146 lines
5.2 KiB
Fortran
146 lines
5.2 KiB
Fortran
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program fsk4hf
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! Simulate characteristics of a potential mode using LDPC (168,84) code,
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! 4-FSK modulation, and 30 s T/R sequences.
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parameter (KK=84) !Information bits (72 + CRC12)
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parameter (ND=84) !Data symbols: LDPC (168,84), r=1/2
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parameter (NS=12) !Sync symbols (3 @ 4x4 Costas arrays)
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parameter (NR=2) !Ramp up/down
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parameter (NN=NR+NS+ND) !Total symbols (98)
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parameter (NSPS=2688/84) !Samples per symbol (32)
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parameter (NZ=NSPS*NN) !Samples in baseband waveform (3760)
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character*8 arg
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complex c0(0:NZ-1) !Complex waveform
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complex c(0:NZ-1) !Complex waveform
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real xnoise(0:NZ-1) !Generated random noise
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real ynoise(0:NZ-1) !Generated random noise
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real rxdata(2*ND),llr(2*ND) !Soft symbols
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real s(0:NSPS,NN)
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real savg(0:NSPS)
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real ps(0:3)
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integer id(ND) !Symbol values (0-3), data only
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integer id1(ND) !Recovered data values
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integer*1 msgbits(KK),decoded(KK),apmask(ND),cw(ND)
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data msgbits/0,0,1,0,0,1,1,1,1,0,0,1,0,0,0,0,0,0,0,0,1,0,0,0,1,1,0,0,0,1, &
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1,1,1,0,1,1,1,1,1,1,1,0,0,1,0,0,1,1,0,1,0,1,1,1,0,1,1,0,1,1, &
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1,1,0,1,0,1,1,0,0,0,0,0,1,0,0,0,0,0,1,0,1,0,1,0/
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nargs=iargc()
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if(nargs.ne.5) then
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print*,'Usage: fsk4hf f0(Hz) delay(ms) fspread(Hz) iters snr(dB)'
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print*,'Example: fsk4hf 20 0 0 10 -20'
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print*,'Set snr=0 to cycle through a range'
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go to 999
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endif
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call getarg(1,arg)
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read(arg,*) f0 !Generated carrier frequency
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call getarg(2,arg)
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read(arg,*) delay !Delta_t (ms) for Watterson model
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call getarg(3,arg)
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read(arg,*) fspread !Fspread (Hz) for Watterson model
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call getarg(4,arg)
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read(arg,*) iters !Iterations at each SNR
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call getarg(5,arg)
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read(arg,*) snrdb !Specified SNR_2500
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twopi=8.0*atan(1.0)
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fs=12000.0/84.0 !Sample rate = 142.857... Hz
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dt=1.0/fs !Sample interval (s)
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tt=NSPS*dt !Duration of "itone" symbols (s)
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baud=1.0/tt !Keying rate for "itone" symbols (baud)
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txt=NZ*dt !Transmission length (s)
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bandwidth_ratio=2500.0/(fs/2.0)
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write(*,1000) f0,delay,fspread,iters,baud,4*baud,txt
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1000 format('f0:',f5.1,' Delay:',f4.1,' fSpread:',f5.2, &
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' Iters:',i6/'Baud:',f7.3,' BW:',f5.1,' TxT:',f5.1,f5.2/)
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write(*,1004)
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1004 format(/' SNR sym bit ser ber fer fsigma'/50('-'))
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call genfsk4hf(msgbits,f0,id,c0) !Generate baseband waveform
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isna=-10
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isnb=-30
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if(snrdb.ne.0.0) then
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isna=nint(snrdb)
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isnb=isna
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endif
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do isnr=isna,isnb,-1 !Loop over SNR range
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snrdb=isnr
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sig=sqrt(bandwidth_ratio) * 10.0**(0.05*snrdb)
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if(snrdb.gt.90.0) sig=1.0
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nhard=0
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nbit=0
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nfe=0
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sqf=0.
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do iter=1,iters !Loop over requested iterations
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c=c0
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if(delay.ne.0.0 .or. fspread.ne.0.0) then
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call watterson(c,NZ,fs,delay,fspread)
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endif
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c=sig*c !Scale to requested SNR
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if(snrdb.lt.90) then
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do i=0,NZ-1 !Generate gaussian noise
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xnoise(i)=gran()
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ynoise(i)=gran()
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enddo
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c=c + cmplx(xnoise,ynoise) !Add AWGN noise
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endif
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df=fs/(2*NSPS)
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i0=nint(f0/df)
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call spec4(c,s,savg)
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do i=0,NSPS
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write(12,3001) i*df,savg(i),db(savg(i))
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3001 format(3f15.3)
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enddo
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do j=1,ND
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nlo=0
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nhi=0
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k=j+5
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if(j.ge.43) k=j+9
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ps=s(i0:i0+6:2,k)
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ps=sqrt(ps) !###
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rlo=max(ps(1),ps(3))-max(ps(0),ps(2))
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rhi=max(ps(2),ps(3))-max(ps(0),ps(1))
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if(rlo.ge.0.0) nlo=1
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if(rhi.ge.0.0) nhi=1
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rxdata(2*j-1)=rhi
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rxdata(2*j)=rlo
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id1(j)=2*nhi+nlo
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enddo
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! write(*,1001) id(1:70)
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! write(*,1001) id1(1:70)
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!1001 format(70i1)
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nhard=nhard+count(id.ne.id1)
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nbit=nbit + count(iand(id,1).ne.iand(id1,1)) + &
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count(iand(id,2).ne.iand(id1,2))
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rxav=sum(rxdata)/ND
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rx2av=sum(rxdata*rxdata)/ND
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rxsig=sqrt(rx2av-rxav*rxav)
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rxdata=rxdata/rxsig
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ss=0.84
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llr=2.0*rxdata/(ss*ss)
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apmask=0
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max_iterations=40
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ifer=0
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call bpdecode168(llr,apmask,max_iterations,decoded,niterations,cw)
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nbadcrc=0
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if(niterations.ge.0) call chkcrc12(decoded,nbadcrc)
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if(niterations.lt.0 .or. count(msgbits.ne.decoded).gt.0 .or. &
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nbadcrc.ne.0) ifer=1
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nfe=nfe+ifer
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enddo
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fsigma=sqrt(sqf/iters)
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ser=float(nhard)/(ND*iters)
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ber=float(nbit)/(2*ND*iters)
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fer=float(nfe)/iters
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write(*,1050) snrdb,nhard,nbit,ser,ber,fer,fsigma
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! write(60,1050) snrdb,nhard,ber,fer,fsigma
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1050 format(f6.1,2i6,2f8.4,f7.3,f8.2)
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enddo
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999 end program fsk4hf
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