Binary Punctured Convolutional Code Class. More...

#include <itpp/comm/punct_convcode.h>

Inheritance diagram for itpp::Punctured_Convolutional_Code:

Public Member Functions
	Punctured_Convolutional_Code (void)
	Constructor.

virtual	~Punctured_Convolutional_Code (void)
	Destructor.

void	set_code (const CONVOLUTIONAL_CODE_TYPE type_of_code, int inverse_rate, int constraint_length)
	Set the code according to built-in tables.

void	set_generator_polynomials (const ivec &gen, int constraint_length)
	Set generator polynomials. Given in Proakis integer form.

ivec	get_generator_polynomials () const
	Get generator polynomials.

virtual double	get_rate () const
	Return rate of code.

void	set_method (const CONVOLUTIONAL_CODE_METHOD method)
	Set encoding and decoding method (Trunc, Tail, or Tailbite)

void	set_puncture_matrix (const bmat &pmatrix)
	Set puncture matrix (size n*Period)

bmat	get_puncture_matrix () const
	Get puncture matrix.

int	get_puncture_period () const
	Get puncturing period.

void	init_encoder ()
	Set the encoder internal state in start_state (set by set_start_state()).

void	encode (const bvec &input, bvec &output)
	Encode a binary vector of inputs using specified method.

bvec	encode (const bvec &input)
	Encode a binary vector of inputs using specified method.

void	encode_trunc (const bvec &input, bvec &output)
	Encode a binary vector of inputs starting from state set by the set_state function.

bvec	encode_trunc (const bvec &input)
	Encode a binary vector of inputs starting from state set by the set_state function.

void	encode_tail (const bvec &input, bvec &output)
	Encoding that begins and ends in the zero state.

bvec	encode_tail (const bvec &input)
	Encoding that begins and ends in the zero state.

void	encode_tailbite (const bvec &input, bvec &output)
	Encode a binary vector of inputs using tailbiting.

bvec	encode_tailbite (const bvec &input)
	Encode a binary vector of inputs using tailbiting.

virtual void	decode (const vec &received_signal, bvec &output)
	Viterbi decoding using specified method.

virtual bvec	decode (const vec &received_signal)
	Viterbi decoding using specified method.

virtual void	decode (const bvec &coded_bits, bvec &decoded_bits)
	Decode a bvec of coded data.

virtual bvec	decode (const bvec &coded_bits)
	Decode a bvec of coded data.

void	decode_trunc (const vec &received_signal, bvec &output)
	Viterbi decoding using truncation of memory (default = 5*K)

bvec	decode_trunc (const vec &received_signal)
	Viterbi decoding using truncation of memory (default = 5*K)

void	decode_tail (const vec &received_signal, bvec &output)
	Decode a block of encoded data where encode_tail has been used.

bvec	decode_tail (const vec &received_signal)
	Decode a block of encoded data where encode_tail has been used.

void	decode_tailbite (const vec &received_signal, bvec &output)
	Decode a block of encoded data where encode_tailbite has been used. Tries all start states.

bvec	decode_tailbite (const vec &received_signal)
	Decode a block of encoded data where encode_tailbite has been used. Tries all start states.

bool	inverse_tail (const bvec coded_sequence, bvec &input)

bool	catastrophic (void)
	Check if the code is catastrophic. Returns true if catastrophic.

void	distance_profile (ivec &dist_prof, int time, int dmax=100000, bool reverse=false)
	Calculate distance profile. If reverse = true calculate for the reverse code instead.

void	calculate_spectrum (Array< ivec > &spectrum, int dmax, int no_terms)
	Calculate spectrum.

void	calculate_spectrum (Array< ivec > &spectrum, int time, int dmax, int no_terms, int block_length=0)
	Calculate spectrum. Suitable when calculating many terms in the spectra. Breadth first search.

int	fast (Array< ivec > &spectrum, int time, int dfree, int no_terms, int d_best_so_far=0, bool test_catastrophic=false)
	Cederwall's fast algorithm.

void	reset ()
	Reset encoder and decoder states.

void	set_start_state (int state)
	Set encoder default start state.

int	get_encoder_state (void) const
	Get the current encoder state.

void	set_truncation_length (const int length)
	Set memory truncation length. Must be at least K.

int	get_truncation_length (void) const
	Get memory truncation length.

void	distance_profile (ivec &dist_prof, int dmax=100000, bool reverse=false)
	Calculate distance profile. If reverse = true calculate for the reverse code instead.

int	fast (Array< ivec > &spectrum, const int dfree, const int no_terms, const int Cdfree=1000000, const bool test_catastrophic=false)
	Cederwall's fast algorithm.


void	encode_bit (const bin &input, bvec &output)
	Encode a binary bit starting from the internal encoder state.

bvec	encode_bit (const bin &input)
	Encode a binary bit starting from the internal encoder state.

