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WSJT-X/lib/qra/qra64/qra64.c
Joe Taylor c7361c66f6 Add APTYPE_CQHISCALL (5), returning 9 [CQ DXcall ?], 10 [CQ DXcall], and 
11 [CQ DXcall DXgrid].


git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6934 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2016-07-21 12:38:26 +00:00

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/*
qra64.c
Encoding/decoding functions for the QRA64 mode
(c) 2016 - Nico Palermo, IV3NWV
-------------------------------------------------------------------------------
qracodes is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
qracodes is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with qracodes source distribution.
If not, see <http://www.gnu.org/licenses/>.
-----------------------------------------------------------------------------
Code used in this sowftware release:
QRA13_64_64_IRR_E: K=13 N=64 Q=64 irregular QRA code (defined in
qra13_64_64_irr_e.h /.c)
Codes with K=13 are designed to include a CRC as the 13th information symbol
and improve the code UER (Undetected Error Rate).
The CRC symbol is not sent along the channel (the codes are punctured) and the
resulting code is a (12,63) code
*/
//----------------------------------------------------------------------------
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include "qra64.h"
#include "../qracodes/qracodes.h"
#include "../qracodes/qra13_64_64_irr_e.h"
#include "../qracodes/pdmath.h"
// Code parameters of the QRA64 mode
#define QRA64_CODE qra_13_64_64_irr_e
#define QRA64_NMSG 218 // Must much value indicated in QRA64_CODE.NMSG
#define QRA64_KC (QRA64_K+1) // Information symbols (crc included)
#define QRA64_NC (QRA64_N+1) // Codeword length (as defined in the code)
#define QRA64_NITER 100 // max number of iterations per decode
// static functions declarations ----------------------------------------------
static int calc_crc6(const int *x, int sz);
static void ix_mask(float *dst, const float *src, const int *mask,
const int *x);
static int qra64_do_decode(int *x, const float *pix, const int *ap_mask,
const int *ap_x);
// a-priori information masks for fields in JT65-like msgs --------------------
#define MASK_CQQRZ 0xFFFFFFC // CQ/QRZ calls common bits
#define MASK_CALL1 0xFFFFFFF
#define MASK_CALL2 0xFFFFFFF
#define MASK_GRIDFULL 0xFFFF
#define MASK_GRIDBIT 0x8000 // b[15] is 1 for free text, 0 otherwise
// ----------------------------------------------------------------------------
qra64codec *qra64_init(int flags)
{
// Eb/No value for which we optimize the decoder metric
const float EbNodBMetric = 2.8f;
const float EbNoMetric = (float)pow(10,EbNodBMetric/10);
const float R = 1.0f*(QRA64_KC)/(QRA64_NC);
qra64codec *pcodec = (qra64codec*)malloc(sizeof(qra64codec));
if (!pcodec)
return 0; // can't allocate memory
pcodec->decEsNoMetric = 1.0f*QRA64_m*R*EbNoMetric;
pcodec->apflags = flags;
memset(pcodec->apmsg_set,0,APTYPE_SIZE*sizeof(int));
if (flags==QRA_NOAP)
return pcodec;
// for QRA_USERAP and QRA_AUTOAP modes we always enable [CQ/QRZ ? ?] mgs look-up.
// encode CQ/QRZ AP messages
// NOTE: Here we handle only CQ and QRZ msgs.
