- This topic has 4 replies, 1 voice, and was last updated 10 years, 6 months ago by Bijoy.
4th September 2010 at 09:53 #64207MKTGuest
I have one doubt.
Suppose if the connectivity between BSC and transcoder is down…
A MS sends a RACH…to request SDCCH?
Question is …
will the MS be able to send RACH at all? Practically I have observed it as NO.
Will the BSC allot an SDCCH?
Finally when it comes to alloting TCH , the BSC will say NO, as the connectivity between BSC and Transcoder is down.
So, will the counter of TCH blocking corresponding to that cell will be incremented or Not?
MKT12th September 2010 at 09:01 #64208BijoyGuest
The scenario you depicted is called “BSC isolation” where BSC lost contact with MSC(all TXCDRS are down),in this case none of the counters in BSC will peg as it is unable to provide any service(Except GPRS if Gb link is not down).
But,if only some A-ters are down,you will definitely get TCH blocking counter incremented & BSC will allot SDCCH as in normal case
Bijoy29th September 2010 at 00:43 #64209MKTGuest
I have some confusion regarding the definition of drop.
how do you define a drop?
a thing has been allotted to you and all of a sudden it gets dropped from your hand without warning, means no nothing just the lights are off.
or it is being told prior to drop that the thing is getting to be drop now, sorry, you can finish the work in hand
just take the case of sdcch drop
MS is allotted an SDCCH by BSC. I hope that BSC don’t need to have a discussion with MSC to get approval for allotting an SDCCH to MS.
MS requests and that’s it, BSC fullfills that request, if it (the cell in question) has the free SDCCH to get alloted.
let us assume a situation when the link between BSC and MSC is down.
In this situation my declarations are
BTS will be radiating
BSC will be working
MS can make packet calls(GPRS) as the PCU(in BSC) & SGSN connectivity is fine.
no new MS can enter into the network( as location updates won’t be possible)
coming back to MS wants to make a call
RACH will be sent successfully to BTS and so as the CHANNEL REQUIRED message to BSC by the BTS
BSC will assign an SDCCH through AGCH
Then MS tells through SDCCH that he wants to make a call
but these words of MS will not be able to reach MSC as the link between BSC & MSC is broken at the moment.
Now here comes the critical time of our question.
Will the BSC will perceive the words of MS
as a TCH request?
will the BSC ( due to its link failure ) will reply saying , sorry TCH can’t be given to you ?
will this reply of BSC will increment the counter of TCH blocking for that cell?
or the request for TCH is not taken directly from MS by BSC rather BSC takes the request for TCH or can say order to allot TCH from MSC?
as in our case the link is broken so there is no question of order from MSC can we assumed this as the case of no request for TCH thus no blocking of TCH
but in reality the MS do have made a request.
When the MS was still on SDCCH & the words of MS ( that he needs to make a call) reaches BSC
the BSC will immediately shuts the light off, mean drop or will the BSC will say the MS to release the SDCCH or will the BSC will tell the MS that I am releasing the SDCCH of you now.
What will happen and will what has happened can be termed as an SDCCH drop?
everything is mixed up while typing
if you don’ get me please ask , i will try to write again
waiting for reply
With regards29th September 2010 at 00:47 #64210MKTGuest
I hope you are from India , me too.
Regards,30th September 2010 at 06:30 #64211BijoyGuest
Why dont you try this on a test BSC & confirm.