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Feature #1572

Circuit Switched Data (CSD) Support

Added by laforge over 4 years ago. Updated 7 months ago.

Status:
New
Priority:
Low
Assignee:
-
Category:
osmo-bts-trx
Target version:
-
Start date:
02/23/2016
Due date:
% Done:

0%

Spec Reference:
Tags:
CSD

Description

Not implemented, but also probably limited interest, except
  • GSM-R heavily uses CSD and might be an intresting niche market
  • some end-to-end encrypted mobile phones also use CSD

This will need the corresponding support in the PHY, of course.


Checklist

  • TS 45.003 coding / interleaving
  • RSL CHAN ACT for CT
  • RA1'/RA1 rate adaptation from/to 64k
  • RFC4040 clear-mode RTP payload

Related issues

Related to OsmoBSC - Feature #4393: Circuit Switched Data (CSD) SupportNew02/13/2020

Related to OsmoMSC - Feature #4394: Circuit Switched Data (CSD) SupportNew02/13/2020

Related to OsmoMGW - Feature #4395: Circuit Switched Data (CSD) SupportNew02/13/2020

Related to OsmocomBB - Feature #4396: Circuit Switched Data (CSD) SupportNew02/13/2020

History

#1 Updated by laforge 7 months ago

  • Checklist item TS 45.003 coding / interleaving added
  • Checklist item RSL CHAN ACT for CT added
  • Checklist item RA1'/RA1 rate adaptation from/to 64k added
  • Checklist item RFC4040 clear-mode RTP payload added
The support in OsmoBTS would entail:
  • implementation of the 45.003 coding / interleaving for the TCH/F9.6, TCH/F4.8, TCH/F2.4, ... channel types
  • activating the above coding/interleaving based on RSL CHAN ACT for such channels
  • performing the RA1'/RA1 rate adaptation function to get from/to 64kbps stream
  • packetize 64k stream as raw "CLEARMODE/8000" RTP as per RFC4040; 160 bytes per RTP packet; RTP payload type 120
Some relevant specs:
  • 3GPP TS 48.004 E1/T1 based L1
  • 3GPP TS 48.020 Rate Adaptation on BSS-MSC interface (RA1)
  • 3GPP TS 48.103 User plane transport / Section 5.6
  • 3GPP TS 44.021 RA1' adaptation function on radio interface
  • 3GPP TS 24.022 RLP for CS bearer and teleservices
  • 3GPP TS 43.010 PLMN connection types
  • ITU-T V.110 RA0 for async->sync

The coding/interleaving part has been started in the laforge/csd branch of libosmocore.git

#2 Updated by laforge 7 months ago

  • Tags set to CSD
  • Subject changed from Circuit Switched Data Support to Circuit Switched Data (CSD) Support

IMHO, it only makes sense to support the transparent mode (no RLP protocol).

#3 Updated by laforge 7 months ago

  • Related to Feature #4393: Circuit Switched Data (CSD) Support added

#4 Updated by laforge 7 months ago

  • Related to Feature #4394: Circuit Switched Data (CSD) Support added

#5 Updated by laforge 7 months ago

  • Related to Feature #4395: Circuit Switched Data (CSD) Support added

#6 Updated by laforge 7 months ago

  • Category set to osmo-bts-trx

Some more notes:

  • Racal 6103 supports termination of data + fax CSD calls (external PC can be connected on RS232). This could be used to establish air-interface (burst level) captures using burst_ind. That in turn could generate test data for the 45.003 de-interleave/decoder part.
  • support in OsmoBTS would be restricted to osmo-bts-trx, as to our current knowledge none of the proprietary PHYs (osmo-bts-{sysmo,lc15,oc2g,octphy} support CSD channel coding

#7 Updated by laforge 7 months ago

  • Related to Feature #4396: Circuit Switched Data (CSD) Support added

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