236 lines
6.6 KiB
C++
236 lines
6.6 KiB
C++
/* -*- c++ -*- */
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/* @file
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* @author Vadim Yanitskiy <axilirator@gmail.com>
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* @section LICENSE
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*
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* Gr-gsm is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3, or (at your option)
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* any later version.
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*
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* Gr-gsm is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with gr-gsm; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <gnuradio/io_signature.h>
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#include <boost/lexical_cast.hpp>
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#include "grgsm/endian.h"
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#include "grgsm/misc_utils/udp_socket.h"
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#include "trx_burst_if_impl.h"
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#define BURST_SIZE 148
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#define DATA_IF_MTU 160
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/**
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* 41-bit RACH synchronization sequence
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* GSM 05.02 Chapter 5.2.7 Access burst (AB)
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*/
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static uint8_t rach_synch_seq[] = {
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0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1,
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1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0,
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1, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0,
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};
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namespace gr {
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namespace gsm {
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trx_burst_if::sptr
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trx_burst_if::make(
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const std::string &bind_addr,
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const std::string &remote_addr,
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const std::string &base_port)
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{
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int base_port_int = boost::lexical_cast<int> (base_port);
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return gnuradio::get_initial_sptr
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(new trx_burst_if_impl(bind_addr, remote_addr,
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base_port_int));
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}
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/*
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* The private constructor
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*/
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trx_burst_if_impl::trx_burst_if_impl(
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const std::string &bind_addr,
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const std::string &remote_addr,
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int base_port
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) : gr::block("trx_burst_if",
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gr::io_signature::make(0, 0, 0),
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gr::io_signature::make(0, 0, 0))
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{
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message_port_register_in(pmt::mp("bursts"));
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message_port_register_out(pmt::mp("bursts"));
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// Bind a port handler
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set_msg_handler(pmt::mp("bursts"),
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boost::bind(&trx_burst_if_impl::handle_dl_burst, this, boost::placeholders::_1));
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// Prepare port numbers
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std::string data_src_port = boost::lexical_cast<std::string> (base_port + 2);
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std::string data_dst_port = boost::lexical_cast<std::string> (base_port + 102);
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// Init DATA interface
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d_data_sock = new udp_socket(bind_addr, data_src_port,
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remote_addr, data_dst_port, DATA_IF_MTU);
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// Bind DATA interface handler
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d_data_sock->udp_rx_handler = boost::bind(
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&trx_burst_if_impl::handle_ul_burst, this, boost::placeholders::_1, boost::placeholders::_2);
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}
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/*
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* Our virtual destructor.
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*/
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trx_burst_if_impl::~trx_burst_if_impl()
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{
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// Release all UDP sockets and free memory
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delete d_data_sock;
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}
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/*
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* Check if burst is a RACH burst
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*/
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bool trx_burst_if_impl::detect_rach(uint8_t *burst)
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{
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// Compare synchronization sequence
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for (int i = 0; i < 41; i++)
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if (burst[i + 8] != rach_synch_seq[i])
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return false;
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// Make sure TB and GP are filled by 0x00
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for (int i = 0; i < 63; i++)
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if (burst[i + 85] != 0x00)
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return false;
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return true;
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}
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/*
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* Create an UDP payload with burst bits
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* and some channel data.
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*/
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void
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trx_burst_if_impl::burst_pack(pmt::pmt_t msg, uint8_t *buf)
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{
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pmt::pmt_t header_plus_burst = pmt::cdr(msg);
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// Extract GSMTAP header from message
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gsmtap_hdr *header = (gsmtap_hdr *)
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pmt::blob_data(header_plus_burst);
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// Pack timeslot index
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buf[0] = header->timeslot;
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// Extract frame number
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uint32_t frame_nr = be32toh(header->frame_number);
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// Pack frame number
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buf[1] = (frame_nr >> 24) & 0xff;
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buf[2] = (frame_nr >> 16) & 0xff;
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buf[3] = (frame_nr >> 8) & 0xff;
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buf[4] = (frame_nr >> 0) & 0xff;
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// Pack RSSI (-dBm)
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buf[5] = -(uint8_t) header->signal_dbm;
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// Pack correlator timing offset (TOA)
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// FIXME: where to find this value?
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buf[6] = 0;
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buf[7] = 0;
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// Extract bits {0..1} from message
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// Despite GR-GSM uses int8_t, they are not real sbits {-127..127}
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uint8_t *burst = (uint8_t *)
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(pmt::blob_data(header_plus_burst)) + sizeof(gsmtap_hdr);
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// Convert to transceiver interface specific bits {255..0}
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for (int i = 0; i < 148; i++)
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buf[8 + i] = burst[i] ? 255 : 0;
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// Fill two unused bytes
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buf[156] = 0x00;
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buf[157] = 0x00;
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}
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void
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trx_burst_if_impl::handle_dl_burst(pmt::pmt_t msg)
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{
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// 8 bytes of header + 148 bytes of burst
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// + two unused, but required bytes
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// otherwise bursts would be rejected
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uint8_t buf[158];
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// Compose a new UDP payload with burst
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burst_pack(msg, buf);
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// Send a burst
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d_data_sock->udp_send(buf, 158);
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}
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void
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trx_burst_if_impl::handle_ul_burst(uint8_t *payload, size_t len)
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{
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// Check length according to the protocol
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if (len != 154)
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return;
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/* Make sure TS index is correct */
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if (payload[0] >= 8)
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return;
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/* Unpack and check frame number */
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uint32_t fn = (payload[1] << 24)
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| (payload[2] << 16)
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| (payload[3] << 8)
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| payload[4];
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if (fn >= 2715648)
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return;
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// Prepare a buffer for GSMTAP header and burst
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uint8_t buf[sizeof(gsmtap_hdr) + BURST_SIZE];
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// Set up pointer to GSMTAP header structure
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struct gsmtap_hdr *header = (struct gsmtap_hdr *) buf;
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memset(header, 0x00, sizeof(struct gsmtap_hdr));
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// Fill in basic info
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header->version = GSMTAP_VERSION;
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header->hdr_len = sizeof(gsmtap_hdr) / 4;
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header->type = GSMTAP_TYPE_UM_BURST;
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// Set timeslot index and frame number
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header->timeslot = payload[0];
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header->frame_number = htobe32(fn);
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// Check if one is a RACH burst
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header->sub_type = detect_rach(payload + 6) ?
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GSMTAP_BURST_ACCESS : GSMTAP_BURST_NORMAL;
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// Copy burst bits (0 & 1) for source message
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memcpy(buf + sizeof(gsmtap_hdr), payload + 6, BURST_SIZE);
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// Create a pmt blob
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pmt::pmt_t blob = pmt::make_blob(buf, sizeof(gsmtap_hdr) + BURST_SIZE);
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pmt::pmt_t msg = pmt::cons(pmt::PMT_NIL, blob);
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/* Send a message to the output */
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message_port_pub(pmt::mp("bursts"), msg);
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}
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} /* namespace gsm */
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} /* namespace gr */
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