diff options
Diffstat (limited to 'gr-digital/lib/ofdm_frame_equalizer_vcvc_impl.cc')
| -rw-r--r-- | gr-digital/lib/ofdm_frame_equalizer_vcvc_impl.cc | 78 |
1 files changed, 70 insertions, 8 deletions
diff --git a/gr-digital/lib/ofdm_frame_equalizer_vcvc_impl.cc b/gr-digital/lib/ofdm_frame_equalizer_vcvc_impl.cc index 8546eb119b..4446306a8b 100644 --- a/gr-digital/lib/ofdm_frame_equalizer_vcvc_impl.cc +++ b/gr-digital/lib/ofdm_frame_equalizer_vcvc_impl.cc @@ -23,15 +23,19 @@ #include "config.h" #endif +#include <gnuradio/expj.h> #include <gnuradio/io_signature.h> #include "ofdm_frame_equalizer_vcvc_impl.h" +#define M_TWOPI (2*M_PI) + namespace gr { namespace digital { ofdm_frame_equalizer_vcvc::sptr ofdm_frame_equalizer_vcvc::make( ofdm_equalizer_base::sptr equalizer, + int cp_len, const std::string &len_tag_key, bool propagate_channel_state, int fixed_frame_len @@ -39,13 +43,14 @@ namespace gr { { return gnuradio::get_initial_sptr ( new ofdm_frame_equalizer_vcvc_impl( - equalizer, len_tag_key, propagate_channel_state, fixed_frame_len + equalizer, cp_len, len_tag_key, propagate_channel_state, fixed_frame_len ) ); } ofdm_frame_equalizer_vcvc_impl::ofdm_frame_equalizer_vcvc_impl( ofdm_equalizer_base::sptr equalizer, + int cp_len, const std::string &len_tag_key, bool propagate_channel_state, int fixed_frame_len @@ -54,26 +59,49 @@ namespace gr { io_signature::make(1, 1, sizeof (gr_complex) * equalizer->fft_len()), len_tag_key), d_fft_len(equalizer->fft_len()), + d_cp_len(cp_len), d_eq(equalizer), d_propagate_channel_state(propagate_channel_state), - d_fixed_frame_len(len_tag_key.empty() ? fixed_frame_len : 0), + d_fixed_frame_len(fixed_frame_len), d_channel_state(equalizer->fft_len(), gr_complex(1, 0)) { + if (len_tag_key.empty() && fixed_frame_len == 0) { + throw std::invalid_argument("Either specify a length tag or a frame length!"); + } + if (d_fixed_frame_len < 0) { + throw std::invalid_argument("Invalid frame length!"); + } if (d_fixed_frame_len) { set_output_multiple(d_fixed_frame_len); } + set_relative_rate(1.0); } ofdm_frame_equalizer_vcvc_impl::~ofdm_frame_equalizer_vcvc_impl() { } + void + ofdm_frame_equalizer_vcvc_impl::parse_length_tags( + const std::vector<std::vector<tag_t> > &tags, + gr_vector_int &n_input_items_reqd + ){ + if (d_fixed_frame_len) { + n_input_items_reqd[0] = d_fixed_frame_len; + } else { + for (unsigned k = 0; k < tags[0].size(); k++) { + if (tags[0][k].key == pmt::string_to_symbol(d_length_tag_key_str)) { + n_input_items_reqd[0] = pmt::to_long(tags[0][k].value); + remove_item_tag(0, tags[0][k]); + } + } + } + } + int ofdm_frame_equalizer_vcvc_impl::work(int noutput_items, - gr_vector_int &ninput_items, - gr_vector_const_void_star &input_items, - gr_vector_void_star &output_items) + gr_vector_int &ninput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items) { const gr_complex *in = (const gr_complex *) input_items[0]; gr_complex *out = (gr_complex *) output_items[0]; @@ -92,20 +120,54 @@ namespace gr { d_channel_state = pmt::c32vector_elements(tags[i].value); remove_item_tag(0, tags[i]); } + if (pmt::symbol_to_string(tags[i].key) == "ofdm_sync_carr_offset") { + carrier_offset = pmt::to_long(tags[i].value); + } } - memcpy((void *) out, (void *) in, sizeof(gr_complex) * d_fft_len * frame_len); + // Copy the frame and the channel state vector such that the symbols are shifted to the correct position + if (carrier_offset < 0) { + memset((void *) out, 0x00, sizeof(gr_complex) * (-carrier_offset)); + memcpy( + (void *) &out[-carrier_offset], (void *) in, + sizeof(gr_complex) * (d_fft_len * frame_len + carrier_offset) + ); + } else { + memset((void *) (out + d_fft_len * frame_len - carrier_offset), 0x00, sizeof(gr_complex) * carrier_offset); + memcpy( + (void *) out, (void *) (in+carrier_offset), + sizeof(gr_complex) * (d_fft_len * frame_len - carrier_offset) + ); + } + + // Correct the frequency shift on the symbols + gr_complex phase_correction; + for (int i = 0; i < frame_len; i++) { + phase_correction = gr_expj(-M_TWOPI * carrier_offset * d_cp_len / d_fft_len * (i+1)); + for (int k = 0; k < d_fft_len; k++) { + out[i*d_fft_len+k] *= phase_correction; + } + } + + // Do the equalizing d_eq->reset(); - d_eq->set_carrier_offset(carrier_offset); d_eq->equalize(out, frame_len, d_channel_state); d_eq->get_channel_state(d_channel_state); + + // Update the channel state regarding the frequency offset + phase_correction = gr_expj(M_TWOPI * carrier_offset * d_cp_len / d_fft_len * frame_len); + for (int k = 0; k < d_fft_len; k++) { + d_channel_state[k] *= phase_correction; + } + + // Housekeeping if (d_propagate_channel_state) { add_item_tag(0, nitems_written(0), pmt::string_to_symbol("ofdm_sync_chan_taps"), pmt::init_c32vector(d_fft_len, d_channel_state)); } - if (d_fixed_frame_len) { + if (d_fixed_frame_len && d_length_tag_key_str.empty()) { consume_each(frame_len); } |