Nokia Siemens Networks Oy

Nokia Siemens Networks S.p.a.

Marco Rastelli

Daniele Tortora

Alessandro De Sanctis

To prevent a handover ping-pong effect between base-station in WiMAX-compliant networks, a priority level is assigned to the trigger causes for handover, and the prioritized causes are coded. Then codes are subdivided into a first class of unrestricted handovers and a second class of restricted handovers. The first class includes the highest priority handovers. The second class includes a subset of handovers with a high or normal priority intended for optimizing resources. Outside this subset the second class also includes handovers for power budget having a normal priority level. When an outgoing handover is decided, the actual serving BS permits or selectively suppresses the Handover Request to the target BS when the latter corresponds to the preceding serving BS for that mobile. The selection mechanism operates on the second class of restricted handovers, during a penalty time triggered by the occurrence of handover causes included in the second class subset.

Method for preventing ping-pong handover effect in mobile WiMAX networks

Handover of a mobile station (MS) from a serving base station (BS) to a target base station in a mobile communication system supporting both MS-initiated handover and BS-initiated handover, is coordinated by ensuring that, both in the case of BS-initiated handover and in the case of MS-initiated handover: the mobile station (MS) and the base station (BS) share information, either via a MO_BSHO-REQ message sent from the BS to the MS in the case of BS-initiated HO or via a MO_MSHO-RETQ message sent from the MS to the BS in the case of MS-initiated HO, indicating a target base station for the mobile station (MS) to attempt handover; and the mobile station (MS) sends an information message (M0B_H0-IND) indicating the base station to which handover was attempted.

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Cesano Boscone, Italy

Marco Rastelli