Attention is currently required from: falconia, pespin.
Hello Jenkins Builder, pespin,
I'd like you to reexamine a change. Please visit
https://gerrit.osmocom.org/c/osmo-bts/+/41049?usp=email
to look at the new patch set (#2).
The following approvals got outdated and were removed: Code-Review+1 by pespin, Verified+1 by Jenkins Builder
Change subject: FR/HR/EFR: implement SID filter in TCH UL path ......................................................................
FR/HR/EFR: implement SID filter in TCH UL path
As a result of how FR/HR/EFR DTX interacts with block diagonal interleaving, at the beginning and end of each DTX pause a correctly functioning TCH receiver will always pick up an artifact consisting of 4 received bursts (2 for TCH/HS) and same number of omitted bursts. Standard channel decoding of this Rx artifact will produce a "half-block" in which half of the bits prior to convolutional decoding will come from a SID repetition whose Tx was notionally suppressed, while the other half will be garbage. As a result of convolutional decoding, the result will often appear as valid SID per classification rules - but passing it as such to the Rx DTX handler is wrong. Classic E1 BTS and GSM MS implementations include a kind of SID filter at this point, setting BFI on these received half-blocks, so that the Rx DTX handler will see an invalid SID condition. Invalid SID means that comfort noise generation is to be continued, but no updated CN parameters are available - which is the truth in half-block Rx situations. Implement the same filter.
Additional background info can be found here:
https://osmocom.org/projects/retro-gsm/wiki/DTXu_half-blocks
Change-Id: I46c62312316b04567bcadf6050597673f071247d --- M include/osmo-bts/lchan.h M src/common/l1sap.c 2 files changed, 58 insertions(+), 8 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/49/41049/2