// 'CQ nnn', 'CQ DX' and 'DE' msgs will be handled by the decoder
// as messages with no a-priori knowledge
qra64_apset(pcodec, CALL_CQ, 0, GRID_BLANK, APTYPE_CQQRZ);
// initialize masks for decoding with a-priori information
encodemsg_jt65(pcodec->apmask_cqqrz, MASK_CQQRZ, 0, MASK_GRIDBIT);
encodemsg_jt65(pcodec->apmask_cqqrz_ooo, MASK_CQQRZ, 0, MASK_GRIDFULL);
encodemsg_jt65(pcodec->apmask_call1, MASK_CALL1, 0, MASK_GRIDBIT);
encodemsg_jt65(pcodec->apmask_call1_ooo, MASK_CALL1, 0, MASK_GRIDFULL);
encodemsg_jt65(pcodec->apmask_call2, 0, MASK_CALL2, MASK_GRIDBIT);
encodemsg_jt65(pcodec->apmask_call2_ooo, 0, MASK_CALL2, MASK_GRIDFULL);
encodemsg_jt65(pcodec->apmask_call1_call2, MASK_CALL1,MASK_CALL2, MASK_GRIDBIT);
encodemsg_jt65(pcodec->apmask_call1_call2_grid,MASK_CALL1,MASK_CALL2, MASK_GRIDFULL);
encodemsg_jt65(pcodec->apmask_cq_call2, MASK_CQQRZ, MASK_CALL2, MASK_GRIDBIT);
encodemsg_jt65(pcodec->apmask_cq_call2_ooo, MASK_CQQRZ, MASK_CALL2, MASK_GRIDFULL);
return pcodec;
}
void qra64_close(qra64codec *pcodec)
{
free(pcodec);
}
int qra64_apset(qra64codec *pcodec, const int mycall, const int hiscall, const int grid, const int aptype)
{
// Set decoder a-priori knowledge accordingly to the type of the message to look up for
// arguments:
// pcodec = pointer to a qra64codec data structure as returned by qra64_init
// mycall = mycall to look for
// hiscall = hiscall to look for
// grid = grid to look for
// aptype = define and masks the type of AP to be set accordingly to the following:
// APTYPE_CQQRZ set [cq/qrz ? ?/blank]
// APTYPE_MYCALL set [mycall ? ?/blank]
// APTYPE_HISCALL set [? hiscall ?/blank]
// APTYPE_BOTHCALLS set [mycall hiscall ?]
// APTYPE_FULL set [mycall hiscall grid]
// APTYPE_CQHISCALL set [cq/qrz hiscall ?/blank] and [cq/qrz hiscall grid]
// returns:
// 0 on success
// -1 when qra64_init was called with the QRA_NOAP flag
// -2 invalid apytpe
if (pcodec->apflags==QRA_NOAP)
return -1;
switch (aptype) {
case APTYPE_CQQRZ:
encodemsg_jt65(pcodec->apmsg_cqqrz, CALL_CQ, 0, GRID_BLANK);
break;
case APTYPE_MYCALL:
encodemsg_jt65(pcodec->apmsg_call1, mycall, 0, GRID_BLANK);
break;
case APTYPE_HISCALL:
encodemsg_jt65(pcodec->apmsg_call2, 0, hiscall, GRID_BLANK);
break;
case APTYPE_BOTHCALLS:
encodemsg_jt65(pcodec->apmsg_call1_call2, mycall, hiscall, GRID_BLANK);
break;
case APTYPE_FULL:
encodemsg_jt65(pcodec->apmsg_call1_call2_grid, mycall, hiscall, grid);
break;
case APTYPE_CQHISCALL:
encodemsg_jt65(pcodec->apmsg_cq_call2, CALL_CQ, hiscall, GRID_BLANK);
encodemsg_jt65(pcodec->apmsg_cq_call2_grid, CALL_CQ, hiscall, grid);
break;
default:
return -2; // invalid ap type
}
pcodec->apmsg_set[aptype]=1; // signal the decoder to look-up for the specified type
return 0;
}
void qra64_apdisable(qra64codec *pcodec, const int aptype)
{
if (pcodec->apflags==QRA_NOAP)
return;
if (aptype<APTYPE_CQQRZ || aptype>=APTYPE_SIZE)
return;
pcodec->apmsg_set[aptype] = 0; // signal the decoder not to look-up to the specified type
}
void qra64_encode(qra64codec *pcodec, int *y, const int *x)
{
int encx[QRA64_KC]; // encoder input buffer
int ency[QRA64_NC]; // encoder output buffer
int hiscall,mycall,grid;
memcpy(encx,x,QRA64_K*sizeof(int)); // Copy input to encoder buffer
encx[QRA64_K]=calc_crc6(encx,QRA64_K); // Compute and add crc symbol
qra_encode(&QRA64_CODE, ency, encx); // encode msg+crc using given QRA code
// copy codeword to output puncturing the crc symbol
memcpy(y,ency,QRA64_K*sizeof(int)); // copy information symbols
memcpy(y+QRA64_K,ency+QRA64_KC,QRA64_C*sizeof(int)); // copy parity symbols
if (pcodec->apflags!=QRA_AUTOAP)
return;
// Here we handle the QRA_AUTOAP mode --------------------------------------------
// When a [hiscall mycall ?] msg is detected we instruct the decoder
// to look for [mycall hiscall ?] msgs
// otherwise when a [cq mycall ?] msg is sent we reset the APTYPE_BOTHCALLS
// look if the msg sent is a std type message (bit15 of grid field = 0)
if ((x[9]&0x80)==1)
return; // no, it's a text message, nothing to do
// It's a [hiscall mycall grid] message
// We assume that mycall is our call (but we don't check it)
// hiscall the station we are calling or a general call (CQ/QRZ/etc..)
