- This topic has 52 replies, 1 voice, and was last updated 1 week, 5 days ago by NG.
21st April 2008 at 09:12 #51903AyatGuest
dear , all
Some venders define GOS grade of service as TCH assignment failure rate (TCH assignment unsuccessful times *100/ TCH attempts)
As we know, GOS is blocking , here in my case I think the GOS is TCH congestion rate which is equal (TCH overflow*100/TCH attempts).
What is the right definition for GOS??????????? Is it TCH assignment failure or TCH congestion?????
2-Can I classify for two parts: – SDCCH GOS, and TCH GOS.
Could you help me!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Ayat21st April 2008 at 13:06 #51904pixGuest
1. the Grade Of Service is usually defined as the blocking rate, or congestion rate, so your formula is ok 🙂
2. yes, of course, you have congestion in SDCCH and/or congestion in TCH, which are usually very different, and uncorrelated !24th April 2008 at 14:19 #51905ayatGuest
many thanks for your support
really i appreaiate your help
i have more question
whats the difference between tch blocking and tch congestion?
thanks24th April 2008 at 16:10 #51906pixGuest
it is the same thing25th April 2008 at 20:22 #51907AyatGuest
Many thanks for your quick reply25th April 2008 at 21:53 #51908pixGuest
ayat, you’re welcome 🙂26th April 2008 at 19:52 #51909AyatGuest
I need your help to Convince my boss by that GOS is = TCH congestion not equal TCH assignment failure, because our vender as I mentioned in the previous mail define GOS as TCH assignment failure I need technical explanation.
Why TCH congestion not TCH assignment failure
As I know TCH congestion leads to TCH assignment failure not Vice versa.
i am NMSI manger (network mangment ssytem interfacing manger ),
And I am responsible to define the KPI formula
thanks26th April 2008 at 23:38 #51910pixGuest
you have to keep in mind that indicators and qos is not standard, so each vendor may have a different approach. So take my words with perspective…
TCH assignment is the phase during call setup when the BSS wants to shift the MS from SDCCH to TCH.
The TCH assignment is divided in 2 parts :
1- the BSS checks that a timeslot TCH is available in the serving cell (or in neighbor cells, with directed retry)
2- the BSS asks the MS to move onto the TCH timeslot and to send an initial confirmation message while on this TCH timeslot.
In part 1 : there is a TCH REQUEST, which leads to a TCH ALLOCATED (= available TCH) or a TCH REJECTED (= no TCH availble)
In part 2 : the MS will try to access this TCH. If the dialog BTS/MS onto this TCH is possible, this is a TCH SUCCESS. If the dialog is not possible, this is a TCH FAILURE.
See, there are three main counters here :
TCH REQUEST -> TCH ALLOCATED -> TCH SUCCESS.
In your vendor, they might have different names, but the spirit should be the same. Try to find on which Abis or A interface message they are linked.
The TCH CONGESTION occurs only in phase 1.
The TCH FAILURE occurs only in phase 2 (with most common problems such as RADIO or HARDWARE PROBLEMS)
The ratio TCH SUCCESS / TCH REQUEST gives you the TCH UNSUCCESS RATE, which the KPI you should monitor.
Do you need more details ? I’ll write you the protocol messages that are linked to requests, allocations and successes, to make it clearer, if you want.
I hope it helps,
Pix6th May 2008 at 08:01 #51911xyGuest
We had a problem with TCH Assignment when introducing E-GSM into the network, in same hopping channel group with P-GSM channels. First guess is that there is a element between BTS and MS that doesn’t support E-GSM (for example repeater), but the wierd thing is that the problem disappeared when we put hopping off. Also, if we put E-GSM in a separate channel group, there isn’t any problem with TCH Assignment.
Anyone has a clue what could be the reason for such behaviour?6th May 2008 at 13:18 #51912pixGuest
this is vendor dependent !17th May 2008 at 22:54 #51913DAOUDAGuest
I NEED THE ALCATEL FORMULAS FOR CSSR.
THANKS19th May 2008 at 09:32 #51914VanderleyGuest
I don’t know a vendor who supports hopping with mixed P and E-GSM frequencies19th May 2008 at 18:55 #51915pixGuest
Alcatel B9 supports it : one cell, one frequancy hopping list can contain a mix of PGSM and EGSM frequencies.19th May 2008 at 18:59 #51916pixGuest
Alcatel CSSR = (1-SDCCH DROP RATE) * (1-TCH ASSIGNMENT UNSUCCESS RATE)20th May 2008 at 06:59 #51917xyGuest
I owe you explanation, since I found out the source of the problem. Some terminals (I won’t mention which ones, but out of 8 tested I noticed the problem on 3, one old, and two very new, one of them isn’t on market yet) doesn’t support hopping with mixed channels.