- This topic has 8 replies, 1 voice, and was last updated 12 years, 6 months ago by pix.
24th August 2008 at 06:24 #53615MKTGuest
As we know that for a SDCCH/8 frame structure we have SACCH associated with it.
To do the signaling with MS when it is on active TCH we have SACCH.
What is the need of SACCH when the MS is already on signaling channel ie SDCCH?
Does the duration of SDCCH lasts for so much of time that for MEAS_REP you need SACCH?
If MEAS_REP are to be sent every 480 ms then does it means that SDCCH holding time is always more tehn 480 ms for the events like LA update, IMSI attach/detach, SMS etc?
MKT24th August 2008 at 07:04 #53616pixGuest
SACCH for the SDCCH is used in exactly the same way as for TCH. It is used to carry system information msg/pwr ctrl command in the DL, and measurement reports in the UL.
Yes, the SDCCH usually lasts longer than 0.5s. In average, it lasts 3.5s. It lasts longer for SMS, and lasts shorter for LU or IMSI detach.24th August 2008 at 07:49 #53617MKTGuest
Thanks24th August 2008 at 08:06 #53618MKTGuest
Why the UL and DL frame structure of SDCCH shows SDCCH and SACCH at different TS.
Where as in TCH it is point to point mapping.
I mean when BTS is on TCH(in DL) the MS is also on TCH(in UL).
when the BTS is on SACCH in DL the MS is on SACCH in UL.
But when the MS is on SDCCH in UL the BTS is on SACCH and vice versa. Why ???
regards24th August 2008 at 11:03 #53619pixGuest
i don’t know the reason behind this choice… sorry.25th August 2008 at 12:32 #53620telecom06Guest
First SACCH is used only on dedicated mode
SDCCH on Idle mode.
If we take sdcch/8, and if we take TS1 of the BCH frequency, then 8 SDCCH will share the same TS (dedicated Channel D0, D1, D2, D3, D4, D5, D6, D7, uplink and downlink),But we don’t have at the same time Dn uplink and Dn downlink
when BTS send for example D0 to the mobileStation m1, after 11 frame BTS will receive D0 from mobile station m1.
But during this 11 Frame the BTS receives SACCH from mobile in Dedicated mode or receives other SDDCH from other mobile in idle mode.
The question is probably why 11 Frame?
11 frames = 4.6ms*11=0.0506s25th August 2008 at 17:23 #53621pixGuest
SDCCH is used in dedicated mode only. The SDCCH is a dedicated channel 🙂25th August 2008 at 19:34 #53622telecom06Guest
oops, I wanted to say active mode,
In fact I wanted to say that SDCCH is used for mobile in Idle mode, and SACCH for mobile in Active mode (communication)
Of course SDCCH and SACCH belongs to the dedicated Control Chanels (DCCH)25th August 2008 at 20:56 #53623pixGuest
ok… it’s not really clear… 🙂
let me recap :
the sdcch provides a dedicated channel, that carries both a SDCCH and SACCH for one user.
on one timeslot, 8 users can be taken care of. It means one timeslot provides 8 SDCCH + 8 SACCH.