sigproc: Add clipping detection on RACH and TSC input
Alert user of overdriven burst input indicated by a positive
threshold detector result. This indication serves as notification
that the receive RF gain level is too high for the configured
transceiver setup.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
diff --git a/Transceiver52M/Transceiver.cpp b/Transceiver52M/Transceiver.cpp
index 4885654..31eea60 100644
--- a/Transceiver52M/Transceiver.cpp
+++ b/Transceiver52M/Transceiver.cpp
@@ -615,8 +615,16 @@
else
success = detectRACH(state, *burst, amp, toa);
- if (!success) {
- state->mNoises.insert(avg);
+ /* Update noise average if no bust detected or alert on error */
+ if (success <= 0) {
+ if (!success) {
+ state->mNoises.insert(avg);
+ } else if (success == -SIGERR_CLIP) {
+ LOG(ALERT) << "Clipping detected on RACH input";
+ } else if (success < 0) {
+ LOG(ALERT) << "Unhandled RACH error";
+ }
+
delete radio_burst;
return NULL;
}
diff --git a/Transceiver52M/sigProcLib.cpp b/Transceiver52M/sigProcLib.cpp
index 54dd8fc..4501a13 100644
--- a/Transceiver52M/sigProcLib.cpp
+++ b/Transceiver52M/sigProcLib.cpp
@@ -40,6 +40,9 @@
#define TABLESIZE 1024
#define DELAYFILTS 64
+/* Clipping detection threshold */
+#define CLIP_THRESH 30000.0f
+
/** Lookup tables for trigonometric approximation */
float cosTable[TABLESIZE+1]; // add 1 element for wrap around
float sinTable[TABLESIZE+1];
@@ -1369,6 +1372,18 @@
return 1;
}
+static int detectClipping(signalVector &burst, float thresh)
+{
+ for (size_t i = 0; i < burst.size(); i++) {
+ if (fabs(burst[i].real()) > thresh)
+ return 1;
+ if (fabs(burst[i].imag()) > thresh)
+ return 1;
+ }
+
+ return 0;
+}
+
/*
* RACH burst detection
*
@@ -1390,7 +1405,10 @@
CorrelationSequence *sync;
if ((sps != 1) && (sps != 4))
- return -1;
+ return -SIGERR_UNSUPPORTED;
+
+ if (detectClipping(rxBurst, CLIP_THRESH))
+ return -SIGERR_CLIP;
target = 8 + 40;
head = 4;
@@ -1406,7 +1424,7 @@
delete corr;
if (rc < 0) {
- return -1;
+ return -SIGERR_INTERNAL;
} else if (!rc) {
if (amp)
*amp = 0.0f;
@@ -1443,7 +1461,10 @@
CorrelationSequence *sync;
if ((tsc < 0) || (tsc > 7) || ((sps != 1) && (sps != 4)))
- return -1;
+ return -SIGERR_UNSUPPORTED;
+
+ if (detectClipping(rxBurst, CLIP_THRESH))
+ return -SIGERR_CLIP;
target = 3 + 58 + 16 + 5;
head = 4;
@@ -1459,7 +1480,7 @@
delete corr;
if (rc < 0) {
- return -1;
+ return -SIGERR_INTERNAL;
} else if (!rc) {
if (amp)
*amp = 0.0f;
diff --git a/Transceiver52M/sigProcLib.h b/Transceiver52M/sigProcLib.h
index 147c14c..f7f6259 100644
--- a/Transceiver52M/sigProcLib.h
+++ b/Transceiver52M/sigProcLib.h
@@ -28,6 +28,14 @@
UNDEFINED,
};
+enum signalError {
+ SIGERR_NONE,
+ SIGERR_BOUNDS,
+ SIGERR_CLIP,
+ SIGERR_UNSUPPORTED,
+ SIGERR_INTERNAL,
+};
+
/** Convert a linear number to a dB value */
float dB(float x);