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Diffstat (limited to 'lib/misc_utils/trx_burst_if_impl.cc')
| -rw-r--r-- | lib/misc_utils/trx_burst_if_impl.cc | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/lib/misc_utils/trx_burst_if_impl.cc b/lib/misc_utils/trx_burst_if_impl.cc new file mode 100644 index 0000000..8f458b0 --- /dev/null +++ b/lib/misc_utils/trx_burst_if_impl.cc @@ -0,0 +1,231 @@ +/* -*- c++ -*- */ +/* @file + * @author Vadim Yanitskiy <axilirator@gmail.com> + * @section LICENSE + * + * Gr-gsm 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. + * + * Gr-gsm 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 gr-gsm; 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 <boost/lexical_cast.hpp> + +#include "udp_socket.h" +#include "trx_burst_if_impl.h" + +#define BURST_SIZE 148 +#define DATA_IF_MTU 160 + +/** + * 41-bit RACH synchronization sequence + * GSM 05.02 Chapter 5.2.7 Access burst (AB) + */ +static uint8_t rach_synch_seq[] = { + 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, + 1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, + 1, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, +}; + +namespace gr { + namespace gsm { + + trx_burst_if::sptr + trx_burst_if::make( + const std::string &remote_addr, + const std::string &base_port) + { + int base_port_int = boost::lexical_cast<int> (base_port); + + return gnuradio::get_initial_sptr + (new trx_burst_if_impl(remote_addr, base_port_int)); + } + + /* + * The private constructor + */ + trx_burst_if_impl::trx_burst_if_impl( + const std::string &remote_addr, + int base_port + ) : gr::block("trx_burst_if", + gr::io_signature::make(0, 0, 0), + gr::io_signature::make(0, 0, 0)) + { + message_port_register_in(pmt::mp("bursts")); + message_port_register_out(pmt::mp("bursts")); + + // Bind a port handler + set_msg_handler(pmt::mp("bursts"), + boost::bind(&trx_burst_if_impl::handle_dl_burst, this, _1)); + + // Prepare port numbers + std::string data_src_port = boost::lexical_cast<std::string> (base_port + 2); + std::string data_dst_port = boost::lexical_cast<std::string> (base_port + 102); + + // Init DATA interface + d_data_sock = new udp_socket(remote_addr, + data_src_port, data_dst_port, DATA_IF_MTU); + + // Bind DATA interface handler + d_data_sock->udp_rx_handler = boost::bind( + &trx_burst_if_impl::handle_ul_burst, this, _1, _2); + } + + /* + * Our virtual destructor. + */ + trx_burst_if_impl::~trx_burst_if_impl() + { + // Release all UDP sockets and free memory + delete d_data_sock; + } + + /* + * Check if burst is a RACH burst + */ + bool trx_burst_if_impl::detect_rach(uint8_t *burst) + { + // Compare synchronization sequence + for (int i = 0; i < 41; i++) + if (burst[i + 8] != rach_synch_seq[i]) + return false; + + // Make sure TB and GP are filled by 0x00 + for (int i = 0; i < 63; i++) + if (burst[i + 85] != 0x00) + return false; + + return true; + } + + /* + * Create an UDP payload with burst bits + * and some channel data. + */ + void + trx_burst_if_impl::burst_pack(pmt::pmt_t msg, uint8_t *buf) + { + pmt::pmt_t header_plus_burst = pmt::cdr(msg); + + // Extract GSMTAP header from message + gsmtap_hdr *header = (gsmtap_hdr *) + pmt::blob_data(header_plus_burst); + + // Pack timeslot index + buf[0] = header->timeslot; + + // Extract frame number + uint32_t frame_nr = be32toh(header->frame_number); + + // Pack frame number + buf[1] = (frame_nr >> 24) & 0xff; + buf[2] = (frame_nr >> 16) & 0xff; + buf[3] = (frame_nr >> 8) & 0xff; + buf[4] = (frame_nr >> 0) & 0xff; + + // Pack RSSI (-dBm) + buf[5] = -(uint8_t) header->signal_dbm; + + // Pack correlator timing offset (TOA) + // FIXME: where to find this value? + buf[6] = 0; + buf[7] = 0; + + // Extract bits {0..1} from message + // Despite GR-GSM uses int8_t, they are not real sbits {-127..127} + uint8_t *burst = (uint8_t *) + (pmt::blob_data(header_plus_burst)) + sizeof(gsmtap_hdr); + + // Convert to transceiver interface specific bits {255..0} + for (int i = 0; i < 148; i++) + buf[8 + i] = burst[i] ? 255 : 0; + + // Fill two unused bytes + buf[156] = 0x00; + buf[157] = 0x00; + } + + void + trx_burst_if_impl::handle_dl_burst(pmt::pmt_t msg) + { + // 8 bytes of header + 148 bytes of burst + // + two unused, but required bytes + // otherwise bursts would be rejected + uint8_t buf[158]; + + // Compose a new UDP payload with burst + burst_pack(msg, buf); + + // Send a burst + d_data_sock->udp_send(buf, 158); + } + + void + trx_burst_if_impl::handle_ul_burst(uint8_t *payload, size_t len) + { + // Check length according to the protocol + if (len != 154) + return; + + /* Make sure TS index is correct */ + if (payload[0] >= 8) + return; + + /* Unpack and check frame number */ + uint32_t fn = (payload[1] << 24) + | (payload[2] << 16) + | (payload[3] << 8) + | payload[4]; + + if (fn >= 2715648) + return; + + // Prepare a buffer for GSMTAP header and burst + uint8_t buf[sizeof(gsmtap_hdr) + BURST_SIZE]; + + // Set up pointer to GSMTAP header structure + struct gsmtap_hdr *header = (struct gsmtap_hdr *) buf; + memset(header, 0x00, sizeof(struct gsmtap_hdr)); + + // Fill in basic info + header->version = GSMTAP_VERSION; + header->hdr_len = sizeof(gsmtap_hdr) / 4; + header->type = GSMTAP_TYPE_UM_BURST; + + // Set timeslot index and frame number + header->timeslot = payload[0]; + header->frame_number = htobe32(fn); + + // Check if one is a RACH burst + header->sub_type = detect_rach(payload + 6) ? + GSMTAP_BURST_ACCESS : GSMTAP_BURST_NORMAL; + + // Copy burst bits (0 & 1) for source message + memcpy(buf + sizeof(gsmtap_hdr), payload + 6, BURST_SIZE); + + // Create a pmt blob + pmt::pmt_t blob = pmt::make_blob(buf, sizeof(gsmtap_hdr) + BURST_SIZE); + pmt::pmt_t msg = pmt::cons(pmt::PMT_NIL, blob); + + /* Send a message to the output */ + message_port_pub(pmt::mp("bursts"), msg); + } + + } /* namespace gsm */ +} /* namespace gr */ |