Handover in relation to cell identity ambiguity

A handover handling node in a wireless communication network for handing over a mobile station from a source cell to a target cell when the identity of the target cell is ambiguous, the node comprising:

• a communication interface, and
• a control unit comprising
• a handover deciding circuit configured to
• receive from a mobile station a measurement report that includes a cell identifier associated with a cell that is a prospective target for handover, and
• determine, based on said report, that the mobile station is to be handed over to said cell as the target cell, and
• an investigating circuit configured to
• investigate whether or not other cells neighboring said target cell share said cell identifier with said target cell, and
• if other cells neighboring said target cell share said cell identifier with said target cell, generate an identity ambiguity indicator that indicates the target cell is not uniquely identified and that will trigger the mobile station to autonomously initiate establishment of a connection to a target base station defining the target cell responsive to failure of handover to a candidate base station defining a cell that shares said cell identifier with said target cell,
• wherein the handover deciding circuit is configured to send a handover instruction to the mobile station that includes said identity ambiguity indicator, wherein the handover instruction comprises a handover command from the candidate base station, and the identity ambiguity indicator triggers the mobile station to initiate establishment of a connection to the target base station irrespective of whether the mobile station receives a handover command from the target base station.

A mobile station configured to be handed over from a source cell to a target cell in a wireless communication network when the identity of the target cell is ambiguous, the mobile station comprising a wireless communication interface, a radio communication unit, and a control unit comprising:

• an reporting circuit configured to send a measurement report to a source base station that includes a cell identifier associated with a cell that is a prospective target for handover, and
• a handover handling circuit configured to:
• receive a handover instruction from a source base station that defines said source cell, wherein said handover instruction comprises a handover command from a candidate base station defining a cell that shares said cell identifier with said target cell and includes an identity ambiguity indicator that will trigger the mobile station to autonomously initiate establishment of a connection to a target base station defining said target cell responsive to failure of handover to the candidate base station, and
• responsive to reception of said identity ambiguity indicator and failure of handover to the candidate base station, autonomously initiate the establishment of a connection to the target base station irrespective of whether the mobile station receives a handover command from the target base station.

A method in a target cell of a wireless communication network for controlling handover of a mobile station from a source cell to the target cell when the identity of the target cell is ambiguous, wherein the source cell is defined by a source base station and the target cell is defined by a target base station, wherein the method comprises:

• receiving a secured handover reference and a cell identifier of the source cell from the mobile station via a connection autonomously initiated by said mobile station responsive to the mobile station failing to handover to a candidate base station defining a cell that shares said cell identifier with said target cell, irrespective of whether the mobile station received a handover command from the target base station, and based on an identity ambiguity indicator that the mobile station received from the source base station and that indicated the target cell is not uniquely identified,
• requesting handover of the mobile station from the source cell using the secured handover reference,
• receiving handover context data from the source base station as a response to the request, and
• completing handover of the mobile station to the target cell.

A node for controlling handover of a mobile station from a source cell to the target cell when the identity of the target cell is ambiguous, wherein the source cell is defined by a source base station and the target cell is defined by a target base station, wherein the node comprises a communication interface and a control unit comprising:

• a handover requesting circuit configured to:
• receive a secured handover reference and a cell identifier of the source cell from the mobile station via a autonomously initiated by said mobile station responsive to the mobile station failing to handover to a candidate base station defining a cell that shares said cell identifier with said target cell, irrespective of whether the mobile station received a handover command from the target base station, and based on an identity ambiguity indicator that the mobile station received from the source base station and that indicated the target cell is not uniquely identified,
• request handover of the mobile station from the source cell using the secured handover reference, and
• a handover processing circuit configured to:
• receive handover context data from the source base station as a response to the request, and
• complete handover of the mobile station to the target cell.

A method of assisting in the handing over of a mobile station from a source cell defined by a source base station to a target cell defined by a target base station in a wireless communication network when the identity of the target cell is ambiguous, comprising:

• responsive to the mobile station failing to handover to a candidate base station defining a cell that shares said cell identifier with said target cell, and irrespective of whether the mobile station received a handover command from the target base station, receiving a message from the target base station, wherein the message comprises a request for handover of the mobile station and includes a secured handover reference associated with the handover to be performed, an identifier of the source base station, and an identifier of the target base station,
• locating a transport network identifier of the source base station based on said identifier of the source base station,
• forwarding the message to the source base station using said transport network identifier,
• receiving a message from the source base station that, as a response to the request, includes handover context data and said identifier of the target base station, and
• forwarding the handover context data to the target base station based on said identifier of the target base station.

A network node of a wireless communication network for assisting in the handing over of a mobile station from a source cell defined by a source base station to a target cell defined by a target base station when the identity of the target cell is ambiguous, the network node comprising a communication interface and a control unit that comprises:

• a base station locating circuit configured to
• responsive to the mobile station failing to handover to a candidate base station defining a cell that shares said cell identifier with said target cell, and irrespective of whether the mobile station received a handover command from the target base station, receive a message from the target base station, wherein the message comprises a request for handover of the mobile station and includes a secured handover reference associated with the handover to be performed, an identifier of the source base station, and an identifier of the target base station, and
• locate a transport network identifier of the source base station based on said identifier of the source base station, and
• a message handling circuit configured to
• forward the message to the source base station using said transport network identifier,
• receive a message from the source base station that, as a response to the request, includes handover context data and said identifier of the target base station, and
• forward the handover context data to the target base station based on said identifier of the target base station.