Summary of OsmoBTS work during 2020
This is a summary of the work that has happened on OsmoBTS in the January 2020 through early February 2021 time frame.
In general, a large focus has been on variuos "enterprise" features that are mostly relevant to operating BTSs with large number of TRX in dense (urban) interference limited networks. This is quite a bit different from the more traditional OsmoBTS use cases in rural applications, where networks are limited by coverage, and not by interference.
OsmoBTS (osmo-bts-trx) has now been tested successfully with configurations up to 8TRX.
Major changes:- BS (downlink) power control
- baseband frequency hopping
- tons of fixes regarding the accuracy of measurement reports (which is very important for proper hand-over performance)
- EWMA based filtering of power control loops
- Repeated downlink SACCH support; 3GPP Release 6 (#4794)
- Repeated uplink SACCH support; 3GPP Release 6 (#4795)
- Repeated downlink FACCH support (#4796)
The slightly more detailed versions below:
Common/General changes¶
- various fixes regarding measurement reporting / averaging
- 11bit RACH support
- print lchan name in all log lines / simplify debugging (#1938)
- improved reporting of BTS features/capabilities to BSC
- BS (downlink) power control
- power ramp-down on BTS shutdown
- power ramp-up/ramp-down during ADM state changes
- many fixes to A-bis OML MO finite state machines
- OML: fix ARFCN range checks
- support setting real-time scheduler priority via VTY
- OML Fix Radio Carrier OPSTATE change report not sent in all scenarios
- OML + PCU interface: Support for IPv6 NS-VCs to PCU
- automatic VTY reference generation --vty-ref-xml (#1601)
- Only send SI13 if PCU is connected (#3075)
- Don't broadcast SI4 GPRS indicator if PCU is not connected (#3075)
- power_control: EWMA based uplink power filtering
- count measurements for FACCH/F only once (#4799)
- count all blocks for "SUB" for TCH/F in signaling mode (#4799)
- fix number of expected measurements (#4799)
- fix integer overflow in measurement processing (#4799)
- fix L1 SAPI activation ordering in hand-over (likely impacts handover performance)
- Repeated downlink SACCH support; 3GPP Release 6 (#4794)
- Repeated uplink SACCH support; 3GPP Release 6 (#4795)
- Repeated downlink FACCH support (#4796)
- Activate DL SACCH only when TA is known (#4008, #4009)
osmo-bts-trx specific changes¶
Traditionally, osmo-bts-trx used to have less features than the other osmo-bts variants (such as osmo-bts-sysmo for sysmoBTS devices).
The focus of the development has meanwhile shifted, and osmo-bts-trx has been catching up significantly, and in some cases even exceeding the capabilities of osmo-bts-{sysmo,lc15,oc2g,octphy}.
- TRX: nope indications; fixes many measurement related issues
- TRX: AMR DTX frame detection (#2978)
- TRX: fix uplink measurement reporting durign hand-over (#4592)
- TRX: power-ramping during BTS power up
- TRX: Fix reading out of buffer during tx of dummy burst on PDCH TS with EGPRS enabled (#4606)
- TRX: baseband frequency hopping support (#4546)
- TRX: Fix crash due to ASSERT related to dynamic timeslots (#4920)
- TRX: Fix crash due to ASSERT related to rf-lock and dynamic timeslots
- TRX: significantly reduce clock advance, reducing latency significantly (#4487)
