summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorBrennan Ashton <bashton@brennanashton.com>2018-04-06 15:00:36 -0700
committerMarcus Müller <marcus@hostalia.de>2018-06-25 20:59:56 +0200
commit28c1644e663b744417d3712f588dcadb98700f40 (patch)
treec41c58702ea308763bce778c34f814f8646fc702
parent0c4e231953c6ac62a1dede2c7ba63a4c3a6b3f43 (diff)
Restore ability to use absolute thresholding with corr_est
Diffstat
-rw-r--r--gr-digital/grc/digital_corr_est_cc.xml14
-rw-r--r--gr-digital/include/gnuradio/digital/corr_est_cc.h24
-rw-r--r--gr-digital/lib/corr_est_cc_impl.cc62
-rw-r--r--gr-digital/lib/corr_est_cc_impl.h5
4 files changed, 82 insertions, 23 deletions
diff --git a/gr-digital/grc/digital_corr_est_cc.xml b/gr-digital/grc/digital_corr_est_cc.xml
index 1a1c449efb..8afd157ea9 100644
--- a/gr-digital/grc/digital_corr_est_cc.xml
+++ b/gr-digital/grc/digital_corr_est_cc.xml
@@ -32,6 +32,20 @@
<type>float</type>
</param>
+ <param>
+ <name>Threshold Method</name>
+ <key>threshold_method</key>
+ <type>enum</type>
+ <option>
+ <name>Absolute</name>
+ <key>digital.corr_est_cc.THRESHOLD_ABSOLUTE</key>
+ </option>
+ <option>
+ <name>Dynamic</name>
+ <key>digital.corr_est_cc.THRESHOLD_DYNAMIC</key>
+ </option>
+ </param>
+
<sink>
<name>in</name>
<type>complex</type>
diff --git a/gr-digital/include/gnuradio/digital/corr_est_cc.h b/gr-digital/include/gnuradio/digital/corr_est_cc.h
index 237a499b6b..f61b62636e 100644
--- a/gr-digital/include/gnuradio/digital/corr_est_cc.h
+++ b/gr-digital/include/gnuradio/digital/corr_est_cc.h
@@ -87,20 +87,28 @@ namespace gr {
public:
typedef boost::shared_ptr<corr_est_cc> sptr;
+ enum tm_type {
+ THRESHOLD_DYNAMIC,
+ THRESHOLD_ABSOLUTE,
+ };
+
/*!
* Make a block that correlates against the \p symbols vector
* and outputs a phase and symbol timing estimate.
*
- * \param symbols Set of symbols to correlate against (e.g., a
- * sync word).
- * \param sps Samples per symbol
- * \param mark_delay tag marking delay in samples after the
- * corr_start tag
- * \param threshold Threshold of correlator, relative to a 100%
- * correlation (1.0). Default is 0.9.
+ * \param symbols Set of symbols to correlate against (e.g., a
+ * sync word).
+ * \param sps Samples per symbol
+ * \param mark_delay tag marking delay in samples after the
+ * corr_start tag
+ * \param threshold Threshold of correlator, relative to a 100%
+ * correlation (1.0). Default is 0.9.
+ * \param threshold_method Method for computing threshold.
+ *
*/
static sptr make(const std::vector<gr_complex> &symbols,
- float sps, unsigned int mark_delay, float threshold=0.9);
+ float sps, unsigned int mark_delay, float threshold=0.9,
+ tm_type threshold_method=THRESHOLD_ABSOLUTE);
virtual std::vector<gr_complex> symbols() const = 0;
virtual void set_symbols(const std::vector<gr_complex> &symbols) = 0;
diff --git a/gr-digital/lib/corr_est_cc_impl.cc b/gr-digital/lib/corr_est_cc_impl.cc
index 5157f8f6de..764781b0e0 100644
--- a/gr-digital/lib/corr_est_cc_impl.cc
+++ b/gr-digital/lib/corr_est_cc_impl.cc
@@ -39,21 +39,25 @@ namespace gr {
corr_est_cc::sptr
corr_est_cc::make(const std::vector<gr_complex> &symbols,
float sps, unsigned int mark_delay,
- float threshold)
+ float threshold,
+ tm_type threshold_method)
{
return gnuradio::get_initial_sptr
- (new corr_est_cc_impl(symbols, sps, mark_delay, threshold));
+ (new corr_est_cc_impl(symbols, sps, mark_delay, threshold,
+ threshold_method));
}
corr_est_cc_impl::corr_est_cc_impl(const std::vector<gr_complex> &symbols,
float sps, unsigned int mark_delay,
- float threshold)
+ float threshold,
+ tm_type threshold_method)
: sync_block("corr_est_cc",
io_signature::make(1, 1, sizeof(gr_complex)),
io_signature::make(1, 2, sizeof(gr_complex))),
d_src_id(pmt::intern(alias()))
{
d_sps = sps;
+ d_threshold_method = threshold_method;
// In order to easily support the optional second output,
// don't deal with an unbounded max number of output items.
