https://osmocom.org/https://osmocom.org/favicon.ico?16647414092021-10-13T17:22:07ZOpen Source Mobile CommunicationsOsmocomBB - Bug #5261: Not able to capture LAPDm packets and gsm_sms packetshttps://osmocom.org/issues/5261?journal_id=226902021-10-13T17:22:07Zfixeria
<ul><li><strong>Category</strong> deleted (<del><i>OsmocomBB Firmware</i></del>)</li><li><strong>Status</strong> changed from <i>New</i> to <i>Rejected</i></li><li><strong>Priority</strong> changed from <i>High</i> to <i>Normal</i></li><li><strong>Target version</strong> deleted (<del><i>GAPK (GSM Audio Pocket Knife) back-end intergation</i></del>)</li><li><strong>Resolution</strong> deleted (<del><i>wontfix</i></del>)</li></ul><p>As the name implies, ccch_scan operates on CCCH (Common Control Channels), while you're talking about DCCH (Dedicated Control Channels). However, there is a hacked version of ccch_scan by Sylvain Munaut in his branch (<a class="external" href="https://git.osmocom.org/osmocom-bb/log/?h=sylvain/burst_ind">https://git.osmocom.org/osmocom-bb/log/?h=sylvain/burst_ind</a>) - I guess this is what you're looking for. It switches to DCCHs from RR Immediate Assignment messages.</p>
<blockquote>
<p>There is no LAPdm packets and no gsm_sms packets (downlink). But when I use RTL-SDR I get both LAPdm packets as well as gsm_sms packets (downlink).</p>
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<p>This works because the flow-graph of grgsm_livemon contains an additional chain for decoding all sub-channels of SDCCH/8 on TS1.</p>