use long preamble for channel estimation and add lms equalizer
This commit is contained in:
Bastian Bloessl
@@ -17,6 +17,9 @@
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#include <ieee802-11/ofdm_equalize_symbols.h>
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#include "utils.h"
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#include "equalizer/base.h"
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#include "equalizer/linear_comb.h"
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#include "equalizer/lms.h"
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#include <gnuradio/io_signature.h>
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using namespace gr::ieee802_11;
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@@ -25,12 +28,14 @@ using namespace gr::ieee802_11;
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class ofdm_equalize_symbols_impl : public ofdm_equalize_symbols {
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public:
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ofdm_equalize_symbols_impl(bool debug) : block("ofdm_equalize_symbols",
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ofdm_equalize_symbols_impl(Equalizer algo, bool debug) : block("ofdm_equalize_symbols",
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gr::io_signature::make(1, 1, 64 * sizeof(gr_complex)),
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gr::io_signature::make(1, 1, 48 * sizeof(gr_complex))),
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d_debug(debug) {
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d_debug(debug), d_equalizer(NULL) {
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set_relative_rate(1);
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set_tag_propagation_policy(block::TPP_DONT);
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set_algorithm(algo);
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}
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~ofdm_equalize_symbols_impl(){
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@@ -40,87 +45,76 @@ int general_work (int noutput_items, gr_vector_int& ninput_items,
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gr_vector_const_void_star& input_items,
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gr_vector_void_star& output_items) {
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gr::thread::scoped_lock lock(d_mutex);
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const gr_complex *in = (const gr_complex*)input_items[0];
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gr_complex *out = (gr_complex*)output_items[0];
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int noutput = noutput_items;
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int i = 0;
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std::vector<gr::tag_t> tags;
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const uint64_t nread = nitems_read(0);
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int o = 0;
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dout << "SYMBOLS: input " << ninput_items[0] << " output " << noutput_items << std::endl;
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while((i < ninput_items[0]) && (i < noutput)) {
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while((i < ninput_items[0]) && (o < noutput_items)) {
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get_tags_in_range(tags, 0, nread + i, nread + i + 1,
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pmt::string_to_symbol("ofdm_start"));
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get_tags_in_window(tags, 0, i, i + 1, pmt::string_to_symbol("ofdm_start"));
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// new WiFi frame
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if(tags.size()) {
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index = 0;
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d_nsym = 0;
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}
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gr_complex p = POLARITY[index];
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index++;
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index %= 127;
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// FIXME: think about this... average over amplitude or power
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double avg_mag = (abs(in[11]) + abs(in[25]) + abs(in[39]) + abs(in[53])) / 4;
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double p1 = arg( p * in[11]);
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double p2 = arg( p * in[25] * conj(p * in[11])) + p1;
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double p3 = arg( p * in[39] * conj(p * in[25])) + p2;
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double p4 = arg(-p * in[53] * conj(p * in[39])) + p3;
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double my = (p1 + p2 + p3 + p4) / 4;
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double mx = (11.0 + 25 + 39 + 53) / 4;
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double var = (((11.0 * 11.0) + (25.0 * 25.0) + (39.0 * 39.0) + (53.0 * 53.0)) / 4) - (mx * mx);
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double cov = (( (p1 * 11) + (p2 * 25) + (p3 * 39) + (p4 * 53) ) / 4) - (mx * my);
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double beta = cov / var;
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double alpha = my - beta * mx;
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int o = 0;
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for(int n = 0; n < 64; n++) {
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if( (n == 11) || (n == 25) || (n == 32) || (n == 39) || (n == 53) || (n < 6) || ( n > 58)) {
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continue;
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} else {
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// FIXME: think about this... square or not
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out[o] = in[n] * exp(gr_complex(0, -n * beta - alpha)) * gr_complex(1 / avg_mag, 0);
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o++;
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}
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// first data symbol (= signal field)
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if(d_nsym == 2) {
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add_item_tag(0, nitems_written(0) + o,
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pmt::string_to_symbol("ofdm_start"),
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pmt::PMT_T,
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pmt::string_to_symbol(name()));
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}
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d_equalizer->equalize(in + (i * 64), out + (o * 48), d_nsym);
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if(d_nsym > 1) {
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o++;
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}
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i++;
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in += 64;
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out += 48;
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d_nsym++;
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}
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dout << "SYMBOLS: produced / consumed " << i << std::endl;
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dout << "SYMBOLS: consumed " << i << " produced " << o << std::endl;
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consume(0, i);
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return i;
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return o;
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}
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void set_algorithm(Equalizer algo) {
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gr::thread::scoped_lock lock(d_mutex);
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delete d_equalizer;
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switch(algo) {
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case LMS:
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dout << "LMS" << std::endl;
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d_equalizer = new equalizer::lms();
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break;
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case LINEAR_COMB:
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dout << "Linear Comb" << std::endl;
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d_equalizer = new equalizer::linear_comb();
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break;
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}
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}
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private:
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int index;
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int d_nsym;
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const bool d_debug;
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static const gr_complex POLARITY[127];
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equalizer::base *d_equalizer;
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std::vector<gr::tag_t> tags;
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gr::thread::mutex d_mutex;
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};
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const gr_complex ofdm_equalize_symbols_impl::POLARITY[127] = {
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1, 1, 1, 1,-1,-1,-1, 1,-1,-1,-1,-1, 1, 1,-1, 1,
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-1,-1, 1, 1,-1, 1, 1,-1, 1, 1, 1, 1, 1, 1,-1, 1,
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1, 1,-1, 1, 1,-1,-1, 1, 1, 1,-1, 1,-1,-1,-1, 1,
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-1, 1,-1,-1, 1,-1,-1, 1, 1, 1, 1, 1,-1,-1, 1, 1,
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-1,-1, 1,-1, 1,-1, 1, 1,-1,-1,-1, 1, 1,-1,-1,-1,
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-1, 1,-1,-1, 1,-1, 1, 1, 1, 1,-1, 1,-1, 1,-1, 1,
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-1,-1,-1,-1,-1, 1,-1, 1, 1,-1, 1,-1, 1, 1, 1,-1,
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-1, 1,-1,-1,-1, 1, 1, 1,-1,-1,-1,-1,-1,-1,-1 };
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ofdm_equalize_symbols::sptr
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ofdm_equalize_symbols::make(bool debug) {
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return gnuradio::get_initial_sptr(new ofdm_equalize_symbols_impl(debug));
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ofdm_equalize_symbols::make(Equalizer algo, bool debug) {
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return gnuradio::get_initial_sptr(new ofdm_equalize_symbols_impl(algo, debug));
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}
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