SDCCH/4 and SDCCH/8

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jagz - 11 May 2006 06:49 GMT

Hi,
What is the basic difference between these two classes of logical
channels? Is there any advantage of having them seperately?

Please do help.

Thanks in advance.

--
Jagadeesh

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krg - 11 May 2006 10:21 GMT

Hi,
sdcch/4 is when sdcch is combined with the bcch channel, thus
the bcch and sdcch remain active for almost half of the time in a
multiframe. this all happens in TS 0. but if you define sdcch/8, sdcch
takes up an entire TCH and keeps trasmitting on that[alongwith SACCH].
now which TCH it is to occupy, can be defined by you, nothing usual
here. you can refer to Gunnar Heine's GSM Networks:Protocols,
Terminology & Implementation.

Care & Take Care,

> Hi,
> What is the basic difference between these two classes of logical
[quoted text clipped - 6 lines]
> --
> Jagadeesh

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jagz - 11 May 2006 11:45 GMT

Hi,
Thanks for the reply. But control related signalling during TCH is
done via FACCH and SACCH right? So, if I am getting you right, SDCCH/8
will use the whole of TCH transmission slot on its behalf. Is it?
Making it similar to a BCCH+TCH combination where TS0 is used for BCCH
always in a TCH frame!

Please do help!!

Thanks in advance.

--
Jagadeesh

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Antti - 11 May 2006 16:59 GMT

> Hi,
> Thanks for the reply. But control related signalling during TCH is
[quoted text clipped - 9 lines]
> --
> Jagadeesh

Hi, on SDCCH channel uses 1/8th of a single timeslot. The terms SDCCH/8
and SDCCH/4 just describe different configurations (as explained already
earlier, SDCCH/4 means the case where SDCCH is combined with BCCH/CCCH
in timeslot 0 ; in this case, half of the timeslot is reserved for
BCCH/CCCH and on the other half timeslot, 4 SDCCH channels are allocated
; SDCCH/8 means a full timeslot is allocated for SDCCH, and in this case
it can accomodate 8 SDCCH channels).

There is no FACCH when SDCCH is used (SACCH does exist, though). When a
connection in TCH is used (such as speech call or CS data), FACCH is
just a logical channel, using the allocated TCH for sending signalling
messages).

In case this didn't make it clear enough, please take a look at 3GPP TS
05.02 (http://www.3gpp.org/ftp/Specs/latest/R1999/05_series/0502-8b0.zip).

I hope this clarifies the issue.

Regards,
Antti

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