SPUC::Rec_Syst_Conv_Code Class Reference
[Forward Error Correcting Codes]

A Recursive Systematic Convolutional Encoder/Decoder class. More...

#include <rec_syst_conv_code.h>

List of all members.

Public Member Functions
	Rec_Syst_Conv_Code (void)
	Class constructor.
void	set_generator_polynomials (const ivec &gen, int constraint_length)
	Set generator polynomials.
void	set_awgn_channel_parameters (double in_Ec, double in_N0)
	Sets the channel parameters needed for MAP-decoding.
void	set_scaling_factor (double in_Lc)
	Set scaling factor for the decoder.
void	encode_tail (const bvec &input, bvec &tail, bmat &parity_bits)
	Encode a binary vector of inputs and also adds a tail of K-1 zeros to force the encoder into the zero state.
void	encode (const bvec &input, bmat &parity_bits)
	Encode a binary vector of inputs starting from zero state without adding of a tail.
void	map_decode (const vec &rec_systematic, const mat &rec_parity, const vec &extrinsic_input, vec &extrinsic_output, bool set_terminated=false)
	Maximum Aposteriori Probability symbol-by-symbol decoder.
void	log_decode (const vec &rec_systematic, const mat &rec_parity, const vec &extrinsic_input, vec &extrinsic_output, bool set_terminated=false, string metric="LOGMAX")
	Log domain implementation of the Maximum Aposteriori Probability symbol-by-symbol decoder.
void	log_decode_n2 (const vec &rec_systematic, const vec &rec_parity, const vec &extrinsic_input, vec &extrinsic_output, bool in_terminated=false, string metric="LOGMAX")
	Special Log-MAP/Log-MAX decoder implementation for n = 2.

---

Detailed Description

A Recursive Systematic Convolutional Encoder/Decoder class.

The main purpose of this class is its use un the Turbo_Codec class which uses two recursive systematic convolutional encoders. It can however be used as a stand alone class. The map_decode member function implementation follows the paper "A Turbo Code Tutorial" by William E. Ryan, New Mexico State University. This paper was found on the web and is probably unpublished.

---

Constructor & Destructor Documentation

SPUC::Rec_Syst_Conv_Code::Rec_Syst_Conv_Code (  void   )  [inline]

Class constructor.

---

Member Function Documentation

void Rec_Syst_Conv_Code::encode (  const bvec &  input, bmat &  parity_bits )

Encode a binary vector of inputs starting from zero state without adding of a tail.

void Rec_Syst_Conv_Code::encode_tail (  const bvec &  input, bvec &  tail, bmat &  parity_bits )

Encode a binary vector of inputs and also adds a tail of K-1 zeros to force the encoder into the zero state. The encoder remembers that the trellis is terminated in the zero state at the end of the input block. This is then utilized by the decoder when going through the trellis in the reverse direction. The tailbits used are returned in tail. Parity bits for both the input part and the tail part of the data are returned in the matrix parity bits.

void Rec_Syst_Conv_Code::log_decode (  const vec &  rec_systematic, const mat &  rec_parity, const vec &  extrinsic_input, vec &  extrinsic_output, bool  set_terminated = false, string  metric = "LOGMAX" )

Log domain implementation of the Maximum Aposteriori Probability symbol-by-symbol decoder. The extrinsic_input is the a priori information on each systematic bit. If no a priori information is availiable, this vector should contain only zeros. The extrinsic_output term may be passed to a subsequent decoder in a Turbo scheme. The decision variable is L = Lc*rec_systematic + extrinsic_output where Lc = 4*sqrt(Ec)/N0 Parameters: rec_systematic  Including both systematic bits and tail bits (if any) rec_parity  Matrix including all parity bits from all polynomials as well as parity bits from the tail (if terminated) extrinsic_input  For all systematic bits extrinsic_output  For all systematic bits set_terminated  Equal to true if the trellis was terminated by the encoder and false otherwise metric  May be "LOGMAP" or "LOGMAX" (default)

void Rec_Syst_Conv_Code::log_decode_n2 (  const vec &  rec_systematic, const vec &  rec_parity, const vec &  extrinsic_input, vec &  extrinsic_output, bool  in_terminated = false, string  metric = "LOGMAX" )

Special Log-MAP/Log-MAX decoder implementation for n = 2. Parameters: rec_systematic  Including both systematic bits and tail bits (if any) rec_parity  Matrix including all parity bits from all polynomials as well as parity bits from the tail (if terminated) extrinsic_input  For all systematic bits extrinsic_output  For all systematic bits in_terminated  Equal to true if the trellis was terminated by the encoder and false otherwise metric  May be "LOGMAP" or "LOGMAX" (default)

void Rec_Syst_Conv_Code::map_decode (  const vec &  rec_systematic, const mat &  rec_parity, const vec &  extrinsic_input, vec &  extrinsic_output, bool  set_terminated = false )

Maximum Aposteriori Probability symbol-by-symbol decoder. The extrinsic_input is the a priori information on each systematic bit. If no a priori information is availiable, this vector should contain only zeros. The extrinsic_output term may be passed to a subsequent decoder in a Turbo scheme. The decision variable is L = Lc*rec_systematic + extrinsic_output where Lc = 4*sqrt(Ec)/N0 Parameters: rec_systematic  Including both systematic bits and tail bits (if any) rec_parity  Matrix including all parity bits from all polynomials as well as parity bits from the tail (if terminated) extrinsic_input  For all systematic bits extrinsic_output  For all systematic bits set_terminated  Equal to true if the trellis was terminated by the encoder and false otherwise

void Rec_Syst_Conv_Code::set_awgn_channel_parameters (  double  in_Ec, double  in_N0 )

Sets the channel parameters needed for MAP-decoding. Parameters: in_Ec  is the energy per channel symbol in_N0  is the single-sided power spectral density of the AWGN on the channel.

void Rec_Syst_Conv_Code::set_generator_polynomials (  const ivec &  gen, int  constraint_length )

Set generator polynomials. The generator polynomials are given in Proakis integer form. First generator (gen(0)) is the recursive polynomial. Parameters: gen  A vector containing the generator polynomials of the RSC Code. constraint_length  The Constraing length of the encoder.

void Rec_Syst_Conv_Code::set_scaling_factor (  double  in_Lc  )

Set scaling factor for the decoder. Parameters: in_Lc  is the channel reliability factor (i.e. Lc = 4 x sqrt( Ec ) / N0)

---

The documentation for this class was generated from the following files:

• comm/rec_syst_conv_code.h
• comm/rec_syst_conv_code.cpp

---