<p>pespin would like tnt to <strong>review</strong> this change.</p><p><a href="https://gerrit.osmocom.org/c/osmo-trx/+/14674">View Change</a></p><pre style="font-family: monospace,monospace; white-space: pre-wrap;">Add C/I computation<br><br>Change-Id: Ib4ceec553f2e5f77bf3f6777724968456a180f5e<br>Signed-off-by: Sylvain Munaut <tnt@246tNt.com><br>---<br>M Transceiver52M/Transceiver.cpp<br>M Transceiver52M/sigProcLib.cpp<br>M Transceiver52M/sigProcLib.h<br>3 files changed, 34 insertions(+), 5 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;">git pull ssh://gerrit.osmocom.org:29418/osmo-trx refs/changes/74/14674/1</pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/Transceiver52M/Transceiver.cpp b/Transceiver52M/Transceiver.cpp</span><br><span>index 32297b6..f90decd 100644</span><br><span>--- a/Transceiver52M/Transceiver.cpp</span><br><span>+++ b/Transceiver52M/Transceiver.cpp</span><br><span>@@ -621,7 +621,7 @@</span><br><span> bi->modulation = (type == EDGE) ? MODULATION_8PSK : MODULATION_GMSK;</span><br><span> bi->tss = 0; /* TODO: we only support tss 0 right now */</span><br><span> bi->tsc = 0;</span><br><span style="color: hsl(0, 100%, 40%);">- bi->ci = 0; /* TODO: calculate C/I and assign the value here, see branch tnt/ci. */</span><br><span style="color: hsl(120, 100%, 40%);">+ bi->ci = 0;</span><br><span> </span><br><span> /* Select the diversity channel with highest energy */</span><br><span> for (size_t i = 0; i < radio_burst->chans(); i++) {</span><br><span>@@ -670,6 +670,7 @@</span><br><span> type = (CorrType) rc;</span><br><span> bi->toa = ebp.toa;</span><br><span> bi->tsc = ebp.tsc;</span><br><span style="color: hsl(120, 100%, 40%);">+ bi->ci = (int16_t) ebp.ci;</span><br><span> rxBurst = demodAnyBurst(*burst, mSPSRx, ebp.amp, ebp.toa, type);</span><br><span> </span><br><span> /* EDGE demodulator returns 444 (gSlotLen * 3) bits */</span><br><span>diff --git a/Transceiver52M/sigProcLib.cpp b/Transceiver52M/sigProcLib.cpp</span><br><span>index c22009a..a65ea5e 100644</span><br><span>--- a/Transceiver52M/sigProcLib.cpp</span><br><span>+++ b/Transceiver52M/sigProcLib.cpp</span><br><span>@@ -1453,6 +1453,28 @@</span><br><span> return out;</span><br><span> };</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+static float computeCI(const signalVector *burst, CorrelationSequence *sync,</span><br><span style="color: hsl(120, 100%, 40%);">+ float toa, int start, complex xcorr)</span><br><span style="color: hsl(120, 100%, 40%);">+{</span><br><span style="color: hsl(120, 100%, 40%);">+ float S, C;</span><br><span style="color: hsl(120, 100%, 40%);">+ int ps;</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Integer position where the sequence starts */</span><br><span style="color: hsl(120, 100%, 40%);">+ ps = start + 1 - sync->sequence->size() + (int)roundf(toa);</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Estimate Signal power */</span><br><span style="color: hsl(120, 100%, 40%);">+ S = 0.0f;</span><br><span style="color: hsl(120, 100%, 40%);">+ for (int i=0, j=ps; i<(int)sync->sequence->size(); i++,j++)</span><br><span style="color: hsl(120, 100%, 40%);">+ S += (*burst)[j].norm2();</span><br><span style="color: hsl(120, 100%, 40%);">+ S /= sync->sequence->size();</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Esimate Carrier power */</span><br><span style="color: hsl(120, 100%, 40%);">+ C = xcorr.norm2() / ((sync->sequence->size() - 1) * sync->gain.abs());</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Interference = Signal - Carrier, so C/I = C / (S - C) */</span><br><span style="color: hsl(120, 100%, 40%);">+ return 3.0103f * log2f(C / (S - C));</span><br><span style="color: hsl(120, 100%, 40%);">+}</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> /*</span><br><span> * Detect a burst based on correlation and peak-to-average ratio</span><br><span> *</span><br><span>@@ -1468,6 +1490,7 @@</span><br><span> {</span><br><span> const signalVector *corr_in;</span><br><span> signalVector *dec = NULL;</span><br><span style="color: hsl(120, 100%, 40%);">+ complex xcorr;</span><br><span> </span><br><span> if (sps == 4) {</span><br><span> dec = downsampleBurst(burst);</span><br><span>@@ -1495,15 +1518,18 @@</span><br><span> if ((ebp->toa < 3 * sps) || (ebp->toa > len - 3 * sps))</span><br><span> return 0;</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- /* Peak -to-average ratio */</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Peak-to-average ratio */</span><br><span> if (computePeakRatio(&corr, sps, ebp->toa, ebp->amp) < thresh)</span><br><span> return 0;</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- /* Compute peak-to-average ratio. Reject if we don't have enough values */</span><br><span style="color: hsl(0, 100%, 40%);">- ebp->amp = peakDetect(corr, &ebp->toa, NULL);</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Refine TOA and correlation value */</span><br><span style="color: hsl(120, 100%, 40%);">+ xcorr = peakDetect(corr, &ebp->toa, NULL);</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Compute C/I */</span><br><span style="color: hsl(120, 100%, 40%);">+ ebp->ci = computeCI(corr_in, sync, ebp->toa, start, xcorr);</span><br><span> </span><br><span> /* Normalize our channel gain */</span><br><span style="color: hsl(0, 100%, 40%);">- ebp->amp = ebp->amp / sync->gain;</span><br><span style="color: hsl(120, 100%, 40%);">+ ebp->amp = xcorr / sync->gain;</span><br><span> </span><br><span> /* Compensate for residuate time lag */</span><br><span> ebp->toa = ebp->toa - sync->toa;</span><br><span>@@ -1563,6 +1589,7 @@</span><br><span> } else if (!rc) {</span><br><span> ebp->amp = 0.0f;</span><br><span> ebp->toa = 0.0f;</span><br><span style="color: hsl(120, 100%, 40%);">+ ebp->ci = 0.0f;</span><br><span> return clipping?-SIGERR_CLIP:SIGERR_NONE;</span><br><span> }</span><br><span> </span><br><span>diff --git a/Transceiver52M/sigProcLib.h b/Transceiver52M/sigProcLib.h</span><br><span>index 6d4ca9b..fd9a5f0 100644</span><br><span>--- a/Transceiver52M/sigProcLib.h</span><br><span>+++ b/Transceiver52M/sigProcLib.h</span><br><span>@@ -111,6 +111,7 @@</span><br><span> complex amp;</span><br><span> float toa;</span><br><span> uint8_t tsc;</span><br><span style="color: hsl(120, 100%, 40%);">+ float ci;</span><br><span> };</span><br><span> /**</span><br><span> 8-PSK/GMSK/RACH burst detector</span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/c/osmo-trx/+/14674">change 14674</a>. 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<div style="display:none"> Gerrit-Project: osmo-trx </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-Change-Id: Ib4ceec553f2e5f77bf3f6777724968456a180f5e </div>
<div style="display:none"> Gerrit-Change-Number: 14674 </div>
<div style="display:none"> Gerrit-PatchSet: 1 </div>
<div style="display:none"> Gerrit-Owner: pespin <pespin@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: tnt <tnt@246tNt.com> </div>
<div style="display:none"> Gerrit-MessageType: newchange </div>