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Feature #5198

Support GPRS on Ericsson RBS

Added by pespin 13 days ago. Updated 11 days ago.

Status:
New
Priority:
Normal
Assignee:
-
Start date:
07/13/2021
Due date:
% Done:

0%

Spec Reference:


Checklist

  • libosmo-abis: encode and decode GPRS/EGPRS TRAU frames in E1 slots/subslots
  • libosmo-abis: SYNC / timing loop for GPRS/EGPRS TRAU frames
  • osmo-bsc: activation of PDCH via OM2000/RSL from BSC side
  • osmo-pcu support for opening e1 timeslots [like bsc, mgw]
  • osmo-pcu using GPRS/EGPRS TRAU frame decoders from above
  • osmo-pcu / osmo-bsc pcu socket interaction (paging, ...)
  • test everything end-to-end with DUG20

History

#1 Updated by laforge 11 days ago

  • Checklist item libosmo-abis: encode and decode GPRS/EGPRS TRAU frames in E1 slots/subslots added
  • Checklist item libosmo-abis: SYNC / timing loop for GPRS/EGPRS TRAU frames added
  • Checklist item osmo-bsc: activation of PDCH via OM2000/RSL from BSC side added
  • Checklist item osmo-pcu support for opening e1 timeslots [like bsc, mgw] added
  • Checklist item osmo-pcu using GPRS/EGPRS TRAU frame decoders from above added
  • Checklist item osmo-pcu / osmo-bsc pcu socket interaction (paging, ...) added
  • Checklist item test everything end-to-end with DUG20 added

a more easily digestible description:

  • GPRS/EGPRS is fully supported within Osmocom when using non-Ericsson BTS
  • E1 based BTS have the CCU in the BTS and the PCU co-located at the BSC
  • RLC/MAC blocks are transferred over E1 sub-slots (16k, GPRS) or slots (64k, EDGE)
  • Ericsson supports three different data formats for back-haul:
    • classic "channelized" Abis with 64k/16k slots/sub-slots as we implement it in osmo-bsc and osmo-mgw
    • PacketAbis over TDM: E1 line is unchannelized (31 concatenated timeslots) with HDLC inside, that ~ 2Mbps superchannel is then used with some LAPD-style protocol to transmit OM2000, RSL, voice frames and GPRS RLC/MAC blocks
    • PacketAbis over IP: Same as above but encapsulated in a slightly modified dialect of L2TP. This is what the Ericsson SIU-02 or TCU speak; they convert from PacketAbis/TDM to PacketAbis/IP
  • Osmocom has implemented GPRS-only support for PacketAbis/IP in osmo-el2tpd, tested with RBS2111 some years ago. As part of that, osmo-bsc received a PCU socket interface

For this ticket, we want to support "classic, channelized E1", so the current CS setup consisting of (DUG20, icE1usb, osmo-e1d, osmo-bsc, osmo-mgw) can be extended with PS services by osmo-pcu. I'm adding chekc-list items.

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