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Multiplexer-related

Satellite-cellular-communication-methods-for-performing-cell-to-cell-handoff

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Satellite cellular communication methods for performing cell-to-cell handoff

Details

Inventors: Olds, Keith A.; Redden, James P.; Kurby, Christopher;
Assignee: Motorola, Inc. (Schaumburg, IL)
Primary Examiner: Eisenzopf; Reinhard J.
Assistant Examiner: Le; Thanh
Attorney, Agent or Firm: McGurk, IV; Harold C.

Handoff methods perform cell-to-cell handoff between cells of the same satellite and between cells of different satellites. Handoff is initiated by an individual subscriber unit (ISU) based on local conditions. Once handoff is needed, the ISU chooses a candidate cell to transfer its communication based on a dynamic handoff candidate list provided by the satellite. After selecting a candidate cell, the ISU requests handoff, the satellite or satellites perform the handoff and communication begins over a new channel in the candidate cell.

DETAILED DESCRIPTION What is claimed is: 1.
A method of handing-off a call of an individual subscriber unit (ISU) from a current cell to one of a plurality of candidate cells in a satellite cellular communication system, a satellite projecting the current cell and the candidate cells onto Earth, the method comprising the steps of: (a) transferring a handoff candidate list comprising a list of candidate cells from the satellite to the ISU; (b) the ISU determining whether the handoff is to occur; (c) the ISU selecting one of the candidate cells to receive the handoff based on the handoff candidate list; (d) the ISU requesting the handoff from the current cell to the candidate cell; and (e) the satellite performing the handoff from the current cell to the candidate cell.
2.
A method as recited in claim 1, wherein the handoff candidate list comprises a list of available candidate cells.
3.
A method as recited in claim 1, wherein step (a) further comprises the step of the ISU selecting one of the candidate cells to receive the handoff from the current cell based on whether the candidate cell is likely to offer a better quality of service than the current cell and whether the candidate cell is available and causes no interference.
4.
A method as recited in claim 1, wherein step (a) comprises the steps of: (a1) determining a position of the ISU relative to an edge of the current cell; (a2) determining how long before the edge of the current cell is reached; and (a3) selecting one of the candidate cells based on availability and whether the available candidate cell will cause any interference.
5.
A method as recited in claim 4, wherein step (d) comprises the step of the ISU requesting the satellite to make the handoff to the available, non-interfering candidate cell selected in step (c).
6.
A method as recited in claim 1, wherein step (e) comprises the steps of: (e1) the satellite denying the request from the ISU to make the handoff to the selected candidate cell; (e2) the ISU selecting an alternative cell if the current cell is still available; (e3) dropping the call if the current cell is not available

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