awgn.h

根据LDPC码中码子的构造方法中的PEG算法

/***************************************
 *
 * Random value generator for AWGN
 * 
 * based on I[j+1] = a*I[j] mod m
 * Since it is not possible to implement this iteration
 * directly (the product a*I may exceed the maximum value
 * of a 32-bit integer) Schrage's algorithm is used 
 * (see Numerical Recipes in C, p.278ff.)
 *
 * (for simulation results and goodness of this
 *  random generator, see ~/svensson/dani/matlab/results/noise.m)
 *
 ***************************************/

#ifndef AWGNH
#define AWGNH

#define IA 16807
#define IM 2147483647 // 2^31 - 1
#define AM (1.0/IM);
#define IQ 127773
#define IR 2836
#define NTAB 32
#define NDIV (1+(IM-1)/NTAB)
#define EPSI 1.2e-7
#define RNMX (1.0-EPSI)
#define NOV 1000000 // number of values that are generated at random

class AWGN {

public:
  // constructor
  AWGN(long seed = 1, double sigma = 1);

  // set the standard deviation of this random variable
  void setSigma(double sigma);

  // get a random value
  double nextValue(void);

  // get the seed
  long getSeed(void);

  // test method
  static void test(void);

private:

  long seed;
  double sigma;
  long iy;
  long iv[NTAB];
  int iset;
  double gset;

  double random(long *idum);

};
 
#endif