mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-16 00:51:56 -05:00
136 lines
3.4 KiB
Fortran
136 lines
3.4 KiB
Fortran
program ldpcsim128_90
|
|
|
|
! Simulate the performance of the (128,90) code that is used in
|
|
! the second incarnation of MSK144.
|
|
|
|
use packjt77
|
|
integer, parameter:: NRECENT=10, N=128, K=90, M=N-K
|
|
character*12 recent_calls(NRECENT)
|
|
character*37 msg,msgsent,msgreceived
|
|
character*77 c77
|
|
character*8 arg
|
|
integer*1 codeword(N), message77(77)
|
|
integer*1 apmask(N),cw(N)
|
|
integer*1 msgbits(77)
|
|
integer*4 i4Msg6BitWords(13)
|
|
integer nerrtot(0:N),nerrdec(0:N)
|
|
logical unpk77_success
|
|
real*8 rxdata(N), rxavgd(N)
|
|
real llr(N)
|
|
|
|
do i=1,NRECENT
|
|
recent_calls(i)=' '
|
|
enddo
|
|
nerrtot=0
|
|
nerrdec=0
|
|
|
|
nargs=iargc()
|
|
if(nargs.ne.4) then
|
|
print*,'Usage: ldpcsim niter navg #trials s '
|
|
print*,'eg: ldpcsim 10 1 1000 0.75'
|
|
return
|
|
endif
|
|
call getarg(1,arg)
|
|
read(arg,*) max_iterations
|
|
call getarg(2,arg)
|
|
read(arg,*) navg
|
|
call getarg(3,arg)
|
|
read(arg,*) ntrials
|
|
call getarg(4,arg)
|
|
read(arg,*) s
|
|
|
|
rate=real(77)/real(N)
|
|
|
|
write(*,*) "rate: ",rate
|
|
write(*,*) "niter= ",max_iterations," navg= ",navg," s= ",s
|
|
|
|
msg="K1ABC RR73; W9XYZ <KH1/KH7Z> -12"
|
|
i3=0
|
|
n3=1
|
|
call pack77(msg,i3,n3,c77)
|
|
call unpack77(c77,msgsent,unpk77_success)
|
|
read(c77,'(77i1)') msgbits
|
|
|
|
write(*,*) "message sent ",msgsent
|
|
|
|
write(*,*) 'msgbits'
|
|
write(*,'(77i1)') msgbits
|
|
|
|
! msgbits is the 77-bit message, codeword is 128 bits
|
|
call encode_128_90(msgbits,codeword)
|
|
|
|
! call init_random_seed()
|
|
|
|
write(*,*) "Eb/N0 SNR2500 ngood nundetected sigma psymerr"
|
|
do idb = 14,0,-1
|
|
db=idb/2.0-1.0
|
|
sigma=1/sqrt( 2*rate*(10**(db/10.0)) )
|
|
ngood=0
|
|
nue=0
|
|
nbadcrc=0
|
|
nsumerr=0
|
|
|
|
do itrial=1, ntrials
|
|
rxavgd=0d0
|
|
do iav=1,navg
|
|
! call sgran()
|
|
! Create a realization of a noisy received word
|
|
do i=1,N
|
|
rxdata(i) = 2.0*codeword(i)-1.0 + sigma*gran()
|
|
enddo
|
|
rxavgd=rxavgd+rxdata
|
|
enddo
|
|
rxdata=rxavgd
|
|
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
|
|
|
|
rxav=sum(rxdata)/N
|
|
rx2av=sum(rxdata*rxdata)/N
|
|
rxsig=sqrt(rx2av-rxav*rxav)
|
|
rxdata=rxdata/rxsig
|
|
! 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 bpdecode128_90(llr, apmask, max_iterations, message77, cw, nharderrors, niterations)
|
|
|
|
! If the decoder finds a valid codeword, nharderrors will be .ge. 0.
|
|
if( nharderrors .ge. 0 ) then
|
|
write(c77,'(77i1)') message77
|
|
call unpack77(c77,msgreceived,unpk77_success)
|
|
nhw=count(cw.ne.codeword)
|
|
if(nhw.eq.0) then ! this is a good decode
|
|
ngood=ngood+1
|
|
nerrdec(nerr)=nerrdec(nerr)+1
|
|
else ! this is an undetected error
|
|
nue=nue+1
|
|
endif
|
|
endif
|
|
nsumerr=nsumerr+nerr
|
|
enddo
|
|
|
|
snr2500=db+10*log10(rate*2000.0/2500.0) ! symbol rate is 2000 s^-1 and ref BW is 2500 Hz.
|
|
pberr=real(nsumerr)/real(ntrials*N)
|
|
write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,7x,f5.2,3x,e10.3)") db,snr2500,ngood,nue,ss,pberr
|
|
|
|
enddo
|
|
|
|
open(unit=23,file='nerrhisto.dat',status='unknown')
|
|
do i=0,N
|
|
write(23,'(i4,2x,i10,i10,f10.2)') i,nerrdec(i),nerrtot(i),real(nerrdec(i))/real(nerrtot(i)+1e-10)
|
|
enddo
|
|
close(23)
|
|
|
|
end program ldpcsim128_90
|