<p>fixeria has uploaded this change for <strong>review</strong>.</p><p><a href="https://gerrit.osmocom.org/c/osmo-bsc/+/24804">View Change</a></p><pre style="font-family: monospace,monospace; white-space: pre-wrap;">power_control: constrain BS power reduction on BCCH carrier<br><br>BS Power Control is not allowed on the BCCH/CCCH carrier, unless<br>the BTS is operating in the BCCH carrier power reduction mode.<br><br>Allow constrained BS power reduction (up to 6 dB) on active logical<br>channels iff BCCH carrier power reduction mode is enabled.<br><br>Take into account that the maximum power difference between a timeslot<br>used for BCCH/CCCH and the timeslot preceding it shall not exceed 3 dB.<br><br>Change-Id: I2cc6a86731984f586ef35b43a8d3de631f7d8a2f<br>Related: SYS#4919, SYS#4918<br>---<br>M doc/manuals/chapters/power_control.adoc<br>M include/osmocom/bsc/gsm_data.h<br>M src/osmo-bsc/bts.c<br>M src/osmo-bsc/lchan_fsm.c<br>4 files changed, 62 insertions(+), 0 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;">git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/04/24804/1</pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/doc/manuals/chapters/power_control.adoc b/doc/manuals/chapters/power_control.adoc</span><br><span>index fe2bf26..b146e2a 100644</span><br><span>--- a/doc/manuals/chapters/power_control.adoc</span><br><span>+++ b/doc/manuals/chapters/power_control.adoc</span><br><span>@@ -357,6 +357,30 @@</span><br><span> power reduction mode" in the feature vector. This can be checked by issuing</span><br><span> `show bts` command in the VTY interface.</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+==== Interworking with static and dynamic power control</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+The key difference between BCCH carrier power reduction and the BS power control</span><br><span style="color: hsl(120, 100%, 40%);">+is that the former affects *inactive* timeslots (or sub-channels), so only dummy</span><br><span style="color: hsl(120, 100%, 40%);">+bursts are affected. The later depends on the Downlink measurement reports sent</span><br><span style="color: hsl(120, 100%, 40%);">+by the MS, and thus applies to *active* channels only. However, both features</span><br><span style="color: hsl(120, 100%, 40%);">+are interconnected: the maximum BCCH carrier power reduction value constrains</span><br><span style="color: hsl(120, 100%, 40%);">+the BS Power value that can be used for dynamic or static BS power control.</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+BS power control on the BCCH carrier will not be enabled unless the BTS is in BCCH</span><br><span style="color: hsl(120, 100%, 40%);">+carrier power reduction mode of operation. Once it is, the BS power reduction</span><br><span style="color: hsl(120, 100%, 40%);">+value in either of `dyn-bts` or `static` modes would be constrained by currently</span><br><span style="color: hsl(120, 100%, 40%);">+applied BCCH power reduction value, and thus would never exceed the maximum of 6 dB.</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+For example, consider a BTS with BS power control configured to use _dynamic_ mode</span><br><span style="color: hsl(120, 100%, 40%);">+and the maximum power reduction of 16 dB. Once this BTS is switched into the BCCH</span><br><span style="color: hsl(120, 100%, 40%);">+carrier power reduction mode with the maximum attenuation of 4 dB, the maximum</span><br><span style="color: hsl(120, 100%, 40%);">+power reduction value for the BS power loop on the C0 carrier would be 4 dB.</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+Moreover, according to 3GPP TS 45.008, between a timeslot used for BCCH/CCCH and</span><br><span style="color: hsl(120, 100%, 40%);">+the timeslot preceding it, the difference in output power actually transmitted by</span><br><span style="color: hsl(120, 100%, 40%);">+the BTS shall not exceed 3 dB. This means that on some timeslots the power</span><br><span style="color: hsl(120, 100%, 40%);">+reduction value can be constrained even further.</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> ==== Managing BCCH carrier power reduction</span><br><span> </span><br><span> The BCCH carrier power reduction can be controlled via the CTRL and VTY interfaces.