/*
 * File: tc-8psk-sect.c
 * Date: January 8, 1998
 * Description: Suboptimal trellis decoder using sector information. 
 */
// ------------------------------------------------------------------------
// This program is complementary material for the book:
//
// R.H. Morelos-Zaragoza, The Art of Error Correcting Coding, Wiley, 2002.
//
// ISBN 0471 49581 6
//
// This and other programs are available at http://the-art-of-ecc.com
//
// You may use this program for academic and personal purposes only. 
// If this program is used to perform simulations whose results are 
// published in a journal or book, please refer to the book above.
//
// The use of this program in a commercial product requires explicit
// written permission from the author. The author is not responsible or 
// liable for damage or loss that may be caused by the use of this program. 
//
// Copyright (c) 2002. Robert H. Morelos-Zaragoza. All rights reserved.
// ------------------------------------------------------------------------
 
#include <stdio.h>
#include <math.h>
#include <float.h>
#include <limits.h>

int k2=1, n2, m2;
int NUM_STATES, OUT_SYM, NUM_TRANS;
long TRUNC_LENGTH;

double RATE;
double INIT_SNR, FINAL_SNR, SNR_INC;
long NUMSIM;

char name1[40], name2[40];
FILE  *fp;                 /* Pointer for trellis data file */

#define MAX_RANDOM LONG_MAX /* Maximum value of random() */

long NUM_SECT;

//#define DELTA 1000
//#define SHOW_PROGRESS       /* Print simulation progress, */

FILE  *fp;                 /* Pointer for trellis data file */

//  unsigned int g2[n2][k2] =  { /* rate-1/2 memory=6 */
//          0x4f, /* REVERSE ORDER */
//          0x6d }; /* */

unsigned int g2[10][10];

unsigned int memory2, output;            /* Memory,output transmit encoder */
unsigned int memory, output2;            /* Memory,output receive encoder */
unsigned int data2;                      /* Data */

unsigned long seed;                      /* Seed for random generator */
unsigned int data_symbol[1024];  /* 1-bit data sequence */
unsigned int data_symbol2[1024];  /* 1-bit data sequence */
unsigned long indxx;                     /* Simulation index */


double psk_I[8], psk_Q[8];        /* Coordinated of 8-PSK signals */

int transmitted;                  /* index of transmitted signal */
double transmitted_I;             /* Transmitted signals/branch */
double transmitted_Q;             /* Transmitted signals/branch */
int reconstructed;                /* Decoded coset index */
int estimate_data2;               /* Estimate of uncoded info. bit */
double snr, amp;

double received_I;                       /* Received signals/branch */
double received_Q;                       /* Received signals/branch */

double received_angle;
double angle_inc;
int sector;
int buffer_sector[1024];
double branch_metric[512][8];

/* int fflush(); /* */

/* Data structures used for trellis sections and survivors */

struct trel {
  int init;                /* initial state */
  int data;                /* data symbol */
  int final;               /* final state */
  int output;              /* index of output coded symbols */
}; 

struct surv {
  double metric;           /* metric */
  int data[1024];  /* estimated data symbols */
  int state[1024];  /* state sequence */
};

/* A trellis section is an array of branches, indexed by an initial
   state and a k2-bit input data. The values that can be read
   are the final state and the index of the output symbols */

struct trel trellis[1024][64];

/* A survivor is a sequence of states and estimated data, of length
   equal to TRUNC_LENGTH, together with its corresponding metric.
   A total of NUM_STATES survivors are needed */

struct surv survivor[1024], surv_temp[1024];

