[srslte-users] Sending RRC Connection Reconfiguration message

Paul Sutton paul at softwareradiosystems.com
Wed Aug 2 11:43:50 UTC 2017


Hi Kewin,

Running your message through an ASN analyzer, I get the attached RRC ASN
decode.
Looking at this, it seems that "No. of ReportConfigToAddModList" is
incorrect which suggests a bug in the ASN packing routines. Can you
compare the decode with your intended LIBLTE_RRC_MEAS_CONFIG_STRUCT to
check?

Thanks,
Paul

On 02/08/17 12:34, Kewin Rausch wrote:
> Hi everyone,
>
> I'm trying to send an RRC Connection Reconfiguration message using
> srsenb to a connected UE, but for some reason I don't see the trace of
> such message incoming at the receiver. 
> The message is about RRC Measurements, which is a feature already
> included by liblte ASN1 parser.
> The receiver is a common Nexus 5, rooted to intercept and show RRC
> messages as they flow from the internal modem.
>
> The message is sent using: send_dl_dcch(&dl_dcch_msg).
> This procedure is present inside rrc::ue nested class, which manages
> UEs as seen by RRC perspective. The procedure performs like the following:
>
> void
> rrc::ue::send_connection_reconf_meas(LIBLTE_RRC_MEAS_CONFIG_STRUCT * msg)
> {
>   LIBLTE_RRC_CONNECTION_RECONFIGURATION_STRUCT * conn_reconf = 0;
>   LIBLTE_RRC_MEAS_CONFIG_STRUCT * mconf = 0;
>
>   LIBLTE_RRC_DL_DCCH_MSG_STRUCT dl_dcch_msg;
>
>   memset(&dl_dcch_msg, 0, sizeof(LIBLTE_RRC_DL_DCCH_MSG_STRUCT));
>
>   dl_dcch_msg.msg_type = LIBLTE_RRC_DL_DCCH_MSG_TYPE_RRC_CON_RECONFIG;
>   dl_dcch_msg.msg.rrc_con_reconfig.rrc_transaction_id =
> (transaction_id++)%4;
>
>   conn_reconf = &dl_dcch_msg.msg.rrc_con_reconfig;
>
>   conn_reconf->N_ded_info_nas        = 0;
>   conn_reconf->rr_cnfg_ded_present   = false;
>   conn_reconf->mob_ctrl_info_present = false;
>   conn_reconf->sec_cnfg_ho_present   = false;
>
>   conn_reconf->meas_cnfg_present     = true;
>
>   mconf = &conn_reconf->meas_cnfg;
>   memcpy(mconf, msg, sizeof(LIBLTE_RRC_MEAS_CONFIG_STRUCT));
>
>   parent->rrc_log->info("Sending RRCMeasConfiguration for
> RNTI:0x%x\n", rnti);
>
>   send_dl_dcch(&dl_dcch_msg);
> }
>
> The last memcpy operation copies the given meas_config inside the
> message that has to be sent.
> Trace of the operation can be seen in the log file of the eNB itself:
>
> 06:10:07.662581 [RRC ] Info    Sending RRC Measurement Configuration
> 06:10:07.662596 [RRC ] Info    SRB1 - rnti=0x46, Sending: RRC
> Connection Reconfiguration
>              0000: 20 10 15 00 00 00 1a 2c a3 c0 02 d2 70 00 00
> 06:10:07.662607 [PDCP] Info    TX SRB1 SDU, do_security = true
>              0000: 20 10 15 00 00 00 1a 2c a3 c0 02 d2 70 00 00
> 06:10:07.662709 [RLC ] Info    SRB1 Tx SDU
>              0000: 05 20 10 15 00 00 00 1a 2c a3 c0 02 d2 70 00 00
>              0010: e9 d9 0d 4a
> 06:10:07.662716 [RLC ] Info    Buffer state: rnti=0x46, lcid=1,
> tx_queue=22
> 06:10:07.663103 [MAC ] Info    [07871] SCHED: DL tx rnti=0x46, pid=0,
> mask=0x1800, dci=1,8, n_rtx=0, tbs=22, buffer=0
> 06:10:07.663120 [RLC ] Info    SRB1 PDU scheduled for tx. SN: 5
> 06:10:07.663148 [PHY1] Info    [07871] PDCCH: DL DCI Format1
>  rnti=0x46, cce_index=8, L=2, tti_tx=7875
> 06:10:07.663158 [PHY1] Info    [07871] PDSCH: rnti=0x46, l_crb= 4,
> mask=0x1800, harq=0, tbs=22, mcs=2, rv=0, tti_tx=7875
>              0000: 01 88 05 05 20 10 15 00 00 00 1a 2c a3 c0 02 d2
>              0010: 70 00 00 e9 d9 0d
> 06:10:07.664124 [MAC ] Info    [07872] SCHED: DL tx rnti=0x46, pid=1,
> mask=0x1800, dci=1,8, n_rtx=0, tbs=11, buffer=0
> 06:10:07.664137 [RLC ] Info    SRB1 Complete SDU scheduled for tx.
> Stack latency: 0 us
>
> No errors are visible from the log file.
> Now I have to find where the error is, and the available options here
> can be:
>
>   * The message is never sent by the eNB.
>   * The ASN1 message is formatted in the wrong way, the UE receives it
>     but discard and don't let me see it.
>
> The question then is:
>
> - Is that log trace enough to consider the message as sent to the UE?
> If yes, then it means that I have to concentrate on how LIBLTE is
> formatting the message, because there can be some problem there.
>
> Thank you,
> Kewin R.
>
>
> _______________________________________________
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> srslte-users at lists.softwareradiosystems.com
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-- 
________________________________________________________________
Paul Sutton Ph.D.

Software Radio Systems (SRS)
http://www.softwareradiosystems.com

+353-87-9813473 | paul at softwareradiosystems.com

PGP Key ID: 3B4A5292
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