decodemsg_jt65(&hiscall,&mycall,&grid,x);
if ((hiscall>=CALL_CQ && hiscall<=CALL_CQ999) || hiscall==CALL_CQDX ||
hiscall==CALL_DE) {
// tell the decoder to look for msgs directed to us
qra64_apset(pcodec,mycall,0,0,APTYPE_MYCALL);
// We are making a general call and don't know who might reply
// Reset APTYPE_BOTHCALLS so decoder won't look for [mycall hiscall ?] msgs
qra64_apdisable(pcodec,APTYPE_BOTHCALLS);
} else {
// We are replying to someone named hiscall
// Set APTYPE_BOTHCALLS so decoder will try for [mycall hiscall ?] msgs
qra64_apset(pcodec,mycall, hiscall, GRID_BLANK, APTYPE_BOTHCALLS);
}
}
#define EBNO_MIN -10.0f // minimum Eb/No value returned by the decoder (in dB)
int qra64_decode(qra64codec *pcodec, float *ebno, int *x, const float *rxen)
{
int k;
float *srctmp, *dsttmp;
float ix[QRA64_NC*QRA64_M]; // (depunctured) intrisic information
int xdec[QRA64_KC]; // decoded message (with crc)
int ydec[QRA64_NC]; // re-encoded message (for snr calculations)
float noisestd; // estimated noise variance
float msge; // estimated message energy
float ebnoval; // estimated Eb/No
int rc;
if (QRA64_NMSG!=QRA64_CODE.NMSG) // sanity check
return -16; // QRA64_NMSG define is wrong
// compute symbols intrinsic probabilities from received energy observations
noisestd = qra_mfskbesselmetric(ix, rxen, QRA64_m, QRA64_N,pcodec->decEsNoMetric);
// de-puncture observations adding a uniform distribution for the crc symbol
// move check symbols distributions one symbol towards the end
dsttmp = PD_ROWADDR(ix,QRA64_M, QRA64_NC-1); //Point to last symbol prob dist
srctmp = dsttmp-QRA64_M; // source is the previous pd
for (k=0;k<QRA64_C;k++) {
pd_init(dsttmp,srctmp,QRA64_M);
dsttmp -=QRA64_M;
srctmp -=QRA64_M;
}
// Initialize crc prob to a uniform distribution
pd_init(dsttmp,pd_uniform(QRA64_m),QRA64_M);
// Attempt to decode without a-priori info --------------------------------
rc = qra64_do_decode(xdec, ix, NULL, NULL);
if (rc>=0) {
rc = 0; // successfull decode with AP0
goto decode_end;
}
else
if (pcodec->apflags==QRA_NOAP)
// nothing more to do
return rc; // rc<0 = unsuccessful decode
// Here we handle decoding with AP knowledge
// Attempt to decode CQ calls
rc = qra64_do_decode(xdec,ix,pcodec->apmask_cqqrz, pcodec->apmsg_cqqrz);
if (rc>=0) { rc = 1; goto decode_end; }; // decoded [cq/qrz ? ?]
rc = qra64_do_decode(xdec, ix, pcodec->apmask_cqqrz_ooo,
pcodec->apmsg_cqqrz);
if (rc>=0) { rc = 2; goto decode_end; }; // decoded [cq ? ooo]
// attempt to decode calls directed to us
if (pcodec->apmsg_set[APTYPE_MYCALL]) {
rc = qra64_do_decode(xdec, ix, pcodec->apmask_call1,
pcodec->apmsg_call1);
if (rc>=0) { rc = 3; goto decode_end; }; // decoded [mycall ? ?]
rc = qra64_do_decode(xdec, ix, pcodec->apmask_call1_ooo,
pcodec->apmsg_call1);
if (rc>=0) { rc = 4; goto decode_end; }; // decoded [mycall ? ooo]
}
// attempt to decode [mycall srccall ?] msgs
if (pcodec->apmsg_set[APTYPE_BOTHCALLS]) {
rc = qra64_do_decode(xdec, ix, pcodec->apmask_call1_call2,
pcodec->apmsg_call1_call2);
if (rc>=0) { rc = 5; goto decode_end; }; // decoded [mycall srccall ?]
