1. A user equipment (UE) comprising:a memory configured to store a plurality of instructions; and
a processor coupled to the memory and configured to execute the plurality of instructions to:
calculate a second paging group index of a second-grade paging group based on a first paging group index of a first-grade paging group and a parameter obtained by the UE via system information, the first paging group index Paging_GroupID is defined by the following formula:
where, Paging_GroupID is the first paging group index, UE_ID is based on an identity of the UE, nB is a parameter associate with paging occasions of a cell in paging cycle and floor denotes a rounded down operation,
wherein the second paging group index is used to determine which narrowband or which carrier the UE performs a paging message reception.