Protected Member Functions
int	weight (const int state, const int input, int time)
	The weight of path from `state` with `input` (0 or 1) at transition `time`.

void	weight (const int state, int &w0, int &w1, int time)
	The weight of the two paths (input 0 or 1) from given state.

int	weight_reverse (const int state, const int input, int time)
	Weight of the reverse code from `state` with `input` (0 or 1) at transition `time`.

void	weight_reverse (const int state, int &w0, int &w1, int time)
	The weight of the reverse code of two paths (input 0 or 1) from given state.

int	next_state (const int instate, const int input)
	Next state from instate given the input.

int	previous_state (const int state, const int input)
	The previous state from state given the input.

void	previous_state (const int state, int &S0, int &S1)
	The previous state from state given the input.

int	weight (const int state, const int input)
	The weight of the transition from given state with the input given.

void	weight (const int state, int &w0, int &w1)
	The weight of the two paths (input 0 or 1) from given state.

int	weight_reverse (const int state, const int input)
	The weight (of the reverse code) of the transition from given state with the input given.

void	weight_reverse (const int state, int &w0, int &w1)
	The weight (of the reverse code) of the two paths (input 0 or 1) from given state.

bvec	output_reverse (const int state, const int input)
	Output on transition (backwards) with input from state.

void	output_reverse (const int state, bvec &zero_output, bvec &one_output)
	Output on transition (backwards) with input from state.

void	output_reverse (const int state, int &zero_output, int &one_output)
	Output on transition (backwards) with input from state.

void	calc_metric_reverse (const int state, const vec &rx_codeword, double &zero_metric, double &one_metric)
	Calculate delta metrics for 0 and 1 input branches reaching state.

void	calc_metric (const vec &rx_codeword, vec &delta_metrics)
	Calculate delta metrics for all possible codewords.

int	get_input (const int state)
	Returns the input that results in state, that is the MSB of state.

Protected Attributes
int	Period
	The puncture period (i.e. the number of columns in the puncture matrix)

int	total
	The number of "1" in the puncture matrix.

bmat	puncture_matrix
	The puncture matrix (n rows and Period columns)

int	n
	Number of generators.

int	K
	Constraint length.

int	m
	Memory of the encoder.

int	no_states
	Number of states.

ivec	gen_pol
	Generator polynomials.

ivec	gen_pol_rev
	Generator polynomials for the reverse code.

int	encoder_state
	The current encoder state.

int	start_state
	The encoder start state.

int	trunc_length
	The decoder truncation length.

double	rate
	The rate of the code.

bvec	xor_int_table
	Auxilary table used by the codec.

imat	output_reverse_int
	output in int format for a given state and input

CONVOLUTIONAL_CODE_METHOD	cc_method
	encoding and decoding method

imat	path_memory
	Path memory (trellis)

Array< bool >	visited_state
	Visited states.

vec	sum_metric
	Metrics accumulator.

int	trunc_ptr
	Truncated path memory pointer.

int	trunc_state
	Truncated memory fill state.

Related Functions
(Note that these are not member functions.)
ITPP_EXPORT int	reverse_int (int length, int in)
	Reverses the bitrepresentation of in (of size length) and converts to an integer.

ITPP_EXPORT int	weight_int (int length, int in)
	Calculate the Hamming weight of the binary representation of in of size length.

ITPP_EXPORT int	compare_spectra (ivec v1, ivec v2)
	Compare two distance spectra. Return 1 if v1 is less, 0 if v2 less, and -1 if equal.

ITPP_EXPORT int	compare_spectra (ivec v1, ivec v2, vec weight_profile)
	Compare two distance spectra using a weight profile.

Detailed Description

Binary Punctured Convolutional Code Class.

The codes are given as feedforward encoders an given in the Proakis form. That is the binary generators (K-tuples) are converted to octal integers. Observe that the constraint length (K) is defined as the number of meomory cells plus one (as in Proakis). The puncture matrix should be of size n * Period, where Period is the puncturing period.

Encoding is performed with the encode function. By default the encode_tail function is called which automatically add a tail of K-1 zeros and also assume that the encoder starts in the zero state. Observe that decode_tail is used for data encoded with encode_tail, and decode_trunc assumes that the memory truncation length either is the default (5*K) or set using the set_truncation_length function. Encoding and decoding method can be changed by calling the set_method() function.

