RAB reconfiguration from HSPA to DCH

[m121]

Hi,
I am interested in what cases NW initiates UE switch from HSPA resources to R99 DCH? I see in traces that sometimes UE receives RAB reconfiguration but I can't find the reason why. If it's due to Traffic volume then why UE is not moved to FACH instead?
RSCP and EcNo are very good, no CM initiated.
Vendor is NSN.

[tukangoptim]

hi,
if you are moving to other cell that not support hsdpa, it will be reconfigured to R99.
If other cell not has enouth resources, it will also reconfigured to R99.


Thats the simplest reason i can give u. For complex reason, lets wait for senior expert member :)

[m121]

Thanks for reply but this is not the case because I see that it also happens for users who are served by only one cell.
It's also not due to cell congestion because it happens to users at 4AM.
My guess is that it's due to Traffic volume for user but I can't figure why DCH not FACH?

[jan74]

Thanks for reply but this is not the case because I see that it also happens for users who are served by only one cell.
It's also not due to cell congestion because it happens to users at 4AM.
My guess is that it's due to Traffic volume for user but I can't figure why DCH not FACH?

Strangely I am having the exact same issue and it is also NSN. There is no possibility to see why the RB was reconfigured as its not in the message. As far as I know, apart from handovers etc, the only reasons why the Bearer can go to R99 is:

i) Low Utilisation
ii) Low Throughput (We have this disabled)
iii) Buffer is empty
iv) Call Drops

I have seen this happening while testing streaming radio so the buffer could not be empty, low utilisation is also not possible and the call did not drop. I am really puzzled as I have also seen it while testing Youtube and it causes ping-pong between carriers. Does anybody else out there know why a HS-DSCH can be reconfigured down when none of the above apply?

[gprastomo]

Just make sure that HSPA compresed mode is enabled, if its disabled , so the UE will initiate H to D Reconf. Just make sure that compressed mode is enable only for RSCP and Ecno, disable the other cause

[jan74]

Just make sure that HSPA compresed mode is enabled, if its disabled , so the UE will initiate H to D Reconf. Just make sure that compressed mode is enable only for RSCP and Ecno, disable the other cause

But why HSPA Compressed Mode? We are not talking about changing cell or carrier.

[gprastomo]

in one of the vendor, H2D reconf, will happen if HSPA compressed mode is disable.
Sample case : -HSPA compressed mode is disabled, currently UE is HSPA, then UE is trying to handover to 2G, then Compressed mode take place, coz the HS compressed mode is disabled so HS to DCH reconf is happen, then UE Move to DCH, (still the same cell).

So as i remember , NSN has many cause of Compressed mode, RSCP eCno, Ue TxPow, Bler, and DPCH power, so even in Good RSCP and Good EcNo, other causes may generate CM.

[jan74]

in one of the vendor, H2D reconf, will happen if HSPA compressed mode is disable.
Sample case : -HSPA compressed mode is disabled, currently UE is HSPA, then UE is trying to handover to 2G, then Compressed mode take place, coz the HS compressed mode is disabled so HS to DCH reconf is happen, then UE Move to DCH, (still the same cell).

So as i remember , NSN has many cause of Compressed mode, RSCP eCno, Ue TxPow, Bler, and DPCH power, so even in Good RSCP and Good EcNo, other causes may generate CM.

That is true, but in these cases, there are no handover procedures. Thats the strange thing.

[gprastomo]

Yes, even there is no handover, if compressed mode is taken then There is no suitable neighbor etc, then it start to ho to DCH.

I saw ping pong carriers, what is the threshold for rscp and ecno compressed mode ?
What strategy you have been using ? dedicated hspa or load balance ??