mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-01 08:07:10 -04:00
f2455c6528
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7633 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
222 lines
6.4 KiB
Fortran
222 lines
6.4 KiB
Fortran
program ldpcsim120
|
|
! End to end test of the (120,60)/crc10 encoder and decoder.
|
|
use crc
|
|
use packjt
|
|
|
|
parameter(NRECENT=10)
|
|
character*12 recent_calls(NRECENT)
|
|
character*22 msg,msgsent,msgreceived
|
|
character*8 arg
|
|
integer*1, allocatable :: codeword(:), decoded(:), message(:)
|
|
integer*1, target:: i1Msg8BitBytes(9)
|
|
integer*1, target:: i1Dec8BitBytes(9)
|
|
integer*1 msgbits(60)
|
|
integer*1 apmask(120)
|
|
integer*1 cw(120)
|
|
integer*2 checksum
|
|
integer colorder(120)
|
|
integer nerrtot(120),nerrdec(120),nmpcbad(60)
|
|
logical checksumok,fsk,bpsk
|
|
real*8, allocatable :: rxdata(:)
|
|
real, allocatable :: llr(:)
|
|
|
|
data colorder/ &
|
|
0,1,2,21,3,4,5,6,7,8,20,10,9,11,12,23,13,28,14,31, &
|
|
15,16,22,26,17,30,18,29,25,32,41,34,19,33,27,36,38,43,42,24, &
|
|
37,39,45,40,35,44,47,46,50,51,53,48,52,56,54,57,55,49,58,61, &
|
|
60,59,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79, &
|
|
80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99, &
|
|
100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119/
|
|
|
|
do i=1,NRECENT
|
|
recent_calls(i)=' '
|
|
enddo
|
|
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.3) then
|
|
print*,'Usage: ldpcsim niter #trials s '
|
|
print*,'eg: ldpcsim 10 1000 0.84'
|
|
print*,'If s is negative, then value is ignored and sigma is calculated from SNR.'
|
|
return
|
|
endif
|
|
call getarg(1,arg)
|
|
read(arg,*) max_iterations
|
|
call getarg(2,arg)
|
|
read(arg,*) ntrials
|
|
call getarg(3,arg)
|
|
read(arg,*) s
|
|
|
|
fsk=.false.
|
|
bpsk=.true.
|
|
|
|
! don't count crc bits as data bits
|
|
N=120
|
|
K=60
|
|
! scale Eb/No for a (120,50) code
|
|
rate=real(50)/real(N)
|
|
|
|
write(*,*) "rate: ",rate
|
|
write(*,*) "niter= ",max_iterations," s= ",s
|
|
|
|
allocate ( codeword(N), decoded(K), message(K) )
|
|
allocate ( rxdata(N), llr(N) )
|
|
|
|
! The message should be packed into the first 7 bytes
|
|
i1Msg8BitBytes(1:6)=85
|
|
i1Msg8BitBytes(7)=64
|
|
! The CRC will be put into the last 2 bytes
|
|
i1Msg8BitBytes(8:9)=0
|
|
checksum = crc10 (c_loc (i1Msg8BitBytes), 9)
|
|
! For reference, the next 3 lines show how to check the CRC
|
|
i1Msg8BitBytes(8)=checksum/256
|
|
i1Msg8BitBytes(9)=iand (checksum,255)
|
|
checksumok = crc10_check(c_loc (i1Msg8BitBytes), 9)
|
|
if( checksumok ) write(*,*) 'Good checksum'
|
|
write(*,*) i1Msg8BitBytes(1:9)
|
|
|
|
mbit=0
|
|
do i=1, 7
|
|
i1=i1Msg8BitBytes(i)
|
|
do ibit=1,8
|
|
mbit=mbit+1
|
|
msgbits(mbit)=iand(1,ishft(i1,ibit-8))
|
|
enddo
|
|
enddo
|
|
i1=i1Msg8BitBytes(8) ! First 2 bits of crc10 are LSB of this byte
|
|
do ibit=1,2
|
|
msgbits(50+ibit)=iand(1,ishft(i1,ibit-2))
|
|
enddo
|
|
i1=i1Msg8BitBytes(9) ! Now shift in last 8 bits of the CRC
|
|
do ibit=1,8
|
|
msgbits(52+ibit)=iand(1,ishft(i1,ibit-8))
|
|
enddo
|
|
|
|
write(*,*) 'message'
|
|
write(*,'(9(8i1,1x))') msgbits
|
|
|
|
call encode120(msgbits,codeword)
|
|
call init_random_seed()
|
|
call sgran()
|
|
|
|
write(*,*) 'codeword'