/* Function prototypes */

void encoder2(void);           /* Encoder in transmitter */
void encoder(void);            /* Encoder in receiver */
int random_data(void);         /* Random data generator */
void transmit(void);           /* Encoder & BPSK modulator */
void awgn(void);               /* AWGN generator */
void find_sect(void);          /* Cartesian to polar conversion */
void viterbi(void);            /* Viterbi decoder */
void re_encode(void);          /* Reencoder of decoded information bit */
void sector_table();           /* Construct branch metric look-up table */
void open_files(void);         /* Open files for output */
void close_files(void);        /* Close files */

main(int argc, char *argv[])
{

  register int i, j, k;
  int init, data, final, output;
  register int error;
  unsigned long error_count;
  FILE  *fp_ber;             /* Pointer for overall BER data file */
  double RATE;
  double ii, reference_I[512], reference_Q[512];

  // Command line processing
  if (argc != 10)
    {
      printf("Usage %s file_input file_output NUM_SECT truncation snr_init snr_final snr_inc num_sim seed\n", argv[0]);
      exit(0);
    }

  sscanf(argv[1],"%s", name1);
  sscanf(argv[2],"%s", name2);
  sscanf(argv[3],"%ld", &NUM_SECT);
  sscanf(argv[4],"%ld", &TRUNC_LENGTH);
  sscanf(argv[5],"%lf", &INIT_SNR);
  sscanf(argv[6],"%lf", &FINAL_SNR);
  sscanf(argv[7],"%lf", &SNR_INC);
  sscanf(argv[8],"%ld", &NUMSIM);
  sscanf(argv[9],"%ld", &seed);

  printf("\nSimulation of TCM decoding with 8-PSK modulation over an AWGN channel\n");
  printf("%ld simulations per Eb/No (dB) point\n", NUMSIM);

  fp_ber = fopen(name2,"w");

  /* Open file with trellis data */
  if (!(fp = fopen(name1,"r")))
    {
    printf("Error opening file!\n");
    exit(1);
    }


  fscanf(fp, "%d %d", &n2, &m2);

  RATE = (2.0 / (double) n2)*3.0;  // 2 bits per symbol if encoder is rate 1/2

  fscanf(fp, "%d %d %d", &NUM_STATES, &OUT_SYM, &NUM_TRANS);
  for (j=0; j<n2; j++)
    fscanf(fp, "%x", &g2[j][0]);

  printf("\n%d-state rate-1/%d binary convolutional encoder\n",
          NUM_STATES, n2);
  printf("with generator polynomials ");
  for (j=0; j<n2; j++) printf("%x ", g2[j][0]); printf("\n");
  printf("\nDecoding depth = %ld\n", TRUNC_LENGTH);
  printf("Number of sectors = %ld\n\n", NUM_SECT);


  /* =================== READ TRELLIS STRUCTURE ==================== */

  for (j=0; j<NUM_STATES; j++) /* For each state in the section */
        for (k=0; k<NUM_TRANS; k++) /* and for each outgoing branch */
          {
            /* Read initial state, input data and final state */
            fscanf(fp,"%d %d %d", &trellis[j][k].init, &trellis[j][k].data,
                   &trellis[j][k].final);
            /* Read the output symbols of the branch */
                fscanf(fp,"%d", &data);
                trellis[j][k].output = data;
          } /* end for states */
    /* end for branches */

  fclose(fp);


  snr = INIT_SNR;
  angle_inc = 2.0*M_PI/(double)NUM_SECT;

  /* Bits-to-8PSK signal mapping as used in Japanese Satellite ISDB */

  psk_I[0] = cos(M_PI/8.0);        psk_Q[0] = sin(M_PI/8.0);
  psk_I[1] = cos(3.0*M_PI/8.0);    psk_Q[1] = sin(3.0*M_PI/8.0);
  psk_I[3] = -cos(3.0*M_PI/8.0);   psk_Q[3] = sin(3.0*M_PI/8.0);
  psk_I[2] = -cos(M_PI/8.0);       psk_Q[2] = sin(M_PI/8.0);
  psk_I[4] = -cos(M_PI/8.0);       psk_Q[4] = -sin(M_PI/8.0);
  psk_I[5] = -cos(3.0*M_PI/8.0);   psk_Q[5] = -sin(3.0*M_PI/8.0);
  psk_I[7] = cos(3.0*M_PI/8.0);    psk_Q[7] = -sin(3.0*M_PI/8.0);
  psk_I[6] = cos(M_PI/8.0);        psk_Q[6] = -sin(M_PI/8.0);

  sector_table(); /* Branch metric lookup table */

  /* ======================== SNR LOOP ============================= */

  while ( snr < (FINAL_SNR+0.001) )

