295 lines
10 KiB
C
295 lines
10 KiB
C
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/*---------------------------------------------------------------------------*\
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FILE........: interldpc.c
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AUTHOR......: David Rowe
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DATE CREATED: April 2018
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Helper functions for interleaved LDPC waveforms.
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\*---------------------------------------------------------------------------*/
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/*
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Copyright (C) 2018 David Rowe
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All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License version 2.1, as
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published by the Free Software Foundation. This program is
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distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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#include <math.h>
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#include "interldpc.h"
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#include "ofdm_internal.h"
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#include "mpdecode_core.h"
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#include "gp_interleaver.h"
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#include "HRA_112_112.h"
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#include "HRAb_396_504.h"
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/* CRC type function, used to compare QPSK vectors when debugging */
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COMP test_acc(COMP v[], int n) {
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COMP acc = {0.0f, 0.0f};
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int i;
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for (i = 0; i < n; i++) {
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acc.real += roundf(v[i].real);
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acc.imag += roundf(v[i].imag);
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}
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return acc;
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}
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void printf_n(COMP v[], int n) {
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int i;
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for (i = 0; i < n; i++) {
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fprintf(stderr, "%d %10f %10f\n", i, round(v[i].real), round(v[i].imag));
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}
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}
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void set_up_ldpc_constants(struct LDPC *ldpc, int code_length, int parity_bits, int bps) {
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/* following provided for convenience and to match Octave variable names */
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/* these remain fixed */
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ldpc->ldpc_data_bits_per_frame = code_length - parity_bits;
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ldpc->ldpc_coded_bits_per_frame = code_length;
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/* in the case there are some unused data bits, these may be
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modified to be less that ldpc->ldpc_xxx versions above. We
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place known bits in the unused data bit positions, which make
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the code stronger, and allow us to mess with different speech
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codec bit allocations without designing new LDPC codes. */
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ldpc->data_bits_per_frame = ldpc->ldpc_data_bits_per_frame;
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ldpc->coded_bits_per_frame = ldpc->ldpc_coded_bits_per_frame;
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ldpc->coded_syms_per_frame = ldpc->coded_bits_per_frame / bps;
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}
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void set_data_bits_per_frame(struct LDPC *ldpc, int new_data_bits_per_frame, int bps) {
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ldpc->data_bits_per_frame = new_data_bits_per_frame;
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ldpc->coded_bits_per_frame = ldpc->data_bits_per_frame + ldpc->NumberParityBits;
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ldpc->coded_syms_per_frame = ldpc->coded_bits_per_frame / bps;
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}
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// TODO: this should be in (n,k) = (224,112) format, fix some time
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void set_up_hra_112_112(struct LDPC *ldpc, struct OFDM_CONFIG *config) {
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ldpc->max_iter = HRA_112_112_MAX_ITER;
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ldpc->dec_type = 0;
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ldpc->q_scale_factor = 1;
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ldpc->r_scale_factor = 1;
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ldpc->CodeLength = HRA_112_112_CODELENGTH;
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ldpc->NumberParityBits = HRA_112_112_NUMBERPARITYBITS;
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ldpc->NumberRowsHcols = HRA_112_112_NUMBERROWSHCOLS;
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ldpc->max_row_weight = HRA_112_112_MAX_ROW_WEIGHT;
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ldpc->max_col_weight = HRA_112_112_MAX_COL_WEIGHT;
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ldpc->H_rows = (uint16_t *) HRA_112_112_H_rows;
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ldpc->H_cols = (uint16_t *) HRA_112_112_H_cols;
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/* provided for convenience and to match Octave variable names */
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set_up_ldpc_constants(ldpc, HRA_112_112_CODELENGTH, HRA_112_112_NUMBERPARITYBITS, config->bps);
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}
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// Note code #defines below should be in (n,k) = (504,396)
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// TODO : fix this some time
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void set_up_hra_504_396(struct LDPC *ldpc, struct OFDM_CONFIG *config) {
