metrics.c

这是一个c＋＋编写的WCDMA链路采用RAKE接收的方针源代码

/*
 |
 | Copyright disclaimer:
 |   This software was developed at the National Institute of Standards
 |   and Technology by employees of the Federal Government in the course
 |   of their official duties. Pursuant to title 17 Section 105 of the
 |   United States Code this software is not subject to copyright
 |   protection and is in the public domain.
 |
 |   We would appreciate acknowledgement if the software is used.
 |
*/

/*
 | Project:     WCDMA simulation environment
 | Module:      Viterbi path metric calculation.
 | Author:      Tommi Makelainen, NIST
 | Date:        January 11, 1999
 |
 | History:
 |              January 11, 1999 Tommi Makelainen
 |                      Initial version.
 |
 |              February 16, 1999 Tommi Makelainen
 |                      Corrected branch metric calculation for soft
 |			bits.
 |
 */

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "metrics.h" 


/* --------------------------------------------------------------- */

/*
 * Function:    MetricTable_R1o3_Init
 * Desc.:       Metric table initialization for Viterbi algorithm.
 *		Constrain length K=9 and coding rate 1/3 are fixed.
 *
 * Note:
 *              'no_of_probabilities' can get max value of 8.
 */
void MetricTable_R1o3_Init(
          MetricTable* this,
          enum metric_type_type metric_type,
          double bit_probabilities_0[],
          double bit_probabilities_1[],
          int no_of_probabilities)
{
    int i, bit;
    double temp;

    this->Metric_Type = metric_type;

    if(metric_type == HAMMING_METRIC) {
		this->Metric_Table[0][0] = 0.0;
		this->Metric_Table[1][0] = -1.0;
		this->Metric_Table[2][0] = -1.0;
		this->Metric_Table[3][0] = -2.0;
		this->Metric_Table[4][0] = -1.0;
		this->Metric_Table[5][0] = -2.0;
		this->Metric_Table[6][0] = -2.0;
		this->Metric_Table[7][0] = -3.0;
		this->Metric_Table[0][1] = -1.0;
		this->Metric_Table[1][1] = 0.0;
		this->Metric_Table[2][1] = -2.0;
		this->Metric_Table[3][1] = -1.0;
		this->Metric_Table[4][1] = -2.0;
		this->Metric_Table[5][1] = -1.0;
		this->Metric_Table[6][1] = -3.0;
		this->Metric_Table[7][1] = -2.0;
		this->Metric_Table[0][2] = -1.0;
		this->Metric_Table[1][2] = -2.0;
		this->Metric_Table[2][2] = 0.0;
		this->Metric_Table[3][2] = -1.0;
		this->Metric_Table[4][2] = -2.0;
		this->Metric_Table[5][2] = -3.0;
		this->Metric_Table[6][2] = -1.0;
		this->Metric_Table[7][2] = -2.0;
		this->Metric_Table[0][3] = -2.0;
		this->Metric_Table[1][3] = -1.0;
		this->Metric_Table[2][3] = -1.0;
		this->Metric_Table[3][3] = 0.0;
		this->Metric_Table[4][3] = -3.0;
		this->Metric_Table[5][3] = -2.0;
		this->Metric_Table[6][3] = -2.0;
		this->Metric_Table[7][3] = -1.0;
		this->Metric_Table[0][4] = -1.0;
		this->Metric_Table[1][4] = -2.0;
		this->Metric_Table[2][4] = -2.0;
		this->Metric_Table[3][4] = -3.0;
		this->Metric_Table[4][4] = 0.0;
		this->Metric_Table[5][4] = -1.0;
		this->Metric_Table[6][4] = -1.0;
		this->Metric_Table[7][4] = -2.0;
		this->Metric_Table[0][5] = -2.0;
		this->Metric_Table[1][5] = -1.0;
		this->Metric_Table[2][5] = -3.0;
		this->Metric_Table[3][5] = -2.0;
		this->Metric_Table[4][5] = -1.0;
		this->Metric_Table[5][5] = 0.0;
		this->Metric_Table[6][5] = -2.0;
		this->Metric_Table[7][5] = -1.0;
		this->Metric_Table[0][6] = -2.0;
		this->Metric_Table[1][6] = -3.0;
		this->Metric_Table[2][6] = -2.0;
		this->Metric_Table[3][6] = -2.0;
		this->Metric_Table[4][6] = -1.0;
		this->Metric_Table[5][6] = -2.0;
		this->Metric_Table[6][6] = 0.0;
		this->Metric_Table[7][6] = -1.0;
		this->Metric_Table[0][7] = -3.0;
		this->Metric_Table[1][7] = -2.0;
		this->Metric_Table[2][7] = -2.0;
		this->Metric_Table[3][7] = -1.0;
		this->Metric_Table[4][7] = -2.0;
		this->Metric_Table[5][7] = -1.0;
		this->Metric_Table[6][7] = -1.0;
		this->Metric_Table[7][7] = 0.0;
		return;
    }

