Feature #3714
open
implement Internal Handover With MSC Support
Added by neels over 5 years ago.
Updated about 3 years ago.
Description
After we have implemented #3645, I have now encountered 3GPP TS 23.009 6.3.1 "General Description of Internal Handover with MSC Support":
If the A-Interface User Plane is carried over IP (or shall be handed over to IP) and one or more of the A-Interface User
Plane parameters need to be modified, for example the Codec Type, or the Codec Configuration (BSS determines that
no compatible Codec Type or Codec Configuration exists for the target cell), or the IP Transport Layer Address, or the
UDP Port, or the CSData Redundancy Level, or the A-Interface Type itself (e.g. from TDM to IP or vice versa), then a
"BSS Internal Handover with MSC support" shall be performed (see 3GPP TS 48.008 [5] subclause 3.1.5c.1).
So if we want to change the codec, we should actually not only tell the MSC about it in the end, but involve it from the start:
Files
- Related to Bug #3645: internal handover: when handover changes the speech codec, it should notify the MSC with BSSMAP Handover Performed added
3GPP TS 23.009 6 "General description of the procedures for intra - MSC handovers":
An "Internal Handover" takes place between channels on a cell or cells controlled by a single BSS, without reference to
the MSC, although the MSC maybe informed of its occurrence after completion. [...]
i.e. that's the case covered by #3645.
A "BSS Internal Handover with MSC Support" shall only be used if AoIP is supported by both MSC and BSS and if the
A-Interface User Plane has to be modified.
I read that such that if we want to change the codec (and we don't transcode to the previously negotiated codec), we need to change the A-interface User Plane so that the MSC knows a new codec is happening, and thus a codec change requires the "With MSC Support" part.
On Tue, Nov 27, 2018 at 11:54:46PM +0000, neels [REDMINE] wrote:
I read that such that if we want to change the codec (and we don't transcode to the previously negotiated codec), we need to change the A-interface User Plane so that the MSC knows a new codec is happening, and thus a codec change requires the "With MSC Support" part.
as indicated in the other ticket: Why even bother? I was very well aware of this, but why
are we attemtping to do a hand-over to a new channel with a different codec in the first place?
Let's keep it simple, unless somebody really needs that feature, please.
- Priority changed from Normal to Low
I think this may be back on the agenda in the context of some HO related work neels is doing for a sysmocom customer in recent weeks?
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