osmocom-bb[fixeria/trx]: fake_trx/ctrl_if_bb.py: add FAKE_RSSI and FAKE_TOA commands

This is merely a historical archive of years 2008-2021, before the migration to mailman3.

A maintained and still updated list archive can be found at https://lists.osmocom.org/hyperkitty/list/gerrit-log@lists.osmocom.org/.

Vadim Yanitskiy gerrit-no-reply at lists.osmocom.org
Wed Feb 28 09:42:31 UTC 2018


Patch Set 3: Code-Review-1

Hi Harald,

finally, the TRX Toolkit also migrated to the integer math now ;)

 > actually, I think setting an absolute value is not a good idea.  We
 > should be able to set/configure a _delta_ value.

Good idea. I would prefer to have the following:

  CMD FAKE_TOA <TOA_BASE> <TOA_TRESHOLD>

where both values define a range of ToA randomization:

  min: TOA_BASE - TOA_TRESHOLD
  max: TOA_BASE + TOA_TRESHOLD

e.g. now the BurstForwarder by default has:

  min: -128
  max: +128

what means +-half of a symbol.

 > In this case we can do full/proper TA loop testing:
 > * trxcon sends with toa=0
 > * fake_trx adds e.g. 512 (2 bits)
 > * osmo-bts sends TA=2 in downlink SACCH
 > * "mobile" can tell trxcon to send with toa=-512 (-2*256)
 > * fake-trx adds -512+512=0
 > * osmo-bts receives TOA=0 which is expected if the timing advance
 > loop is balanced.
 > what do you think?  How do you currently handle TA with the SDR PHY
 > for osmcoom-bb?

Let's first focus on the Uplink path:

  When trxcon sends a burst, it doesn't care about ToA, it shouldn't.
  There is a SETTA command, which forwards the current Timing Advance
  value (indicated by the network) to transceiver, because exactly
  transceiver takes care about the TX burst timings...

  The SETTA command is handled by GRGSM-TRX, but not by FakeTRX for now.
  I think, it makes sense to implement it in FakeTRX too. I'll do this.

Now let's look at the Downlink path:

  The current implementation of trxcon doesn't handle the ToA of
  incoming (Downlink) bursts. If I understand correctly, this value
  should be used to calculate the MS Timing Offset, right?

  But as I know, it isn't implemented in L1CTL nor in the L2&3, and
  actual MS Timing Offset value, being sent in L1 SACCH header, is
  hard-coded somewhere...

  Correct me if I am wrong.

Finally:

  I think, the FAKE_* commands shall be implemented for both
  Uplink and Downlink directions separately in FakeTRX, because
  now we have them in CTRL_BB interface, but each one affects
  both directions at the same time...

  In other words, if you send e.g. FAKE_RSSI on CTRL_BB, then
  the RSSI value would be changed for both directions...
  This is incorrect.

-- 
To view, visit https://gerrit.osmocom.org/6846
To unsubscribe, visit https://gerrit.osmocom.org/settings

Gerrit-MessageType: comment
Gerrit-Change-Id: Ia23becec4104d47e7b22350db67b8834d6f1ad1b
Gerrit-PatchSet: 3
Gerrit-Project: osmocom-bb
Gerrit-Branch: fixeria/trx
Gerrit-Owner: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: Vadim Yanitskiy <axilirator at gmail.com>
Gerrit-HasComments: No



More information about the gerrit-log mailing list