<p>neels has uploaded this change for <strong>review</strong>.</p><p><a href="https://gerrit.osmocom.org/c/osmo-bsc/+/22512">View Change</a></p><pre style="font-family: monospace,monospace; white-space: pre-wrap;">lchan activation: indicate whether TA is known<br><br>On lchan activation, we already know the Timing Advance in most<br>situations: from the Channel Request RACH, or from a previous lchan in<br>the same cell. Place this information in lchan->activate.info.ta.<br><br>So far, the lchan->last_ta (until recently called rqd_ta) was used to<br>store the initial TA for channel activation -- move the initial TA to<br>lchan->activate.info.ta, for proper scoping.<br><br>Only an inter-cell handover does not yet know a Timing Advance (until<br>the Handover Detection RACH is received), so indicate<br>activate.info.ta_known = false for that case.<br><br>If ta_known is false, do not include an Access Delay IE in the Channel<br>Activation message, ensuring that the BTS does not use an arbitrary TA<br>that is likely inaccurate.<br><br>The effect for OsmoBTS is that we will *not* start the downlink SACCH on<br>channel activation for inter-cell handover, but will wait for a HO RACH<br>first, and then use the correct TA when enabling downlink SACCH.<br><br>Related: OS#4008 SYS#5192<br>Change-Id: I986bf93e8acd6aef7eaf63ac962480b680aa894f<br>---<br>M include/osmocom/bsc/gsm_data.h<br>M src/osmo-bsc/abis_rsl.c<br>M src/osmo-bsc/assignment_fsm.c<br>M src/osmo-bsc/handover_fsm.c<br>M src/osmo-bsc/lchan_fsm.c<br>5 files changed, 28 insertions(+), 11 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;">git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/12/22512/1</pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h</span><br><span>index 98822fb..2082971 100644</span><br><span>--- a/include/osmocom/bsc/gsm_data.h</span><br><span>+++ b/include/osmocom/bsc/gsm_data.h</span><br><span>@@ -571,6 +571,8 @@</span><br><span> /* During intra-BSC handover, we keep the MGW endpoint intact and just re-route to the new lchan. This</span><br><span> * activate_info is for the new lchan, the re_use_mgw_endpoint_from_lchan points at the old lchan. */</span><br><span> struct gsm_lchan *re_use_mgw_endpoint_from_lchan;</span><br><span style="color: hsl(120, 100%, 40%);">+ bool ta_known;</span><br><span style="color: hsl(120, 100%, 40%);">+ uint8_t ta;</span><br><span> };</span><br><span> </span><br><span> struct gsm_lchan {</span><br><span>diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c</span><br><span>index 5bd53f1..63ca58f 100644</span><br><span>--- a/src/osmo-bsc/abis_rsl.c</span><br><span>+++ b/src/osmo-bsc/abis_rsl.c</span><br><span>@@ -521,7 +521,6 @@</span><br><span> struct msgb *msg;</span><br><span> int rc;</span><br><span> uint8_t *len;</span><br><span style="color: hsl(0, 100%, 40%);">- uint8_t ta;</span><br><span> </span><br><span> struct rsl_ie_chan_mode cm;</span><br><span> struct gsm48_chan_desc cd;</span><br><span>@@ -541,12 +540,6 @@</span><br><span> return rc;</span><br><span> }</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- ta = lchan->last_ta;</span><br><span style="color: hsl(0, 100%, 40%);">-</span><br><span style="color: hsl(0, 100%, 40%);">- /* BS11 requires TA shifted by 2 bits */</span><br><span