Subscription Update Method, Device, and System

A system, comprising:

• a second mobility management network element configured to:
• receive event subscription information of a first terminal from a first mobility management network element, wherein the event subscription information of the first terminal comprises information about a first subscription to a first event comprising group subscription identification information, wherein the first terminal belongs to a first user group;
• allocate a subscription correlation identifier when the second mobility management network element has no subscription to the first event;
• and
• send a first message comprising a second subscription correlation identifier and the group subscription identification information to a unified data management network element;
• and
• the unified data management network element coupled to the second mobility management network element and configured to receive the first message from the second mobility management network element, wherein the first event is an event subscribed to by the unified data management network element for the first user group.

A second mobility management network element, comprising:

• a processor;
• and
• a memory coupled to the processor and storing instructions that, when executed by the processor, cause the second mobility management network element to be configured to:
• receive event subscription information of a first terminal from a first mobility management network element, wherein the event subscription information of the first terminal comprises information about a first subscription to a first event comprising group subscription identification information, wherein the first terminal belongs to a first user group, and the first event is an event subscribed to by a unified data management network element for the first user group;
• allocate a subscription correlation identifier when the second mobility management network element has no subscription to the first event;
• and
• send a first message to the unified data management network element comprising the subscription correlation identifier and the group subscription identification information to the unified data management network element.