Guys, Here is the next step improvement in bpsk robustness with an interleaver added to the FEC. It should provide better resistance to noise bursts by spreading the errors in time, which make the Viterbi decoder's job easier. Please give it a go as in my tests I was getting an error rate at least 2 times better than the stock BPSK mode one speed lower (e.g. BPSK500 with FEC and interleaver much better than BPSK250). Again here are the two files psk.h for the include directory and psk.cxx for the psk directory. You can drop them in the 3.13AY (and probably earlier) versions onwards. Rein, if you could post a new source pack on the alpha site that would be great. If you can test it, please let me know of it's performance with the FEC only (the previous version). Is there value in building executables for Linux and Windows? Best regards, 73s, John
// ---------------------------------------------------------------------------- // psk.h -- psk modem // // Copyright (C) 2006 // Dave Freese, W1HKJ // // This file is part of fldigi. Adapted from code contained in gmfsk source code // distribution. // // fldigi 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 2 of the License, or // (at your option) any later version. // // fldigi 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 fldigi; if not, write to the Free Software // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA // ---------------------------------------------------------------------------- #ifndef _PSK_H #define _PSK_H #include "complex.h" #include "modem.h" #include "globals.h" #include "viterbi.h" #include "filters.h" #include "pskcoeff.h" #include "pskvaricode.h" #include "viewpsk.h" #include "pskeval.h" //VK2ETA Interleaver #include "interleave.h" //===================================================================== #define PskSampleRate (8000) #define PipeLen (64) #define SNTHRESHOLD 6.0 #define AFCDECAYSLOW 8 #define NUM_FILTERS 3 #define GOERTZEL 288 //96 x 2 must be an integer value //===================================================================== class psk : public modem { private: // tx & rx int symbollen; bool _qpsk; double phaseacc; complex prevsymbol; unsigned int shreg; //VK2ETA FEC unsigned int shreg2; // rx variables & functions C_FIR_filter *fir1; C_FIR_filter *fir2; // C_FIR_filter *fir3; double *fir1c; double *fir2c; Cmovavg *snfilt; Cmovavg *imdfilt; double I1[NUM_FILTERS]; double I2[NUM_FILTERS]; double Q1[NUM_FILTERS]; double Q2[NUM_FILTERS]; double COEF[NUM_FILTERS]; double m_Energy[NUM_FILTERS]; int m_NCount; bool imdValid; encoder *enc; viterbi *dec; //VK2ETA BPSK+FEC with 2nd Viterbi decoder and 2 receive de-interleavers for comparison viterbi *dec2; interleave *Rxinlv; interleave *Rxinlv2; interleave *Txinlv; int bitstate; unsigned int bitshreg; int rxbitstate; unsigned int rxbitshreg; unsigned int rxbitshreg2; int fecmet; int fecmet2; unsigned char symcur[2]; unsigned char symP1[2]; double phase; double freqerr; int bits; double bitclk; double syncbuf[16]; double scope_pipe[2*PipeLen];//[PipeLen]; unsigned int pipeptr; unsigned int dcdshreg; //VK2ETA FEC unsigned int dcdshreg2; int dcd; int dcdbits; complex quality; int acquire; viewpsk* pskviewer; pskeval* evalpsk; void rx_symbol(complex symbol); void rx_bit(int bit); //VK2ETA FEC void rx_bit2(int bit); void rx_qpsk(int bits); double scopedata[16]; // IMD & s/n variables double k0, k1, k2; double I11, I12, I21, I22, I31, I32; double snratio, s2n, imdratio, imd; double