If UE doesn't have any PS session and any CSFB call initiated then UE redirected to WCDMA or GSM and after ending CS session UE moved to LTE network by performing Tracking area update.
But in case PS session is on going and CS call have to be initiated then Handover to WCDMA will be performed. But when CS call finished and PS session is also still ongoing then which procedure will be performed to move again LTE Network? If its Handover then how measurement reporting will be done.