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ldpc->max_iter = HRAb_396_504_MAX_ITER;
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ldpc->dec_type = 0;
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ldpc->q_scale_factor = 1;
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ldpc->r_scale_factor = 1;
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ldpc->CodeLength = HRAb_396_504_CODELENGTH;
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ldpc->NumberParityBits = HRAb_396_504_NUMBERPARITYBITS;
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ldpc->NumberRowsHcols = HRAb_396_504_NUMBERROWSHCOLS;
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ldpc->max_row_weight = HRAb_396_504_MAX_ROW_WEIGHT;
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ldpc->max_col_weight = HRAb_396_504_MAX_COL_WEIGHT;
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ldpc->H_rows = (uint16_t *) HRAb_396_504_H_rows;
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ldpc->H_cols = (uint16_t *) HRAb_396_504_H_cols;
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set_up_ldpc_constants(ldpc, HRAb_396_504_CODELENGTH, HRAb_396_504_NUMBERPARITYBITS, config->bps);
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}
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void ldpc_encode_frame(struct LDPC *ldpc, int codeword[], unsigned char tx_bits_char[]) {
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unsigned char pbits[ldpc->NumberParityBits];
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int i, j;
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if (ldpc->data_bits_per_frame == ldpc->ldpc_data_bits_per_frame) {
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/* we have enough data bits to fill the codeword */
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encode(ldpc, tx_bits_char, pbits);
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} else {
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unsigned char tx_bits_char_padded[ldpc->ldpc_data_bits_per_frame];
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/* some unused data bits, set these to known values to strengthen code */
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memcpy(tx_bits_char_padded, tx_bits_char, ldpc->data_bits_per_frame);
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for (i = ldpc->data_bits_per_frame; i < ldpc->ldpc_data_bits_per_frame; i++)
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tx_bits_char_padded[i] = 1;
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encode(ldpc, tx_bits_char_padded, pbits);
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}
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/* output codeword is concatenation of (used) data bits and parity
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bits, we don't bother sending unused (known) data bits */
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for (i = 0; i < ldpc->data_bits_per_frame; i++) {
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codeword[i] = tx_bits_char[i];
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}
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for (j = 0; j < ldpc->NumberParityBits; i++, j++) {
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codeword[i] = pbits[j];
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}
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}
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void qpsk_modulate_frame(COMP tx_symbols[], int codeword[], int n) {
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int s, i;
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int dibit[2];
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complex float qpsk_symb;
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for (s = 0, i = 0; i < n; s += 2, i++) {
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dibit[0] = codeword[s + 1] & 0x1;
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dibit[1] = codeword[s] & 0x1;
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qpsk_symb = qpsk_mod(dibit);
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tx_symbols[i].real = crealf(qpsk_symb);
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tx_symbols[i].imag = cimagf(qpsk_symb);
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}
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}
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void interleaver_sync_state_machine(struct OFDM *ofdm,
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struct LDPC *ldpc,
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struct OFDM_CONFIG *config,
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COMP codeword_symbols_de[],
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float codeword_amps_de[],
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float EsNo, int interleave_frames,
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int *iter, int *parityCheckCount, int *Nerrs_coded) {
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int coded_syms_per_frame = ldpc->coded_syms_per_frame;
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int coded_bits_per_frame = ldpc->coded_bits_per_frame;
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int data_bits_per_frame = ldpc->data_bits_per_frame;
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float llr[coded_bits_per_frame];
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uint8_t out_char[coded_bits_per_frame];
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State next_sync_state_interleaver;
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next_sync_state_interleaver = ofdm->sync_state_interleaver;
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if ((ofdm->sync_state_interleaver == search) && (ofdm->frame_count >= (interleave_frames - 1))) {
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symbols_to_llrs(llr, codeword_symbols_de, codeword_amps_de, EsNo, ofdm->mean_amp, coded_syms_per_frame);
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iter[0] = run_ldpc_decoder(ldpc, out_char, llr, parityCheckCount);
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Nerrs_coded[0] = data_bits_per_frame - parityCheckCount[0];
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if ((Nerrs_coded[0] == 0) || (interleave_frames == 1)) {
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/* sucessful decode! */
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next_sync_state_interleaver = synced;
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ofdm->frame_count_interleaver = interleave_frames;
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}
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}
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ofdm->sync_state_interleaver = next_sync_state_interleaver;
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}
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/* measure uncoded (raw) bit errors over interleaver frame, note we