E1, E2, E3; double afcmetric; //VK2ETA signal quality double s2n_ncount; double s2n_sum; double s2n_sum2; //VK2ETA FEC for BPSK modes bool firstbit; bool startpreamble; // complex thirdorder; // tx variables & functions double *tx_shape; int preamble; void tx_symbol(int sym); void tx_bit(int bit); void tx_char(unsigned char c); void tx_flush(); void update_syncscope(); void signalquality(); void findsignal(); void phaseafc(); void afc(); void coreafc(); void initSN_IMD(); void resetSN_IMD(); void calcSN_IMD(complex z); //VK2ETA interleaver void clearbits(); public: psk(trx_mode mode); ~psk(); void init(); void rx_init(); void tx_init(SoundBase *sc); void restart(); int rx_process(const double *buf, int len); int tx_process(); void searchDown(); void searchUp(); }; #endif
// ---------------------------------------------------------------------------- // psk.cxx -- psk modem // // Copyright (C) 2006 // Dave Freese, W1HKJ // // This file is part of fldigi. Adapted from code contained in gmfsk // source code distribution. // gmfsk Copyright (C) 2001, 2002, 2003 // Tomi Manninen (oh2bns@xxxxxxx) // // fldigi 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 2 of the License, or // (at your option) any later version. // // fldigi 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 fldigi; if not, write to the Free Software // Foundation, Inc., 59 Temple Place, Suite 330, // Boston, MA 02111-1307 USA // -------------------------------------------------------------------- #include <config.h> #include <stdlib.h> #include <stdio.h> #include <iomanip> #include "psk.h" #include "main.h" #include "fl_digi.h" #include "trx.h" #include "misc.h" #include "waterfall.h" #include "configuration.h" #include "status.h" #include "viewpsk.h" #include "pskeval.h" extern waterfall *wf; // Change the following for DCD low pass filter adjustment #define SQLCOEFF 0.01 #define SQLDECAY 50 //===================================================================== //#define K 5 //#define POLY1 0x17 //#define POLY2 0x19 //VK2ETA QPSK+FEC #define K 7 #define POLY1 0x6d #define POLY2 0x4f #define EOT 0x04 //EOT ascii character char pskmsg[80]; viewpsk *pskviewer = (viewpsk *)0; void psk::tx_init(SoundBase *sc) { scard = sc; phaseacc = 0; prevsymbol = complex (1.0, 0.0); preamble = dcdbits; shreg = 0; shreg2 = 0; videoText(); //VK2ETA interleaver bitshreg = 0; bitstate = 0; startpreamble = true; } void psk::rx_init() { phaseacc = 0; prevsymbol = complex (1.0, 0.0); quality = complex (0.0, 0.0); shreg = 0; shreg2 = 0; dcdshreg = 0; dcdshreg2 = 0; dcd = 0; bitclk = 0; freqerr = 0.0; if (mailserver && progdefaults.PSKmailSweetSpot) sigsearch = SIGSEARCH; put_MODEstatus(mode); resetSN_IMD(); imdValid = false; afcmetric = 0.0; //VK2ETA interleaver rxbitshreg = 0; rxbitshreg2 = 0; rxbitstate = 0; } void psk::restart() { pskviewer->restart(mode); evalpsk->setbw(bandwidth); } void psk::init() { modem::init(); restart(); set_scope_mode(Digiscope::PHASE); initSN_IMD(); snratio = 1.0; imdratio = 0.001; rx_init(); } psk::~psk() { if (tx_shape) delete [] tx_shape; if (enc) delete enc; if (dec) delete dec; //VK2ETA 2nd Viterbi decoder if (dec2) delete dec2; //VK2ETA FEC + INTERLEAVER if (fir1) delete fir1; if (fir2) delete fir2; if (snfilt) delete snfilt; if (imdfilt) delete imdfilt; if (::pskviewer == pskviewer) ::pskviewer = 0; delete pskviewer; delete evalpsk; //VK2ETA Interleaver if (Rxinlv) delete Rxinlv; if (Rxinlv2) delete Rxinlv2; if (Txinlv) delete