Subscriber unit for beam acquisition in a satellite communication system and method therefor

• US 6,272,314 B1
• Filed: 04/30/1999
• Issued: 08/07/2001
• Est. Priority Date: 04/30/1999
• Status: Active Grant

• Current Assignee: CDC Propriete Intellectuelle
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Chen, Susan, Startup, Jim, Emmons, Thomas Peter Jr., Hogberg, Shawn, Davieau, Gerald Joseph
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US09/302,331
• Time in Patent Office: 830 Days
• Field of Search: 455/12.1, 455/13.1, 455/13.2, 455/427, 455/428, 455/429, 455/430, 455/450, 455/436, 455/437, 455/452, 455/464, 455/509, 455/512, 455/513, 455/525, 455/67.6, 455/60, 455/62, 455/516, 342/357-1-3
• US Class Current: 455/12.1
• CPC Class Codes: H04B 7/18539 Arrangements for managing radio, resources, i.e. for establishing or releasing a connection

Abstract

In a communications system, an earth-based subscriber unit (40, FIG. 1) receives at least one communications beam (50, 60, FIG. 1) transmitted from one or more moving satellite communications nodes (10, 20). The earthbased subscriber unit evaluates which communications beam should be selected based on the power received (FIG. 2, 210), Doppler frequency shift (270), link quality, (290), interference level (300), and satellite and network specific parameters (310). By considering these factors, the earth-based subscriber unit selects the communications beam (50, 60) that will provide the optimum service and reduce the likelihood that an inter-satellite hand over of the call will be required while the call is in progress.

Claims

1. In a subscriber unit, a method for selecting an optimum communications beam from a plurality of communications beams transmitted from a plurality of communications nodes, comprising the steps of:

measuring a propagation delay of said plurality of communications beams;

measuring a Doppler frequency shift of said plurality of communications beams;

comparing said propagation delay and said Doppler frequency shift of said plurality of communications beams; and

selecting said optimum communications beam based on said comparing step.

2. The method of claim 1, wherein said selecting step further comprises the step of selecting said optimum communications beam based on a minimum propagation delay and a maximum positive Doppler frequency shift.

3. The method of claim 1, additionally comprising the step of adjusting said propagation delay of said plurality of communications beams based on said Doppler frequency shift.

4. The method of claim 1 additionally comprising the step of receiving status of at least one of said plurality of communications nodes.

5. The method of claim 4, wherein said status conveys resource availability of said at least one of said plurality of communications nodes.

6. The method of claim 1, additionally comprising the step of receiving channel assignment from said optimum communications beam.