Dynamic TCH/F_PDCH does not work for CS call

[Harald Welte]

On Tue, Nov 15, 2016 at 10:32:59AM +0100, Neels Hofmeyr wrote:
> But thanks for this clarification. My impression so far was that AMR on
> TCH/H has fair enough quality that the voice call experience isn't
> noticeably different to TCH/F and "everyone is using it anyways"...?

this is true. the concern is primarily about handsets too old to support
AMR, so they would only be able to do HRv1.  And that is really crappy.
So on such handsets, you typically try to fall back to TCH/F.

At least whenever I did traces here in Berlin with German operators, it
was pretty standard that AMR/HR was used at all time [with phones that
support it], irrespective on which Operator.

> Also how do "people use" TCH/F? Is it a choice the MS user is able to
> make? Or is this always a choice on the CN side?

please see the various discussions and tickets on codec selection.

* the MS reports its codec capability
* the BTS has a codec capability
* the BSC and MSC/MGW might have codec capabilities
* there is operator policy involved

so you need to find the common codec sub-set accross all components in
the path, and then take operator policy into consideration, as well as
current channel load in the cell, etc.

-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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