Mobility management method for use in cellular mobile communication system
Disclosed is a mobility management method for use in a cellular mobile communication system. The mobility management method is configured to save radio resources and provide a stable service by detecting a cell in which a dwell time of user equipment (UE) is short as an island cell and performing a direct handover (HO) to an appropriate cell without handing over the UE to the island cell. There are provided three methods including a base station-based method, a UE measurement-based method, and a UE history-based method according to how to measure a dwell time in which the UE stays in a cell, a component in which obtained information is received within a network, and how to process an HO using the information.
1. A mobility management method of a target base station for use in a cellular mobile communication system, comprising:
(a) receiving, from the source base station, information specifying a source base station and at least one of information indicating a dwell time in the source base station of UE and information indicating that the dwell time is equal to or less than a predetermined threshold during an HO of the UE; and
(b) storing the information along with the same type of the information, which is transmitted from a base station other than the source base station and determining priority of an HO candidate on the basis of the stored information upon decision of a candidate base station when the UE is handed over from the target base station.
2. The mobility management method of claim 1 , wherein the dwell time in the source base station of the UE is a time from when the source base station has received an HO complete RRC message from the UE to when the source base station has transmitted an HO command RRC message to the UE.
3. The mobility management method of claim 1 , wherein operation (a) includes receiving the information indicating the dwell time and specifying the source base station by using an HO request X2AP message from the source base station.
4. The mobility management method of claim 1 , wherein, when the target base station stores the information in operation (b), latest information is preferentially stored if the amount of information exceeds an amount of information capable of being stored.
5. The mobility management method of claim 1 , wherein, when the target base station stores the information in operation (b), a dwell time for a source base station in which the dwell time is short and information specifying the source base station are preferentially stored if the amount of information exceeds an amount of information capable of being stored.
6. The mobility management method of claim 1 , wherein, when the target base station determines the priority of the HO candidate on the basis of the stored information in operation (b), a base station in which a dwell time is short has low HO priority and is excluded from the HO candidate.
7. The mobility management method of claim 3 , wherein the information indicating that the dwell time is equal to or less than the predetermined threshold in operation (a) is designated as one HO report type, which is an enumerated information element (IE) defined in the HO report X2AP message.
8. The mobility management method of claim 1 , wherein the information specifying the source base station is enhanced cell global identifier (ECGI) information of the source base station.