convolutional.h File Reference

General functions used to implement convolutional encoding. More...

#include <volk_gnsssdr/volk_gnsssdr.h>
#include <vector>

Go to the source code of this file.

Functions
int	parity_counter (int symbol, int length)
	Determines if a symbol has odd (1) or even (0) parity Output parameters: More...
int	nsc_enc_bit (int state_out_p[], int input, int state_in, const int g[], int KK, int nn)
	Convolutionally encodes a single bit using a rate 1/n encoder. Takes in one input bit at a time, and produces a n-bit output. More...
void	nsc_transit (int output_p[], int trans_p[], int input, int g[], int KK, int nn)
	Function that creates the transit and output vectors. More...
float	Gamma (const float rec_array[], int symbol, int nn)
	Computes the branch metric used for decoding. More...
void	Viterbi (int output_u_int[], const int out0[], const int state0[], const int out1[], const int state1[], const float input_c[], int KK, int nn, int LL)
	Uses the Viterbi algorithm to perform hard-decision decoding of a convolutional code. More...

Variables
const float	MAXLOG = 1e7

Detailed Description

General functions used to implement convolutional encoding.

Author

Matthew C. Valenti, 2006-2008.

C. Fernandez-Prades, 2019.

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Copyright (C) 2006-2008 Matthew C. Valenti Copyright (C) 2019 C. Fernandez-Prades

GNSS-SDR is a software defined Global Navigation Satellite Systems receiver

This file is part of GNSS-SDR.

SPDX-License-Identifier: GPL-3.0-or-later

This file is a derived work of the original file, which had this note:

The functions in this file are part of the Iterative Solutions Coded Modulation Library. The Iterative Solutions Coded Modulation Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

Definition in file convolutional.h.

Function Documentation

Gamma()

float Gamma ( const float  rec_array[], int  symbol, int  nn  )

inline

Computes the branch metric used for decoding.

Returns

(returned float) The metric between the hypothetical symbol and the received vector

Parameters

[in]	rec_array	The received vector, of length nn
[in]	symbol	The hypothetical symbol
[in]	nn	The length of the received vector

Definition at line 145 of file convolutional.h.

nsc_enc_bit()

int nsc_enc_bit ( int  state_out_p[], int  input, int  state_in, const int  g[], int  KK, int  nn  )

inline

Convolutionally encodes a single bit using a rate 1/n encoder. Takes in one input bit at a time, and produces a n-bit output.

Parameters

[in]	input	The input data bit (i.e. a 0 or 1).
[in]	state_in	The starting state of the encoder (an int from 0 to 2^m-1).
[in]	g[]	An n-element vector containing the code generators in binary form.
[in]	KK	The constraint length of the convolutional code.
[out]	output_p[]	An n-element vector containing the encoded bits.
[out]	state_out_p[]	An integer containing the final state of the encoder (i.e. the state after encoding this bit)

This function is used by nsc_transit()

Definition at line 86 of file convolutional.h.

References parity_counter().

Referenced by nsc_transit().

nsc_transit()

void nsc_transit ( int  output_p[], int  trans_p[], int  input, int  g[], int  KK, int  nn  )

inline

Function that creates the transit and output vectors.

Definition at line 116 of file convolutional.h.

References nsc_enc_bit().

parity_counter()

int parity_counter ( int  symbol, int  length  )

inline

Determines if a symbol has odd (1) or even (0) parity Output parameters:

Returns

(returned int): The symbol's parity = 1 for odd and 0 for even

Parameters

[in]	symbol	The integer-valued symbol
[in]	length	The highest bit position in the symbol

This function is used by nsc_enc_bit(), rsc_enc_bit(), and rsc_tail()

Definition at line 58 of file convolutional.h.

Referenced by nsc_enc_bit().

Viterbi()

void Viterbi ( int  output_u_int[], const int  out0[], const int  state0[], const int  out1[], const int  state1[], const float  input_c[], int  KK, int  nn, int  LL  )

inline

Uses the Viterbi algorithm to perform hard-decision decoding of a convolutional code.

Parameters

[in]	out0[]	The output bits for each state if input is a 0.
[in]	state0[]	The next state if input is a 0.
[in]	out1[]	The output bits for each state if input is a 1.
[in]	state1[]	The next state if input is a 1.
[in]	r[]	The received signal in LLR-form. For BPSK, must be in form r = 2*a*y/(sigma^2).
[in]	KK	The constraint length of the convolutional code.
[in]	LL	The number of data bits.
[out]	output_u_int[]	Hard decisions on the data bits

Definition at line 177 of file convolutional.h.