1) ACCESSIBILITYRRC Faults- UE cannot search cells- Authentication fails- A fault in RFERAB Faults- Resources are insufficientPossible Causes- Parameters UE/eNodeB incorrectly configured- RF environment abnormal- EPC parameters incorrectly configured- UE is abnormalSOLVEParameter configuration issues- Cell parameters are incorrectly configured: EARFCN, PLMN ID, threshold used in the evaluation of cell camping, pilot strength, and access class.- UE with special requirements for authentication this is just for certain user failures- SIM card or registration-related parameters on HSS are incorrectly configured this is just for certain user failures- Authentication and encryption algorithms are incorrectly configured on the EPC this is for certain user or massive failures- IP path related parameters are incorrectly configured this is for all the setup attempts in certain nodeRF environment issues- RF interference: DL interference from neighbouring cells, DL interference from external systems, and UL interference, etc.- Weak coverage: if RSRP values reported by UEs are relatively low, it is highly probable that issue is weak coverage (lack of coverage or cross-cell coverage)- Imbalance between UL and DL power- eNodeB hardware: tilts and azimuth (if two antennas are placed, they should have same tilt and azimuth), physical connectors, patch cords, etc