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don't include txt bits as this is done after we dissassemmble the
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frame */
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int count_uncoded_errors(struct LDPC *ldpc, struct OFDM_CONFIG *config, int Nerrs_raw[], int interleave_frames, COMP codeword_symbols_de[]) {
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int i, j, Nerrs, Terrs;
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int coded_syms_per_frame = ldpc->coded_syms_per_frame;
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int coded_bits_per_frame = ldpc->coded_bits_per_frame;
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int data_bits_per_frame = ldpc->data_bits_per_frame;
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int rx_bits_raw[coded_bits_per_frame];
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/* generate test codeword from known payload data bits */
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int test_codeword[coded_bits_per_frame];
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uint16_t r[data_bits_per_frame];
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uint8_t tx_bits[data_bits_per_frame];
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ofdm_rand(r, data_bits_per_frame);
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for (i = 0; i < data_bits_per_frame; i++) {
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tx_bits[i] = r[i] > 16384;
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}
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ldpc_encode_frame(ldpc, test_codeword, tx_bits);
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Terrs = 0;
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for (j = 0; j < interleave_frames; j++) {
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for (i = 0; i < coded_syms_per_frame; i++) {
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int bits[2];
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complex float s = codeword_symbols_de[j * coded_syms_per_frame + i].real + I * codeword_symbols_de[j * coded_syms_per_frame + i].imag;
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qpsk_demod(s, bits);
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rx_bits_raw[config->bps * i] = bits[1];
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rx_bits_raw[config->bps * i + 1] = bits[0];
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}
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Nerrs = 0;
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for (i = 0; i < coded_bits_per_frame; i++) {
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if (test_codeword[i] != rx_bits_raw[i]) {
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Nerrs++;
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}
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}
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Nerrs_raw[j] = Nerrs;
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Terrs += Nerrs;
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}
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return Terrs;
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}
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int count_errors(uint8_t tx_bits[], uint8_t rx_bits[], int n) {
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int i;
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int Nerrs = 0;
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for (i = 0; i < n; i++) {
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if (tx_bits[i] != rx_bits[i]) {
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Nerrs++;
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}
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}
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return Nerrs;
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}
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/*
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Given an array of tx_bits, LDPC encodes, interleaves, and OFDM
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modulates.
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Note this could be refactored to save memory, e.g. for embedded
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applications we could call ofdm_txframe on a frame by frame
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basis
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*/
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void ofdm_ldpc_interleave_tx(struct OFDM *ofdm, struct LDPC *ldpc, complex float tx_sams[], uint8_t tx_bits[], uint8_t txt_bits[], int interleave_frames, struct OFDM_CONFIG *config) {
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int coded_syms_per_frame = ldpc->coded_syms_per_frame;
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int coded_bits_per_frame = ldpc->coded_bits_per_frame;
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int data_bits_per_frame = ldpc->data_bits_per_frame;
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int ofdm_bitsperframe = ofdm_get_bits_per_frame();
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int codeword[coded_bits_per_frame];
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COMP coded_symbols[interleave_frames * coded_syms_per_frame];
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COMP coded_symbols_inter[interleave_frames * coded_syms_per_frame];
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int Nsamperframe = ofdm_get_samples_per_frame();
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complex float tx_symbols[ofdm_bitsperframe / config->bps];
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int j;
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for (j = 0; j < interleave_frames; j++) {
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ldpc_encode_frame(ldpc, codeword, &tx_bits[j * data_bits_per_frame]);
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qpsk_modulate_frame(&coded_symbols[j * coded_syms_per_frame], codeword, coded_syms_per_frame);
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}
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gp_interleave_comp(coded_symbols_inter, coded_symbols, interleave_frames * coded_syms_per_frame);
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for (j = 0; j < interleave_frames; j++) {
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ofdm_assemble_modem_frame_symbols(tx_symbols, &coded_symbols_inter[j * coded_syms_per_frame], &txt_bits[config->txtbits * j]);
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ofdm_txframe(ofdm, &tx_sams[j * Nsamperframe], tx_symbols);
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}
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}
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