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Diffstat (limited to 'src/ldpc_dec.c')
| -rw-r--r-- | src/ldpc_dec.c | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/src/ldpc_dec.c b/src/ldpc_dec.c new file mode 100644 index 0000000..94d5c33 --- /dev/null +++ b/src/ldpc_dec.c @@ -0,0 +1,236 @@ +/* + FILE...: ldpc_dec.c + AUTHOR.: Matthew C. Valenti, Rohit Iyer Seshadri, David Rowe + CREATED: Sep 2016 + + Command line C LDPC decoder derived from MpDecode.c in the CML + library. Allows us to run the same decoder in Octave and C. +*/ + +#include <assert.h> +#include <errno.h> +#include <math.h> +#include <stdlib.h> +#include <stdint.h> +#include <string.h> +#include <stdio.h> + +#include "mpdecode_core.h" +#include "ldpc_codes.h" +#include "ofdm_internal.h" + +int opt_exists(char *argv[], int argc, char opt[]) { + int i; + for (i=0; i<argc; i++) { + if (strcmp(argv[i], opt) == 0) { + return i; + } + } + return 0; +} + + +int main(int argc, char *argv[]) +{ + int CodeLength, NumberParityBits; + int i, codename, parityCheckCount, mute, testframes; + int data_bits_per_frame; + struct LDPC ldpc; + int iter, total_iters; + int Tbits, Terrs, Tbits_raw, Terrs_raw, Tpackets, Tpacketerrs; + + int unused_data_bits = 84; + + if (argc < 2) { + fprintf(stderr, "\n"); + fprintf(stderr, "usage: %s --listcodes\n\n", argv[0]); + fprintf(stderr, " List supported codes (more can be added via using Octave ldpc scripts)\n"); + fprintf(stderr, "\n"); + fprintf(stderr, "usage: %s InOneSymbolPerFloat OutOneBitPerByte [--sd] [--half] [--code CodeName] [--testframes]", argv[0]); + fprintf(stderr, " [--unused numUnusedDataBits]\n\n"); + fprintf(stderr, " InOneSymbolPerFloat Input file of float LLRs, use - for the \n"); + fprintf(stderr, " file names to use stdin/stdout\n"); + fprintf(stderr, " --code Use LDPC code CodeName\n"); + fprintf(stderr, " --listcodes List available LDPC codes\n"); + fprintf(stderr, " --sd Treat input file samples as BPSK Soft Decision\n"); + fprintf(stderr, " demod outputs rather than LLRs\n"); + fprintf(stderr, " --mute Only output frames with < 10%% parity check fails\n"); + fprintf(stderr, " --testframes built in test frame modem, requires --testframes at encoder\n"); + fprintf(stderr, " --unused number of unused data bits, which are set to 1's at enc and dec\n"); + fprintf(stderr, "\n"); + + fprintf(stderr, "Example in testframe mode:\n\n"); + fprintf(stderr, " $ ./ldpc_enc /dev/zero - --sd --code HRA_112_112 --testframes 10 |\n"); + fprintf(stderr, " ./ldpc_dec - /dev/null --code HRA_112_112 --sd --testframes\n"); + exit(0); + } + + if ((codename = opt_exists(argv, argc, "--listcodes")) != 0) { + ldpc_codes_list(); + exit(0); + } + + /* set up LDPC code */ + + int code_index = 0; + if ((codename = opt_exists(argv, argc, "--code")) != 0) + code_index = ldpc_codes_find(argv[codename+1]); + memcpy(&ldpc,&ldpc_codes[code_index],sizeof(struct LDPC)); + fprintf(stderr, "Using: %s\n", ldpc.name); + + CodeLength = ldpc.CodeLength; /* length of entire codeword */ + NumberParityBits = ldpc.NumberParityBits; + data_bits_per_frame = ldpc.NumberRowsHcols; + unsigned char ibits[data_bits_per_frame]; + unsigned char pbits[NumberParityBits]; + uint8_t out_char[CodeLength]; + + testframes = 0; + total_iters = 0; + Tbits = Terrs = Tbits_raw = Terrs_raw = Tpackets = Tpacketerrs = 0; + + FILE *fin, *fout; + int sdinput, nread, offset=0; + + /* File I/O mode ------------------------------------------------*/ + + if (strcmp(argv[1], "-") == 0) fin = stdin; + else if ( (fin = fopen(argv[1],"rb")) == NULL ) { + fprintf(stderr, "Error opening input SD file: %s: %s.\n", + argv[1], strerror(errno)); + exit(1); + } + + if (strcmp(argv[2], "-") == 0) fout = stdout; + else if ( (fout = fopen(argv[2],"wb")) == NULL ) { + fprintf(stderr, "Error opening output bit file: %s: %s.