}
// attempt to decode [? hiscall ?/b] msgs
if (pcodec->apmsg_set[APTYPE_HISCALL]) {
rc = qra64_do_decode(xdec, ix, pcodec->apmask_call2,
pcodec->apmsg_call2);
if (rc>=0) { rc = 6; goto decode_end; }; // decoded [? hiscall ?]
rc = qra64_do_decode(xdec, ix, pcodec->apmask_call2_ooo,
pcodec->apmsg_call2);
if (rc>=0) { rc = 7; goto decode_end; }; // decoded [? hiscall ooo]
}
// attempt to decode [cq/qrz hiscall ?/b/grid] msgs
if (pcodec->apmsg_set[APTYPE_CQHISCALL]) {
rc = qra64_do_decode(xdec, ix, pcodec->apmask_cq_call2,
pcodec->apmsg_cq_call2);
if (rc>=0) { rc = 9; goto decode_end; }; // decoded [cq/qrz hiscall ?]
rc = qra64_do_decode(xdec, ix, pcodec->apmask_cq_call2_ooo,
pcodec->apmsg_cq_call2_grid);
if (rc>=0) { rc = 11; goto decode_end; }; // decoded [cq/qrz hiscall grid]
rc = qra64_do_decode(xdec, ix, pcodec->apmask_cq_call2_ooo,
pcodec->apmsg_cq_call2);
if (rc>=0) { rc = 10; goto decode_end; }; // decoded [cq/qrz hiscall ]
}
// attempt to decode [mycall hiscall grid]
if (pcodec->apmsg_set[APTYPE_FULL]) {
rc = qra64_do_decode(xdec, ix, pcodec->apmask_call1_call2_grid,
pcodec->apmsg_call1_call2_grid);
if (rc>=0) { rc = 8; goto decode_end; }; // decoded [mycall hiscall grid]
}
// all decoding attempts failed
return rc;
decode_end: // successfull decode
// copy decoded message (without crc) to output buffer
memcpy(x,xdec,QRA64_K*sizeof(int));
if (ebno==0) // null pointer indicates we are not interested in the Eb/No estimate
return rc;
// reencode message and estimate Eb/No
qra_encode(&QRA64_CODE, ydec, xdec);
// puncture crc
memmove(ydec+QRA64_K,ydec+QRA64_KC,QRA64_C*sizeof(int));
// compute total power of decoded message
msge = 0;
for (k=0;k<QRA64_N;k++) {
msge +=rxen[ydec[k]]; // add energy of current symbol
rxen+=QRA64_M; // ptr to next symbol
}
// NOTE:
// To make a more accurate Eb/No estimation we should compute the noise variance
// on all the rxen values but the transmitted symbols.
// Noisestd is compute by qra_mfskbesselmetric assuming that
// the signal power is much less than the total noise power in the QRA64_M tones
// but this is true only if the Eb/No is low.
