ldpc_decode.c

This a framework to test new ideas in transmission technology. Actual development is a LDPC-coder in

/***************************************************************************
 *    ldpc_decode.c  - LDPC decoding
 *                           -------------------
 *   begin                :  01/2003
 *   authors              :  Bernhard Bruhn
 *   emails               :  [e-mail]
 ***************************************************************************/

/***************************************************************************
 *                                Changes
 *                                -------
 * date - name - description
 * 03/04/25 - ineiti - added snr to the stats, so that one can check what
 *                     snr has been used when decoding
 * 03/05/09 - ineiti - added a done-stats to know when it's finished
 *
 * 03/09/01 - chiurtu - modified for the 2fold decoding (either multiple taps
 *                      or multiple antennas)
 * 04/03/05 - ineiti - removed config->channel_param and adjusted description
 *
 **************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program 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.                                   *
 *                                                                         *
 ***************************************************************************/


/**
 * LDPC-decoder using the 2fold-techinque to decode a stream coming from a
 * MIMO environment.
 */

#include "spc.h"
#include "graphcreate.h"
#include "decodehelpers.h"
#include "std.h"

#define DBG_LVL 0


typedef struct {
  // The total iteration-number. For each iteration, iterations_left
  // followed by iterations_right are done.
  int iterations; // 30
  // How many iterations to the left are done per total iteration
  int iterations_left; // 1
  // How many iterations to the right are done per total iteration
  int iterations_right;  // 1
  // The number of 
  // The index of the ldpc-code. For the moment, three codes
  // are implemented:
  // 1 - rate .25, size 4000
  // 2 - rate .5, size 3992
  // 3 - rate .75, size 3992
  int ldpc_code_id; // 1
  //Block-id of the ChEst1 block. This will provide variance and h11 and h12.
  int chest1; // -1
  //Block-id of the ChEst2 block. This will provide variance and h21 and h22.
  int chest2; // -1
} config_t;

typedef struct{
  // The calculated SNR in case of a AWGN channel
  double snr;
} stats_t;

typedef struct{
  graphs *graph;
  int *iphi;
  int gap;
  int ldpc_code_id;
  int bits_per_symbol;
  int iterations;
  int iterations_left;
  int iterations_right;
  int chest1, chest2;
} private_t;


/*
 * The initialisation function, or constructor,
 * is called the each time this module is instantiated.
 */

int rcv_init( swr_sdb_t *context )
{
  // Begin system-definitions {
  config_t *config;
  stats_t *stats;
  MOD_INC_USE_COUNT;
  
  if ( sizeof( private_t ) > 0 ) context->private_data = swr_malloc( sizeof( private_t ) );
  swr_sdb_get_config_struct( context->id, (void**)&config );
  swr_sdb_get_stats_struct( context->id, (void**)&stats );
  // } End of system-definitions


  config->ldpc_code_id	= 1;
  config->iterations	= 30;
  config->iterations_left = 1;
  config->iterations_right = 1;
  config->chest1 = -1;
  config->chest2 = -1;
  stats->snr = -2.3;
  private->bits_per_symbol= 2;
  private->ldpc_code_id = -1;

  //allocate memory for graph
  private->graph=(graphs *)swr_malloc(sizeof(graphs));
  private->graph->vnodenum=0;
  private->graph->cnodenum=0;
  private->graph->f = NULL;


  // Begin system-definitions
  swr_sdb_free_stats_struct( context->id, (void**)&stats );
  swr_sdb_free_config_struct( context->id, (void**)&config );
  return 0;
  // End system-definitions
}


/*
 * Every time modules from the outside change the value of a configuration parameter,
 * this function is called.
 */

int rcv_reconfig( swr_sdb_t *context )
{
  // Definition of variables - don't touch
  config_t *config;
  stats_t *stats;
  int vnodenum=0, cnodenum=0;

  swr_sdb_get_config_struct( context->id, (void**)&config );
  swr_sdb_get_stats_struct( context->id, (void**)&stats );