\n", + argv[2], strerror(errno)); + exit(1); + } + + sdinput = 0; mute = 0; testframes = 0; + if (opt_exists(argv, argc, "--sd")) { + sdinput = 1; + } + if (opt_exists(argv, argc, "--mute")) { + mute = 1; + } + unused_data_bits = 0; int arg; + if ((arg = opt_exists(argv, argc, "--unused"))) { + unused_data_bits = atoi(argv[arg+1]); + } + if (opt_exists(argv, argc, "--testframes")) { + testframes = 1; + uint16_t r[data_bits_per_frame]; + ofdm_rand(r, data_bits_per_frame); + + for(i=0; i<data_bits_per_frame-unused_data_bits; i++) { + ibits[i] = r[i] > 16384; + } + for(i=data_bits_per_frame-unused_data_bits; i<data_bits_per_frame; i++) { + ibits[i] = 1; + } + encode(&ldpc, ibits, pbits); + } + + float *input_float = calloc(CodeLength, sizeof(float)); + + nread = CodeLength - unused_data_bits; + fprintf(stderr, "CodeLength: %d offset: %d\n", CodeLength, offset); + + while(fread(input_float, sizeof(float), nread, fin) == nread) { + if (testframes) { + /* BPSK SD and bit LLRs get mapped roughly the same way so this just happens to work for both */ + char in_char; + for (i=0; i<data_bits_per_frame-unused_data_bits; i++) { + in_char = input_float[i] < 0; + if (in_char != ibits[i]) { + Terrs_raw++; + } + Tbits_raw++; + } + for (i=0; i<NumberParityBits; i++) { + in_char = input_float[i+data_bits_per_frame-unused_data_bits] < 0; + if (in_char != pbits[i]) { + Terrs_raw++; + } + Tbits_raw++; + } + } + + if (sdinput) { + /* map BPSK SDs to bit LLRs */ + float llr[CodeLength-unused_data_bits]; + sd_to_llr(llr, input_float, CodeLength-unused_data_bits); + + /* insert unused data LLRs */ + + float llr_tmp[CodeLength]; + for(i=0; i<data_bits_per_frame-unused_data_bits; i++) + llr_tmp[i] = llr[i]; // rx data bits + for(i=data_bits_per_frame-unused_data_bits; i<data_bits_per_frame; i++) + llr_tmp[i] = -10.0; // known data bits high likelhood + for(i=data_bits_per_frame; i<CodeLength; i++) + llr_tmp[i] = llr[i-unused_data_bits]; // rx parity bits + memcpy(input_float, llr_tmp, sizeof(float)*CodeLength); + } + + iter = run_ldpc_decoder(&ldpc, out_char, input_float, &parityCheckCount); + //fprintf(stderr, "iter: %d\n", iter); + total_iters += iter; + + if (mute) { + + // Output data bits only if decoder converged, or was + // within 10% of all parity checks converging (10% est + // BER). Useful for real world operation as it can + // resync and won't send crappy packets to the decoder + + float ber_est = (float)(ldpc.NumberParityBits - parityCheckCount)/ldpc.NumberParityBits; + //fprintf(stderr, "iter: %4d parityCheckErrors: %4d ber: %3.2f\n", iter, ldpc.NumberParityBits - parityCheckCount, ber_est); + if (ber_est < 0.1) { + fwrite(out_char, sizeof(char), ldpc.NumberRowsHcols, fout); + } + + } + + fwrite(out_char, sizeof(char), data_bits_per_frame, fout); + + if (testframes) { + int perr = 0; + for (i=0; i<data_bits_per_frame; i++) { + if (out_char[i] != ibits[i]) { + Terrs++; + perr = 1; + } + Tbits++; + } + Tpackets++; if (perr) { Tpacketerrs++; fprintf(stderr,"x"); } else fprintf(stderr,"."); + } + //fprintf(stderr, "Terrs_raw: %d Tbits_raw: %d Terr: %d Tbits: %d\n", Terrs_raw, Tbits_raw, Terrs, Tbits); + } + + free(input_float); + if (fin != NULL) fclose(fin); + if (fout != NULL) fclose(fout); + + fprintf(stderr, "total iters %d\n", total_iters); + + if (testframes) { + fprintf(stderr, "Raw Tbits: %6d Terr: %6d BER: %4.3f\n", Tbits_raw, Terrs_raw, + (float)Terrs_raw/(Tbits_raw+1E-12)); + float coded_ber = (float)Terrs/(Tbits+1E-12); + fprintf(stderr, "Coded Tbits: %6d Terr: %6d BER: %4.3f\n", Tbits, Terrs, coded_ber); + fprintf(stderr, " Tpkts: %6d Tper: %6d PER: %4.3f\n", Tpackets, Tpacketerrs, Tpacketerrs/(Tpackets+1E-12)); + + /* set return code for Ctest */ + if (Tpackets && (coded_ber < 0.01)) + return 0; + else + return 1; + } + + return 0; +} + + |