// Here, in order to improve accuracy, we linearize the estimated Eb/No value empirically
// (it gets compressed when it is very high as in this case the noise variance
// is overestimated)
// this would be the exact value if the noisestd were not overestimated at high Eb/No
ebnoval = (0.5f/(QRA64_K*QRA64_m))*msge/(noisestd*noisestd)-1.0f;
// Empirical linearization (to remove the noise variance overestimation)
// the resulting SNR is accurate up to +20 dB (51 dB Eb/No)
if (ebnoval>57.004f)
ebnoval=57.004f;
ebnoval = ebnoval*57.03f/(57.03f-ebnoval);
// compute value in dB
if (ebnoval<=0)
ebnoval = EBNO_MIN; // assume a minimum, positive value
else
ebnoval = 10.0f*(float)log10(ebnoval);
if (ebnoval<EBNO_MIN)
ebnoval = EBNO_MIN;
*ebno = ebnoval;
return rc;
}
// Static functions definitions ----------------------------------------------
// Decode with given a-priori information
static int qra64_do_decode(int *xdec, const float *pix, const int *ap_mask,
const int *ap_x)
{
int rc;
const float *ixsrc;
float ix_masked[QRA64_NC*QRA64_M]; // Masked intrinsic information
float ex[QRA64_NC*QRA64_M]; // Extrinsic information from the decoder
float v2cmsg[QRA64_NMSG*QRA64_M]; // buffers for the decoder messages
float c2vmsg[QRA64_NMSG*QRA64_M];
if (ap_mask==NULL) { // no a-priori information
ixsrc = pix; // intrinsic source is what passed as argument
} else {
// a-priori information provided
// mask channel observations with a-priori
ix_mask(ix_masked,pix,ap_mask,ap_x);
ixsrc = ix_masked; // intrinsic source is the masked version
}
// run the decoding algorithm
rc = qra_extrinsic(&QRA64_CODE,ex,ixsrc,QRA64_NITER,v2cmsg,c2vmsg);
if (rc<0)
return -1; // no convergence in given iterations
// decode
qra_mapdecode(&QRA64_CODE,xdec,ex,ixsrc);
// verify crc
if (calc_crc6(xdec,QRA64_K)!=xdec[QRA64_K]) // crc doesn't match (detected error)
return -2; // decoding was succesfull but crc doesn't match
return 0;
}
// crc functions --------------------------------------------------------------
// crc-6 generator polynomial
// g(x) = x^6 + a5*x^5 + ... + a1*x + a0
// g(x) = x^6 + x + 1
#define CRC6_GEN_POL 0x30 // MSB=a0 LSB=a5
// g(x) = x^6 + x^2 + x + 1 (See: https://users.ece.cmu.edu/~koopman/crc/)
// #define CRC6_GEN_POL 0x38 // MSB=a0 LSB=a5. Simulation results are similar
static int calc_crc6(const int *x, int sz)
{
// todo: compute it faster using a look up table
int k,j,t,sr = 0;
for (k=0;k<sz;k++) {
t = x[k];
for (j=0;j<6;j++) {
if ((t^sr)&0x01)
sr = (sr>>1) ^ CRC6_GEN_POL;
else
sr = (sr>>1);
t>>=1;
}
}
return sr;
}
static void ix_mask(float *dst, const float *src, const int *mask,
const int *x)
{
// mask intrinsic information (channel observations) with a priori knowledge
int k,kk, smask;
float *row;
memcpy(dst,src,(QRA64_NC*QRA64_M)*sizeof(float));
for (k=0;k<QRA64_K;k++) { // we can mask only information symbols distrib
smask = mask[k];
row = PD_ROWADDR(dst,QRA64_M,k);
if (smask) {
for (kk=0;kk<QRA64_M;kk++)
if (((kk^x[k])&smask)!=0)
*(row+kk) = 0.f;
pd_norm(row,QRA64_m);
}
}
}
// encode/decode msgs as done in JT65
void encodemsg_jt65(int *y, const int call1, const int call2, const int grid)
{
y[0]= (call1>>22)&0x3F;
y[1]= (call1>>16)&0x3F;
y[2]= (call1>>10)&0x3F;
y[3]= (call1>>4)&0x3F;
y[4]= (call1<<2)&0x3F;
y[4] |= (call2>>26)&0x3F;
y[5]= (call2>>20)&0x3F;
y[6]= (call2>>14)&0x3F;
y[7]= (call2>>8)&0x3F;
y[8]= (call2>>2)&0x3F;
y[9]= (call2<<4)&0x3F;
y[9] |= (grid>>12)&0x3F;
y[10]= (grid>>6)&0x3F;
y[11]= (grid)&0x3F;
}
void decodemsg_jt65(int *call1, int *call2, int *grid, const int *x)
{
int nc1, nc2, ng;
nc1 = x[4]>>2;
nc1 |= x[3]<<4;
nc1 |= x[2]<<10;
nc1 |= x[1]<<16;
nc1 |= x[0]<<22;
nc2 = x[9]>>4;
nc2 |= x[8]<<2;
nc2 |= x[7]<<8;
nc2 |= x[6]<<14;
nc2 |= x[5]<<20;
nc2 |= (x[4]&0x03)<<26;
ng = x[11];
ng |= x[10]<<6;
ng |= (x[9]&0x0F)<<12;
*call1 = nc1;
*call2 = nc2;
*grid = ng;
}
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