style="color: hsl(0, 100%, 40%);">- if (bts->type == GSM_BTS_TYPE_BS11)</span><br><span style="color: hsl(0, 100%, 40%);">- ta <<= 2;</span><br><span style="color: hsl(0, 100%, 40%);">-</span><br><span> memset(&cd, 0, sizeof(cd));</span><br><span> gsm48_lchan2chan_desc(&cd, lchan);</span><br><span> </span><br><span>@@ -601,7 +594,13 @@</span><br><span> if (bts->ms_power_ctrl.mode != GSM_PWR_CTRL_MODE_NONE)</span><br><span> msgb_tv_put(msg, RSL_IE_MS_POWER, lchan->ms_power);</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- msgb_tv_put(msg, RSL_IE_TIMING_ADVANCE, ta);</span><br><span style="color: hsl(120, 100%, 40%);">+ if (lchan->activate.info.ta_known) {</span><br><span style="color: hsl(120, 100%, 40%);">+ uint8_t ta = lchan->activate.info.ta;</span><br><span style="color: hsl(120, 100%, 40%);">+ /* BS11 requires TA shifted by 2 bits */</span><br><span style="color: hsl(120, 100%, 40%);">+ if (bts->type == GSM_BTS_TYPE_BS11)</span><br><span style="color: hsl(120, 100%, 40%);">+ ta <<= 2;</span><br><span style="color: hsl(120, 100%, 40%);">+ msgb_tv_put(msg, RSL_IE_TIMING_ADVANCE, ta);</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span> </span><br><span> /* BS/MS Power Control Parameters (if supported by BTS model) */</span><br><span> add_power_control_params(msg, RSL_IE_BS_POWER_PARAM, lchan);</span><br><span>@@ -1744,13 +1743,14 @@</span><br><span> OSMO_ASSERT(lchan->rqd_ref);</span><br><span> </span><br><span> *(lchan->rqd_ref) = rqd->ref;</span><br><span style="color: hsl(0, 100%, 40%);">- lchan->last_ta = rqd->ta;</span><br><span> </span><br><span> LOG_LCHAN(lchan, LOGL_DEBUG, "MS: Channel Request: reason=%s ra=0x%02x ta=%d\n",</span><br><span> gsm_chreq_name(rqd->reason), rqd->ref.ra, rqd->ta);</span><br><span> info = (struct lchan_activate_info){</span><br><span> .activ_for = FOR_MS_CHANNEL_REQUEST,</span><br><span> .chan_mode = GSM48_CMODE_SIGN,</span><br><span style="color: hsl(120, 100%, 40%);">+ .ta = rqd->ta,</span><br><span style="color: hsl(120, 100%, 40%);">+ .ta_known = true,</span><br><span> };</span><br><span> </span><br><span> lchan_activate(lchan, &info);</span><br><span>diff --git a/src/osmo-bsc/assignment_fsm.c b/src/osmo-bsc/assignment_fsm.c</span><br><span>index 83822a1..b938ded 100644</span><br><span>--- a/src/osmo-bsc/assignment_fsm.c</span><br><span>+++ b/src/osmo-bsc/assignment_fsm.c</span><br><span>@@ -478,6 +478,8 @@</span><br><span> .requires_voice_stream = conn->assignment.requires_voice_stream,</span><br><span> .msc_assigned_cic = req->msc_assigned_cic,</span><br><span> .re_use_mgw_endpoint_from_lchan = conn->lchan,</span><br><span style="color: hsl(120, 100%, 40%);">+ .ta = conn->lchan->last_ta,</span><br><span style="color: hsl(120, 100%, 40%);">+ .ta_known = true,</span><br><span> };</span><br><span> </span><br><span> osmo_fsm_inst_dispatch(conn->lchan->fi, LCHAN_EV_REQUEST_MODE_MODIFY, &info);</span><br><span>@@ -553,6 +555,8 @@</span><br><span> .requires_voice_stream = conn->assignment.requires_voice_stream,</span><br><span> .msc_assigned_cic = req->msc_assigned_cic,</span><br><span> .re_use_mgw_endpoint_from_lchan = conn->lchan,</span><br><span style="color: hsl(120, 100%, 40%);">+ .ta = conn->lchan->last_ta,</span><br><span style="color: hsl(120, 