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Differences between revisions 11 and 12
Revision 11 as of 2009-09-18 16:40:31
Size: 3521
Comment: Update after adding UAT table to configure LCID -> drb mappings
Revision 12 as of 2009-10-13 14:12:19
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Comment: Add new pref
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 * Attempt to detect DL HARQ resends. Works by comparing last DL PDU, checking PDU contents, subframe number and timing. Default is TRUE.

Medium Access Control (MAC) for LTE

This protocol is layer 2 of the LTE air interface (connecting an LTE UE with an eNodeB).

Protocol dependencies

  • MAC-LTE runs over the PHY layer
  • A UDP framing format for MAC-LTE has been defined (described in packet-mac-lte.h, purely for use with Wireshark)

  • Can call RLC dissector SDUs (see Preference Settings below)
  • BCH, PCH and CCCH payloads can be decoded by the LTE RRC dissector
  • RAR UL Grant field can be broken down according to 3GPP TS 36.213

Example traffic

mac-lte1.png

Wireshark

The MAC-LTE dissector is fully functional. There is support for reading MAC-LTE frames from:

  • DCT2000 log files, or

  • using the UDP format defined in packet-mac-lte.h. This (BSD-licensed) program gives an example of how you might send MAC-LTE frames in this format.

MAC-LTE statistics can be viewed in a window (see Telephony | LTE MAC ...)

mac-lte-stats.png

Preference Settings

  • Warn if reserved bits are not 0. This controls whether or not expert info should be displayed if reserved bits are non-zero. Default is TRUE.
  • Number of Re-Transmits before expert warning triggered. Default is 3.
  • Attempt to decode BCH, PCH and CCCH data using LTE RRC dissector. Default is TRUE.
  • Attempt to decode details of RAR UL grant field (from breakdown in 3GPP TS 36.213, section 6.2). Default is TRUE.
  • Dissect frames that have failed CRC check. Default is FALSE.
  • Try Heuristic LTE-MAC framing over UDP. Default is FALSE.
  • Attempt to dissect LCID 1&2 as srb 1&2. Default is FALSE.

  • LCID -> DRB Mappings Table. Can configure data channel ID and RLC mode so that RLC-LTE dissector can be called for these SDUs.

  • Attempt to detect DL HARQ resends. Works by comparing last DL PDU, checking PDU contents, subframe number and timing. Default is TRUE.

Example capture file

XXX - Add a simple example capture file to the SampleCaptures page and link from here (see below). Keep this file short, it's also a good idea to gzip it to make it even smaller, as Wireshark can open gzipped files automatically.

Display Filter

A complete list of MAC-LTE display filter fields can be found in the display filter reference

  • Show only the MAC-LTE based traffic:

     mac-lte 

Capture Filter

You cannot directly filter MAC-LTE protocol frames while capturing. But, if you are using the supported UDP framing format, you may be able to filter on the UDP port you know that you are using, e.g.

  udp port 9999 

  • 3GPP TS 36.321 Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification

  • 3GPP TS 36.213 Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures

  • Example program that generates and sends frames using the supported UDP framing format

Discussion

It is recommended that you use current sources or a recent automated build for this dissector - the 1.2 branch is not up-to-date.

MAC-LTE (last edited 2015-11-26 14:50:17 by PascalQuantin)