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
This commit is contained in:
Steven Franke 2016-01-31 01:47:30 +00:00
parent ef8c2ad0bb
commit 5d6a502a87

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lib/JTMSKfer.f90 Normal file
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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