Hybrid paging and location tracking scheme for inactive 5G UEs

User Equipment (UE) paging and location tracking are influenced by the underling state handling model. There are recent proposals to introduce a new RRC state called RRC Inactive as a main state for inactive UEs in 5th Generation (5G) cellular systems. One of the characteristics of the new state is that the interface between the Radio Access Network (RAN) and Core Network (CN) is kept. Considering this characteristic, there are proposals for a RAN controlled paging and location tracking schemes for RRC Inactive UEs. In this paper, we show that this approach is not always beneficial, especially for high mobility UEs. Instead, we propose a hybrid paging and location tracking scheme where both RAN and CN are involved in the paging and location tracking of RRC Inactive UEs. This is done transparently to the UE. We further propose a hierarchical paging and location tracking scheme to reduce the signaling overhead from paging and location tracking updates. The scheme is applicable to both RAN based and CN based paging and location tracking schemes.