https://projects.osmocom.org/https://projects.osmocom.org/favicon.ico?16647414092018-02-19T14:29:36ZOpen Source Mobile CommunicationsCellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=76882018-02-19T14:29:36Zneelsnhofmeyr@sysmocom.de
<ul><li><strong>Blocks</strong> <i><a class="issue tracker-2 status-3 priority-3 priority-high3 closed" href="/issues/1606">Feature #1606</a>: hand-over for load distribution among BTSs</i> added</li></ul> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=76902018-02-19T15:03:58Zneelsnhofmeyr@sysmocom.de
<ul></ul><p>With two sysmoBTS and the osmo-bsc branch neels/ho2, with 'handover algorithm 2' set in the config, this is what the problem looks like on the HODEC logging output:</p>
<p>Initially:<br /><pre>
DHODEC DEBUG handover_decision_2.c:1129 (lchan 1.020 TCH/F) (subscr unknown) MEASUREMENT REPORT
DHODEC DEBUG handover_decision_2.c:1134 (lchan 1.020 TCH/F) (subscr unknown) 0: arfcn=868 bsic=63 neigh_idx=0 rxlev=57 flags=0
DHODEC DEBUG handover_decision_2.c:291 (lchan 1.020 TCH/F) (subscr unknown) neigh 868 new in report rxlev=57 last_seen_nr=0
DHODEC DEBUG handover_decision_2.c:1156 (lchan 1.020 TCH/F) (subscr unknown) HODEC2: evaluating measurement report
</pre></p>
<p>Once the error is occuring, I see:<br /><pre>
DHODEC DEBUG handover_decision_2.c:1129 (lchan 0.020 TCH/F) (subscr unknown) MEASUREMENT REPORT
DHODEC DEBUG handover_decision_2.c:1134 (lchan 0.020 TCH/F) (subscr unknown) 0: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
DHODEC DEBUG handover_decision_2.c:1134 (lchan 0.020 TCH/F) (subscr unknown) 1: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
DHODEC DEBUG handover_decision_2.c:1134 (lchan 0.020 TCH/F) (subscr unknown) 2: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
DHODEC DEBUG handover_decision_2.c:1134 (lchan 0.020 TCH/F) (subscr unknown) 3: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
DHODEC DEBUG handover_decision_2.c:1134 (lchan 0.020 TCH/F) (subscr unknown) 4: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
DHODEC DEBUG handover_decision_2.c:1134 (lchan 0.020 TCH/F) (subscr unknown) 5: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
DHODEC DEBUG handover_decision_2.c:1134 (lchan 0.020 TCH/F) (subscr unknown) 6: arfcn=0 bsic=0 neigh_idx=0 rxlev=0 flags=0
DHODEC DEBUG handover_decision_2.c:1156 (lchan 0.020 TCH/F) (subscr unknown) HODEC2: evaluating measurement report
</pre></p>
<p>The obviously weird thing is that there is a list of six neighbors zeroed out. Before, the list length was a useful value and reflected the single reported neighbor.</p>
<p>The RR Measurement Report PDU does not actually pass ARFCNs directly, the above list is computed. So bugs are possible there...</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=76912018-02-19T15:04:15Zneelsnhofmeyr@sysmocom.de
<ul><li><strong>Description</strong> updated (<a title="View differences" href="/journals/7691/diff?detail_id=12201">diff</a>)</li></ul> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=78352018-02-26T00:05:56Zneelsnhofmeyr@sysmocom.de
<ul><li><strong>Blocks</strong> <i><a class="issue tracker-1 status-1 priority-2 priority-default" href="/issues/3002">Bug #3002</a>: HO2: handover decision for dynamic timeslots</i> added</li></ul> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=79382018-03-01T16:36:35Zlaforge
<ul></ul><p>with all the changes/fixes going into OsmoBTS during the last 7-10 days, it might be worth re-testing if this issue still persists at all.</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=79962018-03-02T03:24:55Zneelsnhofmeyr@sysmocom.de
<ul></ul><p>I thought the same, and, when was it, like 24 hours ago I still got the same symptoms, unfortunately. Still need to hunt it, it seems.</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=80702018-03-07T15:31:03Zneelsnhofmeyr@sysmocom.de
<ul><li><strong>Status</strong> changed from <i>New</i> to <i>In Progress</i></li><li><strong>Assignee</strong> set to <i>neels</i></li></ul> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=80822018-03-08T03:53:29Zneelsnhofmeyr@sysmocom.de
<ul><li><strong>File</strong> <a href="/attachments/2987">si2_and_meas_rep.pcapng</a> <a class="icon-only icon-download" title="Download" href="/attachments/download/2987/si2_and_meas_rep.pcapng">si2_and_meas_rep.pcapng</a> added</li><li><strong>% Done</strong> changed from <i>0</i> to <i>10</i></li></ul><p>Tested again today; besides seeing various oddities, I also still see the measurement reports missing for neighbors after a handover.<br />There is a fix on gerrit for the weird list of seven(!) empty neighbors: <a class="external" href="https://gerrit.osmocom.org/7149">https://gerrit.osmocom.org/7149</a></p>
<p>And I verified again that SI2 does include the respective other neighbor.<br />Attached pcap (with just two packets) shows the SI2 with the neighboring ARFCN and the empty neighbor measurements; the two packets were actually adjacent in the taken overall trace.</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=80832018-03-08T04:27:22Zneelsnhofmeyr@sysmocom.de
<ul><li><strong>File</strong> <a href="/attachments/2988">neighbor_cells_are_correct.pcapng</a> <a class="icon-only icon-download" title="Download" href="/attachments/download/2988/neighbor_cells_are_correct.pcapng">neighbor_cells_are_correct.pcapng</a> added</li></ul><p>In 3GPP TS 04.18 10.5.2.10, it says<br />"1 1 1 Neighbour cell information not available for serving cell" <br />Which sounds almost like the cell was asked to measure itself as a neighbor, as if we told it that its own ARFCN were its neighbor.</p>
