Dynamic TCH/F_PDCH does not work for CS call

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Neels Hofmeyr nhofmeyr at sysmocom.de
Tue Nov 15 09:32:59 UTC 2016


On Mon, Nov 14, 2016 at 07:59:16PM -0800, Alexander Chemeris wrote:
> The reason why people use TCH/F is because it offers higher quality than TCH/H.
> E.g. if you're using AMR, you can go only up to 7.95 mode in TCH/H
> (see https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_audio_codec).
> So just saying that TCH/H is "more efficient" is not correct. It's
> more efficient in exchange to some loss in quality.

IMHO twice the number of timeslots qualifies for saying "more efficiently
using the available timeslots" :)

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"...?

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?

~N

-- 
- Neels Hofmeyr <nhofmeyr at sysmocom.de>          http://www.sysmocom.de/
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