when are SDCCH/4 and SDCCH/8 implemented ?

[coursekec]

Under which conditions are SDCCH/4 and SDCCH/8 implemented ? what are the advantages and disadvantages in both the cases ?

[RF engineer]

Under which conditions are SDCCH/4 and SDCCH/8 implemented ? what are the advantages and disadvantages in both the cases ?

There two type of common control channel configuration which you see it in cell paraMeter in your OMC which call combined-BCCH in this type you have to configure SDCCH/4 or if you configure a cell with non combinedBCCH you will have to use SDCCH/8 advantage of SDCCH/4 is that if you have TRX configuration 1or 2 TRX you can use combined bcch and diadvantage is more than advantage because you will have few resource for location update and paging.

[coursekec]

thanks for the reply..but i have one more confusion..how many subscribers can get access to SDCCH under SDCCH/4 and under SDCCH/8 configuration..?

[RF engineer]

thanks for the reply..but i have one more confusion..how many subscribers can get access to SDCCH under SDCCH/4 and under SDCCH/8 configuration..?

just simply use erlang B table and take GOS 0.5 % and check for 8 and 4 it gives you Erlang and take 0.025 mERl/sub it gives you number of sub i leave the calculation for you.
BR
RF

[coursekec]

thanks RF engineer,

I have calculated the no of subscribers supported by SDCCH/4 in the following fashion

no of circuits (N)= 4
Probability of loss (blocking probability) =0.5% or 0.005, from erlang table total offered traffic (erlangs) = 0.702, erlangs per subscriber = 0.025 Erl/sub,
Total subscriber supported = 0.702/ 0.025 = 28.08
Is this correct..??

[RF engineer]

thanks RF engineer,

I have calculated the no of subscribers supported by SDCCH/4 in the following fashion

no of circuits (N)= 4
Probability of loss (blocking probability) =0.5% or 0.005, from erlang table total offered traffic (erlangs) = 0.702, erlangs per subscriber = 0.025 Erl/sub,
Total subscriber supported = 0.702/ 0.025 = 28.08
Is this correct..??

it is Correct

[s52d]

SImple designing rule:
1. In big location area you have to use SDCCH/8 only in order to have paging capacity.
2. in smaller LA you do:
4 SDCCH for one TRX cell
12 SDCCH for two to four TRX cells
20 SDCCH for bigger cells.

Observe statistics: if needed, increase. If smaller number can do, decrease.
If you use features to lower SDCCH congestion like direct assignment to TCH
or dynamic reconfiguration of TCH to SDCCH/8, then some congestion might be allowed.

I've seen 4 TRX cells working fine with 4 SDCCH and 31 TCH.

As ratio of LAU/SMS/calls is different, not to mention impact of national roamning,
calculations are just initial guess.


BR

[hakimgsm]

Hi
The following doc is very useful to known more the SDCCH .
Best regards.

SImple designing rule:
1. In big location area you have to use SDCCH/8 only in order to have paging capacity.
2. in smaller LA you do:
4 SDCCH for one TRX cell
12 SDCCH for two to four TRX cells
20 SDCCH for bigger cells.

Observe statistics: if needed, increase. If smaller number can do, decrease.
If you use features to lower SDCCH congestion like direct assignment to TCH
or dynamic reconfiguration of TCH to SDCCH/8, then some congestion might be allowed.

I've seen 4 TRX cells working fine with 4 SDCCH and 31 TCH.

As ratio of LAU/SMS/calls is different, not to mention impact of national roamning,
calculations are just initial guess.


BR

[jitendra1020]

Hi,
share password

[hakimgsm]

Password : mobilis

Good luck