100%, 40%);">+ .ta_known = true,</span><br><span> };</span><br><span> lchan_activate(conn->assignment.new_lchan, &info);</span><br><span> }</span><br><span>diff --git a/src/osmo-bsc/handover_fsm.c b/src/osmo-bsc/handover_fsm.c</span><br><span>index 573f249..8747b80 100644</span><br><span>--- a/src/osmo-bsc/handover_fsm.c</span><br><span>+++ b/src/osmo-bsc/handover_fsm.c</span><br><span>@@ -408,6 +408,13 @@</span><br><span> .s15_s0 = conn->lchan->activate.info.s15_s0,</span><br><span> };</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+ /* For intra-cell handover, we know the accurate Timing Advance from the previous lchan. For inter-cell</span><br><span style="color: hsl(120, 100%, 40%);">+ * handover, no Timing Advance for the new cell is known, so leave it unset. */</span><br><span style="color: hsl(120, 100%, 40%);">+ if (ho->new_bts == bts) {</span><br><span style="color: hsl(120, 100%, 40%);">+ info.ta = conn->lchan->last_ta;</span><br><span style="color: hsl(120, 100%, 40%);">+ info.ta_known = true;</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> lchan_activate(ho->new_lchan, &info);</span><br><span> }</span><br><span> </span><br><span>diff --git a/src/osmo-bsc/lchan_fsm.c b/src/osmo-bsc/lchan_fsm.c</span><br><span>index 80ac1a1..d3a2d57 100644</span><br><span>--- a/src/osmo-bsc/lchan_fsm.c</span><br><span>+++ b/src/osmo-bsc/lchan_fsm.c</span><br><span>@@ -580,7 +580,6 @@</span><br><span> ms_power_dbm = ms_pwr_dbm(bts->band, old_lchan->ms_power);</span><br><span> lchan_update_ms_power_ctrl_level(lchan, ms_power_dbm >= 0 ? ms_power_dbm : bts->ms_max_power);</span><br><span> lchan->bs_power = old_lchan->bs_power;</span><br><span style="color: hsl(0, 100%, 40%);">- lchan->last_ta = old_lchan->last_ta;</span><br><span> } else {</span><br><span> lchan_update_ms_power_ctrl_level(lchan, bts->ms_max_power);</span><br><span> /* Upon last entering the UNUSED state, from lchan_reset():</span><br><span>@@ -702,8 +701,13 @@</span><br><span> lchan->encr = lchan->activate.info.encr;</span><br><span> </span><br><span> rc = rsl_tx_chan_activ(lchan, act_type, ho_ref);</span><br><span style="color: hsl(0, 100%, 40%);">- if (rc)</span><br><span style="color: hsl(120, 100%, 40%);">+ if (rc) {</span><br><span> lchan_fail_to(LCHAN_ST_UNUSED, "Tx Chan Activ failed: %s (%d)", strerror(-rc), rc);</span><br><span style="color: hsl(120, 100%, 40%);">+ return;</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ if (lchan->activate.info.ta_known)</span><br><span style="color: hsl(120, 100%, 40%);">+ lchan->last_ta = lchan->activate.info.ta;</span><br><span> }</span><br><span> </span><br><span> static void lchan_fsm_post_activ_ack(struct osmo_fsm_inst *fi);</span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/c/osmo-bsc/+/22512">change 22512</a>. 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<div style="display:none"> Gerrit-Project: osmo-bsc </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-Change-Id: I986bf93e8acd6aef7eaf63ac962480b680aa894f </div>
<div style="display:none"> Gerrit-Change-Number: 22512 </div>
<div style="display:none"> Gerrit-PatchSet: 1 </div>
<div style="display:none"> Gerrit-Owner: neels <nhofmeyr@sysmocom.de> </div>
<div style="display:none"> Gerrit-MessageType: newchange </div>