diff options
author | Vadim Yanitskiy <vyanitskiy@sysmocom.de> | 2021-11-02 02:22:20 +0300 |
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committer | Vadim Yanitskiy <vyanitskiy@sysmocom.de> | 2021-11-10 14:42:17 +0300 |
commit | dd0dabbffce82c365a5de5295a24d21fabb14315 (patch) | |
tree | b0b2ad73e4a373b2f97ff353d0bebb91e8507556 /doc | |
parent | 16b3b50830d99138893b572734d6933553f010c8 (diff) |
doc/manuals: add documentation for interference reporting
Change-Id: I3c15b11bbcba0811e3a15fe64365067bf8ad0dae
Related: SYS#5313
Diffstat (limited to 'doc')
-rw-r--r-- | doc/manuals/chapters/interf_meas.adoc | 72 | ||||
-rw-r--r-- | doc/manuals/osmobsc-usermanual.adoc | 2 |
2 files changed, 74 insertions, 0 deletions
diff --git a/doc/manuals/chapters/interf_meas.adoc b/doc/manuals/chapters/interf_meas.adoc new file mode 100644 index 000000000..62b08c4ae --- /dev/null +++ b/doc/manuals/chapters/interf_meas.adoc @@ -0,0 +1,72 @@ +== Interference reporting + +According to 3GPP 48.058, section 6.1, the BTS shall periodically report the +interference levels on *idle* channels using the "Radio resource indication" +procedure. This is done by sending the `RF RESource INDication` message, +which is specified in sections 8.6.1 and 9.3.21. + +// TODO: BSC -> MSC reporting (3GPP TS 48.008, section 3.1.3) + +=== Interference reporting parameters + +The interference band is calculated by the BTS based on the `Interference level +Boundaries` and the `Averaging period`. These parameters are sent by the BSC +over the A-bis/OML, and can be configured via the VTY interface. + +Below are the default values for them: + +---- +network + bts 0 + interference-meas avg-period 6 <1> + interference-meas level-bounds -85 <2> -91 -97 -103 -109 -115 <3> +---- +<1> Averaging period (`Intave`) in SACCH multiframe periods (480ms). +<2> Interference level boundary `0` (in dBm). +<3> Interference level boundary `X5` (in dBm). + +The `Intave` parameter defines the averaging and reporting period. With the +default value of 6 SACCH multiframe periods the BTS is instructed to report +averaged interference levels approximately every 3 seconds. + +According to 3GPP TS 48.008, there exist five interference bands and six +`Interference level Boundaries` (`0`, `X1`, ... `X5`). The BTS shall map the +averaged interference levels (initially in dBm) into these 5 bands. + +---- +-85 dBm -91 dBm -97 dBm -103 dBm -109 dBm -115 dBm + | <1> | <2> | <3> | <4> | <5> | <6> + +----------+----------+----------+----------+----------+ + | band 1 | band 2 | band 3 | band 4 | band 5 | + +----------+----------+----------+----------+----------+ +---- +<1> Interference level boundary `0` (outer). +<2> Interference level boundary `X1`. +<3> Interference level boundary `X2`. +<4> Interference level boundary `X3`. +<5> Interference level boundary `X4`. +<6> Interference level boundary `X5` (outer). + +Unfortunately, it's not clearly defined by 3GPP how the BTS is supposed to map +dBm values outside of the outer boundaries (`0` and `X5`) to band values. The +ip.access nanoBTS, for example, would map values -75 dBm and -120 dBm to bands +1 and 5, respectively. osmo-bts replicates this behavior. + +=== PDCH and dynamic timeslot handling + +The BTS may optionally report interference levels for PDCH timeslots. This +may be useful for the BSC to determine whether dynamic PDCH timeslots might +be better used for new circuit switched connections, or whether alternative +PDCH resources should be allocated for interference reasons. + +NOTE: Currently osmo-bsc makes no use of PDCH interference reports, neither +they get forwarded to the BSC co-located PCU over the PCUIF. + +For dynamic timeslots (`TCH/F_TCH/H_SDCCH/8_PDCH` and `TCH/F_PDCH`), the +following expectations apply: + +* when in TCH/F mode: no interference reports, because the only sub-channel is active; +* when in TCH/H mode: interference reports for *inactive* sub-channels only; +* when in SDCCH mode: interference reports for *inactive* sub-channels only; +* when in PDCH mode: optional interference reports; +** measurements can be performed during IDLE TDMA frames. diff --git a/doc/manuals/osmobsc-usermanual.adoc b/doc/manuals/osmobsc-usermanual.adoc index 120fe2c21..0afa0158c 100644 --- a/doc/manuals/osmobsc-usermanual.adoc +++ b/doc/manuals/osmobsc-usermanual.adoc @@ -26,6 +26,8 @@ include::{srcdir}/chapters/bsc.adoc[] include::{srcdir}/chapters/power_control.adoc[] +include::{srcdir}/chapters/interf_meas.adoc[] + include::{srcdir}/chapters/handover.adoc[] include::{srcdir}/chapters/smscb.adoc[] |