|
|
write(*,'(15(8i1,1x))') codeword
|
|
|
|
write(*,*) "Es/N0 SNR2500 ngood nundetected nbadcrc sigma"
|
|
do idb = -10, 24
|
|
db=idb/2.0-1.0
|
|
! sigma=1/sqrt( 2*rate*(10**(db/10.0)) ) ! to make db represent Eb/No
|
|
sigma=1/sqrt( 2*(10**(db/10.0)) ) ! db represents Es/No
|
|
ngood=0
|
|
nue=0
|
|
nbadcrc=0
|
|
nberr=0
|
|
do itrial=1, ntrials
|
|
! Create a realization of a noisy received word
|
|
do i=1,N
|
|
if( bpsk ) then
|
|
rxdata(i) = 2.0*codeword(i)-1.0 + sigma*gran()
|
|
elseif( fsk ) then
|
|
if( codeword(i) .eq. 1 ) then
|
|
r1=(1.0 + sigma*gran())**2 + (sigma*gran())**2
|
|
r2=(sigma*gran())**2 + (sigma*gran())**2
|
|
elseif( codeword(i) .eq. 0 ) then
|
|
r2=(1.0 + sigma*gran())**2 + (sigma*gran())**2
|
|
r1=(sigma*gran())**2 + (sigma*gran())**2
|
|
endif
|
|
rxdata(i)=0.35*(sqrt(r1)-sqrt(r2))
|
|
! rxdata(i)=0.35*(exp(r1)-exp(r2))
|
|
! rxdata(i)=0.12*(log(r1)-log(r2))
|
|
endif
|
|
enddo
|
|
nerr=0
|
|
do i=1,N
|
|
if( rxdata(i)*(2*codeword(i)-1.0) .lt. 0 ) nerr=nerr+1
|
|
enddo
|
|
nerrtot(nerr)=nerrtot(nerr)+1
|
|
nberr=nberr+nerr
|
|
|
|
! 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
|
|
! To match the metric to the channel, s should be set to the noise standard deviation.
|
|
! For now, set s to the value that optimizes decode probability near threshold.
|
|
! The s parameter can be tuned to trade a few tenth's dB of threshold for an order of
|
|
! magnitude in UER
|
|
if( s .lt. 0 ) then
|
|
ss=sigma
|
|
else
|
|
ss=s
|
|
endif
|
|
|
|
llr=2.0*rxdata/(ss*ss)
|
|
apmask=0
|
|
|
|
! max_iterations is max number of belief propagation iterations
|
|
call bpdecode120(llr, apmask, max_iterations, decoded, niterations, cw)
|
|
|
|
|
|
! If the decoder finds a valid codeword, niterations will be .ge. 0.
|
|
if( niterations .ge. 0 ) then
|
|
! Check the CRC
|
|
do ibyte=1,6
|
|
itmp=0
|
|
do ibit=1,8
|
|
itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*8+ibit))
|
|
enddo
|
|
i1Dec8BitBytes(ibyte)=itmp
|
|
enddo
|
|
i1Dec8BitBytes(7)=decoded(49)*128+decoded(50)*64
|
|
! Need to pack the received crc into bytes 8 and 9 for crc10_check
|
|
i1Dec8BitBytes(8)=decoded(51)*2+decoded(52)
|
|
i1Dec8BitBytes(9)=decoded(53)*128+decoded(54)*64+decoded(55)*32+decoded(56)*16
|
|
i1Dec8BitBytes(9)=i1Dec8BitBytes(9)+decoded(57)*8+decoded(58)*4+decoded(59)*2+decoded(60)*1
|
|
ncrcflag=0
|
|
if( crc10_check( c_loc( i1Dec8BitBytes ), 9 ) ) ncrcflag=1
|
|
|
|
if( ncrcflag .ne. 1 ) then
|
|
nbadcrc=nbadcrc+1
|
|
endif
|
|
nueflag=0
|
|
|
|
nerrmpc=0
|
|
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
|
|
nmpcbad(nerrmpc)=nmpcbad(nerrmpc)+1 ! This histogram should inform our selection of CRC poly
|
|
if( ncrcflag .eq. 1 .and. nueflag .eq. 0 ) then
|
|
ngood=ngood+1
|
|
nerrdec(nerr)=nerrdec(nerr)+1
|
|
else if( ncrcflag .eq. 1 .and. nueflag .eq. 1 ) then
|
|
nue=nue+1;
|
|
endif
|
|
endif
|
|
enddo
|
|
snr2500=db+10*log10(0.4166/2500.0)
|
|
pberr=real(nberr)/(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
|
|
|
|
enddo
|
|
|
|
open(unit=23,file='nerrhisto.dat',status='unknown')
|
|
do i=1,120
|
|
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=1,60
|
|
write(25,'(i4,2x,i10)') i,nmpcbad(i)
|
|
enddo
|
|
close(25)
|
|
|
|
|
|
|
|
end program ldpcsim120
|