  // Put you code here
  // ADD HERE

  // put new code into private->graph if config->ldpc_code_id has changed
  if(config->ldpc_code_id!=-1 && private->ldpc_code_id!=config->ldpc_code_id) {
     PR_DBG( 2, "loading ldpc code with ID %i\n", config->ldpc_code_id );
     if(private->ldpc_code_id!=-1) freeGraph(private->graph, private->iphi);
     private->ldpc_code_id = config->ldpc_code_id;
     if ( getGraph(private->ldpc_code_id, private->graph, &(private->gap), &(private->iphi)) ){
       private->ldpc_code_id = -1;
     } else {
       vnodenum=private->graph->vnodenum;
       cnodenum=private->graph->cnodenum;
       size_out(0) = ( vnodenum - cnodenum ) / 8;
       PR_DBG( 2, "Put output-size to %i bytes\n", size_out(0) );
     }
  }
  private->iterations	=config->iterations;
  private->iterations_left	=config->iterations_left;
  private->iterations_right	=config->iterations_right;
  private->chest1       =config->chest1;
  private->chest2       =config->chest2;

  // Definition - don't touch
  swr_sdb_free_stats_struct( context->id, (void**)&stats );
  swr_sdb_free_config_struct( context->id, (void**)&config );
  return 0;
}


/*
 * This is the function that implements the `main method' of the class
 * Every class has got just ONE method/working-mode.
 */
int rcv_pdata( swr_sdb_t *context )
{
  
  stats_t *stats;
  SYMBOL_COMPLEX *in1, *in2, *ch1, *ch2,
    y1, y2, h11, h12, h21, h22;
  U8 *out;
  int vnodenum=0, cnodenum=0, dnodenum=0, var1, var2;
  int *decisions;
  int i,j,n, ch_length;
  
  // If we have a matched-filter, then get the correct values
  if ( !data_available( 0 ) || !data_available( 1 ) ){
    PR_DBG( 1, "Missing data on port %i\n", 0 );
    return 0;
  }

  in1=buffer_in(0);
  in2=buffer_in(1);
  out=buffer_out(0);
  
  vnodenum=(*private->graph).vnodenum;
  cnodenum=(*private->graph).cnodenum;
  // d is data nodes
  dnodenum=vnodenum - cnodenum;
  
  PR_DBG( 1, "vnodenum=%d, cnodenum=%d, size_in=%d bytes\n", 
	  vnodenum, cnodenum, size_in(0));
  
  PR_DBG( 2,"allocating %i decisions, dec_in\n", vnodenum);
  decisions=(int*)swr_malloc(sizeof(int)*vnodenum);

  //AWGN Channel
  //compute LLRs for symbols from 'in' to the decoder input vector 'dec_in'
  if( size_in(0)*4 >= vnodenum ) {

    // TODO: implement initialisation of the input
    // The respectives f_b's are
    // graph->f[node * ( 1 << BITSPERLEFTCHECKNODE ) + b ]
    // in1 comes from rcv-antenna 1
    // in2 comes from rcv-antenna 2
    // h11 = ch1[0]
    // h12 = ch1[ch_length]
    // h21 = ch2[0]
    // h22 = ch2[ch_length]
    // var1 is the variance of rcv-antenna 1
    // var2 is the variance of rcv-antenna 2
    if ( private->chest1 < 0 || private->chest2 < 0 ){
      PR_DBG( 0, "Either chest1 or chest2 is not defined\n" );
      return -1;
    }
    var1 = max( swr_sdb_get_stats_int( private->chest1, "noise_var_real" ), 1 );
    var2 = max( swr_sdb_get_stats_int( private->chest2, "noise_var_real" ), 1 );
    ch_length = swr_sdb_get_stats_int( private->chest1, "ch_length" );
    ch1 = swr_sdb_get_stats_block( private->chest1, "channel" ).data;
    ch2 = swr_sdb_get_stats_block( private->chest2, "channel" ).data;


    // =============== ME !  PAY ATTENTION !!! :-))

