| 摘要 |
Location-based services are provided in a communication system comprising a wireless network. In one aspect, a mobile user device sends a trigger message to a server over a wireless link of the network. The server in response to the trigger message sends an update message to the mobile user device over the wireless link. The update message is sent within a period of time after the trigger message that is less than a dormancy time of the wireless link. The update message may specify, for example, a defined area around a location identified in the trigger message, one or more stationary fences associated with the mobile user device that overlap with the defined area and that are active or become active within a designated time frame, and a projected time frame within which a proximity-crossing event is likely to occur for at least one user device pair that includes the mobile user device.
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