Added typical signalization channels (CCCH, BCCH, SDCCH) decoder and demapper for BCCH.
The implementation is quite dirty at this moment.
diff --git a/lib/decoding/fire_crc.c b/lib/decoding/fire_crc.c
new file mode 100644
index 0000000..7cdfc0b
--- /dev/null
+++ b/lib/decoding/fire_crc.c
@@ -0,0 +1,179 @@
+//TODO: this file shouldn't be part of the GSM Receiver
+/* -*- c++ -*- */
+/*
+ * Copyright 2005 Free Software Foundation, Inc.
+ *
+ * This file is part of GNU Radio
+ *
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * GNU Radio 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING. If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "fire_crc.h"
+#include <stdio.h>
+#include <string.h>
+
+#define REM(x, y) (x) % (y)
+
+static int FC_syndrome_shift(FC_CTX *ctx, unsigned int bit);
+
+static int
+outit(int *data, int len)
+{
+ int i;
+
+ for (i = 0; i < len; i++)
+ printf("%d ", data[i]);
+ printf("\n");
+}
+
+int
+FC_init(FC_CTX *ctx, unsigned int crc_size, unsigned int data_size)
+{
+ ctx->crc_size = crc_size;
+ ctx->data_size = data_size;
+ ctx->syn_start = 0;
+
+ return 0;
+}
+
+int
+FC_check_crc(FC_CTX *ctx, unsigned char *input_bits, unsigned char *control_data)
+{
+ int j,error_count = 0, error_index = 0, success_flag = 0, syn_index = 0;
+ unsigned int i;
+
+ ctx->syn_start = 0;
+ // reset the syndrome register
+ memset(ctx->syndrome_reg, 0, sizeof ctx->syndrome_reg);
+
+ // shift in the data bits
+ for (i=0; i < ctx->data_size; i++) {
+ error_count = FC_syndrome_shift(ctx, input_bits[i]);
+ control_data[i] = input_bits[i];
+ }
+
+ // shift in the crc bits
+ for (i=0; i < ctx->crc_size; i++) {
+ error_count = FC_syndrome_shift(ctx, 1-input_bits[i+ctx->data_size]);
+ }
+
+ // Find position of error burst
+ if (error_count == 0) {
+ error_index = 0;
+ }
+ else {
+ error_index = 1;
+ error_count = FC_syndrome_shift(ctx, 0);
+ error_index += 1;
+ while (error_index < (ctx->data_size + ctx->crc_size) ) {
+ error_count = FC_syndrome_shift(ctx, 0);
+ error_index += 1;
+ if ( error_count == 0 ) break;
+ }
+ }
+
+ // Test for correctable errors
+ //printf("error_index %d\n",error_index);
+ if (error_index == 224) success_flag = 0;
+ else {
+
+ // correct index depending on the position of the error
+ if (error_index == 0) syn_index = error_index;
+ else syn_index = error_index - 1;
+
+ // error burst lies within data bits
+ if (error_index < 184) {
+ //printf("error < bit 184,%d\n",error_index);
+ j = error_index;
+ while ( j < (error_index+12) ) {
+ if (j < 184) {
+ control_data[j] = control_data[j] ^
+ ctx->syndrome_reg[REM(ctx->syn_start+39-j+syn_index,40)];
+ }
+ else break;
+ j = j + 1;
+ }
+ }
+ else if ( error_index > 212 ) {
+ //printf("error > bit 212,%d\n",error_index);
+ j = 0;
+ while ( j < (error_index - 212) ) {
+ control_data[j] = control_data[j] ^
+ ctx->syndrome_reg[REM(ctx->syn_start+39-j-224+syn_index,40)];
+ j = j + 1;
+ }
+ }
+ // for 183 < error_index < 213 error in parity alone so ignore
+ success_flag = 1;
+ }
+ return success_flag;
+}
+
+static int
+FC_syndrome_shift(FC_CTX *ctx, unsigned int bit)
+{
+ int error_count = 0;
+ unsigned int i;
+
+ if (ctx->syn_start == 0)
+ ctx->syn_start = 39;
+ else ctx->syn_start -= 1;
+
+ int temp_syndrome_reg[sizeof ctx->syndrome_reg];
+
+ memcpy(temp_syndrome_reg, ctx->syndrome_reg, sizeof temp_syndrome_reg);
+
+ temp_syndrome_reg[REM(ctx->syn_start+3,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+3,40)] ^
+ ctx->syndrome_reg[ctx->syn_start];
+ temp_syndrome_reg[REM(ctx->syn_start+17,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+17,40)] ^
+ ctx->syndrome_reg[ctx->syn_start];
+ temp_syndrome_reg[REM(ctx->syn_start+23,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+23,40)] ^
+ ctx->syndrome_reg[ctx->syn_start];
+ temp_syndrome_reg[REM(ctx->syn_start+26,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+26,40)] ^
+ ctx->syndrome_reg[ctx->syn_start];
+
+ temp_syndrome_reg[REM(ctx->syn_start+4,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+4,40)] ^ bit;
+ temp_syndrome_reg[REM(ctx->syn_start+6,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+6,40)] ^ bit;
+ temp_syndrome_reg[REM(ctx->syn_start+10,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+10,40)] ^ bit;
+ temp_syndrome_reg[REM(ctx->syn_start+16,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+16,40)] ^ bit;
+ temp_syndrome_reg[REM(ctx->syn_start+27,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+27,40)] ^ bit;
+ temp_syndrome_reg[REM(ctx->syn_start+29,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+29,40)] ^ bit;
+ temp_syndrome_reg[REM(ctx->syn_start+33,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+33,40)] ^ bit;
+ temp_syndrome_reg[REM(ctx->syn_start+39,40)] =
+ ctx->syndrome_reg[REM(ctx->syn_start+39,40)] ^ bit;
+
+ temp_syndrome_reg[ctx->syn_start] = ctx->syndrome_reg[ctx->syn_start] ^ bit;
+
+ memcpy(ctx->syndrome_reg, temp_syndrome_reg, sizeof ctx->syndrome_reg);
+
+ for (i = 0; i < 28; i++) {
+ error_count = error_count + ctx->syndrome_reg[REM(ctx->syn_start+i,40)];
+ }
+ return error_count;
+}
+
+