Example of use: (rate 1/3 constraint length K=7 ODS code using BPSK over AWGN)

BPSK bpsk;
Punctured_Convolutional_Code code;
ivec generator(3);
generator(0)=0133;
generator(1)=0165;
generator(2)=0171;
code.set_generator_polynomials(generator, 7);
bmat puncture_matrix = "1 1;0 1";
code.set_puncture_matrix(puncture_matrix);
code.set_truncation_length(30);
bvec bits=randb(100), encoded_bits, decoded_bits;
vec tx_signal, rx_signal;
code.encode(bits, encoded_bits);
tx_signal = bpsk.modulate_bits(encoded_bits);
rx_signal = tx_signal + sqrt(0.5)*randn(tx_signal.size());
code.decode(rx_signal, decoded_bits);

Definition at line 80 of file punct_convcode.h.

Member Function Documentation

void itpp::Punctured_Convolutional_Code::set_code	(	const CONVOLUTIONAL_CODE_TYPE	type_of_code,
		int	inverse_rate,
		int	constraint_length
	)

inline

Set the code according to built-in tables.

The type_of_code can be either MFD or ODS for maximum free distance codes (according to Proakis) or Optimum Distance Spectrum Codes according to Frenger, Orten and Ottosson.

Definition at line 94 of file punct_convcode.h.

References itpp::Convolutional_Code::set_code().

void itpp::Punctured_Convolutional_Code::encode_tail	(	const bvec &	input,
		bvec &	output
	)

Encoding that begins and ends in the zero state.

Encode a binary vector of inputs starting from zero state and also adds a tail of K-1 zeros to force the encoder into the zero state. Well suited for packet transmission.

Definition at line 172 of file punct_convcode.cpp.

References itpp::Convolutional_Code::encode_tail(), itpp::Convolutional_Code::n, Period, and puncture_matrix.

Referenced by encode().

bvec itpp::Punctured_Convolutional_Code::encode_tail ( const bvec & input )

inline

Encoding that begins and ends in the zero state.

Encode a binary vector of inputs starting from zero state and also adds a tail of K-1 zeros to force the encoder into the zero state. Well suited for packet transmission.

Definition at line 143 of file punct_convcode.h.

References encode_tail().

Referenced by encode_tail().

void itpp::Punctured_Convolutional_Code::decode_tail	(	const vec &	received_signal,
		bvec &	output
	)

virtual

Decode a block of encoded data where encode_tail has been used.

Thus is assumes a decoder start state of zero and that a tail of K-1 zeros has been added. No memory truncation.

Reimplemented from itpp::Convolutional_Code.

Definition at line 294 of file punct_convcode.cpp.

References itpp::Convolutional_Code::decode_tail(), it_warning, itpp::Convolutional_Code::n, Period, puncture_matrix, and total.

Referenced by decode().

bvec itpp::Punctured_Convolutional_Code::decode_tail ( const vec & received_signal )

inlinevirtual

Decode a block of encoded data where encode_tail has been used.

Thus is assumes a decoder start state of zero and that a tail of K-1 zeros has been added. No memory truncation.

Reimplemented from itpp::Convolutional_Code.

Definition at line 179 of file punct_convcode.h.

References decode_tail().

Referenced by decode_tail().

void itpp::Punctured_Convolutional_Code::calculate_spectrum	(	Array< ivec > &	spectrum,
		int	dmax,
		int	no_terms
	)

Calculate spectrum.

Calculates both the weight spectrum (Ad) and the information weight spectrum (Cd) and returns it as ivec:s in the 0:th and 1:st component of spectrum, respectively. For a punctrued code the spectrum is a sum of the spectras of all starting positions. Suitable for calculating many terms in the spectra (uses an breadth first algorithm). It is assumed that the code is non-catastrophic or else it is a possibility for an eternal loop.

dmax = an upper bound on the free distance
no_terms = number of terms including the dmax term that should be calculated

Observe that there is a risk that some of the integers are overflow if many terms are calculated in the spectrum.

Definition at line 734 of file punct_convcode.cpp.

References Period, itpp::Array< T >::set_size(), and itpp::spectrum().

void itpp::Punctured_Convolutional_Code::calculate_spectrum	(	Array< ivec > &	spectrum,
		int	time,
		int	dmax,
		int	no_terms,
		int	block_length = `0`
	)

Calculate spectrum. Suitable when calculating many terms in the spectra. Breadth first search.

