Feature #3714
implement Internal Handover With MSC Support
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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:
Related issues
History
#2 Updated by neels 6 months ago
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.
#3 Updated by laforge 6 months ago
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.