<p>However, attached pcap confirms that the BTS with ip 192.168.0.21 has ARFCN 870 (see packet 839, where OML sets the ARFCN BTS attribute)<br />and advertises neighbor 868 in its SI2 (see packet 1476)<br />yet says the above bits in the Measurement Report, packet 1488.</p>
<p>I'm still in the dark about why we get empty neighbor cell lists in the measurement reports.</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=80842018-03-08T04:38:41Zneelsnhofmeyr@sysmocom.de
<ul></ul><p>Could the Extended Measurement Report be related? According to 3GPP TS 04.18 we would send a Extended Measurement Order to the MS with a list of frequencies to report on, and would receive an Extended Measurement Report on those. However, if we already expect six neighbors as inidicated in SI2 to be reported in the non-extended Measurement Report, I don't see the need to use the Extended one.</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=80852018-03-08T07:38:38Zlaforge
<ul></ul><p>On Thu, Mar 08, 2018 at 04:38:41AM +0000, neels [REDMINE] wrote:</p>
<blockquote>
<p>Could the Extended Measurement Report be related? According to 3GPP TS 04.18 we would send a Extended Measurement Order to the MS with a list of frequencies to report on, and would receive an Extended Measurement Report on those. However, if we already expect six neighbors as inidicated in SI2 to be reported in the non-extended Measurement Report, I don't see the need to use the Extended one.</p>
</blockquote>
<p>indeed. extended is only required for meaurement of cells of different RAT or more cells, AFAIK.</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=80872018-03-08T07:38:42Zlaforge
<ul></ul><p>Would be a good idea to verify the decoded SI2 message with e.g. a TEMS phone<br />or some eother third-party decoder. Maybe wireshark is displaying an erroneous<br />message without indicating any "ERROR", but the phone is discarding it due to some<br />wrong bit somewhere.</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=81392018-03-10T22:32:04Zlaforge
<ul></ul><p>actually, not SI2 is the important message in this context, but SI5.</p>
<p>After the handover to the new BTS, the phone of cours has no way of knowing what's broadcast on the BCCH. Instead, it relies on the SI5/5bis/5ter messages sent by the new cell in its SACCH downlink.</p>
<p>So if the new cell had some errors in its SI5* messages, that would explain why measurement reports cease to contain neighbors after handover.</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=81422018-03-11T00:58:26Zneelsnhofmeyr@sysmocom.de
<ul></ul><p>well, shucks, looks like my network isn't even sending out any SI5* to begin with.</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=81492018-03-11T19:16:54Zlaforge
<ul></ul><p>On Sun, Mar 11, 2018 at 12:58:26AM +0000, neels [REDMINE] wrote:</p>
<blockquote>
<p>well, shucks, looks like my network isn't even sending out any SI5* to begin with.</p>
</blockquote>
<p>Do you see the SACCH FILLING for SI5 on Abis/RSL durning RSL start-up? If yes,<br />then it's a BTS problem. If not, it's the BSC.</p>
<p>But at least there's a clean explanation now.</p>
<p>btw: I've just started working on SACCH tests in BTS_Tests.ttcn. So far I only<br />have the test to check if DEACT SACCH works on all channel combinations.</p>
<p>SACCH FILL and SACCH INFO MODIFY is currently in progress, as is testing for<br />different SI combinations (5/5bis/5ter/6) on SACCH.</p> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=81532018-03-11T19:54:13Zlaforge
<ul><li><strong>Related to</strong> <i><a class="issue tracker-1 status-3 priority-2 priority-default closed" href="/issues/3057">Bug #3057</a>: OsmoBTS fails to schedule SACCH filling like SI5</i> added</li></ul> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=81612018-03-11T23:03:40Zlaforge
<ul><li><strong>Related to</strong> <i><a class="issue tracker-1 status-3 priority-3 priority-high3 closed" href="/issues/3059">Bug #3059</a>: System Information on SACCH missing L2 Pseudo-Length</i> added</li></ul> Cellular Network Infrastructure - Bug #2963: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)https://projects.osmocom.org/issues/2963?journal_id=81672018-03-12T02:08:34Zneelsnhofmeyr@sysmocom.de
<ul><li><strong>Status</strong> changed from <i>In Progress</i> to <i>Resolved</i></li><li><strong>% Done</strong> changed from <i>10</i> to <i>100</i></li></ul><p>The problem is <strong>fixed</strong> by <a class="issue tracker-1 status-3 priority-2 priority-default closed" title="Bug: OsmoBTS fails to schedule SACCH filling like SI5 (Resolved)" href="https://projects.osmocom.org/issues/3057">#3057</a> and <a class="issue tracker-1 status-3 priority-3 priority-high3 closed" title="Bug: System Information on SACCH missing L2 Pseudo-Length (Resolved)" href="https://projects.osmocom.org/issues/3059">#3059</a>! i.e. <a class="external" href="https://gerrit.osmocom.org/7220">https://gerrit.osmocom.org/7220</a> and <a class="external" href="https://gerrit.osmocom.org/#/c/7218/">https://gerrit.osmocom.org/#/c/7218/</a><br />A lot of head scratching is finally <strong>over</strong> and I can go on to properly test handover decision 2! Thank the holy powers of two.<br />Let me resolve this here and leave tracking to those other two issues.</p>