From 5d6a502a8798a7318140863dd41c59547be7d683 Mon Sep 17 00:00:00 2001 From: Steven Franke Date: Sun, 31 Jan 2016 01:47:30 +0000 Subject: [PATCH] Generate fer vs Eb/N0 for rate 1/2 K=13 convolutional code. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6451 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 --- lib/JTMSKfer.f90 | 128 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 128 insertions(+) create mode 100644 lib/JTMSKfer.f90 diff --git a/lib/JTMSKfer.f90 b/lib/JTMSKfer.f90 new file mode 100644 index 000000000..e5416b6ba --- /dev/null +++ b/lib/JTMSKfer.f90 @@ -0,0 +1,128 @@ +program JTMSKfer + +! Measure the frame error rate (fer) of the rate 1/2, K=13 conv. code with +! coherent BPSK, Viterbi decoding, perfect sync. The results are to be +! compared with LDPC fer's produced by the routines in the ldpc sandbox folder. +! These coherent BPSK results will not correspond to JTMSK. + + use iso_c_binding, only: c_loc,c_size_t + use hashing + use packjt + character msg*22,decoded*22,msgtype*13 + integer*4 i4tone(234) !Channel symbols (values 0-1) + integer*1 e1(201) + integer*4 r1(201) + real rd(201), tmp + integer*1, target :: d8(13) + integer mettab(0:255,0:1) !Metric table for BPSK modulation + integer*1 i1hash(4) + integer*4 i4Msg6BitWords(12) !72-bit message as 6-bit words + character*72 c72 +! real*8 twopi,dt,f0,f1,f,phi,dphi + real xp(29) + equivalence (ihash,i1hash) + data xp/0.500000, 0.401241, 0.309897, 0.231832, 0.168095, & + 0.119704, 0.083523, 0.057387, 0.039215, 0.026890, & + 0.018084, 0.012184, 0.008196, 0.005475, 0.003808, & + 0.002481, 0.001710, 0.001052, 0.000789, 0.000469, & + 0.000329, 0.000225, 0.000187, 0.000086, 0.000063, & + 0.000017, 0.000091, 0.000032, 0.000045/ + include 'testmsg.f90' + + nmsg=1 + +! Get the metric table + bias=0.0 + scale=20.0 + xln2=log(2.0) + do i=128,156 + x0=log(max(0.0001,2.0*xp(i-127)))/xln2 + x1=log(max(0.001,2.0*(1.0-xp(i-127))))/xln2 + mettab(i,0)=nint(scale*(x0-bias)) + mettab(i,1)=nint(scale*(x1-bias)) + mettab(256-i,0)=mettab(i,1) + mettab(256-i,1)=mettab(i,0) + enddo + do i=157,255 + mettab(i,0)=mettab(156,0) + mettab(i,1)=mettab(156,1) + mettab(256-i,0)=mettab(i,1) + mettab(256-i,1)=mettab(i,0) + enddo + + rdscale=2.0 ! empirically optiized + ntrials=1000000 + rate=72.0/198.0 + msg="123" +! call sgran() + + do idb=0,10 + db=idb/2.0-0.5 ! Eb/N0=1/(2*R*sigma^2), so sigma= sqrt( 1/(2*R*Eb/N0) ) + sigma=1/sqrt( 2*rate*(10**(db/10.0)) ) + + call fmtmsg(msg,iz) !To upper case, collapse multiple blanks + ichk=0 + call genmsk(msg,ichk,decoded,i4tone,itype) !Encode message into tone #s + msgtype="" + if(itype.eq.1) msgtype="Std Msg" + if(itype.eq.2) msgtype="Type 1 prefix" + if(itype.eq.3) msgtype="Type 1 suffix" + if(itype.eq.4) msgtype="Type 2 prefix" + if(itype.eq.5) msgtype="Type 2 suffix" + if(itype.eq.6) msgtype="Free text" + +! Extract the data symbols, skipping over sync and parity bits + n1=35 + n2=69 + n3=94 + + r1(1:n1)=i4tone(11+1:11+n1) + r1(n1+1:n1+n2)=i4tone(23+n1+1:23+n1+n2) + r1(n1+n2+1:n1+n2+n3)=i4tone(35+n1+n2+1:35+n1+n2+n3) + + ngood=0 ! decoded = msg + ngoodhash=0 ! will include undetected errors plus actual good ones + + do itrial=1,ntrials + do i=1,n1+n2+n3 + tmp=( 2.0 * ( r1(i)-0.5 ) + sigma*gran() )*rdscale + if( tmp .lt. 0 ) then + rd(i)=min(127.0,-tmp) + elseif( tmp .gt.0 ) then + rd(i)=max(-tmp,-127.0) + endif + enddo + + j=0 + do i=1,99 + j=j+1 + e1(j)=rd(i) + j=j+1 + e1(j)=rd(i+99) + enddo + + nb1=87 + call vit213(e1,nb1,mettab,d8,metric) + + igoodhash=0 + ihash=nhash(c_loc(d8),int(9,c_size_t),146) + ihash=2*iand(ihash,32767) + decoded=" " + if(d8(10).eq.i1hash(2) .and. d8(11).eq.i1hash(1)) then + igoodhash=1 + write(c72,1012) d8(1:9) +1012 format(9b8.8) + read(c72,1014) i4Msg6BitWords +1014 format(12b6.6) + call unpackmsg(i4Msg6BitWords,decoded) !Unpack to get msgsent + endif + + if( igoodhash .eq. 1) ngoodhash=ngoodhash+1 + if( decoded .eq. msg ) ngood=ngood+1 + + enddo + + write(*,1023) db,sigma,ntrials,ngood,ngoodhash-ngood +1023 format("db:",f6.2," sigma:",f6.2," ntot:",i8," good:",i8," undet:",i8) +enddo +999 end program JTMSKfer