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/.
Neels Hofmeyr gerrit-no-reply at lists.osmocom.orgPatch Set 1: Note that a detailed description of this patch can be found in http://lists.osmocom.org/pipermail/openbsc/2018-January/011648.html Help required for non-sync Handover Muhammad Awais Aslam mawais.aslam985 at gmail.com Mon Jan 15 13:31:32 UTC 2018 Quoting: We took code related to handover from the osmocom-bb jolly branch by manually adding/deleting stuff in the master branch as updating to the latest copy was giving us issues. We added code from the “Safely change TPU offset on TS change or sync change” commit till the “Use only sel_si for information about the current cell” commit. Using the handover code in the jolly branch and after making the changes we were able to obtain the handover command from the BTS. The synchronized handover case works sometimes though still not every time, however the non-synchronized case doesn't work at all as we are not able to get the physical information command from the new cell. I'll explain the changes/additions we made to achieve this. Firstly, we noted that in dedicated mode SB burst was not being detected. Changes were required at three main places in order to correctly perform FB/SB detection: - It was seen that the results for SB were being read from DSP API location dsp_api.db_r->a_sch which is for the idle mode. The results had to be read from the dsp_api.ndb->a_sch26 location for the dedicated case if TCH_SB_DSP_TASK is used. - After reading the FB we needed to update the quarter-bit offset of the TPU using the TOA of the FB to sync it with the start of frame of the neighbour cell in order to catch the SB (by changing the vaule of l1s.tpu_offset using the TOA of the FB). - Frequency compensation needed to be performed using the afc_correct function before reading the SB. * We actually kind of cheated a bit by adding 3 frames to the original idle frame in order to give us more time to perform FB/SB detection including the synchronizations mentioned above. This was because we weren't that proficient with the code and someone with more understanding could do this better. The call did not get dropped. We used the initial added “idle” frame to perform the quarter-bit and frequency compensation which was reversed in the idle frame with the response function to tune back to the serving cell. These things, when added to the code did the trick and BSIC of the neighbours was obtained. Once the BSICs were decoded the measurement report sent to the BTS became meaningful and the handover command was received. Upon receiving handover command, access bursts needed to be sent on the new channel which again was not currently being implemented properly as in order to tune to the new cell we needed to know its quarter-bit offset for start of frame, frequency compensation and absolute frame number which were not previously being obtained. Now that we were able to detect FB and SB these values were stored for the neighbours following detection of these bursts and were used to tune to a neighbour cell in case of a handover to it before the sending of access bursts. However, here is where we are stuck. We were expecting a physical information message following the access bursts but were not able to receive it due to which the handover failed. If only that could be achieved we believe handover should be successful. Either we are not syncing properly to the new cell or we might not be following GSM protocol properly. We also might not be reading the FACCH properly for physical information message after tuning to the new cell as we couldn't really understand that bit very well. We wanted someone expertise on this matter and were hoping our work could be of use. -- To view, visit https://gerrit.osmocom.org/5490 To unsubscribe, visit https://gerrit.osmocom.org/settings Gerrit-MessageType: comment Gerrit-Change-Id: Ib01460b796d2107c4599d327e184eb42340999d2 Gerrit-PatchSet: 1 Gerrit-Project: osmocom-bb Gerrit-Branch: master Gerrit-Owner: Muhammad Awais Aslam <mawais.aslam985 at gmail.com> Gerrit-Reviewer: Jenkins Builder Gerrit-Reviewer: Max <msuraev at sysmocom.de> Gerrit-Reviewer: Neels Hofmeyr <nhofmeyr at sysmocom.de> Gerrit-Reviewer: Vadim Yanitskiy <axilirator at gmail.com> Gerrit-Reviewer: fixeria <axilirator at gmail.com> Gerrit-HasComments: No