ogsxmit.c

OpenGPSSim是一个gps模拟程序

      didx      = HalfChip_Counter[prn];             // now 0,...,2046     
      didx      = (didx % 2046) / 2;

//  C/A code
//      assert( didx >= 0 && didx < 1023);
//      assert( prn >= 1 && prn < 32);

      ca_prompt = CACode[prn][didx];   // didx=0,...,1022

//  for (i=1;i<=32;i++)
//    for (j=0;j<1023;j++)
//    {
//      if ( abs( CACode[i][j]) != 1)
//        printf("CACode[%d][%d] = %d\n", i,j,CACode[i][j]);
//    }    
//  getchar();


//      if (!( ca_prompt == 1 || ca_prompt == -1))
//      {
//        printf( "ca_prompt = %d\n", ca_prompt);
//        printf("CACode[%d][%d] = %d\n", prn,didx,CACode[prn][didx]);
//        getchar();
//      }

//  C/A code
      nidx      = CACode_Counter[prn] / 20;   // 20 C/A periods <-> 1 bit
//      assert( nidx >= 0 && nidx < NAVMSGLEN);
      navbit    = NavBit[prn][nidx%NAVMSGLEN];   // nidx=0,...,1499

//      printf("navbit = %d\n", navbit);

//  resolution is 1/1024 cycles
      XmtrInfo[prn].carrier_dco_phase = (long)( Carrier_DCO_Cycle[prn] * 1024);  

      sgn += Carrier_DCO_I[cidx] * ca_prompt * navbit;     

//      assert( sgn == 0);
//      sgn += Carrier_DCO_I[cidx] * ca_prompt;
      
#if 0
      if ( 0)
      {
        static int ii;
        
        printf( "cidx = %d", cidx);
        printf( " ca = %d", ca_prompt);
        printf( " carcyc = %.4f", (double)(Carrier_Cycle[prn]) / (double)(0x1L<<27)); // 24+3!
        printf( " CACode1 = %d", CACode[prn][ii]);
        printf( " DCO = %d", Carrier_DCO_I[ii%8]);
        printf( " sgn = %d\n", sgn);
        
        if (ii > 20)
          getchar();
        ii += 1;
      }
#endif

//      printf("sgn = %d\n", sgn);
//      printf("Carrier_DCO_I = %d, cidx=%d\n", Carrier_DCO_I[cidx], cidx);
//      printf("ca_prompt = %d, didx = %d\n", ca_prompt, didx);
//      printf("navbit = %d\n", navbit);
//      printf("cidx=%d, didx=%d, nidx = %d\n", cidx, didx, nidx);
//      getchar();
//      nofprn += 1;

    }  // --- if ( NavBit[prn]) ---
  }  // --- for ( prn=1; prn <= NOFSAT; prn++) ---
  
// add white noise  
  if ( Noise_Ampl > 0)
  {

    sgnflt = (float)( sgn) + Noise_Ampl * randn( 0.0, 1.0);

//    printf("sgn=%d, sgnflt=%e (Noise_Ampl=%e)\n", sgn, sgnflt, Noise_Ampl);
//    getchar();  

//    printf( "noise = %e\n", tmp);
//    getchar();
//    printf("sgn = %d, noise = %e, sum = %e \n", sgn, tmp, sgnflt);
//    printf("sizeof( float) = %d \n", sizeof( float));
//    getchar();  

  }  
  else  
    sgnflt = (float)( sgn);

// quantize and map to [0,1,2,3]
  sgn = ( sgnflt >= 0.0) ? 1 : -1;
  if ( fabs( sgnflt) > QuantThresh)
    sgn *= 3;

// map -3,-1,1,3 to 0,1,2,3
  sgn = (sgn+3) / 2; 

  return (sgn);
}

//
//  main function
//
int main( int argc, char *argv[])
{
  int j, nof, sgn, ofs;
  long i, nofwritten;
  unsigned long cntMSB;
//  char outfile[] = "ogsraw.dat";   // default output file name
//       navfilefmt[] = "navmsg-in-%02d.dat",
//       navfile[sizeof(navfilefmt)];      // d <= 2 digits!
  char *outpath, *navpath, *ptr, *navfilefmt, *navfile;
  float t, dt;  // 30 sec <-> 1500 nav bits
  double samplfrq = 40e6 / 7.0;               // sampling frequency
  double nofsamples = 0.0;
  FILE *Fp, *FpNav;

  set_directories( argv[0]);

//  process options
  getargs( argc, argv);

  check_options();

//  if ( OutputFileName)
//    ptr = OutputFileName;
//  else  
//    ptr = outfile;

  outpath = conmalloc( strlen( OGSDataDir) + strlen( OutputFileName) + 1);
  strcpy( outpath, OGSDataDir);
  strcat( outpath, OutputFileName);

//  welcome
  printf("-------------------------------- OpenGPSSim ---------------------------------\n");
  printf("ogsxmit   version %s\n", Version);
  printf("Copyright (C) 2001-2006 G. Beyerle, A. Tabernero, C. Kelley and others.      \n");
  printf("ogsxmit comes with ABSOLUTELY NO WARRANTY; for details see file 'warranty'.\n");
  printf("This is free software, and you are welcome to redistribute it under          \n");
  printf("certain conditions; see file 'copying' for details.                          \n");
  printf("-----------------------------------------------------------------------------\n");

//  initialize
  init_struct_xmitter();