    {

  /* ==================== INITIALIZE SEQUENCES ===================== */
      
  /* Random seed from current time */
  srandom(seed);

  amp = sqrt(2.0*RATE*pow(10.0,(snr/10.0)));

  /* Initialize transmitted data sequence */
      
  for (i=0; i<TRUNC_LENGTH; i++)
    {
      data_symbol[i]=0;
      data_symbol2[i]=0;

      buffer_sector[i] = 0;
    }
      
  /* Initialize survivor sequences and metrics */
      
  for (i=0; i<NUM_STATES; i++)
	{
	  survivor[i].metric = 0.0;             /* Metric = 0 */

	  for (j=0; j<TRUNC_LENGTH; j++)
	    {
	      survivor[i].data[j] = 0;        /* Estimated data = 0 */
	      survivor[i].state[j] = 0;       /* Estimated state = 0 */
	    }
	}
      
  /* Index used in simulation loop */

  indxx = 0;
      
  /* Initialize encoder memories */

  memory2 = 0;
  memory = 0;

  /* Error counters */

  error_count = 0;

  /* ===================== SIMULATION LOOP ========================= */
      
  while (indxx < NUMSIM) 

	{ 
	
	  /* GENERATE random two-bit symbols */
	  
      i = random_data();
	  data_symbol[indxx % TRUNC_LENGTH] = (i & 1); /* */
	  data_symbol2[indxx % TRUNC_LENGTH] = ( (i>>1) & 1 ); /* */
	  
#ifdef PRINT
	  printf("Transmitted data sequence:\n");
	  printf("%2d %x   ",(indxx % TRUNC_LENGTH),
		 data_symbol[indxx % TRUNC_LENGTH]);
	  for (i=0; i<TRUNC_LENGTH; i++)
	    printf("%x", data_symbol[i]);
	  printf("\n");
#endif
	  
	  /* ENCODE AND MODULATE (BPSK) data bit */
	  
	  transmit();
	  
#ifdef PRI
	  printf("Transmitted = ");
	  printf("%d ", transmitted);
	  printf("\n");
#endif
	  
	
	  /* ADD ADDITIVE WHITE GAUSSIAN NOISE */
	  
	  awgn(); /* */
	  

      /* CARTESIAN TO POLAR COORDINATE */

      find_sect();

      /* Store sector in buffer */

      buffer_sector[indxx % TRUNC_LENGTH] = sector;


	  /* VITERBI DECODE (FOR THE ENCODED INFORMATION BIT) */
	  
	  viterbi();

	  indxx += 1;           /* Increase simulation index */

      /* ESTIMATE UNCODED INFORMATION BIT */

      re_encode();

      estimate_data2 = 0;

#ifdef HARD_DECISION
      /* The half-plane defines uncoded bit */
      if (buffer_sector[indxx%TRUNC_LENGTH] > NUM_SECT/2)
        estimate_data2 = 1;
#else
      if ( ( pow((cos(buffer_sector[indxx%TRUNC_LENGTH]*angle_inc)
                      - psk_I[reconstructed]),2.0)
           + pow((sin(buffer_sector[indxx%TRUNC_LENGTH]*angle_inc)
                      - psk_Q[reconstructed]),2.0))
           > ( pow((cos(buffer_sector[indxx%TRUNC_LENGTH]*angle_inc)
                      - psk_I[reconstructed+4]),2.0)
            + pow((sin(buffer_sector[indxx%TRUNC_LENGTH]*angle_inc)
                      - psk_Q[reconstructed+4]),2.0)) )
        estimate_data2 = 1;
#endif

