subroutine genmsk144(msg0,ichk,msgsent,i4tone,itype,pchk_file) !!!!!!!!!!!!!!!!!! Experimental small blocklength ldpc version ! s8 + 48bits + s8 + 80 bits = 144 bits (72ms message duration) ! ! Encode a JTMSK message ! Input: ! - msg0 requested message to be transmitted ! - ichk if ichk=1, return only msgsent ! if ichk.ge.10000, set imsg=ichk-10000 for short msg ! - msgsent message as it will be decoded ! - i4tone array of audio tone values, 0 or 1 ! - itype message type ! 1 = standard message "Call_1 Call_2 Grid/Rpt" ! 2 = type 1 prefix ! 3 = type 1 suffix ! 4 = type 2 prefix ! 5 = type 2 suffix ! 6 = free text (up to 13 characters) ! 7 = short message " Rpt" use iso_c_binding, only: c_loc,c_size_t use packjt use hashing character*512 pchk_file,gen_file character*22 msg0 character*22 message !Message to be generated character*22 msgsent !Message as it will be received integer*4 i4Msg6BitWords(13) !72-bit message as 6-bit words integer*4 i4tone(144) ! integer*1, target:: i1Msg8BitBytes(10) !80 bits represented in 10 bytes integer*1 codeword(128) !Encoded bits before re-ordering integer*1 msgbits(80) !72-bit message + 8-bit hash integer*1 reorderedcodeword(128) !Odd bits first, then even integer*1 bitseq(144) !Tone #s, data and sync (values 0-1) integer*1 i1hash(4) integer*1 b7(7) integer*1 s8(8) integer*1 b11(11) integer*1 b13(13) real*8 pp(12) real*8 xi(864),xq(864),pi,twopi data b7/1,1,1,0,0,1,0/ data s8/0,1,1,1,0,0,1,0/ data b11/1,1,1,0,0,0,1,0,0,1,0/ !Barker 11 code data b13/1,1,1,1,1,0,0,1,1,0,1,0,1/ !Barker 13 code equivalence (ihash,i1hash) logical first data first/.true./ save if( first ) then first=.false. nsym=128 i=index(pchk_file,".pchk") gen_file=pchk_file(1:i-1)//".gen" call init_ldpc(trim(pchk_file)//char(0),trim(gen_file)//char(0)) pi=4.*atan(1.0) twopi=8.*atan(1.0) do i=1,12 pp(i)=sin( (i-1)*pi/12 ) enddo endif if(msg0(1:1).eq.'@') then !Generate a fixed tone read(msg0(2:5),*,end=1,err=1) nfreq !at specified frequency go to 2 1 nfreq=1000 2 i4tone(1)=nfreq else message=msg0 do i=1,22 if(ichar(message(i:i)).eq.0) then message(i:)=' ' exit endif enddo do i=1,22 !Strip leading blanks if(message(1:1).ne.' ') exit message=message(i+1:) enddo if(message(1:1).eq.'<') then call genmsk32(message,msgsent,ichk,i4tone,itype) if(itype.lt.0) go to 999 i4tone(33)=-35 go to 999 endif call packmsg(message,i4Msg6BitWords,itype) !Pack into 12 6-bit bytes call unpackmsg(i4Msg6BitWords,msgsent) !Unpack to get msgsent if(ichk.eq.1) go to 999 i4=0 ik=0 im=0 do i=1,12 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 ihash=nhash(c_loc(i1Msg8BitBytes),int(9,c_size_t),146) ihash=2*iand(ihash,32767) !Generate the 8-bit hash i1Msg8BitBytes(10)=i1hash(1) !CRC to byte 10 mbit=0 do i=1, 10 i1=i1Msg8BitBytes(i) do ibit=1,8 mbit=mbit+1 msgbits(mbit)=iand(1,ishft(i1,ibit-8)) enddo enddo call ldpc_encode(msgbits,codeword) ! Reorder the bits. reorderedcodeword(1:64)=codeword(1:127:2) reorderedcodeword(65:128)=codeword(2:128:2) !Create 144-bit channel vector: !8-bit sync word + 48 bits + 8-bit sync word + 80 bits bitseq=0 bitseq(1:8)=s8 bitseq(9:56)=reorderedcodeword(1:48) bitseq(57:64)=s8 bitseq(65:144)=reorderedcodeword(49:128) bitseq=2*bitseq-1 xq(1:6)=bitseq(1)*pp(7:12) !first bit is mapped to 1st half-symbol on q do i=1,71 is=(i-1)*12+7 xq(is:is+11)=bitseq(2*i+1)*pp enddo xq(864-5:864)=bitseq(1)*pp(1:6) !last half symbol do i=1,72 is=(i-1)*12+1 xi(is:is+11)=bitseq(2*i)*pp enddo ! Map I and Q to tones. i4tone=0 do i=1,72 i4tone(2*i-1)=(bitseq(2*i)*bitseq(2*i-1)+1)/2; i4tone(2*i)=-(bitseq(2*i)*bitseq(mod(2*i,144)+1)-1)/2; enddo endif ! Flip polarity i4tone=-i4tone+1 999 return end subroutine genmsk144