    // Here we prepare the table of f's needed for the "left" itterations
    // Attention at the mapping! we map [x0 x1 x2 x3] in bar[x3 x2 x1 x0]
    // This is because we need them like that in the algorithm in  decodehelpers.c


    h11 = ch1[0];
    h12 = ch1[ch_length];
    h21 = ch2[0];
    h22 = ch2[ch_length];
    PR_DBG_CL( 4, "h11(%i:%ii) h12(%i:%ii) h21(%i:%ii) h22(%i:%ii) var1(%i) var2(%i)\n",
	    h11.real, h11.imag, h12.real, h12.imag,
	    h21.real, h21.imag, h22.real, h22.imag,
	    var1, var2 );
    //    return -1;

    for (n=0; n<vnodenum/4; n++){
    //    for (n=0; n<20; n++){
      double x[BITSPERLEFTCHECKNODE];
      double e1, e2, e3, e4, f;

      y1 = in1[n];
      y2 = in2[n];
      PR_DBG_CL( 4, "y1(%i:%ii) y2(%i:%ii)\n",
		 y1.real, y1.imag, y2.real, y2.imag );
      for( i  = 0; i < (1 << BITSPERLEFTCHECKNODE); i++){
	for(j = 0; j < BITSPERLEFTCHECKNODE; j++){
	  x[j] = ((1 << j) & i) ? -1:1;
	  x[j] /= sqrt(2);
	  PR_DBG_CL( 4, "%2g ", x[j] );
	}
	j = n*( 1 << BITSPERLEFTCHECKNODE )+i;
	e1 = pow(y1.real - h11.real*x[0] + h11.imag*x[1] - 
		 h12.real*x[2] + h12.imag*x[3], 2)/(2*var1);
	e2 = pow(y1.imag - h11.imag*x[0] - h11.real*x[1] - 
		 h12.imag*x[2] - h12.real*x[3], 2)/(2*var1);
	e3 = pow(y2.real - h21.real*x[0] + h21.imag*x[1] - 
		 h22.real*x[2] + h22.imag*x[3], 2)/(2*var2);
	e4 = pow(y2.imag - h21.imag*x[0] - h21.real*x[1] - 
		 h22.imag*x[2] - h22.real*x[3], 2)/(2*var2);
	f =-( e1 + e2 + e3 + e4 );
	//f = min( -1., f );
	//f = max( -10., f );
	private->graph->f[j] = f;
	PR_DBG_CL( 4, " f[%i]=%g/%g %g %g %g %g %g %g %g\n", j, private->graph->f[j],
		   y1.real - h11.real*x[0] + h11.imag*x[1] - 
		   h12.real*x[2] + h12.imag*x[3], e1,
		   y1.imag - h11.imag*x[0] - h11.real*x[1] - 
		   h12.imag*x[2] - h12.real*x[3], e2,
		   y2.real - h21.real*x[0] + h21.imag*x[1] - 
		   h22.real*x[2] + h22.imag*x[3], e3,
		   y2.imag - h21.imag*x[0] - h21.real*x[1] - 
		   h22.imag*x[2] - h22.real*x[3], e4 );
      }
      PR_DBG_CL( 4, "\n" );
    }
     //        return -1;

    // =====================================================

  } else {
    PR_DBG( 0, "size_in(0)*4<vnodenum ( %i*2<%i ) => unable to decode\n", 
	    size_in(0),vnodenum );
    return 0;
  }
  

  initializegraph(private->graph);
  for ( i=0; i<private->iterations; i++ ){
    for ( j=0; j<private->iterations_left; j++ ){
      leftfoldmap( private->graph );
    }
    for ( j=0; j<private->iterations_right; j++ ){
      variablemessagemap(private->graph);
      checkmessagemap(private->graph);
    }
  }
  makedecisions(private->graph, decisions);