@@ -195,7 +199,23 @@ namespace gr {
corr_est_cc_impl::_set_threshold(float threshold)
{
d_stashed_threshold = threshold;
- d_pfa = -logf(1.0f-threshold);
+
+ // TODO: Right now two methods are computed this should be conditional
+ switch (d_threshold_method) {
+ case THRESHOLD_DYNAMIC:
+ d_pfa = -logf(1.0f-threshold);
+ break;
+ case THRESHOLD_ABSOLUTE:
+ default:
+ // Compute a correlation threshold.
+ // Compute the value of the discrete autocorrelation of the matched
+ // filter with offset 0 (aka the autocorrelation peak).
+ float corr = 0;
+ for(size_t i = 0; i < d_symbols.size(); i++)
+ corr += abs(d_symbols[i]*conj(d_symbols[i]));
+ d_thresh = threshold*corr*corr;
+ break;
+ }
}
void
@@ -231,21 +251,35 @@ namespace gr {
volk_32fc_magnitude_squared_32f(&d_corr_mag[0], corr, noutput_items);
float detection = 0;
- for(int i = 0; i < noutput_items; i++) {
- detection += d_corr_mag[i];
+ if(d_threshold_method == THRESHOLD_DYNAMIC)
+ {
+ for(int i = 0; i < noutput_items; i++) {
+ detection += d_corr_mag[i];
+ }
+ detection /= static_cast<float>(noutput_items);
+ detection *= d_pfa;
}
- detection /= static_cast<float>(noutput_items);
- detection *= d_pfa;
int isps = (int)(d_sps + 0.5f);
int i = 0;
while(i < noutput_items) {
- // Look for the correlator output to cross the threshold.
- // Sum power over two consecutive symbols in case we're offset
- // in time. If off by 1/2 a symbol, the peak of any one point
- // is much lower.
- float corr_mag = d_corr_mag[i] + d_corr_mag[i+1];
- if(corr_mag <= 4*detection) {
+ float corr_mag;
+ switch (d_threshold_method) {
+ case THRESHOLD_DYNAMIC:
+ // Look for the correlator output to cross the threshold.
+ // Sum power over two consecutive symbols in case we're offset
+ // in time. If off by 1/2 a symbol, the peak of any one point
+ // is much lower.
+ corr_mag = (d_corr_mag[i] + d_corr_mag[i+1]) * 0.5f;
+ d_thresh = 2 * detection;
+ break;
+ case THRESHOLD_ABSOLUTE:
+ default:
+ corr_mag = d_corr_mag[i];
+ break;
+ }
+
+ if (corr_mag <= d_thresh) {
i++;
continue;
}
diff --git a/gr-digital/lib/corr_est_cc_impl.h b/gr-digital/lib/corr_est_cc_impl.h
index e0d4c8ef25..75f9e2c700 100644
--- a/gr-digital/lib/corr_est_cc_impl.h
+++ b/gr-digital/lib/corr_est_cc_impl.h
@@ -47,13 +47,16 @@ namespace gr {
float d_scale;
float d_pfa; // probability of false alarm
+ tm_type d_threshold_method;
+
void _set_mark_delay(unsigned int mark_delay);
void _set_threshold(float threshold);
public:
corr_est_cc_impl(const std::vector<gr_complex> &symbols,
float sps, unsigned int mark_delay,
- float threshold=0.9);
+ float threshold=0.9,
+ tm_type threshold_method=THRESHOLD_ABSOLUTE);
~corr_est_cc_impl();
std::vector<gr_complex> symbols() const;
generated by cgit v1.2.3 (git 2.39.1) at 2025-03-25 16:45:42 +0000