Txinlv; } psk::psk(trx_mode pskmode) : modem() { cap = CAP_AFC | CAP_AFC_SR; mode = pskmode; switch (mode) { case MODE_BPSK31: symbollen = 256; _qpsk = false; dcdbits = 32; break; case MODE_QPSK31: //VK2ETA FEC test replace qpsk31 by BPSK500 + MFEC // symbollen = 256; // _qpsk = true; // dcdbits = 32; symbollen = 16; _qpsk = true; dcdbits = 512; //VK2ETA BPSK+FEC cap |= CAP_REV; break; case MODE_PSK63: symbollen = 128; _qpsk = false; dcdbits = 64; break; case MODE_QPSK63: symbollen = 128; _qpsk = true; dcdbits = 64; //VK2ETA BPSK+FEC cap |= CAP_REV; break; case MODE_PSK125: symbollen = 64; _qpsk = false; dcdbits = 128; break; case MODE_QPSK125: symbollen = 64; _qpsk = true; dcdbits = 128; //VK2ETA BPSK+FEC cap |= CAP_REV; break; case MODE_PSK250: symbollen = 32; _qpsk = false; dcdbits = 256; break; case MODE_QPSK250: symbollen = 32; _qpsk = true; dcdbits = 256; //VK2ETA BPSK+FEC cap |= CAP_REV; break; case MODE_PSK500: symbollen = 16; _qpsk = false; dcdbits = 512; break; default: mode = MODE_BPSK31; symbollen = 256; _qpsk = false; dcdbits = 32; } enc = (encoder *)0; dec = (viterbi *)0; //VK2ETA BPSK+FEC - 2nd Viterbi decoder and de-interleaver dec2 = (viterbi *)0; Txinlv = (interleave *)0; Rxinlv = (interleave *)0; Rxinlv2 = (interleave *)0; // create impulse response for experimental FIR filters double fir1c[64]; double fir2c[64]; fir1 = new C_FIR_filter(); fir2 = new C_FIR_filter(); switch (progdefaults.PSK_filter) { case 1: // use the original gmfsk matched filters for (int i = 0; i < 64; i++) { fir1c[i] = gmfir1c[i]; fir2c[i] = gmfir2c[i]; } fir1->init(FIRLEN, symbollen / 16, fir1c, fir1c); fir2->init(FIRLEN, 1, fir2c, fir2c); break; case 2: // creates fir1c matched sin(x)/x filter w hamming wsincfilt(fir1c, 1.0 / symbollen, false); fir1->init(FIRLEN, symbollen / 16, fir1c, fir1c); // creates fir2c matched sin(x)/x filter w hamming wsincfilt(fir2c, 1.0 / 16.0, false); fir2->init(FIRLEN, 1, fir2c, fir2c); break; case 3: // creates fir1c matched sin(x)/x filter w hamming wsincfilt(fir1c, 1.0 / symbollen, false); fir1->init(FIRLEN, symbollen / 16, fir1c, fir1c); // 1/22 with Hamming window nearly identical to gmfir2c wsincfilt(fir2c, 1.0 / 22.0, false); fir2->init(FIRLEN, 1, fir2c, fir2c); break; case 4: fir1->init_lowpass (FIRLEN, 16, 1.5 / symbollen); wsincfilt(fir2c, 1.5 / 16.0, true); fir2->init(FIRLEN, 1, fir2c, fir2c); case 0: default : // creates fir1c matched sin(x)/x filter w blackman wsincfilt(fir1c, 1.0 / symbollen, true); fir1->init(FIRLEN, symbollen / 16, fir1c, fir1c); // creates fir2c matched sin(x)/x filter w blackman wsincfilt(fir2c, 1.0 / 16.0, true); fir2->init(FIRLEN, 1, fir2c, fir2c); } snfilt = new Cmovavg(16); imdfilt = new Cmovavg(16); if (_qpsk) { enc = new encoder(K, POLY1, POLY2); dec = new viterbi(K, POLY1, POLY2); //VK2ETA FEC for BPSK. Use a 2nd Viterbi decoder for comparison dec->setchunksize(4); dec2 = new viterbi(K, POLY1, POLY2); dec2->setchunksize(4); //VK2ETA interleaver Txinlv = new interleave (2, INTERLEAVE_FWD); // 2x2x10 Rxinlv = new interleave (2, INTERLEAVE_REV); // 2x2x10 Rxinlv2 = new interleave (2, INTERLEAVE_REV); // 2x2x10 bitshreg = 0; bitstate = 0; rxbitshreg = 0; rxbitshreg2 = 0; rxbitstate = 0; startpreamble = true; } tx_shape = new double[symbollen]; /* raised cosine shape for the transmitter */ for ( int i = 0; i < symbollen; i++) tx_shape[i] = 0.5 * cos(i * M_PI / symbollen) + 0.5; samplerate = PskSampleRate; fragmentsize = symbollen; bandwidth = samplerate / symbollen; snratio = s2n = imdratio = imd = 0; if (mailserver && progdefaults.PSKmailSweetSpot) sigsearch = SIGSEARCH; else sigsearch = 0; for (int i = 0; i < 16; i++) syncbuf[i] = 0.0; E1 = E2 = E3 = 0.0; acquire = 0; evalpsk = new pskeval; ::pskviewer = pskviewer = new viewpsk(evalpsk, mode); init(); } //============================================================================= //=========================== psk31 receive routines ========================== //============================================================================= void psk::rx_bit(int bit) { int c; char qualityfb[100]; unsigned i,limit; static double s2n_avg; static double s2n_stddev; dcdshreg = (dcdshreg << 2) | bit; switch (dcdshreg) { case 0xAAAAAAAA: /* DCD on by preamble */ dcd = true; acquire = 0; quality = complex (1.0, 0.0); imdValid = true; //VK2ETA signal report s2n_sum = s2n_sum2 = s2n_ncount = 0; break; case 0: /* DCD off by postamble */ //VK2ETA don't cut too soon, we need to get the rest of the decoding dcd = false; // dcd = true; acquire = 0; // quality = complex (0.0, 0.0); // imdValid = false; break; } shreg = (shreg << 1) | !!bit; if ((shreg & 3) == 0) { c = psk_varicode_decode(shreg >> 2); if ((fecmet >= fecmet2) || (_qpsk == false)) { if ((c != -1) && (dcd == true)) { // put_rx_char('<'); put_rx_char(c); } } shreg = 0; } } void psk::rx_bit2(int bit) { int c; dcdshreg2 = (dcdshreg2 << 2) | bit; switch (dcdshreg2) { case 0xAAAAAAAA: /* DCD on by preamble */ dcd = true; acquire = 0; quality = complex (1.0, 0.0); imdValid = true; //VK2ETA signal report s2n_sum = s2n_sum2 = s2n_ncount = 0; break; case 0: /* DCD off by postamble */ //VK2ETA don't cut too soon, we need to get the rest of the decoding dcd = false; // dcd = true; acquire = 0; // quality = complex (0.0, 0.0); // imdValid = false; break; } shreg2 = (shreg2 << 1) | !!bit; if ((shreg2 & 3) == 0) { c = psk_varicode_decode(shreg2 >> 2); if (fecmet < fecmet2) { if ((c != -1) && (dcd == true)) { // put_rx_char('>'); put_rx_char(c); } } shreg2 = 0; } } void psk::rx_qpsk(int bits) { int met; unsigned int rbits; int c; //Accumulate the bits for the interleaver THEN submit to Viterbi decoder rxbitshreg2 = (rxbitshreg2 << 1) | (bits & 1); rxbitshreg = (rxbitshreg << 1) | (bits & 1); if (rxbitstate == 0) { rxbitstate++; //De-interleave Rxinlv2->bits(&rxbitshreg2); firstbit = false; for (int i = 1; i >-1; i--) { rbits = (rxbitshreg2 & (1 << i)) >> i; if (firstbit) { symP1[0] = (rbits & 1) ? 255 : 0; } else { symP1[1] = (rbits & 1) ? 255 : 0; //Then viterbi decoder c = dec2->decode(symP1, &met); if (c != -1) { //VK2ETA only take metric measurement after backtrace fecmet2 = decayavg(fecmet2, met, 10); rx_bit2(c & 0x08); rx_bit2(c & 0x04); rx_bit2(c & 0x02); rx_bit2(c & 0x01); } } firstbit = ! firstbit; } rxbitshreg2 = 0; } else { rxbitstate = 0; //De-interleave Rxinlv->bits(&rxbitshreg); firstbit = false; for (int i = 1; i >-1; i--) { rbits = (rxbitshreg & (1 << i)) >> i; if (firstbit) { symcur[0] = (rbits & 1) ? 255 : 0; } else { symcur[1] = (rbits & 1) ? 