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/control_channels_decoder_impl.cc b/lib/decoding/control_channels_decoder_impl.cc
new file mode 100644
index 0000000..544e6bb
--- /dev/null
+++ b/lib/decoding/control_channels_decoder_impl.cc
@@ -0,0 +1,147 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2014 <+YOU OR YOUR COMPANY+>.
+ *
+ * This 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 3, or (at your option)
+ * any later version.
+ *
+ * This software 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 this software; see the file COPYING. If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gnuradio/io_signature.h>
+#include <gsm/gsmtap.h>
+#include "control_channels_decoder_impl.h"
+
+namespace gr {
+ namespace gsm {
+
+ control_channels_decoder::sptr
+ control_channels_decoder::make()
+ {
+ return gnuradio::get_initial_sptr
+ (new control_channels_decoder_impl());
+ }
+
+ /*
+ * The private constructor
+ */
+ control_channels_decoder_impl::control_channels_decoder_impl()
+ : gr::block("control_channels_decoder",
+ gr::io_signature::make(0, 0, 0),
+ gr::io_signature::make(0, 0, 0)),
+ d_collected_bursts_num(0)
+ {
+ //initialize de/interleaver
+ int j, k, B;
+ for (k = 0; k < CONV_SIZE; k++)
+ {
+ B = k % 4;
+ j = 2 * ((49 * k) % 57) + ((k % 8) / 4);
+ interleave_trans[k] = B * 114 + j; //114=57 + 57
+ }
+
+ FC_init(&fc_ctx, 40, 184);
+ message_port_register_in(pmt::mp("bursts"));
+ set_msg_handler(pmt::mp("bursts"), boost::bind(&control_channels_decoder_impl::decode, this, _1));
+// message_port_register_out(pmt::mp(""));
+ }
+
+ /*
+ * Our virtual destructor.
+ */
+ control_channels_decoder_impl::~control_channels_decoder_impl()
+ {
+ }
+
+ void control_channels_decoder_impl::decode(pmt::pmt_t msg)
+ {
+ unsigned char iBLOCK[BLOCKS*iBLOCK_SIZE], hl, hn, conv_data[CONV_SIZE], decoded_data[PARITY_OUTPUT_SIZE];
+ d_bursts[d_collected_bursts_num] = msg;
+ d_collected_bursts_num++;
+ //get convecutive bursts
+ pmt::pmt_t header_blob = pmt::car(msg);
+ gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(header_blob);
+
+ if(d_collected_bursts_num==4)
+ {
+ d_collected_bursts_num=0;
+ //reorganize data
+ for(int ii = 0; ii < 4; ii++)
+ {
+ pmt::pmt_t burst_content = pmt::cdr(d_bursts[ii]);
+ int8_t * burst_bits = (int8_t *)pmt::blob_data(burst_content);
+
+ for(int jj = 0; jj < 57; jj++)
+ {
+ iBLOCK[ii*iBLOCK_SIZE+jj] = burst_bits[jj + 3];
+ iBLOCK[ii*iBLOCK_SIZE+jj+57] = burst_bits[jj + 88]; //88 = 3+57+1+26+1
+ }
+ }
+ //deinterleave
+ for (int k = 0; k < CONV_SIZE; k++)
+ {
+ conv_data[k] = iBLOCK[interleave_trans[k]];
+ }
+ //convolutional code decode
+ int errors = conv_decode(decoded_data, conv_data);
+ //std::cout << "Errors:" << errors << " " << parity_check(decoded_data) << std::endl;
+ // check parity
+ // If parity check error detected try to fix it.
+
+ if (parity_check(decoded_data))
+ {
+ FC_init(&fc_ctx, 40, 184);
+ unsigned char crc_result[PARITY_OUTPUT_SIZE];
+ if (FC_check_crc(&fc_ctx, decoded_data, crc_result) == 0)
+ {
+ //("error: sacch: parity error (errors=%d fn=%d)\n", errors, ctx->fn);
+ //std::cout << "Uncorrectable errors!" << std::endl;
+ errors = -1;
+ } else {
+ //DEBUGF("Successfully corrected parity bits! (errors=%d fn=%d)\n", errors, ctx->fn);
+ //std::cout << "Corrected some errors" << std::endl;
+ memcpy(decoded_data, crc_result, PARITY_OUTPUT_SIZE);
+ errors = 0;
+ }
+ } else {
+ //std::cout << "Everything correct" << std::endl;
+ }
+ //compress bits
+ unsigned char outmsg[27];
+ unsigned char sbuf_len=224;
+ int i, j, c, pos=0;
+ for(i = 0; i < sbuf_len; i += 8) {
+ for(j = 0, c = 0; (j < 8) && (i + j < sbuf_len); j++){
+ c |= (!!decoded_data[i + j]) << j;
+ }
+ outmsg[pos++] = c & 0xff;
+ }
+
+ //printf("%6d %d:", (0 + 1), 0);
+ int jj=0;
+ while (jj < 23){
+ printf(" %02x", outmsg[jj]);//decoded_data[jj]);
+ jj++;
+ }
+ printf("\n");
+ fflush(stdout);
+ }
+ return;
+ }
+ } /* namespace gsm */
+} /* namespace gr */
+