  //copy decoded data to output
  j=-1;
  if( size_out(0)*8 < dnodenum ){
    PR_DBG( 1,"output to small: decoded information (%i) does not fit in %i\n",
	    size_out(0) * 8, dnodenum );
  }
  for ( i=0; i<min( dnodenum, size_out(0)*8 ); i++ ){
    if ( !( i % 8 ) ){
      j++;
      out[j] = 0;
    }
    out[j] += decisions[i] << ( i % 8 );
  }

  for ( i=dnodenum; i<size_out(0)*8; i++ ){
    if ( !( i % 8 ) ){
      j++;
      out[j] = 0;
    }
  }

  // Clean up
  swr_free (decisions);

  // And calculate the snr for further use
  swr_sdb_get_stats_struct( context->id, (void**)&stats );
  swr_sdb_free_stats_struct( context->id, (void**)&stats );

  return(0);
}

/**
 * User messages
 */
int rcv_custom_msg( swr_sdb_t *context, swr_usr_msg_t *data, swr_msgq ret ){
  return 0;
}

/*
 * This is the `destructor'.
 */
int rcv_finalize( swr_sdb_t *context )
{
  swr_free( private->graph );
  if ( sizeof( private_t ) > 0 ) swr_free( private );

  MOD_DEC_USE_COUNT;
  return 0;
}


/*
 * This function is called upon "insmod" and is used to register the
 * different parts of the module to the SPM.
 */
swr_spc_id_t rcv_id;
int rcv_module_init(void){
  swr_spc_desc_t *desc;


//  int i;

  /**
   * Get a description-part from CDB
   * Give the following parameters:
   * Input-ports, output-ports, config-params, stat-params
   */
  desc = swr_spc_get_new_desc( 2, 1, 6, 1 );
  if ( !desc ){
    PR_DBG( 0, "Can't initialise the module. This is BAD!\n" );
    return -1;
  }

  /**
   * Define the different parts of config and stats. You have to define
   * them in the same order as they appear in the structures. The names
   * can be freely chosen.
   *
   * UM_CONFIG_{INT,DOUBLE,STRING128,POINTER}( "name" );
   * UM_STATS_{INT,DOUBLE,STRING128,POINTER,BLOCK}( "name" );
   */
  UM_CONFIG_INT( "iterations" );
  UM_CONFIG_INT( "iterations_left" );
  UM_CONFIG_INT( "iterations_right" );
  UM_CONFIG_INT( "ldpc_code_id" );
  UM_CONFIG_INT( "chest1" );
  UM_CONFIG_INT( "chest2" );
  UM_STATS_DOUBLE( "snr" );
  /**
   * The in- and outputs have also to be defined in the right order. First
   * port first. The additional flag is not used yet, but it will...
   *
   * UM_INPUT( SIG_{U8,SYMBOL_{S16,COMPLEX,MMX},SAMPLE_S12,S32}, 0 );
   * UM_OUTPUT( SIG_{U8,SYMBOL_{S16,COMPLEX,MMX},SAMPLE_S12,S32}, 0 );
   */

  UM_INPUT( SIG_SYMBOL_COMPLEX, 0 );
  UM_INPUT( SIG_SYMBOL_COMPLEX, 0 );
  UM_OUTPUT( SIG_U8, 0 );

  // Initialise the callback-functions. Delete the ones you don't use
  desc->fn_init              = rcv_init;
  desc->fn_reconfigure       = rcv_reconfig;
  desc->fn_process_data      = rcv_pdata;
  desc->fn_custom_msg        = rcv_custom_msg;
  desc->fn_finalize          = rcv_finalize;

  // And register the module in the SPM. Change the name!
  rcv_id = swr_cdb_register_spc( &desc, "ldpc_decode_2fold" );
  if ( rcv_id == SWR_SPM_INVALID_ID ){
    swr_spc_free_desc( desc );
    PR_DBG( 0, "Couldn't register the module!\n" );
    return 1;
  }
  PR_DBG( 4, "Ready\n" );
  return 0;
}


/*
 * This is called upon rmmod
 */
void rcv_module_exit( void ){
  PR_DBG( 4, "Freeing id: %i\n", rcv_id );
  if ( swr_cdb_unregister_spc( rcv_id ) < 0 ){
    PR_DBG( 0, "Still in use somewhere\n" );
  }
}