sigproc: Adjust burst detection threshold criteria

Reduce the burst detection threshold to pass more bursts to upper
layers, but force stricter requirements on the computation itself.
For the latter, we now require at least 5 samples (rather than 2)
to compute a peak-to-average value.

End result is increased burst detection at low SNR conditions with
a small increase in false positive bursts when no signal is present.

Signed-off-by: Tom Tsou <tom.tsou@ettus.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/Transceiver52M/sigProcLib.cpp b/Transceiver52M/sigProcLib.cpp
index 6495b1e..3682227 100644
--- a/Transceiver52M/sigProcLib.cpp
+++ b/Transceiver52M/sigProcLib.cpp
@@ -1678,6 +1678,17 @@ release:
   return status;
 }
 
+/*
+ * Peak-to-average computation +/- range from peak in symbols
+ */
+#define COMPUTE_PEAK_MIN     2
+#define COMPUTE_PEAK_MAX     5
+
+/*
+ * Minimum number of values needed to compute peak-to-average
+ */
+#define COMPUTE_PEAK_CNT     5
+
 static float computePeakRatio(signalVector *corr,
                               int sps, float toa, complex amp)
 {
@@ -1691,7 +1702,7 @@ static float computePeakRatio(signalVector *corr,
 
   peak = corr->begin() + (int) rint(toa);
 
-  for (int i = 2 * sps; i <= 5 * sps; i++) {
+  for (int i = COMPUTE_PEAK_MIN * sps; i <= COMPUTE_PEAK_MAX * sps; i++) {
     if (peak - i >= corr->begin()) {
       avg += (peak - i)->norm2();
       num++;
@@ -1702,7 +1713,7 @@ static float computePeakRatio(signalVector *corr,
     }
   }
 
-  if (num < 2)
+  if (num < COMPUTE_PEAK_CNT)
     return 0.0;
 
   rms = sqrtf(avg / (float) num) + 0.00001;