<p>fixeria has uploaded this change for <strong>review</strong>.</p><p><a href="https://gerrit.osmocom.org/c/osmo-bts/+/21907">View Change</a></p><pre style="font-family: monospace,monospace; white-space: pre-wrap;">power_control: generalize the arguments of do_pf_ewma()<br><br>This way EWMA based filtering can also be applied to RxQual.<br><br>Change-Id: I439c00b394da670e314f217b3246cc85ce8213c6<br>Related: SYS#4918, SYS#4917<br>---<br>M src/common/power_control.c<br>1 file changed, 13 insertions(+), 17 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;">git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/07/21907/1</pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/src/common/power_control.c b/src/common/power_control.c</span><br><span>index a616f18..9e6fb45 100644</span><br><span>--- a/src/common/power_control.c</span><br><span>+++ b/src/common/power_control.c</span><br><span>@@ -38,29 +38,29 @@</span><br><span> </span><br><span> /* Base Low-Pass Single-Pole IIR Filter (EWMA) formula:</span><br><span> *</span><br><span style="color: hsl(0, 100%, 40%);">- * Avg[n] = a * Pwr[n] + (1 - a) * Avg[n - 1]</span><br><span style="color: hsl(120, 100%, 40%);">+ * Avg[n] = a * Val[n] + (1 - a) * Avg[n - 1]</span><br><span> *</span><br><span> * where parameter 'a' determines how much weight of the latest UL RSSI measurement</span><br><span style="color: hsl(0, 100%, 40%);">- * result 'Pwr[n]' carries vs the weight of the average 'Avg[n - 1]'. The value of</span><br><span style="color: hsl(120, 100%, 40%);">+ * result 'Val[n]' carries vs the weight of the average 'Avg[n - 1]'. The value of</span><br><span> * 'a' is usually a float in range 0 .. 1, so:</span><br><span> *</span><br><span style="color: hsl(0, 100%, 40%);">- * - value 0.5 gives equal weight to both 'Pwr[n]' and 'Avg[n - 1]';</span><br><span style="color: hsl(120, 100%, 40%);">+ * - value 0.5 gives equal weight to both 'Val[n]' and 'Avg[n - 1]';</span><br><span> * - value 1.0 means no filtering at all (pass through);</span><br><span> * - value 0.0 makes no sense.</span><br><span> *</span><br><span> * Further optimization:</span><br><span> *</span><br><span style="color: hsl(0, 100%, 40%);">- * Avg[n] = a * Pwr[n] + Avg[n - 1] - a * Avg[n - 1]</span><br><span style="color: hsl(120, 100%, 40%);">+ * Avg[n] = a * Val[n] + Avg[n - 1] - a * Avg[n - 1]</span><br><span> * ^^^^^^ ^^^^^^^^^^</span><br><span> *</span><br><span> * a) this can be implemented in C using '+=' operator:</span><br><span> *</span><br><span style="color: hsl(0, 100%, 40%);">- * Avg += a * Pwr - a * Avg</span><br><span style="color: hsl(0, 100%, 40%);">- * Avg += a * (Pwr - Avg)</span><br><span style="color: hsl(120, 100%, 40%);">+ * Avg += a * Val - a * Avg</span><br><span style="color: hsl(120, 100%, 40%);">+ * Avg += a * (Val - Avg)</span><br><span> *</span><br><span> * b) everything is scaled up by 100 to avoid floating point stuff:</span><br><span> *</span><br><span style="color: hsl(0, 100%, 40%);">- * Avg100 += A * (Pwr - Avg)</span><br><span style="color: hsl(120, 100%, 40%);">+ * Avg100 += A * (Val - Avg)</span><br><span> *</span><br><span> * where 'Avg100' is 'Avg * 100' and 'A' is 'a * 100'.</span><br><span> *</span><br><span>@@ -70,20 +70,15 @@</span><br><span> * https://en.wikipedia.org/wiki/Low-pass_filter#Simple_infinite_impulse_response_filter</span><br><span> * https://tomroelandts.com/articles/low-pass-single-pole-iir-filter</span><br><span> */</span><br><span style="color: hsl(0, 100%, 40%);">-static int8_t do_pf_ewma(const struct bts_power_ctrl_params *params,</span><br><span style="color: hsl(0, 100%, 40%);">- struct lchan_power_ctrl_state *state,</span><br><span style="color: hsl(0, 100%, 40%);">- const int8_t Pwr)</span><br><span style="color: hsl(120, 100%, 40%);">+static int do_pf_ewma(int *Avg100, const int Val, const uint8_t A)</span><br><span> {</span><br><span style="color: hsl(0, 100%, 40%);">- const uint8_t A = params->pf.ewma.alpha;</span><br><span style="color: hsl(0, 100%, 40%);">- int *Avg100 = &state->avg100_rxlev_dbm;</span><br><span style="color: hsl(0, 100%, 40%);">-</span><br><span> /* We don't have 'Avg[n - 1]' if this is the first run */</span><br><span> if (*Avg100 == 0) {</span><br><span style="color: hsl(0, 100%, 40%);">- *Avg100 = Pwr * EWMA_SCALE_FACTOR;</span><br><span style="color: hsl(0, 100%, 40%);">- return Pwr;</span><br><span style="color: hsl(120, 100%, 40%);">+ *Avg100 = Val * EWMA_SCALE_FACTOR;</span><br><span style="color: hsl(120, 100%, 40%);">+ return Val;</span><br><span> }</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- *Avg100 += A * (Pwr - *Avg100 / EWMA_SCALE_FACTOR);</span><br><span style="color: hsl(120, 100%, 40%);">+ *Avg100 += A * (Val - *Avg100 / EWMA_SCALE_FACTOR);</span><br><span> return *Avg100 / EWMA_SCALE_FACTOR;</span><br><span> }</span><br><span> </span><br><span>@@ -99,7 +94,8 @@</span><br><span> /* Filter input value(s) to reduce unnecessary Tx power oscillations */</span><br><span> switch (params->pf_algo) {</span><br><span> case BTS_PF_ALGO_EWMA:</span><br><span style="color: hsl(0, 100%, 40%);">- rxlev_dbm_avg = do_pf_ewma(params, state, rxlev_dbm);</span><br><span style="color: hsl(120, 100%, 40%);">+ rxlev_dbm_avg = do_pf_ewma(&state->avg100_rxlev_dbm, rxlev_dbm,</span><br><span style="color: hsl(120, 100%, 40%);">+ params->pf.ewma.alpha);</span><br><span> break;</span><br><span> case BTS_PF_ALGO_NONE:</span><br><span> default:</span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/c/osmo-bts/+/21907">change 21907</a>. 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<div style="display:none"> Gerrit-Project: osmo-bts </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-Change-Id: I439c00b394da670e314f217b3246cc85ce8213c6 </div>
<div style="display:none"> Gerrit-Change-Number: 21907 </div>
<div style="display:none"> Gerrit-PatchSet: 1 </div>
<div style="display:none"> Gerrit-Owner: fixeria <vyanitskiy@sysmocom.de> </div>
<div style="display:none"> Gerrit-MessageType: newchange </div>