#ifdef ABS
      estimate_data2 = 0;
      if ( ( fabs(cos(buffer_sector[indxx%TRUNC_LENGTH]*angle_inc)
                      - psk_I[reconstructed])
           + fabs(sin(buffer_sector[indxx%TRUNC_LENGTH]*angle_inc)
                      - psk_Q[reconstructed]))
           > ( fabs(cos(buffer_sector[indxx%TRUNC_LENGTH]*angle_inc)
                      - psk_I[reconstructed+4])
            + fabs(sin(buffer_sector[indxx%TRUNC_LENGTH]*angle_inc)
                      - psk_Q[reconstructed+4])) )
        estimate_data2 = 1;
#endif

#ifdef PRINT
printf("Sector buffer:\n");
for (i=0; i<TRUNC_LENGTH; i++)
printf("%d", buffer_sector[i]);
printf("\n");
printf("coset = %d, estimate_data2 = %d\toriginal data2 = %d\n", 
reconstructed, estimate_data2, data_symbol2[indxx % TRUNC_LENGTH]);
#endif
	  
	  /* COMPUTE ERRORS */
	  
	  error = survivor[0].data[indxx % TRUNC_LENGTH]
	          ^ data_symbol[indxx % TRUNC_LENGTH]; 
  
	  error += (estimate_data2 ^ data_symbol2[indxx % TRUNC_LENGTH]); 

	  if (error)
	    error_count+=error;
	  
#ifdef SHOW_PROGRESS
	  if ( (indxx % DELTA) == 0 )
	    {
        printf("index = %ld\n", indxx);
	      for (i=0; i<TRUNC_LENGTH; i++)
		printf("%x", survivor[0].data[i]);
	      printf("\n--- errors = %ld\n", error_count);
	    }
#endif
	  
	}
      
      printf("%10.5f  %10.4e  %10ld %10ld %4ld\n",
	     snr, ( (double) error_count / ((double) indxx * 2.0) ), 
	     indxx, error_count, NUM_SECT);
      
      fprintf(fp_ber, "%f %20.15f\n", snr,
	      ( (double) error_count / ((double) indxx * 2.0) ));

      fflush(stdout);
      fflush(fp_ber);

      snr += SNR_INC;

    }
  
  fclose(fp_ber);

  return 0;

}



int random_data()
{
  /* 
   * ---------------------------------------------------------------------
   * Random two-bit number generator 
   * ---------------------------------------------------------------------
   */

  return( (random() >> 5) & 3 );
}

void encoder2()
{
  /* 
   * ---------------------------------------------------------------------
   * Conventional convolutional encoder, rate 1/n2 (fixed k_2=1) 
   * ---------------------------------------------------------------------
   */
  register int i, j, result, temp;
  
  temp = memory2;
  output = 0;

 temp = (temp<<1) ^ data_symbol[indxx % TRUNC_LENGTH];

  for (i=0; i<n2; i++)
   {
     result = 0;
     for (j=m2; j>=0; j--)
       result ^= ( ( temp & g2[i][0] ) >> j ) & 1;
     output = ( output<<1 ) ^ result;
   }
  memory2 = temp ;
}


void encoder()
{
  /* 
   * ---------------------------------------------------------------------
   * Conventional convolutional encoder, rate 1/n2 (fixed k_2=1) 
   * ---------------------------------------------------------------------
   */
  register int i, j, result, temp;
  
  temp = memory;
  output2 = 0;

 temp = (temp<<1) ^ survivor[0].data[indxx % TRUNC_LENGTH];

  for (i=0; i<n2; i++)
   {
     result = 0;
     for (j=m2; j>=0; j--)
       result ^= ( ( temp & g2[i][0] ) >> j ) & 1;
     output2 = ( output2<<1 ) ^ result;
   }
  memory = temp ;
}



void transmit()
{
  /* 
   * ---------------------------------------------------------------------
   * Encode and modulate a 1-bit data sequence
   * ---------------------------------------------------------------------
   */
  int i;

  encoder2(); /* */

#ifdef DEB
  printf("memory2 = %x\n", memory2);
#endif

  transmitted = output + 4*data_symbol2[indxx % TRUNC_LENGTH];

