Summary of OsmoBTS work during 2020

Added by laforge about 3 years ago

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)


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