//  read parameter controlling signal transmission
  read_xmit_par();

  if ( Noise_dB > -1000.0)
    Noise_Ampl = pow( 10.0, (double)( Noise_dB)/20.0);
  else
    Noise_Ampl = 0.0;
  
  srand(1);        // initialize random generator
  
// calculate C/A-code and store in global CACode[1,...,NOFSATS][1,..,NOFCHIPS]
  calc_cacode();

  if ( !OverWrite)
  {
    Fp = fopen( outpath, "rb");
    if ( Fp)
    {
      printf("Data file '%s' already exists.\nPlease remove it and try again.\n", 
        outpath);
      exit(0);
    }
  }

  Fp = fopen( outpath, "wb");
  if ( !Fp)
  {
    printf( "error opening file '%s'\n", outpath);
    perror( NULL);
    exit(-1);
  }


//  FILE *TmpFp;
//  TmpFp = fopen( "C:/home/Src/osgpsim/data/osgraw-c-chr.dat", "w");
//  if ( !TmpFp)
//  {
//    perror( NULL);
//    exit(-1);
//  }
//  printf( "*** opened C:/home/Src/osgpsim/data/osgraw-c-chr.dat\n");

  printf( "\nRead navigation data bits from file(s) ...\n");

//  printf( "NavFilePattern = %s\n", NavFilePattern);
//  getchar();

  ptr = strstr( NavFilePattern, "PRN");
  if ( !ptr)
  {
    printf( "Substring 'PRN' not found in %s.\n", NavFilePattern);
    exit(-1);    
  }
  
  ofs = ptr - NavFilePattern; 

  navfilefmt = conmalloc( strlen( NavFilePattern) + 4);
  navfile    = conmalloc( strlen( NavFilePattern) + 4);
  
  strcpy( navfilefmt, NavFilePattern);
  strcpy( navfilefmt + ofs, "%02d");
  strcpy( navfilefmt + ofs + 4, ptr + 3);

//  printf( "navfilefmt = %s\n", navfilefmt);
//  getchar();
  
  navpath = conmalloc( strlen( OGSDataDir) + strlen( navfilefmt) + 1);

  for ( i=1; i<=NOFSAT; i++)
  {

    sprintf( navfile, navfilefmt, i);

    strcpy( navpath, OGSDataDir);
    strcat( navpath, navfile);

    FpNav = fopen( navpath, "rb");
    if ( FpNav)
    {
      printf( " '%s'.\n", navpath);

      NavBit[i] = (char*) malloc( NAVMSGLEN);
      if ( !NavBit[i])
      {
        printf( "malloc() failed in %s at line %d\n", __FILE__, __LINE__);
        exit(-1);
      }

      nof = fread( NavBit[i], sizeof( char), NAVMSGLEN, FpNav);
      if ( nof < NAVMSGLEN)
      {
        printf( "read only %d bytes from file '%s'.\n", nof, navpath);
        exit(-1);
      }
//      else
//        printf( "read %d bytes from file '%s'.\n", nof, navpath);
      
      fclose( FpNav);
      
//  re-write: 0 -> -1, 1 -> 1
      for ( j=0; j<NAVMSGLEN; j++)
        NavBit[i][j] = (NavBit[i][j] > 0) ? 1 : -1;
      
    }
  }


  int foundone = 0;

  for ( i=1; i<=NOFSAT; i++)
  {
    if ( NavBit[i])
      foundone = 1;
  }

  if ( !foundone)
  {
    printf("Not a single file found for pattern >%s<.\n", NavFilePattern);
    exit(-1);
  }

//  for (i=1;i<=32;i++)
//    for (j=0;j<1023;j++)
//    {
//      if ( abs( CACode[i][j]) != 1)
//        printf("CACode[%d][%d] = %d\n", i,j,CACode[i][j]);
//    }    

//  TmpFP = fopen( "c:/tmp/testdata.dat", "w");
//  if ( !TmpFP)
//  {
//    printf( "Error opening file 'c:/tmp/testdata.dat'\n");
//    perror( NULL);
//    exit(-1);
//  }

  printf( "\n");
  printf( "construct GPS signal, add noise, quantize\n");
  printf( "and write to file '%s' ...\n", outpath);

//  we store 4 times 2 bit (4 level) signal samples into one byte,
//  fill XmtrBuf[XMTRBUFLEN] and write to file

// 4 samples per byte
  dt = XMTRBUFLEN * 4.0 / samplfrq;

  for ( t=0; t<MaxTime; t+=dt)  
  {

    cntMSB = 0;
    for ( i=0; i<XMTRBUFLEN; i++)
    {
//      char savsgn[4];
      
      XmtrBuf[i] = 0;
      for ( j=0; j<4; j++)
      {
        sgn = calc_raw_sgn();
//        savsgn[j] = sgn;
        XmtrBuf[i] |= ((sgn & 0x3) << (3-j)*2);

//  magnitude bit should be set in 30% of the samples
        if (sgn == 3 || sgn == 0)
          cntMSB += 1;
      }  
    }    

    printf( "%5.2f of %.2f sec (MAG bit: %.2f%%)\n", 
      t, MaxTime, (100.0 * cntMSB) / (4.0*XMTRBUFLEN));
    
    nofwritten = fwrite( XmtrBuf, sizeof( char), XMTRBUFLEN, Fp);
    if ( nofwritten != XMTRBUFLEN)
    {
      printf( "Could only write %d of %d bytes. Disk full?\n", 
        nofwritten, XMTRBUFLEN);
      fclose( Fp);
      exit(-1);        
    }
    
    nofsamples += 4.0*XMTRBUFLEN;
  }  // --- for ( t=0; t<MaxTime; t += dt) ---

  fclose( Fp);
//  fclose( TmpFp);
//  if ( TmpFP) fclose( TmpFP);

  printf( "%.0f samples written to %s.\n", nofsamples, outpath);

  exit(0);
}

/* ------------------------------ end of file ----------------------------- */