    if (metric_type == SOFT_METRIC) {
        /*
         * Convert bit probabilities for soft metrics to suitable branch
         * metric values.
         *    branch_metric = 2 * log2( p(rx_symbol|tx_symbol) - 0.05)
         * Channel can be also non-symmetric, so the probabilities for 0
         * and 1 can be different.
         */
        for (i=0; i < no_of_probabilities; i++) {
            if (bit_probabilities_0[i] < 0.1) {
              this->Metric_Table[i][0] = -8.0;
            } else {
              this->Metric_Table[i][0] = 0 -
                  floor(abs(2 * log(bit_probabilities_0[i] - 0.1 + 0.05)));
            }
        }
        for (i=0; i < no_of_probabilities; i++) {
            if (bit_probabilities_1[i] < 0.1) {
              this->Metric_Table[i][1] = -8.0;
            } else {
              this->Metric_Table[i][1] = 0 -
                  floor(abs(2 * log(bit_probabilities_1[i] - 0.1 + 0.05)));
            }
        }

#ifdef WCDMA_DEBUG_OUTPUT
        printf("\nSoft probability branch metrices: \n");
        for (i=0; i < no_of_probabilities; i++) {
            printf("[%d][0] = %g, [%d][1] = %g \n",
                i, this->Metric_Table[i][0], i, this->Metric_Table[i][1]);
        } /* for */
        printf("\n");
#endif /* WCDMA_DEBUG_OUTPUT */

        return;

    }
    printf("invalid metric type passed to metric builder\n");
    return;	
}

/* --------------------------------------------------------------- */
/*
 * Function:    MetricTable_R1o2_Init
 * Desc.:       Metric table initialization for Viterbi algorithm.
 *		Constrain length K=9 and coding rate 1/2 are fixed.
 *
 * Note:
 *              'no_of_probabilities' can get max value of 8.
 */
void MetricTable_R1o2_Init(
          MetricTable* this,
          enum metric_type_type metric_type,
          double bit_probabilities_0[],
          double bit_probabilities_1[],
          int no_of_probabilities)
{
    int i, bit;
    double temp;

    this->Metric_Type = metric_type;

    if(metric_type == HAMMING_METRIC) {
		this->Metric_Table[0][0] = 0.0;
		this->Metric_Table[1][0] = -1.0;
		this->Metric_Table[2][0] = -1.0;
		this->Metric_Table[3][0] = -2.0;
		this->Metric_Table[0][1] = -1.0;
		this->Metric_Table[1][1] = 0.0;
		this->Metric_Table[2][1] = -2.0;
		this->Metric_Table[3][1] = -1.0;
		this->Metric_Table[0][2] = -1.0;
		this->Metric_Table[1][2] = -2.0;
		this->Metric_Table[2][2] = 0.0;
		this->Metric_Table[3][2] = -1.0;
		this->Metric_Table[0][3] = -2.0;
		this->Metric_Table[1][3] = -1.0;
		this->Metric_Table[2][3] = -1.0;
		this->Metric_Table[3][3] = 0.0;
		return;
    }

    if (metric_type == SOFT_METRIC) {
        /*
         * Convert bit probabilities for soft metrics to suitable branch
         * metric values.
         *    branch_metric = 2 * log2( p(rx_symbol|tx_symbol) - 0.05)
         * Channel can be also non-symmetric, so the probabilities for 0
         * and 1 can be different.
         */
        for (i=0; i < no_of_probabilities; i++) {
            if (bit_probabilities_0[i] < 0.1) {
              this->Metric_Table[i][0] = -8.0;
            } else {
              this->Metric_Table[i][0] = 0 -
                  floor(abs(2 * log(bit_probabilities_0[i] - 0.1 + 0.05)));
            }
        }
        for (i=0; i < no_of_probabilities; i++) {
            if (bit_probabilities_1[i] < 0.1) {
              this->Metric_Table[i][1] = -8.0;
            } else {
              this->Metric_Table[i][1] = 0 -
                  floor(abs(2 * log(bit_probabilities_1[i] - 0.1 + 0.05)));
            }
        }

