iand(ihash,1023) !10-bit hash
ig=64*ihash + irpt !6-bit report
else
ig=ichk-10000
endif
ncodeword=ig32(ig)
! write(*,*) 'codeword is: ',ncodeword,'message is: ',ig,'report index: ',irpt,'hash: ',ihash
do i=1,32
codeword(i)=iand(1,ishft(ncodeword,1-i))
enddo
bitseq=codeword
bitseq=2*bitseq-1
! Map I and Q to tones.
itone=0
do i=1, 16
itone(2*i-1)=(bitseq(2*i)*bitseq(2*i-1)+1)/2;
itone(2*i)=-(bitseq(2*i)*bitseq(mod(2*i,32)+1)-1)/2;
enddo
! Flip polarity
itone=-itone+1
msgsent=msg
itype=7
900 return
end subroutine genmsk32