ldpc_decode_ics.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)
 * 10 Dec 2003 - chiurtu - modified for 4 by 4 MIMO
 * 04/03/31 - ineiti - added some debugging messages
 * 17 June 2004 - chiurtu - compute the true sigma and the true SNR
 *
 **************************************************************************/

/***************************************************************************
 *                                                                         *
 *   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"
#include <complex.h>

#define DBG_LVL 0

#define MAX_NO_RX 4
#define MAX_NO_TX 4


typedef struct {
  // The total iteration-number. For each iteration, iterations_left
  // followed by iterations_right are done.
  int iterations;
  // How many iterations to the left are done per total iteration
  int iterations_left;
  // How many iterations to the right are done per total iteration
  int iterations_right;

  // The ID of the LDPC code
  int ldpc_code_id; // 1

  // 'a/variance' for AWGN
  double channel_param;  // 0.07
  
  // How many input channels
  int no_tx; // 4
  // How many output channels
  int no_rx; // 4

  //Block-id of the ChEst  blocks. They will provide H
  int chest [MAX_NO_RX]; // [-1 -1 -1 -1]

  // How many blocks to drop
  int drop_blocks; // 0

} 
config_t;

typedef struct{
  // The calculated variance of the h_{ij}'s
  double h_var;
  // The claculated true sigma
  double true_sigma;
  // The calculated true snr
  double true_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;
  double channel_param; // either 'p' or 'a/variance'
  int no_tx;
  int no_rx;
  int chest[MAX_NO_RX];
  int counter;
  int drop_blocks;
} 
private_t;


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

int ics_rcv_init( swr_sdb_t *context ) {
  int i;
  // Begin system-definitions {
  config_t *config;
  stats_t *stats;
  MOD_INC_USE_COUNT;

  SET_STATUS( MULTI_IN );
  
  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->channel_param	= 0.07;
  
  config->no_rx = MAX_NO_RX;
  config->no_tx = MAX_NO_TX;

  for ( i=0; i<MAX_NO_RX; i++){
    config->chest[i] = -1;
  }

  config->drop_blocks = 0;

  stats->h_var = -1;
  stats->true_sigma = -1;
  stats->true_snr = -20;
  
  private->bits_per_symbol= 2;
  private->ldpc_code_id = -1;
  private->counter=0;
  
  //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 ics_rcv_reconfig( swr_sdb_t *context ) {
  int i;
  // 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

 
  
  
  private->graph->bits_per_left_checknode = config->no_tx * 2;
  if ( private->graph->bits_per_left_checknode ){
    PR_DBG( 4, "BPLCN: %i\n", private->graph->bits_per_left_checknode );
    // 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->channel_param=config->channel_param;

  private->no_rx = config->no_rx;
  private->no_tx = config->no_tx;
  
  private->drop_blocks  =config->drop_blocks;

  for ( i=0; i<config->no_rx; i++){
    private->chest[i] = config->chest[i] ;
  }
  
  // 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 ics_rcv_pdata( swr_sdb_t *context ) {
  
  stats_t *stats;
  SYMBOL_COMPLEX *in[MAX_NO_RX], *ch[MAX_NO_RX];
  SYMBOL_COMPLEX y[MAX_NO_RX], h[MAX_NO_RX][MAX_NO_TX];

  U8 *out;
  int vnodenum=0, cnodenum=0, dnodenum=0;
  int *decisions;
  int i, j, n, k, p;
  int var_real[MAX_NO_RX], var_imag[MAX_NO_RX];


  double x[private->graph->bits_per_left_checknode];
  double f;
  complex double u, z, w;

  double mean_h, var_h;
  double mean_sigmanoise;

  double true_snr;
  double true_sigma;
  double code_rate;

  PR_DBG( 4, "Entry for %i receivers\n", private->no_rx );
  
  // If we have a matched-filter, then get the correct values
  // Return if not all data available yet
  j = 0;
  for ( i=0; i<private->no_rx; i++ ){
    j += !!data_available( i ) * ( 1 << i );
  }
  if ( j != ( 1 << private->no_rx ) - 1 ){
    PR_DBG( 3, "Not all data here yet:%x\n", j );
    return -1;
  }
  PR_DBG( 3, "All %i inputs are filled, processing\n", private->no_rx );
  

  for (i = 0; i < private->no_rx; i++){
    in[i] =  buffer_in(i);
  }


  // To avoid calculating all the time and to give some processing-power
  // to the linux-kernel
  if ( private->drop_blocks > 0 ){
    if ( private->counter++ % private->drop_blocks ){
      return -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) * private->graph->bits_per_left_checknode < vnodenum ) {
    PR_DBG( 0, "size_in(0)*bits_per_left_checknode<vnodenum ( %i*2<%i ) => "
	    "unable to decode\n", 
	    size_in(0) * private->graph->bits_per_left_checknode, vnodenum );
    return -1;
  } else {
    // TODO: implement initialisation of the input
    // The respectives f_b's are
    // graph->f[node * ( 1 << private->graph->bits_per_left_checknode ) + b ]
    // in1 comes from rcv-antenna 1
    // in2 comes from rcv-antenna 2
    // h11 = ch1[0]
    // h12 = ch1[1]
    // h21 = ch2[0]
    // h22 = ch2[1]
    // var1 is the variance of rcv-antenna 1
    // var2 is the variance of rcv-antenna 2
    
    for ( i=0; i<private->no_rx; i++ ){
      if ( private->chest[i] < 0 ){