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+/* -*- 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 "grgsm/misc_utils/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 */