PS Inter-RAT HO

hi,

i didn’t know the PS Handovers already existed in 2G. Which vendor is it ?

I don’t see any cons, but I assume it requires a good tuning of parameters so that RNC and BSC can communicate.
the pros is that there is no interruption of the PS transfer while the MS is moving from 3G to 2G. A reselection would take about 2s to 5s to complete, during which the transfer is stopped.

regards
pix

hi !

ok, now it makes more sense 😉

i’d favour going to 2G when the 3G coverage starts to be too low. You don’t want to extend your 3G coverage beyond its nominal cell range. Indeed, that would generate more noise for every other 3G user.

So I would activate the 3G-2G reselection in PTM mode, just before it is too late.
I guess you already actiavted this reselection in Idle Mode ?

And of course, activate it the other way around, but with enough hysteresis to avoid ping pong reselections…

(I know it all sounds very theoretical, but finding the perfect solution for you would require drivetests and extensive stats analysis…)

hi,

I’m not sure I understand. Could you explain what you mean by

“Having heavy 3G data usage will send u to 2G most of the times.”

Thanks

Pix

hi,

it sounds like you have a great test scenario that you should do with a drivetest 🙂 With qoS stats, I’m sure you could assess how badly the 3G is while it is loaded (looking at reselection %, coding scheme used, etc)

IMO if the 3G is so bad that the MS reselects the 2G, even with the most aggressive thresholds, then be it. But that has to be verified on the field.

Regards
pix

Hi Kamal,

Can you please share the required definitions at SGSN end.We are facing issue with 3G-2G PS HO.The cell order chage message we are getting but after GPRS suspension requestPDP context is being activated in 2G and after that it comes under Standby mode.Speed becomes zero and we needto switch off the phone again to use data services.

Regards,
Niraj

Hello Ayat,

you should better use the first formula as it is based on 2G neighbor measurements (real HO) whereas cell change is rather reselection/redirection which in fact doESn’t need neighbors to happen; therefore is not assimilated to HO

hi Ayat,

CCO is not a handover : resource is not reserved beforehand, network doesn’t know that mobile is changing cell, and mobile has to do a standard (full) setup on the target cell.

It is possible to perform a real PS HO from 3G to 2G, involving a procedure which is specified in 3GPP
as “IRAT HO”. Alternatively it is also possible to use the CCO to perform mobility from 3G to 2G. Both procedures exist, and the operator has to choose whether or not to activate PS HO.
Activating PS HO will (mostly) replace the CCO.
Most operators I know do not activate PS HO, in order to avoid compressed mode during PS transfer. They’d rather let the PS transfer continue until the drop. Since it is “bursty”, there are very high chances that the transfer will be over before the drop.

So yeah, back to the point, you can define the KPI for mobility PS 3G to 2G based on CCO and/or PS HO, whichever one is used.

Cheers
pix