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Bug #6201

open

modem: signal proper MS Radio Access Capability

Added by fixeria 5 months ago. Updated 5 months ago.

Status:
New
Priority:
Normal
Assignee:
-
Category:
-
Target version:
Start date:
10/04/2023
Due date:
% Done:

0%

Resolution:
Spec Reference:
Tags:

Description

The modem app is currently sending hard-coded MS RACap to the PCU. It's hard-coded in libosmo-gprs-rlcmac:

/* 11.2.16 Packet Resource Request */
void gprs_rlcmac_enc_prepare_pkt_resource_req(RlcMacUplink_t *block,
                                              struct gprs_rlcmac_ul_tbf *ul_tbf,
                                              enum gprs_rlcmac_access_type acc_type)
{
        Packet_Resource_Request_t *req;
        struct gprs_rlcmac_entity *gre = ul_tbf->tbf.gre;

        memset(block, 0, sizeof(*block));

        req = &block->u.Packet_Resource_Request;
        req->MESSAGE_TYPE = OSMO_GPRS_RLCMAC_UL_MSGT_PACKET_RESOURCE_REQUEST;

        /* ... */

        req->ID.UnionType = 1; /* Use TLLI */
        req->ID.u.TLLI = gre->tlli; /* Use TLLI */
        req->Exist_MS_Radio_Access_capability2 = 1;

        req->MS_Radio_Access_capability2.Count_MS_RA_capability_value = 1;
        /* TODO: fill Content_t: */
        /* req->MS_Radio_Access_capability2.MS_RA_capability_value[0].Content.* */

We definitely want to send something more meaningful than all zeroes.

  • There needs to be a way (API) to "tell" libosmo-gprs-rlcmac which MS RACap to use.
  • We may also want to make some parts of the RACap configurable via the VTY.

Related issues

Related to OsmocomBB - Feature #5500: MS-Side GPRS RLC/MAC implementationResolvedpespin07/01/2022

Actions
Actions #1

Updated by fixeria 5 months ago

  • Related to Feature #5500: MS-Side GPRS RLC/MAC implementation added
Actions #2

Updated by pespin 5 months ago

Note: It's sometimes fine depending on the use/case/scenario to send no MS RA capabilities durign PKT RES REQ, see for instance #4947.

From TS 44.060 Table 11.2.16.2:

This information element is sent only during two phase access
and shall not be include by MS operating in Iu mode. Additionally, this information element shall be sent in one phase
EGPRS TBF establishment procedure if ordered by the network.

My understanding of "if ordered by the network." in the sentence "this information element shall be sent in one phase
EGPRS TBF establishment procedure if ordered by the network." is: if the MS requested 1phase access but network sent an ImmAss forcing 2 phase access (our osmo-pcu "two-phase-access" VTY command).

So in summary, I'd say:
  • as answer to SBA to do 2phase access: Add MS RA cap
  • as way to request a new TBF from an older one or
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