</span><br><span>diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h</span><br><span>index 569e288..19a168e 100644</span><br><span>--- a/include/osmocom/bsc/gsm_data.h</span><br><span>+++ b/include/osmocom/bsc/gsm_data.h</span><br><span>@@ -841,6 +841,9 @@</span><br><span> } rbs2000;</span><br><span> };</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+ /* Maximum BCCH carrier power reduction */</span><br><span style="color: hsl(120, 100%, 40%);">+ uint8_t bcch_max_power_red_db;</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> /* Maximum number of lchans that could become usable, for example by switching a dynamic timeslot's type or by</span><br><span> * enabling VAMOS secondary lchans. This does include the maximum count of possible VAMOS secondary lchans. */</span><br><span> uint8_t max_lchans_possible;</span><br><span>diff --git a/src/osmo-bsc/bts.c b/src/osmo-bsc/bts.c</span><br><span>index e055981..05d52a7 100644</span><br><span>--- a/src/osmo-bsc/bts.c</span><br><span>+++ b/src/osmo-bsc/bts.c</span><br><span>@@ -749,6 +749,8 @@</span><br><span> </span><br><span> int gsm_bts_set_bcch_power_red(struct gsm_bts *bts, const uint8_t red)</span><br><span> {</span><br><span style="color: hsl(120, 100%, 40%);">+ struct gsm_bts_trx *c0 = bts->c0;</span><br><span style="color: hsl(120, 100%, 40%);">+ unsigned int tn;</span><br><span> int rc;</span><br><span> </span><br><span> if (!osmo_bts_has_feature(&bts->features, BTS_FEAT_BCCH_POWER_RED))</span><br><span>@@ -762,6 +764,32 @@</span><br><span> </span><br><span> bts->bcch_max_power_red_db = red;</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+ /* Timeslot 0 is always transmitting BCCH/CCCH */</span><br><span style="color: hsl(120, 100%, 40%);">+ c0->ts[0].bcch_max_power_red_db = 0;</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ for (tn = 1; tn < ARRAY_SIZE(c0->ts); tn++) {</span><br><span style="color: hsl(120, 100%, 40%);">+ struct gsm_bts_trx_ts *ts = &c0->ts[tn];</span><br><span style="color: hsl(120, 100%, 40%);">+ const struct gsm_bts_trx_ts *next;</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ if (ts->pchan_is == GSM_PCHAN_CCCH)</span><br><span style="color: hsl(120, 100%, 40%);">+ ts->bcch_max_power_red_db = 0;</span><br><span style="color: hsl(120, 100%, 40%);">+ else</span><br><span style="color: hsl(120, 100%, 40%);">+ ts->bcch_max_power_red_db = red;</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ if (ts->bcch_max_power_red_db > 0) {</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Next timeslot following this one */</span><br><span style="color: hsl(120, 100%, 40%);">+ next = &c0->ts[(tn + 1) % 8];</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* If BCCH/CCCH follows, limit to 2 dB */</span><br><span style="color: hsl(120, 100%, 40%);">+ if (next->pchan_is == GSM_PCHAN_CCCH)</span><br><span style="color: hsl(120, 100%, 40%);">+ ts->bcch_max_power_red_db = 2;</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Timeslot 7 is always preceding BCCH/CCCH */</span><br><span style="color: hsl(120, 100%, 40%);">+ if (c0->ts[7].bcch_max_power_red_db > 0)</span><br><span style="color: hsl(120, 100%, 40%);">+ c0->ts[7].bcch_max_power_red_db = 2;</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> return 0;</span><br><span> }</span><br><span> </span><br><span>diff --git a/src/osmo-bsc/lchan_fsm.c b/src/osmo-bsc/lchan_fsm.c</span><br><span>index 03ccec0..8ae83da 100644</span><br><span>--- a/src/osmo-bsc/lchan_fsm.c</span><br><span>+++ b/src/osmo-bsc/lchan_fsm.c</span><br><span>@@ -675,6 +675,13 @@</span><br><span> lchan->bs_power_db = bts->bs_power_ctrl.bs_power_val_db;</span><br><span> }</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+ /* BS Power Control is generally not allowed on the BCCH/CCCH carrier.</span><br><span style="color: hsl(120, 100%, 40%);">+ * However, we allow it in the BCCH carrier power reduction mode of operation. */</span><br><span style="color: hsl(120, 100%, 40%);">+ if (lchan->ts->trx == bts->c0) {</span><br><span style="color: hsl(120, 100%, 40%);">+ lchan->bs_power_db = OSMO_MIN(lchan->ts->bcch_max_power_red_db,</span><br><span style="color: hsl(120, 100%, 40%);">+ lchan->bs_power_db);</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> if (lchan_activate_set_ch_mode_rate_and_mr_config(lchan))</span><br><span> return;</span><br><span> </span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/c/osmo-bsc/+/24804">change 24804</a>. 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<div style="display:none"> Gerrit-Project: osmo-bsc </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-Change-Id: I2cc6a86731984f586ef35b43a8d3de631f7d8a2f </div>
<div style="display:none"> Gerrit-Change-Number: 24804 </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>