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fixeria gerrit-no-reply at lists.osmocom.orgfixeria has submitted this change. ( https://gerrit.osmocom.org/c/osmo-bsc/+/26227 ) Change subject: doc/manuals: add documentation for Temporary ACCH Overpower ...................................................................... doc/manuals: add documentation for Temporary ACCH Overpower Change-Id: Ie995dac6c7083a2b0b4d582f71f55b3736381edb Related: SYS#5319 --- M doc/manuals/chapters/power_control.adoc 1 file changed, 58 insertions(+), 0 deletions(-) Approvals: Jenkins Builder: Verified pespin: Looks good to me, but someone else must approve Hoernchen: Looks good to me, but someone else must approve fixeria: Looks good to me, approved diff --git a/doc/manuals/chapters/power_control.adoc b/doc/manuals/chapters/power_control.adoc index f94dd2e..dee0470 100644 --- a/doc/manuals/chapters/power_control.adoc +++ b/doc/manuals/chapters/power_control.adoc @@ -565,3 +565,61 @@ ---- <1> Remote address of the host running osmo-bsc (localhost in this example) <2> Maximum BCCH carrier power reduction currently applied + +=== Temporary ACCH overpower + +Temporary overpower (TOP) is a power control technique that allows to improve +SACCH/FACCH performance in case of bad C/I. The key idea of TOP is to +increment the BS transmit power by 2..4 dB only for FACCH/SACCH bursts, while +keeping all voice bursts at the lower (normal) level as determined by the +downlink power control loop. This allows to reduce call drop rate and +increase capacity in deployments with tight frequency reuse. + +NOTE: It's not possible to increase the current BS power beyond the maximum +transmit power level supported by the PHY. Thus if the BTS is already +transmitting at full power, the overpower logic cannot increase it even +further. This is also why TOP must be employed *together with BS power +control*, either static or dynamic. + +The main area of use for TOP is traffic channels employing the AMR (Adaptive +Multi Rate) codec, which is more robust to interference than the associated +signalling channels. While AMR provides sufficient speech quality even at +very low C/I levels, the associated signalling channels may be suffering from +channel coding errors. This imbalance can be compensated by employing TOP, +which can be efficiently combined with the ACCH repetition technique. + +This feature requires no support on the mobile station side and can be used +with UEs implementing the most recent 3GPP relese features, as well as legacy +UEs. However, it needs to be implemented in the BTS. Given that TOP itself +is not specified in 3GPP specifications, osmo-bsc uses Osmocom specific +A-bis/RSL IEs in order to activate it. Therefore, only the recent osmo-bts +versions may be instructed to activate this feature. Make sure that feature +#023 "FACCH/SACCH Temporary overpower" is present in the feature vector. +This can be checked by issuing `show bts` command in OsmoBSC's VTY interface. + +TOP is disabled by default. Below is a configuration example enabling it: + +---- +network + bts 0 + overpower dl-acch 2 <1> + overpower rxqual 4 <2> +---- +<1> Overpower of maximum 2 dB for both SACCH and FACCH. +<2> Enable TOP only if RxQual is worse than 4 (BER >= 1.6%). + +It's also possible to enable TOP only for FACCH or SACCH selectively, or +or keep it enabled permanently regardless of the reported RxQual: + +---- +OsmoBSC(config-net-bts)# overpower ? + dl-acch Enable overpower for both SACCH and FACCH + dl-sacch Enable overpower for SACCH only + dl-facch Enable overpower for FACCH only + +OsmoBSC(config-net-bts)# overpower rxqual 0? + 0 BER >= 0% (always on) +---- + +These parameters are indicated to the BTS during a logical channel activation +or modifications procedures, so they can be changed at run-time. -- To view, visit https://gerrit.osmocom.org/c/osmo-bsc/+/26227 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: osmo-bsc Gerrit-Branch: master Gerrit-Change-Id: Ie995dac6c7083a2b0b4d582f71f55b3736381edb Gerrit-Change-Number: 26227 Gerrit-PatchSet: 2 Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de> Gerrit-Reviewer: Hoernchen <ewild at sysmocom.de> Gerrit-Reviewer: Jenkins Builder Gerrit-Reviewer: fixeria <vyanitskiy at sysmocom.de> Gerrit-Reviewer: laforge <laforge at osmocom.org> Gerrit-Reviewer: osmith <osmith at sysmocom.de> Gerrit-Reviewer: pespin <pespin at sysmocom.de> Gerrit-MessageType: merged -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/gerrit-log/attachments/20211112/cd05f975/attachment.htm>