From d3e4cbda2af3d6944031127d674ee2d5ce7ae3ea Mon Sep 17 00:00:00 2001 From: Harald Welte Date: Tue, 2 Jul 2019 14:06:15 +0800 Subject: osmodevcon2019-lte: add html rendering --- .../osmodevcon2019-osmocom_and_lte.html | 4148 ++++++++++++++++++++ 1 file changed, 4148 insertions(+) create mode 100644 2019/osmodevcon2019-osmocom_and_lte/osmodevcon2019-osmocom_and_lte.html diff --git a/2019/osmodevcon2019-osmocom_and_lte/osmodevcon2019-osmocom_and_lte.html b/2019/osmodevcon2019-osmocom_and_lte/osmodevcon2019-osmocom_and_lte.html new file mode 100644 index 0000000..0d71db4 --- /dev/null +++ b/2019/osmodevcon2019-osmocom_and_lte/osmodevcon2019-osmocom_and_lte.html @@ -0,0 +1,4148 @@ + + + + +Osmocom and LTE + + + + + + + + +
+

Osmocom and LTE

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+
    +
  • + +most of Osmocom CNI is written by paid developers these days + +
    • +
  • + +developments mostly determined by customer requirements + +
    • +
  • + +sysmocom isn’t facing any significnat LTE requirements for years + +
    • +
  • + +Result: No native LTE support in any Osmocom components + +
    • +
  • + +However: we do have small LTE related bits + +
      +
    • + +SI2quater for broadcasting eUTRAN neighbors over GSM + +
      • +
    • + +SGs interface for 2G/3G side of CSFB and for SMS-over-SGs + +
      • +
    +
    • +
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Irrespective of Osmocom…

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What do we need to run a combined 2G/4G network?

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    +
  1. + +shared subscriber database (HLR + HSS) + +
    2. +
  2. + +advertisement of respective neighbor cells + +
    3. +
  3. + +shared PS tunnel endpoint (GGSN + P-GW) + +
    4. +
+

optionally:

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    +
  • + +SGs interface in MME and MSC for CSGB + SMS-over-SGs + +
    • +
  • + +Inter-RAT PS handover + +
    • +
  • + +SRVCC (Single Radio Voice Call Continuity) + +
    • +
+
+
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+

Shared Subscriber Database

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+
    +
  • + +Required mainly for Authentication + +
    • +
  • + +poor man’s hack: Simply install same IMSI/Key material in both HLR and HSS + +
      +
    • + +will result in auth re-sync on every authentication due to non-synchronized SEQ/SQN of UMTS AKA + +
      • +
    +
    • +
  • + +proper solution: + +
      +
    • + +Single HLR with both GSUP and DIAMETER, or + +
      • +
    • + +DIAMETER-to-GSUP translator (to make LTE use OsmoHLR), or + +
      • +
    • + +GSUP-to-DIAMETER translator (to make OsmoMSC/SGSN use HSS) + +
      • +
    +
    • +
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Advertisement of neighbor cells

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+
    +
  • + +GSM must advertise eUTRAN neighbors + +
      +
    • + +we have SI2quater support in osmo-bts + +
      • +
    • + +TEMS phones show proper/valid decode + +
      • +
    +
    • +
  • + +LTE must advertise GSM neighbors + +
      +
    • + +no "OML" for S1-AP + +
      • +
    • + +configuration mechanism is vendor-proprietary + +
      • +
    +
    • +
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Shared PS tunnel endpoint

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+
    +
  • + +if the MS/eUE moves from GPRS to LTE, it wants to keep PDP/PDN contexts + +
    • +
  • + +solution: implementing P-GW and GGSN functionality in one element + +
      +
    • + +ergw might be able to do that (untested, complex) + +
      • +
    • + +OsmoGGSN doesn’t speak GTPv2C (required for P-GW) + +
      • +
    • + +nextepc P-GW doesn’t speak GTPv1C (required for GGSN) + +
      • +
    +
    • +
+

Solution:

+
    +
  • + +play with ergw, or + +
    • +
  • + +adopt nextepc GTPv2C code generator to use msgb/libosmo* and add GTPv2C to OsmoGGSN + +
    • +
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SGs interface

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    +
  • + +Osmocom already implements full SGs interface + +
    • +
  • + +Interaction with MME on LTE side needs only interop testing + +
    • +
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Inter-RAT PS handover

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+
    +
  • + +inter-RAT HO offers seamless migration between GERAN + eUTRAN + +
    • +
  • + +uses S3 interface between MME and SGSN (GTPv2C based) + +
    • +
  • + +uses S4 interface between S-GW and SGSN (GTPv2C based) + +
    • +
  • + +tbh, I don’t know the details here. + +
    • +
  • + +any help appreciated + +
    • +
  • + +https://www.tech-invite.com/3m23/toc/tinv-3gpp-23-401_zh.html + +
    • +
  • + +probably a long way for Osmocom to support it, given that we don’t really do any inter-SGSN HO even inside a single RAT. + +
    • +
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Conclusions

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The logical steps to improve our LTE interworking are:

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    +
  1. + +split HLR/HSS and split GGSN/P-GW (today) + +
    2. +
  2. + +GSUP-to-DIAMETER translator for shared HLR/HSS + +
    3. +
  3. + +shared GGSN/P-GW for + +
    4. +
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EOF

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