255 : 0; //Then viterbi decoder c = dec->decode(symcur, &met); if (c != -1) { //VK2ETA only take metric measurement after backtrace fecmet = decayavg(fecmet, met, 10); rx_bit(c & 0x08); rx_bit(c & 0x04); rx_bit(c & 0x02); rx_bit(c & 0x01); } } firstbit = ! firstbit; } rxbitshreg = 0; } } void psk::searchDown() { double srchfreq = frequency - bandwidth * 2; double minfreq = bandwidth * 2; double spwr, npwr; while (srchfreq > minfreq) { spwr = wf->powerDensity(srchfreq, bandwidth); npwr = wf->powerDensity(srchfreq + bandwidth, bandwidth/2) + 1e-10; if (spwr / npwr > pow(10, progdefaults.ServerACQsn / 10)) { frequency = srchfreq; set_freq(frequency); sigsearch = SIGSEARCH; break; } srchfreq -= bandwidth; } } void psk::searchUp() { double srchfreq = frequency + bandwidth * 2; double maxfreq = IMAGE_WIDTH - bandwidth * 2; double spwr, npwr; while (srchfreq < maxfreq) { spwr = wf->powerDensity(srchfreq, bandwidth/2); npwr = wf->powerDensity(srchfreq - bandwidth, bandwidth/2) + 1e-10; if (spwr / npwr > pow(10, progdefaults.ServerACQsn / 10)) { frequency = srchfreq; set_freq(frequency); sigsearch = SIGSEARCH; break; } srchfreq += bandwidth; } } int waitcount = 0; void psk::findsignal() { int ftest, f1, f2; if (sigsearch > 0) { sigsearch--; if (mailserver) { // mail server search algorithm if (progdefaults.PSKmailSweetSpot) { f1 = (int)(progdefaults.ServerCarrier - progdefaults.ServerOffset); f2 = (int)(progdefaults.ServerCarrier + progdefaults.ServerOffset); } else { f1 = (int)(frequency - progdefaults.ServerOffset); f2 = (int)(frequency + progdefaults.ServerOffset); } if (evalpsk->sigpeak(ftest, f1, f2) > pow(10, progdefaults.ServerACQsn / 10) ) { if (progdefaults.PSKmailSweetSpot) { if (fabs(ftest - progdefaults.ServerCarrier) < progdefaults.ServerOffset) { frequency = ftest; set_freq(frequency); freqerr = 0.0; } else { frequency = progdefaults.ServerCarrier; set_freq(frequency); freqerr = 0.0; } } else { frequency = ftest; set_freq(frequency); freqerr = 0.0; } } else { // less than the detection threshold if (progdefaults.PSKmailSweetSpot) { frequency = progdefaults.ServerCarrier; set_freq(frequency); sigsearch = SIGSEARCH; } } } else { // normal signal search algorithm f1 = (int)(frequency - progdefaults.SearchRange/2); f2 = (int)(frequency + progdefaults.SearchRange/2); if (evalpsk->sigpeak(ftest, f1, f2) > pow(10, progdefaults.ACQsn / 10.0) ) { frequency = ftest; set_freq(frequency); freqerr = 0.0; sigsearch = 0; acquire = dcdbits; } } } } void psk::phaseafc() { double error; if (afcmetric < 0.05) return; error = (phase - bits * M_PI / 2.0); if (error < -M_PI / 2.0 || error > M_PI / 2.0) return; error *= samplerate / (TWOPI * symbollen); if (fabs(error) < bandwidth ) { freqerr = error / dcdbits; frequency -= freqerr; if (mailserver) { if (frequency < progdefaults.ServerCarrier - progdefaults.ServerAFCrange) frequency = progdefaults.ServerCarrier - progdefaults.ServerAFCrange; if (frequency > progdefaults.ServerCarrier + progdefaults.ServerAFCrange) frequency = progdefaults.ServerCarrier + progdefaults.ServerAFCrange; } set_freq (frequency); } if (acquire) acquire--; } void psk::afc() { if (!progStatus.afconoff) return; if (dcd == true || acquire) phaseafc(); } void psk::rx_symbol(complex symbol) { int n; phase = (prevsymbol % symbol).arg(); prevsymbol = symbol; if (phase < 0) phase += TWOPI; //VK2ETA BPSK+FEC // if (_qpsk) { // bits = ((int) (phase / M_PI_2 + 0.5)) & 3; // n = 4; // } else { bits = (((int) (phase / M_PI + 0.5)) & 1) << 1; n = 2; // } // simple low pass filter for quality of signal quality.re = decayavg(quality.re, cos(n*phase), SQLDECAY); quality.im = decayavg(quality.im, sin(n*phase), SQLDECAY); metric = 100.0 * quality.norm(); //VK2ETA FEC: adjust squelch for extra sensitivity if (_qpsk) { metric = metric * 2.5; if (metric > 100) metric = 100; } afcmetric = decayavg(afcmetric, quality.norm(), 50); if (metric > progStatus.sldrSquelchValue || progStatus.sqlonoff == false) { dcd = true; } else { dcd = false; //VK2ETA was it supposed to be here instead: imdValid = false; } imdValid = false; //VK2ETA FEC: moved below the rx_bit to used proper value for dcd // set_phase(phase, quality.norm(), dcd); //VK2ETA FEC always process, then decide to print characters later // if (dcd == true) { if (_qpsk) //VK2ETA (reverse the bit for FEC too rx_qpsk(bits); rx_qpsk(!bits); else rx_bit(!bits); // } set_phase(phase, quality.norm(), dcd); } void psk::signalquality() { if (m_Energy[1]) snratio = snfilt->run(m_Energy[0]/m_Energy[1]); else snratio = snfilt->run(1.0); if (m_Energy[0] && imdValid) imdratio = imdfilt->run(m_Energy[2]/m_Energy[0]); else imdratio = imdfilt->run(0.001); } void psk::update_syncscope() { static char msg1[15]; static char msg2[15]; display_metric(metric); s2n = 10.0*log10( snratio ); snprintf(msg1, sizeof(msg1), "s/n %2d dB", (int)(floor(s2n))); imd = 10.0*log10( imdratio ); snprintf(msg2, sizeof(msg2), "imd %3d dB", (int)(floor(imd))); if (imdValid) { put_Status1(msg1, progdefaults.StatusTimeout, progdefaults.StatusDim ? STATUS_DIM : STATUS_CLEAR); put_Status2(msg2, progdefaults.StatusTimeout, progdefaults.StatusDim ? STATUS_DIM : STATUS_CLEAR); } } char bitstatus[100]; int psk::rx_process(const double *buf, int len) { double delta; complex z, z2; if (pskviewer && !bHistory) pskviewer->rx_process(buf, len); if (evalpsk) evalpsk->sigdensity(); delta = TWOPI * frequency / samplerate; while (len-- > 0) { // Mix with the internal NCO z = complex ( *buf * cos(phaseacc), *buf * sin(phaseacc) ); buf++; phaseacc += delta; if (phaseacc > M_PI) phaseacc -= TWOPI; // Filter and downsample // by 16 (psk31, qpsk31) // by 8 (psk63, qpsk63) // by 4 (psk125, qpsk125) // by 2 (psk250, qpsk250) // first filter if (fir1->run( z, z )) { // fir1 returns true every Nth sample // final filter fir2->run( z, z2 ); // fir2 returns value on every sample calcSN_IMD(z); // fir3->run( z, z3); // coreafc(z3); int idx = (int) bitclk; double sum = 0.0; double ampsum = 0.0; syncbuf[idx] = 0.8 * syncbuf[idx] + 0.2 * z2.mag(); for (int i = 0; i < 8; i++) { sum += (syncbuf[i] - syncbuf[i+8]); ampsum += (syncbuf[i] + syncbuf[i+8]); } // added correction as per PocketDigi sum = (ampsum == 0 ? 0 : sum / ampsum); bitclk -= sum / 5.0; bitclk += 1; if (bitclk < 0) bitclk += 16.0; if (bitclk >= 16.0) { bitclk -= 16.0; rx_symbol(z2); update_syncscope(); afc(); } } } if (sigsearch) findsignal(); else if (mailserver) { if (waitcount > 0) { --waitcount; if (waitcount == 0) { if (progdefaults.PSKmailSweetSpot) { frequency = progdefaults.PSKsweetspot; set_freq(frequency); } sigsearch = SIGSEARCH; } } else if ( E1/ E2 <= 1.0) { //(snratio <= 1.0) { waitcount = 8; sigsearch = 0; } } return 0; } //===================================================================== // transmit processes //===================================================================== void psk::tx_symbol(int sym) { double delta; double ival, qval, shapeA, shapeB; complex symbol; //VK2ETA BPSK+FEC // if (_qpsk && !reverse) // sym = (4 - sym) & 3; /* differential QPSK modulation - top bit flipped */ switch (sym) { case 0: symbol = complex (-1.0, 0.0); // 180 degrees break; case 1: symbol = complex (0.0, -1.0); // 270 degrees break; case 2: symbol = complex (1.0, 0.0); // 0 degrees break; case 3: symbol = complex (0.0, 1.0); // 90 degrees break; } symbol = prevsymbol * symbol; // complex multiplication delta = 2.0 * M_PI * get_txfreq_woffset() / samplerate; for (int i = 0; i < symbollen; i++) { shapeA = tx_shape[i]; shapeB = (1.0 - shapeA); ival = shapeA * prevsymbol.real() + shapeB * symbol.real(); qval = shapeA * prevsymbol.imag() + shapeB * symbol.imag(); outbuf[i] = ival * cos(phaseacc) + qval * sin(phaseacc); phaseacc += delta; if (phaseacc > M_PI) phaseacc -= 2.0 * M_PI; } ModulateXmtr(outbuf, symbollen); prevsymbol = symbol; } void psk::tx_bit(int bit) { unsigned int sym; //VK2ETA PSK+FEC Send encoded bit(s) (result is two bits to send sequencially since R = 1/2) if (_qpsk) { //Encode into two bits bitshreg = enc->encode(bit); //pass through interleaver Txinlv->bits(&bitshreg); //Send low bit first sym = (bitshreg & 1) << 1; tx_symbol(sym); sym = bitshreg & 2; tx_symbol(sym); } else { sym = bit << 1; tx_symbol(sym); } } void psk::tx_char(unsigned char c) { const char *code; code = psk_varicode_encode(c); while (*code) { tx_bit((*code - '0')); code++; } tx_bit(0); tx_bit(0); } void psk::tx_flush() { // flush the encoder (QPSK only) if (_qpsk) { //VK2ETA FEC : replace unmodulated carrier by an encoded sequence of zeros for (int i = 0; i < dcdbits; i++) tx_bit(0); } else { // DCD off sequence (unmodulated carrier) for (int i = 0; i < dcdbits; i++) tx_symbol(2); } } void psk::clearbits() { bitshreg = enc->encode(0); for (int k = 0; k < 100; k++) { Txinlv->bits(&bitshreg); } } int psk::tx_process() { int c; if (preamble > 0) { if (_qpsk) { if (startpreamble == true) { clearbits(); startpreamble = false; } //VK2ETA FEC prep the encoder with one/zero sequences of bits preamble--; preamble--; tx_bit(1); tx_bit(0); //VK2ETA FEC Mark start of first character with a double zero if (preamble == 0) tx_bit(0); return 0; } else{ preamble--; tx_symbol(0); /* send phase reversals */ return 0; } } c = get_tx_char(); if (c == 0x03 || stopflag) { tx_flush(); stopflag = false; cwid(); return -1; /* we're done */ } if (c == -1) tx_bit(0); else { tx_char(c); put_echo_char(c); } return 0; } //============================================================================ // psk signal evaluation // using Goertzel IIR filter // derived from pskcore by Moe Wheatley, AE4JY //============================================================================ void psk::initSN_IMD() { for(int i = 0; i < NUM_FILTERS; i++) { I1[i] = I2[i] = Q1[i] = Q2[i] = 0.0; m_Energy[i] = 0.0; } m_NCount = 0; COEF[0] = 2.0 * cos(TWOPI * 9 / GOERTZEL); COEF[1] = 2.0 * cos(TWOPI * 18 / GOERTZEL); COEF[2] = 2.0 * cos(TWOPI * 27 / GOERTZEL); } void psk::resetSN_IMD() { for(int i = 0; i < NUM_FILTERS; i++) { I1[i] = I2[i] = Q1[i] = Q2[i] = 0.0; } m_NCount = 0; } //============================================================================ // This routine calculates the energy in the frequency bands of // carrier=F0(15.625), noise=F1(31.25), and // 3rd order product=F2(46.875) // It is called with complex data samples at 500 Hz. //============================================================================ void psk::calcSN_IMD(complex z) { int i; complex temp; for(i = 0; i < NUM_FILTERS; i++) { temp.re = I1[i]; temp.im = Q1[i]; I1[i] = I1[i] * COEF[i]- I2[i] + z.re; Q1[i] = Q1[i] * COEF[i]- Q2[i] + z.im; I2[i] = temp.re; Q2[i] = temp.im; } if( ++m_NCount >= GOERTZEL ) { m_NCount = 0; for(i = 0; i < NUM_FILTERS; i++) { m_Energy[i] = I1[i]*I1[i] + Q1[i]*Q1[i] + I2[i]*I2[i] + Q2[i]*Q2[i] - I1[i]*I2[i]*COEF[i] - Q1[i]*Q2[i]*COEF[i]; I1[i] = I2[i] = Q1[i] = Q2[i] = 0.0; } signalquality(); } }