<p>fixeria <strong>submitted</strong> this change.</p><p><a href="https://gerrit.osmocom.org/c/osmo-bts/+/24846">View Change</a></p><div style="white-space:pre-wrap">Approvals:
laforge: Looks good to me, approved
dexter: Looks good to me, but someone else must approve
osmith: Looks good to me, but someone else must approve
Jenkins Builder: Verified
</div><pre style="font-family: monospace,monospace; white-space: pre-wrap;">osmo-bts-trx: send dummy FACCH in the absense of RTP frames<br><br>If for whatever reason the transmit queue of a TCH/{F,H} contains<br>neither speech frames nor signalling blocks, osmo-bts-trx would<br>currently transmit garbage. Of course, this causes decoding<br>errors at the MS side.<br><br>Ideally, we should employ an ECU (Error Concealment Unit) for the<br>given codec in use. However, a simpler solution is to transmit<br>dummy LAPDm frames over FACCH. This is what e.g. nanoBTS does.<br><br>Change-Id: I868afecbcb6890f40c8f146e3ce00e836b794dd3<br>Related: OS#4823<br>---<br>M src/osmo-bts-trx/sched_lchan_tchf.c<br>M src/osmo-bts-trx/sched_lchan_tchh.c<br>2 files changed, 16 insertions(+), 2 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/src/osmo-bts-trx/sched_lchan_tchf.c b/src/osmo-bts-trx/sched_lchan_tchf.c</span><br><span>index 689925f..8e6298c 100644</span><br><span>--- a/src/osmo-bts-trx/sched_lchan_tchf.c</span><br><span>+++ b/src/osmo-bts-trx/sched_lchan_tchf.c</span><br><span>@@ -530,9 +530,16 @@</span><br><span> memset(*bursts_p + 464, 0, 464);</span><br><span> }</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- /* no message at all */</span><br><span style="color: hsl(120, 100%, 40%);">+ /* no message at all, send a dummy L2 frame on FACCH */</span><br><span> if (!msg_tch && !msg_facch) {</span><br><span style="color: hsl(120, 100%, 40%);">+ static const uint8_t dummy[GSM_MACBLOCK_LEN] = {</span><br><span style="color: hsl(120, 100%, 40%);">+ 0x03, 0x03, 0x01, /* TODO: use randomized padding */</span><br><span style="color: hsl(120, 100%, 40%);">+ 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b,</span><br><span style="color: hsl(120, 100%, 40%);">+ 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b,</span><br><span style="color: hsl(120, 100%, 40%);">+ };</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> LOGL1SB(DL1P, LOGL_INFO, l1ts, br, "No TCH or FACCH prim for transmit.\n");</span><br><span style="color: hsl(120, 100%, 40%);">+ gsm0503_tch_fr_encode(*bursts_p, dummy, sizeof(dummy), 1);</span><br><span> goto send_burst;</span><br><span> }</span><br><span> </span><br><span>diff --git a/src/osmo-bts-trx/sched_lchan_tchh.c b/src/osmo-bts-trx/sched_lchan_tchh.c</span><br><span>index 4f03bd1..bfebb66 100644</span><br><span>--- a/src/osmo-bts-trx/sched_lchan_tchh.c</span><br><span>+++ b/src/osmo-bts-trx/sched_lchan_tchh.c</span><br><span>@@ -417,9 +417,16 @@</span><br><span> }</span><br><span> }</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- /* no message at all */</span><br><span style="color: hsl(120, 100%, 40%);">+ /* no message at all, send a dummy L2 frame on FACCH */</span><br><span> if (!msg_tch && !msg_facch && !chan_state->dl_ongoing_facch) {</span><br><span style="color: hsl(120, 100%, 40%);">+ static const uint8_t dummy[GSM_MACBLOCK_LEN] = {</span><br><span style="color: hsl(120, 100%, 40%);">+ 0x03, 0x03, 0x01, /* TODO: use randomized padding */</span><br><span style="color: hsl(120, 100%, 40%);">+ 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b,</span><br><span style="color: hsl(120, 100%, 40%);">+ 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b,</span><br><span style="color: hsl(120, 100%, 40%);">+ };</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> LOGL1SB(DL1P, LOGL_INFO, l1ts, br, "No TCH or FACCH prim for transmit.\n");</span><br><span style="color: hsl(120, 100%, 40%);">+ gsm0503_tch_hr_encode(*bursts_p, dummy, sizeof(dummy));</span><br><span> goto send_burst;</span><br><span> }</span><br><span> </span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/c/osmo-bts/+/24846">change 24846</a>. To unsubscribe, or for help writing mail filters, visit <a href="https://gerrit.osmocom.org/settings">settings</a>.</p><div itemscope itemtype="http://schema.org/EmailMessage"><div itemscope itemprop="action" itemtype="http://schema.org/ViewAction"><link itemprop="url" href="https://gerrit.osmocom.org/c/osmo-bts/+/24846"/><meta itemprop="name" content="View Change"/></div></div>
<div style="display:none"> Gerrit-Project: osmo-bts </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-Change-Id: I868afecbcb6890f40c8f146e3ce00e836b794dd3 </div>
<div style="display:none"> Gerrit-Change-Number: 24846 </div>
<div style="display:none"> Gerrit-PatchSet: 4 </div>
<div style="display:none"> Gerrit-Owner: fixeria <vyanitskiy@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: Jenkins Builder </div>
<div style="display:none"> Gerrit-Reviewer: dexter <pmaier@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: fixeria <vyanitskiy@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: laforge <laforge@osmocom.org> </div>
<div style="display:none"> Gerrit-Reviewer: osmith <osmith@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: pespin <pespin@sysmocom.de> </div>
<div style="display:none"> Gerrit-MessageType: merged </div>