3G to 2G excessive ping pong in idle mode

[foufou007]

Dear experts,

We are experiencing very excessive ping pong effect between 3G and 2G network in idle mode. This is causing excessive signaling in the network. what is from your experience the golden configuration for the IRAT cell reselection parameters in order to minimize or avoid this effect as much as possible?
Any other ideas on solving this phenomena are welcome.

Thanks

[usama0795]

Normally FDDQMIN (parameter defines a minimum Ec/Io threshold which must be exceeded before a non-GPRS capable dual mode mobile is allowed to make a reselection from the serving GSM cell to an adjacent WCDMA RAN cell that is using frequency division duplex (FDD) type access technology/mode ) is set somewhat between -6dB to -10dB; in order to avoid ping pong this parameter value should be set in accordance with parameters QQUALMIN (parameter defines the minimum required quality level in the cell (Ec/No). The parameter is used for cell selection and re-selection in both idle and connected mode. This parameter has impact also on the initial cell selection -> low value. With high value, unnecessary cell selection can start.) & Ssearch_RAT (parameter defines the RAT-specific threshold for inter-RAT measurement rules. The parameter is used for cell selection and re-selection in idle mode. Note: If no threshold is given, MS performs measurements)....a hsterisis of 6 to 8 dB is normally recommended between FDDQMIN and Sserach_RAT+QQUALMIN......and in addition Qserach parameters change to 7 for UE to measure only 3G neighbors.....

[foufou007]

Thanks for the response, what do you think is the best setting for QQUALMIN? Any other parameters you think we need to look into?

Thanks

[usama0795]

try going with the default value at first -18dB then increase it down 2 to 4dB at the time becuase i think to reduce ping pong cell reslections with impacting KPIs is between -6dB to -10dB.....

[agenov]

also you may evaluate possible implementation of single LAC if your CN support it of course

br
alex

[foufou007]

What do you mean possible implementation of single LAC? single LAC between 3G and 2G?

[djordjebeg]

That means same LAC for 2G and collocated 3G cell.It is possible only if 2G and 3G cells are on the same MSC or if you have MSC in Pool activated.In that case you can improve paging success rate but be careful about paging load for this harmonized ( unified) LAC.

[ninjafine]

Thanks for the response, what do you think is the best setting for QQUALMIN? Any other parameters you think we need to look into?

Thanks

Hi! QQualMin is responsible for EcNo. But you may leave UTRAN due poor RSCP, so i'd recommend to use FDD_Qoffset (FDDQOFF), then if CPICH RSCP > RLA + FDDQOFF you may reselect to UTRAN.
Using FDDQOFF = -20 ... -16 dB you restrict reselection to distant 3G cells from greenfield 2G.

Thanks and reps are appreciated.