}


void re_encode()
{
  /* Re-encode decoded information bit to obtain coset index */

  encoder();
  reconstructed = output2;
}


void awgn()
{
  /* 
   * ---------------------------------------------------------------------
   * Add AWGN to transmitted sequence
   * ---------------------------------------------------------------------
   */
  double u1,u2,s,noise,randmum;
  int i;

#ifdef PRINT
      printf("Received    = ");
#endif

  do
	{	
	  randmum = (double)(random())/MAX_RANDOM;
	  u1 = randmum*2.0 - 1.0;
	  randmum = (double)(random())/MAX_RANDOM;
	  u2 = randmum*2.0 - 1.0;
	  s = u1*u1 + u2*u2;
	} while( s >= 1);

  noise = u1 * sqrt( (-2.0*log(s))/s )/amp;
#ifdef NO_NOISE
  noise = 0.0;
#endif
  received_I = psk_I[transmitted] + noise;

  do
    {
      randmum = (double)(random())/MAX_RANDOM;
      u1 = randmum*2.0 - 1.0;
      randmum = (double)(random())/MAX_RANDOM;
      u2 = randmum*2.0 - 1.0;
      s = u1*u1 + u2*u2;
    } while( s >= 1);

  noise = u1 * sqrt( (-2.0*log(s))/s )/amp;
#ifdef NO_NOISE
  noise = 0.0;
#endif
  received_Q = psk_Q[transmitted] + noise;

#ifdef PRINT
  printf("%4.2lf %4.2lf ", received_I, received_Q);
#endif

#ifdef PRINT
  printf("\n");
#endif

}


void find_sect()
{
  /* ---------------------------------------------------------------------
   * Determine the sector in which the received point lies
   * ---------------------------------------------------------------------
   */

  register int i;
  double ii, phase1, phase2;

  received_angle = atan2(received_Q, received_I);

#ifdef SECTOR
printf("atan2(%lf,%lf)=%lf \t",received_I, received_Q, 
                                               (180.0/3.0)*received_angle);
#endif

  for (i=0; i<NUM_SECT; i++)
    {
      ii = (double) i;
      phase1 = ii*angle_inc;
      if ( phase1 > M_PI )
        phase1 = phase1 - 2.0*M_PI;
      phase2 = (ii+1.0)*angle_inc;
      if ( phase2 > M_PI )
        phase2 = phase2 - 2.0*M_PI;
      if ( (received_angle > phase1) && (received_angle < phase2) )
        sector = i;
    }

#ifdef SECTOR
 printf("--> \tsector = %d\n", sector);
#endif

}



void viterbi()
{
  /* 
   * ---------------------------------------------------------------------
   * Viterbi decoder
   * ---------------------------------------------------------------------
   */

  double aux_metric, surv_metric[NUM_STATES];
  register int i,j,k;

  for (i=0; i<NUM_STATES; i++) /* Initialize survivor branch metric */
    surv_metric[i] = DBL_MAX;

  for (i=0; i<NUM_STATES; i++) /* Loop over inital states */
    {
    for (j=0; j<NUM_TRANS; j++) /* Loop over data */
      {

	  /* Compute metric between received and coded symbols */

      aux_metric = branch_metric[sector][trellis[i][j].output];

	  aux_metric += survivor[i].metric;

