Change in ...osmocom-bb[master]: trxcon/scheduler: fix handling of PTCCH logical channel

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/.

fixeria gerrit-no-reply at lists.osmocom.org
Fri Oct 4 20:18:40 UTC 2019


fixeria has submitted this change and it was merged. ( https://gerrit.osmocom.org/c/osmocom-bb/+/15626 )

Change subject: trxcon/scheduler: fix handling of PTCCH logical channel
......................................................................

trxcon/scheduler: fix handling of PTCCH logical channel

According to 3GPP TS 45.010, section 5.6.2, for packet-switched
channels the BTS shall monitor the delay of the Access Bursts
sent by the MS on PTCCH and respond with timing advance values
for all MS performing the procedure on that PDCH.

According to 3GPP TS 45.002, section 3.3.4.2, PTCCH (Packet Timing
advance control channel) is a packet dedicated channel, that is
used for continuous Timing Advance control (mentioned above).

There are two sub-types of that logical channel:

  - PTCCH/U (Uplink): used to transmit random Access Bursts
    to allow estimation of the Timing Advance for one MS in
    packet transfer mode.

  - PTCCH/D (Downlink): used by the network to transmit
    Timing Advance updates for several MS.

As per 3GPP TS 45.003, section 5.2, the coding scheme used for
PTCCH/U is the same as for PRACH as specified in subclause 5.3,
while the coding scheme used for PTCCH/D is the same as for
CS-1 as specified in subclause 5.1.1.

The way we used to handle both PTCCH/U and PTCCH/D is absolutely
wrong - it has nothing to do with xCCH coding. Instead, we need
to use rx_pdtch_fn() for Downlink and tx_rach_fn() for Uplink.

Also, since we only have a shared RSL channel number for PDCH
(Osmocom-specific RSL_CHAN_OSMO_PDCH), there should be a way
to distinguish both PDTCH and PTCCH logical channels. Let's
introduce TRX_CH_LID_PTCCH for that.

Change-Id: I2d1e9b8a66f027047f8d7bdc3f82ff9d8ebcc25e
---
M src/host/trxcon/sched_lchan_desc.c
M src/host/trxcon/sched_trx.h
2 files changed, 12 insertions(+), 3 deletions(-)

Approvals:
  Jenkins Builder: Verified
  pespin: Looks good to me, but someone else must approve
  fixeria: Looks good to me, approved



diff --git a/src/host/trxcon/sched_lchan_desc.c b/src/host/trxcon/sched_lchan_desc.c
index 5b9d676..67f770c 100644
--- a/src/host/trxcon/sched_lchan_desc.c
+++ b/src/host/trxcon/sched_lchan_desc.c
@@ -516,12 +516,17 @@
 		.name = "PTCCH", /* 3GPP TS 05.02, section 3.3.4.2 */
 		.desc = "Packet Timing advance control channel",
 		.chan_nr = RSL_CHAN_OSMO_PDCH,
+		.link_id = TRX_CH_LID_PTCCH,
 
-		/* Same as for TRXC_BCCH (xCCH), see above. */
+		/* On the Uplink, mobile stations transmit random Access Bursts
+		 * to allow estimation of the timing advance for one MS in packet
+		 * transfer mode. On Downlink, the network sends timing advance
+		 * updates for several mobile stations. The coding scheme used
+		 * for PTCCH/D messages is the same as for PDTCH CS-1. */
 		.burst_buf_size = 4 * GSM_BURST_PL_LEN,
 		.flags = TRX_CH_FLAG_PDCH,
-		.rx_fn = rx_data_fn,
-		.tx_fn = tx_data_fn,
+		.rx_fn = rx_pdtch_fn,
+		.tx_fn = tx_rach_fn,
 	},
 	[TRXC_SDCCH4_CBCH] = {
 		.name = "SDCCH/4(CBCH)", /* 3GPP TS 05.02, section 3.3.5 */
diff --git a/src/host/trxcon/sched_trx.h b/src/host/trxcon/sched_trx.h
index 6ef9ce4..0d42499 100644
--- a/src/host/trxcon/sched_trx.h
+++ b/src/host/trxcon/sched_trx.h
@@ -23,6 +23,10 @@
 #define TRX_CH_LID_DEDIC	0x00
 #define TRX_CH_LID_SACCH	0x40
 
+/* Osmocom-specific extension for PTCCH (see 3GPP TS 45.002, section 3.3.4.2).
+ * Shall be used to distinguish PTCCH and PDTCH channels on a PDCH time-slot. */
+#define TRX_CH_LID_PTCCH	0x80
+
 /* Is a channel related to PDCH (GPRS) */
 #define TRX_CH_FLAG_PDCH	(1 << 0)
 /* Should a channel be activated automatically */

-- 
To view, visit https://gerrit.osmocom.org/c/osmocom-bb/+/15626
To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings

Gerrit-Project: osmocom-bb
Gerrit-Branch: master
Gerrit-Change-Id: I2d1e9b8a66f027047f8d7bdc3f82ff9d8ebcc25e
Gerrit-Change-Number: 15626
Gerrit-PatchSet: 1
Gerrit-Owner: fixeria <axilirator at gmail.com>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: fixeria <axilirator at gmail.com>
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-Reviewer: lynxis lazus <lynxis at fe80.eu>
Gerrit-Reviewer: pespin <pespin at sysmocom.de>
Gerrit-MessageType: merged
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osmocom.org/pipermail/gerrit-log/attachments/20191004/1fd5597e/attachment.htm>


More information about the gerrit-log mailing list