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/* -*- c++ -*- */
/*
* Copyright 2004-2006,2011 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 3, 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., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifndef INCLUDED_DIGITAL_OFDM_CYCLIC_PREFIXER_H
#define INCLUDED_DIGITAL_OFDM_CYCLIC_PREFIXER_H
#include <digital_api.h>
#include <gr_tagged_stream_block.h>
class digital_ofdm_cyclic_prefixer;
typedef boost::shared_ptr<digital_ofdm_cyclic_prefixer> digital_ofdm_cyclic_prefixer_sptr;
/*!
* \param input_size FFT length (i.e. length of the OFDM symbols)
* \param output_size FFT length + cyclic prefix length (in samples)
* \param rolloff_len Length of the rolloff flank in samples
* \param len_tag_key For framed processing the key of the length tag
*/
DIGITAL_API digital_ofdm_cyclic_prefixer_sptr
digital_make_ofdm_cyclic_prefixer (size_t input_size,
size_t output_size,
int rolloff_len=0,
const std::string &len_tag_key="");
/*!
* \brief Adds a cyclic prefix and performs pulse shaping on OFDM symbols.
* \ingroup ofdm_blk
*
* Input: OFDM symbols (in the time domain, i.e. after the IFFT). Optionally,
* entire frames can be processed. In this case, \p len_tag_key must be
* specified which holds the key of the tag that denotes how
* many OFDM symbols are in a frame.
* Output: A stream of (scalar) complex symbols, which include the cyclic prefix
* and the pulse shaping.
* Note: If complete frames are processed, and \p rolloff_len is greater
* than zero, the final OFDM symbol is followed by the delay line of
* the pulse shaping.
*
* The pulse shape is a raised cosine in the time domain.
*/
class DIGITAL_API digital_ofdm_cyclic_prefixer : public gr_tagged_stream_block
{
friend DIGITAL_API digital_ofdm_cyclic_prefixer_sptr
digital_make_ofdm_cyclic_prefixer (size_t input_size, size_t output_size, int rolloff_len, const std::string &len_tag_key);
protected:
digital_ofdm_cyclic_prefixer (size_t input_size, size_t output_size, int rolloff_len, const std::string &len_tag_key);
//! Return the number of complex samples from the number of OFDM symbols (includes rolloff)
int calculate_output_stream_length(const gr_vector_int &ninput_items);
public:
int work(int noutput_items,
gr_vector_int &ninput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items);
private:
size_t d_fft_len;
//! FFT length + CP length in samples
size_t d_output_size;
//! Length of the cyclic prefix in samples
int d_cp_size;
//! Length of pulse rolloff in samples
int d_rolloff_len;
//! Buffers the up-flank (at the beginning of the cyclic prefix)
std::vector<float> d_up_flank;
//! Buffers the down-flank (which trails the symbol)
std::vector<float> d_down_flank;
std::vector<gr_complex> d_delay_line; // We do this explicitly to avoid outputting zeroes (i.e. no history!)
};
#endif /* INCLUDED_DIGITAL_OFDM_CYCLIC_PREFIXER_H */
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