SDCCH

[Alex_R]

Dear All,
What is the difference between SDCCH/8 and SDCCH/4

[Mdaf]

Dear All,
What is the difference between SDCCH/8 and SDCCH/4
4 is used in case of combined BCCH i.e SDCCH is being used in TS0 for the BCCH (101 multi frame), while 8 is being used by replacing TCH and the BCCH has only, BCH,CCCH.
4 is used in rural site where you have low number of TRXs and you don't want to replace TCHs by SDCCH.

[juancru1974]

The number after the / is for the amount of SDCCH sub-channels you have in that specific RTSL configuration (you will see this for SACCH too).
So the basic difference between SDCCH/8 and SDCCH/4 is that you will have 8 or 4 SDCCH sub-channels in that RTSL.

As Mdaf says, you will have SDCCH/4 in any of the combined BCCH channel types (actually 2):

1. MBCCHC = FCCH+SCH+BCCH+CCCH+SDCCH/4+SACCH/C4 (TCH type 5 for NSN)
2. MBCCB = FCCH+SCH+BCCH+CCCH+SDCCH/4+SACCH/C4+CBCH (TCH type 7 for NSN)

and you will have SDCCH/8+SACCH/C8 in any fixed SDCCH channel (TCH type 3 for NSN).

Another SDCCH configuration is SDCCB (TCH type 8 for NSN) with SDCCH/8+SACCH/C8+CBCH

In sites with low traffic (and a small number of TRXs) you con use combined BCCH, to avoid wasting RTSLs for signalling.
In high capacity sites you can use non-combined BCCH with combined SDCCH (plus Dynamic SDCCH allocation).

So, the number after the bar, for any channel will give you the number of sub-channels available.