1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to handover control.
2. Introduction
A wireless communication network is deployed over a defined geographical area to provide various types of services (e.g., voice, data, multimedia services, etc.) to users within that geographical area. In a typical implementation, access points (e.g., corresponding to different cells or sectors) are distributed throughout a network to provide wireless connectivity for access terminals (e.g., cell phones) that are operating within the geographical area served by the network. In general, at a given point in time, the access terminal will be served by a given one of these access points. As the access terminal roams throughout this geographical area, the access terminal may move away from its serving access point and move closer to another access point. In addition, signal conditions within a given cell may change, whereby an access terminal may be better served by another access point. In these cases, the access terminal may be handed-over from its serving access point to be served by the other access point to maintain mobility for the access terminal.
An example of how the serving access point for an access terminal may be changed follows. The access terminal may regularly perform radio frequency (“RF”) measurements and determine that the signals being received from a neighbor access point (e.g., a so-called target access point) are stronger than the signals being received from the current serving access point by a certain margin. As a result, the access terminal sends a measurement report with this information to the network (e.g., to the serving access point). The serving access point then performs backhaul communication with the target access point to negotiate resources for the access terminal on the target access point. In addition, the serving access point sends a handover command to the access terminal, wherein the handover command identifies the resources assigned to the access terminal on the target access point. Finally, the access terminal connects to the target access point using these resources.
In some networks, access points may be deployed whereby only specified subscribers are allowed to access a given set of one or more access points. For example, a closed subscriber group (CSG) may be defined such that only users that are subscribed with that CSG are allowed to access an access point that is a member of the CSG. All other users in the network may then be rejected if they attempt to access an access point that is a member of the CSG (an exception may be made for emergency calls). Accordingly, there is a need for effective mechanisms to control access to such access points during handover.