Return from 2G to LTE with packet data off

4G LTE
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Hi! Yesterday we found such a thing on the network, both subscribers are on LTE, but data transmission is turned off, both have data transmission turned off. I make a call, we are thrown into the network below, I go to 3G, the second subscriber in 2g. We end the call, after the call I immediately return to LTE, the second subscriber, who was thrown in 2g, remains in it for 15-16 seconds. Can you suggest something about this? We did a test with the radio frequency, I see that after the end of the call, BTS gives LTE frequencies, that is, there is a fast return, but the phone does not go into LTE, it freezes somewhere.

Vendor Huawe LTE, BSC, RNC.

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Check Fast return to LTE feature is properly enabled or not. also check if the 2Quarter switch is enabled or not

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Hi! Enabled on BSC, but on cell disabled. Do you mean this command?

SET GCELLPRIEUTRANSYS:IDTYPE=BYNAME,CELLNAME=“XXX”,SI2QUATEROPTFORLTESW=ON;

Fast return enabled on GSM by this commands
// CSFB Support in cell

SET GCELLSOFT:IDTYPE=BYNAME,CELLNAME=“XXX”,CSFBPAGRSPBCSWITCH=NO,SUPPORTCSFB=SUPPORT,UTRANCMDELAYFORCSFBSW=OFF,CSFBIDENTIFYMOSW=OFF,CSFBIDENTIFYMTSW=OFF;

// The early classmark sending control.

SET GCELLCCBASIC:IDTYPE=BYNAME,CELLNAME=“XXX”,ECSC=YES;

// LTE Fast Reselect Freq Send Optimize Switch

SET GCELLOTHBASIC:IDTYPE=BYNAME,CELLNAME=“XXX”,LTEFASTRETURNFRQSENDOPTSW=ON;

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Hi,

As far I remember you will require the below set of Parameters from GSM end for Fast return:

ADD GLTENCELL: IDTYPE=BYNAME, SRCLTENCELLNAME=“Ce110”,
NBRLTENCELLNAME=“Cell1”, SPTRESEL=SUPPORT, SPTRAPIDSEL=SUPPORT;

SET GCELLPRIEUTRANSYS: IDTYPE=BYNAME, CELLNAME=“Ce110”,
FASTRETURNMEASSPT=ON; SI2QUATEROPTFORLTESW=ON;

SET GCELLCSFBPARA: IDTYPE=BYNAME, CELLNAME=Ce110,
CSFBFastReturnBaseCfgSw=ON;

SET GCELL2GBA1: IDTYPE=BYNAME, CELLNAME=“Cell0”, CELL2GBA1TAG=AUTO, CELL2GBA1OPTSW=ON, CELL2GBA1OPTENHSW=OFF;

SET BSCBASIC: AVer=GSM_PHASE_2Plus, AbisVer=GSM_PHASE_2Plus,
UmVer=GSM_PHASE_2Plus;

ADD GEXTLTECELL: EXTLTECELLID=8048, EXTLTECELLNAME=“Cell1”, MCC=“460”,
MNC=“10”, ENODEBTYPE=MACRO, CI=0, TAC=1, FREQ=100, PCID=0,
EUTRANTYPE=FDD;

SET GCELLCCBASIC: IDTYPE=BYID, CELLID=0, ECSC=YES;

SET GCELLOTHBASIC: IDTYPE=BYNAME, CELLNAME=Ce110,
LTEFastReturnFrqSendOptSw=ON;

For SRVCC:

SET GCELLSRVCC: IDTYPE=BYNAME, CELLNAME=“Cell0”, SRVCCRapidSelSw=ON,
SRVCCRapidSelMeasOptSw=ON, SRVCCRapidSelBaseCfgSw=ON,
SRVCCStatInterRanHo=ON;

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Because mobile data (IMS) is off, the call uses CS fallback, so phones drop from LTE to 3G/2G for voice. After hang-up, the phone must reselect back to LTE. A 15–16s delay usually comes from cell-reselection priorities/timers on 2G (C1/C2, Treselection, qHyst) or missing LTE neighbor info. What to check (simple list): Use VoLTE (IMS APN on) → no fallback, instant stay on LTE. Enable Huawei “Fast Return to LTE / Release with Redirect (RWR)” on BSC/RNC. Priorities: set LTE > 3G > 2G (absolute priority reselection). Timers: reduce TReselectionEUTRA (aim ~1–2s) and hysteresis. Neighbors broadcast: make sure 2G (SI2quater) and 3G (SIB19) include correct LTE EARFCNs/PCI lists. Coverage mismatch/device: check 2G/LTE RF levels and handset firmware; some UEs linger longer on 2G if thresholds aren’t met.

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