#ifdef WCDMA_DEBUG_OUTPUT
        printf("\nSoft probability branch metrices: \n");
        for (i=0; i < no_of_probabilities; i++) {
            printf("[%d][0] = %g, [%d][1] = %g \n",
                i, this->Metric_Table[i][0], i, this->Metric_Table[i][1]);
        } /* for */
        printf("\n");
#endif /* WCDMA_DEBUG_OUTPUT */

        return;

    }
    printf("invalid metric type passed to metric builder\n");
    return;	
}


/* --------------------------------------------------------------- */


/*
 * Function:    MetricTable_R1o3_SoftSymbolMetric
 * Desc.:       Soft metric calculation. The metric is calculated
 *		as an euclidean distance between tx and rx symbols.
 *
 * Note:
 */
double MetricTable_R1o3_SoftSymbolMetric(
          MetricTable* this,
          int rx_symbol,
          int tx_symbol) 
{
  int rx_bit1, rx_bit2, rx_bit3, tx_bit1, tx_bit2, tx_bit3;
  double metric_val;                               

  /*
   * Decompose rx_symbol into bits
   */
  rx_bit1 = (rx_symbol >> 2) & 0x1;
  rx_bit2 = (rx_symbol >> 1) & 0x1;
  rx_bit3 = rx_symbol & 0x1;

  /*
   * Decompose tx_symbol into bits  
   */
  tx_bit1 = (tx_symbol >> 2) & 0x1;
  tx_bit2 = (tx_symbol >> 1) & 0x1;
  tx_bit3 = tx_symbol & 0x1;

  /*
   * Look up bit metrics and add them together   
   */
  metric_val = this->Metric_Table[rx_bit1][tx_bit1] 
			+ this->Metric_Table[rx_bit2][tx_bit2]
                        + this->Metric_Table[rx_bit3][tx_bit3];
  return(metric_val);
};


/* --------------------------------------------------------------- */


/*
 * Function:    MetricTable_R1o2_SoftSymbolMetric
 * Desc.:       Soft metric calculation. The metric is calculated
 *		as an euclidean distance between tx and rx symbols.
 *
 * Note:
 */
double MetricTable_R1o2_SoftSymbolMetric(
          MetricTable* this,
          int rx_symbol,
          int tx_symbol) 
{
  int rx_bit1, rx_bit2, tx_bit1, tx_bit2;
  double metric_val;                               

  /*
   * Decompose rx_symbol into bits
   */
  rx_bit1 = (rx_symbol >> 1) & 0x1;
  rx_bit2 = rx_symbol & 0x1;

  /*
   * Decompose tx_symbol into bits  
   */
  tx_bit1 = (tx_symbol >> 1) & 0x1;
  tx_bit2 = tx_symbol & 0x1;

  /*
   * Look up bit metrics and add them together   
   */
  metric_val = this->Metric_Table[rx_bit1][tx_bit1] 
			+ this->Metric_Table[rx_bit2][tx_bit2];
  return(metric_val);
};


/* --------------------------------------------------------------- */

/*
 * Function:    MetricTable_R1o2_GetBranchMetric
 * Desc.:       Returns a branch metric value for a given tx and rx
 *		symbols.
 *
 * Note:
 */
double MetricTable_R1o2_GetBranchMetric(
          MetricTable* this,
          int rx_symbol,
          double soft_metric,
          int tx_symbol) 
{
  if(this->Metric_Type == SOFT_METRIC) {
        return( /* soft_metric * */
            MetricTable_R1o2_SoftSymbolMetric(this, rx_symbol, tx_symbol) );
  } else {					
	return(this->Metric_Table[rx_symbol][tx_symbol]);
  }
};
  

/* --------------------------------------------------------------- */

/*
 * Function:    MetricTable_R1o3_GetBranchMetric
 * Desc.:       Returns a branch metric value for a given tx and rx
 *		symbols.
 *
 * Note:
 */
double MetricTable_R1o3_GetBranchMetric(
          MetricTable* this,
          int rx_symbol,
          double soft_metric,
          int tx_symbol) 
{
  if(this->Metric_Type == SOFT_METRIC) {
        return( /* soft_metric * */
            MetricTable_R1o3_SoftSymbolMetric(this, rx_symbol, tx_symbol) );
  } else {					
	return(this->Metric_Table[rx_symbol][tx_symbol]);
  }
};
  

/* --------------------------------------------------------------- */