Use this function to evaluate the spectum whith a speccific puncturing period, or to calculate the spectrum for block transmission. To calculate spectra for block transmission:

Use time = 0 if the puncturing is restarted at each block.
Use block_length = 0 (default value) for infinite blocks.

Definition at line 750 of file punct_convcode.cpp.

References itpp::elem_mult(), itpp::Convolutional_Code::K, itpp::Convolutional_Code::m, itpp::Convolutional_Code::next_state(), Period, itpp::Array< T >::set_size(), itpp::spectrum(), and weight().

int itpp::Punctured_Convolutional_Code::fast	(	Array< ivec > &	spectrum,
		int	time,
		int	dfree,
		int	no_terms,
		int	d_best_so_far = `0`,
		bool	test_catastrophic = `false`
	)

Cederwall's fast algorithm.

See IEEE Trans. Information Theory No. 6, pp. 1146-1159, Nov. 1989 for details.
Calculates both the weight spectrum (Ad) and the information weight spectrum (Cd) and returns it as ivec:s in the 0:th and 1:st component of spectrum, respectively.
The algorithm returns -1 if the code tested is worse that the input dfree and Cdfree.
It returns 0 if the code MAY be catastrophic (assuming that test_catastrophic is true), and returns 1 if everything went right.
dfree = the free distance of the code (or an upper bound).
no_terms = Number of terms including the dfree term that should be calculated.
d_best_so_far = the best value of the free distance found so far.
The FAST algorithm is good for calculating only a few terms in the spectrum. If many terms are desired, use calc_spectrum instead.

Observe that there is a risk that some of the integers are overflow if many terms are calculated in the spectrum.

Definition at line 589 of file punct_convcode.cpp.

References distance_profile(), itpp::Convolutional_Code::K, itpp::Convolutional_Code::m, itpp::Convolutional_Code::next_state(), Period, itpp::reverse(), itpp::Array< T >::set_size(), itpp::spectrum(), weight(), and weight_reverse().

void itpp::Convolutional_Code::encode_bit	(	const bin &	input,
		bvec &	output
	)

inherited

Encode a binary bit starting from the internal encoder state.

To initialize the encoder state use set_start_state() and init_encoder()

Definition at line 719 of file convcode.cpp.

References itpp::Convolutional_Code::encoder_state, itpp::Convolutional_Code::gen_pol, itpp::Convolutional_Code::m, itpp::Convolutional_Code::n, and itpp::Convolutional_Code::xor_int_table.

bvec itpp::Convolutional_Code::encode_bit ( const bin & input )

inlineinherited

Encode a binary bit starting from the internal encoder state.

To initialize the encoder state use set_start_state() and init_encoder()

Definition at line 214 of file convcode.h.

int itpp::Convolutional_Code::fast	(	Array< ivec > &	spectrum,
		const int	dfree,
		const int	no_terms,
		const int	Cdfree = `1000000`,
		const bool	test_catastrophic = `false`
	)

inherited

Cederwall's fast algorithm.

Calculates both the weight spectrum (Ad) and the information weight spectrum (Cd) and returns it as ivec:s in the 0:th and 1:st component of spectrum, respectively. The FAST algorithm is good for calculating only a few terms in the spectrum. If many terms are desired, use calc_spectrum instead. The algorithm returns -1 if the code tested is worse that the input dfree and Cdfree. It returns 0 if the code MAY be catastrophic (assuming that test_catastrophic is true), and returns 1 if everything went right.

dfree the free distance of the code (or an upper bound)
no_terms including the dfree term that should be calculated
Cdfree is the best value of information weight spectrum found so far

Observe that there is a risk that some of the integers are overflow if many terms are calculated in the spectrum.

See IT No. 6, pp. 1146-1159, Nov. 1989 for details.

Definition at line 1299 of file convcode.cpp.

References itpp::Convolutional_Code::distance_profile(), itpp::Convolutional_Code::K, itpp::Convolutional_Code::m, itpp::Convolutional_Code::next_state(), itpp::reverse(), itpp::Array< T >::set_size(), itpp::spectrum(), itpp::Convolutional_Code::weight(), and itpp::Convolutional_Code::weight_reverse().

Friends And Related Function Documentation

ITPP_EXPORT int compare_spectra	(	ivec	v1,
		ivec	v2,
		vec	weight_profile
	)

Return 1 if v1 is less, 0 if v2 less, and -1 if equal.

Definition at line 1492 of file convcode.cpp.

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

itpp/comm/punct_convcode.h
itpp/comm/punct_convcode.cpp

Public Member Functions

Protected Member Functions

Protected Attributes

Related Functions

Detailed Description

Member Function Documentation

Friends And Related Function Documentation