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Bug #2406

CS-PAGING not implemented

Added by laforge over 3 years ago. Updated 4 months ago.

Status:
Resolved
Priority:
Low
Assignee:
Target version:
-
Start date:
07/29/2017
Due date:
% Done:

100%

Spec Reference:

Description

BSSGP PAGING CS is used to deliver a circuit-switched paging request to a MS while it is engaged in transferring GPRS data. The related paging request is not sent via Broadcast/PCH, but via PACCH to that MS.


Related issues

Related to OsmoPCU - Bug #3927: Missing PCU_Tests.ttcn Paging testsResolved04/15/2019

Related to OsmoPCU - Bug #2403: PS-PAGING and CS-PAGING not implemented on PTP-BVCIResolved07/29/2017

Related to OsmoBSC - Feature #4485: osmo-bsc: We should be announcing NMO I instead of NMO IIRejected04/06/2020

History

#1 Updated by laforge about 3 years ago

  • Priority changed from Normal to Low

#2 Updated by laforge about 2 years ago

#3 Updated by laforge about 2 years ago

  • Assignee changed from laforge to msuraev

#4 Updated by laforge over 1 year ago

  • Assignee changed from msuraev to lynxis

#5 Updated by laforge about 1 year ago

  • Assignee changed from lynxis to osmith

Please note this is mostly relevant with other core networks than osmocom. In osmcoom, the MSC pages the BSC and the BSC pages the BTS, which then passes it to the PCU for transmission. This works.

However, when using a non-osmocom core with Gs interface between MSC and SGSN for paging coordination, the SGSN will likely send us CS-PAGING and we have to implement it in the PCU for interoperability.

#6 Updated by osmith about 1 year ago

  • Status changed from New to In Progress

#7 Updated by pespin 11 months ago

  • Related to Bug #3927: Missing PCU_Tests.ttcn Paging tests added

#8 Updated by pespin 11 months ago

While developing some TTCN3 PCU tests (#3927) I also tried to understand better this scenario. Some references I could fine:
TS 23.060 sec 6.3.3 CS Paging (A/Gb mode)
TS 48-008 sec 3.1.10 Paging
TS 24.008 sec 4.7.9 Paging procedure
TS 44.018 sec 3.2.2.2 paging
TS 48.018 sec 5.2.4, 7.1
PAGING-PS: TS 48.018 10.3.1
PAGING-CS: TS 48.018 10.3.2

Specially important are the last 2, where the SGSN->PCU PDUs requesting the paging are described.

As far as I understand, we already implement paging (not sure if correctly) in the SGSN: it uses libosmocore's bssgp_tx_paging().
In libosmocore, we also have a symbol which afaiu we should use in osmo-pcu and which I think is not yet use by anybody:

gprs_bssgp_bss.c:
/* Parse a single GMM-PAGING.req to a given NSEI/NS-BVCI */
int bssgp_rx_paging(struct bssgp_paging_info *pinfo,
            struct msgb *msg)

It seems PS-PAGING is already supported by osmo-pcu, while CS-PAGING is not:

    case BSSGP_PDUT_PAGING_PS:
        gprs_bssgp_pcu_rx_paging_ps(msg, tp);
...
    case BSSGP_PDUT_PAGING_CS:
    case BSSGP_PDUT_FLUSH_LL:
    case BSSGP_PDUT_SGSN_INVOKE_TRACE:
        LOGP(DBSSGP, LOGL_INFO, "Rx BSSGP BVCI=%d (SIGN) PDU type %s not implemented\n",
             bvci, bssgp_pdu_str(pdu_type));
        break;

If I understand correctly, what's missing here is to do something similar to what we do when PCU receives a struct gsm_pcu_if_pag_req with type PCU_IF_MSG_PAG_REQ on pcu_rx_pag_req() from BTS. That path is already covered by PCU_Tests_RAW.TC_paging_cs_from_bts, where a DL_PACKET_PAGING_REQUEST is sent over PACCH. The only difference in this scenario is that the PAGING_REQUEST must be retriggered on reception of the CS-PAGING message from SGSN in gprs_bssgp_pcu.cpp.

So mainly calling libosmocore's bssgp_rx_paging() and then calling similar to what pcu_rx_pag_req() does:

    return BTS::main_bts()->add_paging(pag_req->chan_needed,
                        pag_req->identity_lv);

#9 Updated by pespin 11 months ago

  • Related to Bug #2403: PS-PAGING and CS-PAGING not implemented on PTP-BVCI added

#10 Updated by pespin 11 months ago

  • Status changed from In Progress to Feedback
  • % Done changed from 0 to 90

Done so far:
remote: https://gerrit.osmocom.org/c/osmo-pcu/+/16536 Allow Gb PAGING-PS without P-TMSI
remote: https://gerrit.osmocom.org/c/osmo-pcu/+/16537 Support Gb PAGING-CS

Can be tested with TTCN3 PCU test TC_paging_cs_from_sgsn.

#11 Updated by pespin 10 months ago

  • Assignee changed from osmith to pespin

Testing is done here:
https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/16528 pcu: Introduce tests for CS and PS paging from SGSN/Gb

#12 Updated by pespin 9 months ago

  • Status changed from Feedback to Resolved
  • % Done changed from 90 to 100

#13 Updated by fixeria 7 months ago

  • Status changed from Resolved to Feedback

BTW, there is BSS_PAGING_COORDINATION in SI13 / GPRS Cell Options IE (see 3GPP TS 44.060, table 12.24.2):

This field indicates the network support of CS paging co-ordination in packet transfer mode
during network mode of operation II and III. [...] It is coded as follows:

0    The cell does not support Circuit-Switched paging coordination
1    The cell supports Circuit-Switched paging coordination

OsmoBSC currently hard-codes this option to 0. Should we make it configurable?

As per section 6.1.3 "Paging initiation using PACCH", "if such indication is received, a mobile station in packet transfer mode shall expect the paging messages to be received on the PACCH". So does it mean that otherwise (if BSS_PAGING_COORDINATION is set to 0) the MS would ignore our paging messages?

#14 Updated by fixeria 7 months ago

  • Related to Feature #4485: osmo-bsc: We should be announcing NMO I instead of NMO II added

#15 Updated by laforge 4 months ago

  • Status changed from Feedback to In Progress
  • Assignee changed from pespin to laforge

fixeria wrote:

BTW, there is BSS_PAGING_COORDINATION in SI13 / GPRS Cell Options IE (see 3GPP TS 44.060, table 12.24.2):

nice catch. I'm adding related code in https://gerrit.osmocom.org/c/libosmocore/+/18934 and https://gerrit.osmocom.org/c/osmo-bsc/+/18936

#16 Updated by laforge 4 months ago

  • Status changed from In Progress to Resolved

laforge wrote:

fixeria wrote:

BTW, there is BSS_PAGING_COORDINATION in SI13 / GPRS Cell Options IE (see 3GPP TS 44.060, table 12.24.2):

nice catch. I'm adding related code in https://gerrit.osmocom.org/c/libosmocore/+/18934 and https://gerrit.osmocom.org/c/osmo-bsc/+/18936

patch merged.

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