#ifdef PRINT
	  printf("rec_I   rec_Q  index_coded\n");
	  printf("%6.2lf %6.2lf %d\n", received_I,received_Q,trellis[i][j].output);
	  printf("init, data, final, metric = %2d %2d %2d %lf\n", i, j,
		 trellis[i][j].final, aux_metric);
#endif

	  /* compare with survivor metric at final state */
      if ( aux_metric < surv_metric[trellis[i][j].final] )

	    { /* Good candidate found */

	      surv_metric[trellis[i][j].final] = aux_metric;

	      /* Update data and state paths */
	      for (k=0; k<TRUNC_LENGTH; k++)
		    {
		      surv_temp[trellis[i][j].final].data[k] =
		        survivor[i].data[k];
		      surv_temp[trellis[i][j].final].state[k] =
		        survivor[i].state[k];
		    }

          surv_temp[trellis[i][j].final].data[indxx%TRUNC_LENGTH] = j;
          surv_temp[trellis[i][j].final].state[indxx%TRUNC_LENGTH] = 
		          trellis[i][j].final;
	    }
      }
    }
  
  for (i=0; i<NUM_STATES; i++)
    {
      /* Update survivor metrics */
      survivor[i].metric = surv_metric[i];

      for (k=0; k<TRUNC_LENGTH; k++)
        {
          survivor[i].data[k] = surv_temp[i].data[k];
          survivor[i].state[k] = surv_temp[i].state[k];
        }
    }
  
#ifdef PRINT
  for (i=0; i<NUM_STATES; i++)
    {
      printf("survivor %2d, initial state = %2d metric = %10.5lf, ", i,
	     survivor[i].state[(indxx-1) % TRUNC_LENGTH], survivor[i].metric);
      printf("\t estimate = %d\n", survivor[i].data[indxx % TRUNC_LENGTH]);
    }
  printf("\n");
#endif

#ifdef DEBUG
  printf("Surviving paths (data):\n");
   for (i=0; i<NUM_STATES; i++)
     {
       printf("%2d --> ",i);
       for (k=0; k<TRUNC_LENGTH; k++)
	 printf("%1x", survivor[i].data[k]);
       printf("\n");
     }
  printf("\n");
#endif

}



void sector_table()
{
  /*
   * ---------------------------------------------------------------------
   * Compute sector metric table:
   * branch_metric[sector][index_ref_signal]
   * ---------------------------------------------------------------------
   */
  register int i,j;
  double ii, ref_I[512], ref_Q[512];
  double phase, metric1, metric2;

  for (i=0; i<NUM_SECT; i++)    /* The sector number is i */
    {
      ii = (double) i;
      phase = (ii+1.0)*angle_inc;
      phase = (ii)*angle_inc;
      ref_I[i] = cos(phase);
      ref_Q[i] = sin(phase);

      for (j=0; j<4; j++)       /* The reference signals are 8-PSK */
        {
          metric1 = ((ref_I[i]-psk_I[j])*(ref_I[i]-psk_I[j]))
                    + ((ref_Q[i]-psk_Q[j])*(ref_Q[i]-psk_Q[j]));
          metric2 = ((ref_I[i]-psk_I[j+4])*(ref_I[i]-psk_I[j+4]))
                    + ((ref_Q[i]-psk_Q[j+4])*(ref_Q[i]-psk_Q[j+4]));
          if (metric1 < metric2)
            branch_metric[i][j] = metric1;
          else
            branch_metric[i][j] = metric2;
        }
    }

#ifdef PRINT_TABLE
printf("--- metric_table --- \n");
  for (i=0; i<NUM_SECT; i++)
  { 
      ii = (double) i;
      phase = (ii+1.0)*angle_inc;

  printf("%7.2lf  |  ", (180.0/M_PI)*phase);
  for (j=0; j<4;j++) printf("%lf  ", branch_metric[i][j]);
  printf("\n");
  }
printf("\n");
#endif

}