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fixeria gerrit-no-reply at lists.osmocom.orgfixeria has submitted this change. ( https://gerrit.osmocom.org/c/osmo-bsc/+/24804 ) Change subject: power_control: constrain BS power reduction on BCCH carrier ...................................................................... power_control: constrain BS power reduction on BCCH carrier BS Power Control is not allowed on the BCCH/CCCH carrier, unless the BTS is operating in the BCCH carrier power reduction mode. Allow constrained BS power reduction (up to 6 dB) on active logical channels iff BCCH carrier power reduction mode is enabled. Take into account that the maximum power difference between a timeslot used for BCCH/CCCH and the timeslot preceding it shall not exceed 3 dB. Change-Id: I2cc6a86731984f586ef35b43a8d3de631f7d8a2f Related: SYS#4919, SYS#4918 --- M doc/manuals/chapters/power_control.adoc M include/osmocom/bsc/gsm_data.h M src/osmo-bsc/bts.c M src/osmo-bsc/lchan_fsm.c 4 files changed, 65 insertions(+), 0 deletions(-) Approvals: laforge: Looks good to me, but someone else must approve fixeria: Looks good to me, approved pespin: Looks good to me, but someone else must approve Jenkins Builder: Verified diff --git a/doc/manuals/chapters/power_control.adoc b/doc/manuals/chapters/power_control.adoc index bb87c85..d456484 100644 --- a/doc/manuals/chapters/power_control.adoc +++ b/doc/manuals/chapters/power_control.adoc @@ -357,6 +357,30 @@ power reduction mode" in the feature vector. This can be checked by issuing `show bts` command in OsmoBSC's VTY interface. +==== Interworking with static and dynamic power control + +The key difference between BCCH carrier power reduction and the BS power control +is that the former affects *inactive* timeslots (or sub-channels), so only dummy +bursts are affected. The later depends on the Downlink measurement reports sent +by the MS, and thus applies to *active* channels only. However, both features +are interconnected: the maximum BCCH carrier power reduction value constrains +the BS Power value that can be used for dynamic or static BS power control. + +BS power control on the BCCH carrier will not be enabled unless the BTS is in BCCH +carrier power reduction mode of operation. Once it is, the BS power reduction +value in either of `dyn-bts` or `static` modes would be constrained by currently +applied BCCH power reduction value, and thus would never exceed the maximum of 6 dB. + +For example, consider a BTS with BS power control configured to use _dynamic_ mode +and the maximum power reduction of 16 dB. Once this BTS is switched into the BCCH +carrier power reduction mode with the maximum attenuation of 4 dB, the maximum +power reduction value for the BS power loop on the C0 carrier would be 4 dB. + +Moreover, according to 3GPP TS 45.008, between a timeslot used for BCCH/CCCH and +the timeslot preceding it, the difference in output power actually transmitted by +the BTS shall not exceed 3 dB. This means that on some timeslots the power +reduction value can be constrained even further. + ==== Managing BCCH carrier power reduction The BCCH carrier power reduction can be controlled via the CTRL and VTY interfaces. diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h index 569e288..31759cc 100644 --- a/include/osmocom/bsc/gsm_data.h +++ b/include/osmocom/bsc/gsm_data.h @@ -841,6 +841,9 @@ } rbs2000; }; + /* Maximum BCCH carrier power reduction */ + uint8_t c0_max_power_red_db; + /* Maximum number of lchans that could become usable, for example by switching a dynamic timeslot's type or by * enabling VAMOS secondary lchans. This does include the maximum count of possible VAMOS secondary lchans. */ uint8_t max_lchans_possible; diff --git a/src/osmo-bsc/bts.c b/src/osmo-bsc/bts.c index c1f09ff..8608767 100644 --- a/src/osmo-bsc/bts.c +++ b/src/osmo-bsc/bts.c @@ -749,6 +749,8 @@ int gsm_bts_set_c0_power_red(struct gsm_bts *bts, const uint8_t red) { + struct gsm_bts_trx *c0 = bts->c0; + unsigned int tn; int rc; if (!osmo_bts_has_feature(&bts->features, BTS_FEAT_BCCH_POWER_RED)) @@ -760,6 +762,35 @@ if (rc != 0) return rc; + /* Timeslot 0 is always transmitting BCCH/CCCH */ + c0->ts[0].c0_max_power_red_db = 0; + + for (tn = 1; tn < ARRAY_SIZE(c0->ts); tn++) { + struct gsm_bts_trx_ts *ts = &c0->ts[tn]; + struct gsm_bts_trx_ts *prev = ts - 1; + + switch (ts->pchan_is) { + /* Not allowed on CCCH/BCCH */ + case GSM_PCHAN_CCCH: + /* Preceeding timeslot shall not exceed 2 dB */ + if (prev->c0_max_power_red_db > 0) + prev->c0_max_power_red_db = 2; + /* fall-through */ + /* Not recommended on SDCCH/8 */ + case GSM_PCHAN_SDCCH8_SACCH8C: + case GSM_PCHAN_SDCCH8_SACCH8C_CBCH: + ts->c0_max_power_red_db = 0; + break; + default: + ts->c0_max_power_red_db = red; + break; + } + } + + /* Timeslot 7 is always preceding BCCH/CCCH */ + if (c0->ts[7].c0_max_power_red_db > 0) + c0->ts[7].c0_max_power_red_db = 2; + bts->c0_max_power_red_db = red; return 0; diff --git a/src/osmo-bsc/lchan_fsm.c b/src/osmo-bsc/lchan_fsm.c index 03ccec0..6350481 100644 --- a/src/osmo-bsc/lchan_fsm.c +++ b/src/osmo-bsc/lchan_fsm.c @@ -675,6 +675,13 @@ lchan->bs_power_db = bts->bs_power_ctrl.bs_power_val_db; } + /* BS Power Control is generally not allowed on the BCCH/CCCH carrier. + * However, we allow it in the BCCH carrier power reduction mode of operation. */ + if (lchan->ts->trx == bts->c0) { + lchan->bs_power_db = OSMO_MIN(lchan->ts->c0_max_power_red_db, + lchan->bs_power_db); + } + if (lchan_activate_set_ch_mode_rate_and_mr_config(lchan)) return; -- To view, visit https://gerrit.osmocom.org/c/osmo-bsc/+/24804 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: osmo-bsc Gerrit-Branch: master Gerrit-Change-Id: I2cc6a86731984f586ef35b43a8d3de631f7d8a2f Gerrit-Change-Number: 24804 Gerrit-PatchSet: 4 Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de> Gerrit-Reviewer: Jenkins Builder Gerrit-Reviewer: fixeria <vyanitskiy at sysmocom.de> Gerrit-Reviewer: laforge <laforge at osmocom.org> Gerrit-Reviewer: pespin <pespin at sysmocom.de> Gerrit-MessageType: merged -------------- next part -------------- An HTML attachment was scrubbed... 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