With the Wimax (World Interoperability for Microwave Access) as a new force suddenly rises, the 3rd Generation Mobile Communication System should improve its network performance and reduce the cost of network construction and operation in order to sustain its strong competitiveness in the field of mobile communication. Therefore, the standardization workgroup of 3GPP (3rd Generation Partnership Project) is now working on evolving into PS Core (Packet Switch Core) and UTRAN (Universal Mobile Telecommunication System Radio Access Network), the research topic is System Architecture Evolution (SAE) and its target is to make the evolved PS Core (E-PS Core) be capable of providing higher transmission speed, shorter transmission delay and optimal packet, and supporting mobility management among E-UTRAN (Evolved UTRAN), UTRAN, WLAN (Wireless Local Area Network) and other non-3GPP access networks.
Nowadays, the architecture of the SAE is shown as FIG. 1, which comprises the following network elements:
E-RAN (Evolved Radio Access Network), which could provide higher uplink and downlink speeds, shorter transmission delay and more reliable radio transmission. The network element included in E-RAN is eNodeB (Evolved NodeB) which provides radio resource for the subscriber access.
HSS (Home Subscriber Server), which is used for permanently storing the subscription data.
PDN (Packet Data Network), which is a network providing services for the subscribers.
E-Packet Core (Evolved Packet Network), which provides shorter delay and allows the access of more radio access systems, and comprises the following network elements:
MME (Mobility Management Entity): a control plane functional entity, and a server for temporarily storing the subscriber data, being responsible for managing and storing the context of UE (User Equipment) (such as the UE/subscriber identifier, mobility management status, subscriber security parameters, and so on), distributing temporary identifier for the subscriber, and processing all messages in the non-access-layer between MME and UE when the UE being in the tracking area or the network is responsible for authorizing the subscriber;
Serving GW (Gateway): Serving Gateway, which is a subscriber plane entity responsible for route processing the subscriber plane data and terminating the downlink data of the UE in idle status; managing and storing SAE bearer context of UE, such as the IP bearer service parameters and network internal route information, and so on; the anchor point of the subscriber plane within the 3GPP system, and one subscriber can only have one Serving GW at one time;
PDN GW: Packet Data Network Gateway, which is responsible for the gateway function of the UE accessing to PDN and is the mobility anchor point of 3GPP and non-3GPP access systems. And the subscriber can access to several PDN GWs at the same time.
The mobility management is an evident characteristic of the radio communication system. When a subscriber moves from an area controlled by one eNodeB to another area controlled by another eNodeB, the corresponding MME and Serving GW might change. If the subscriber moves in the idle mode, the UE will initiates the process of tracking area update, and if the subscriber moves in the active mode, the process of handover will be initiated. In these processes, the subscriber data and the related context will be reestablished in the target MME which might reselect a new Serving GW, and the resource related to the subscriber in the original MME and in the Serving GW will be released.
In the prior art, the release of the resource related to the subscriber in the original Serving GW will be initiated by the original MME, as shown in FIG. 2.
Step 201: the target MME sends a request for updating the subscriber data to the HSS to request the HSS to send the subscription data to the target MME;
Step 202: the HSS returns a response of subscriber data updated to the target MME after sending the subscription data to the target MME;
Step 203: the HSS sends a request for deleting the subscriber data to the original MME to delete the subscriber data in the original MME;
Step 204: if a Serving GW used by the subscriber was found in the original MME, a request for deleting bearer context is sent to the Serving GW; and the Serving GW is called as the original Serving GW or the old Serving GW.
Step 205: the original Serving GW returns a response of bearer context deleted after deleting the context of the corresponding subscriber;
Step 206: the original MME returns a response of subscriber data deleted to the HHS after deleting the subscriber data.
In this technology, when the target MME still uses the old Serving GW instead of selecting a new Serving GW, the original MME will still initiates a request for deleting the subscriber bearer context to the old Serving GW, which will result in the resource related to the subscriber in the old Serving GW being released mistakenly. In this scheme, the original MME can not know whether the target MME selects a new Serving GW or not.