Mobile satellite communication system utilizing polarization diversity combining

• US 7,043,198 B2
• Filed: 09/06/2002
• Issued: 05/09/2006
• Est. Priority Date: 03/03/2000
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Emmons, Thomas Peter Jr., Monsen, Peter, Startup, James William, Kleiner, Norbert, Hanson, Duke Edward, Peters, Robert Anthony
• Primary Examiner(s): LE, LANA N
• Application Number:
  US10/236,428
• Publication Number:
  US 20030008614A1
• Time in Patent Office: 1,341 Days
• Field of Search: 455/13.1, 455/296, 455303-306, 4554561-4566, 455/429, 342/361, 342359-366, 342371-374
• US Class Current: 455/13.1
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

The present invention utilizes a dual polarization reception system (200) that utilizes the energy available in orthogonal polarizations to effectively increase link margin, thereby allowing for adequate signal quality reception in difficult environments. A co-polarized and a cross-polarized signal are separately downconverted and demultiplexed. The signals from each demultiplexed output are then sampled and weighted. The weighted samples for each polarity are combined in soft decision combining/decoding circuitry (255, 360), and this circuitry determines the most likely state of a received symbol'"'"'s transmitted value.

Claims

1. A method of operating a satellite in a dual-polarization reception system, said method comprising the steps of:

acquiring a signal from a subscriber unit via an access channel;

detmnnining a location for said subscriber unit, wherein said satellite receives message information comprising location data;

determining if a dual-polarization beam exists at said location;

measuring received signal power, when said dual-polarization beam exists at said location;

determining whether said received signal power is greater than a first threshold value;

converting from a single polarization beam to a dual-polarization beam, when said received signal power is greater than said first threshold value; and

updating a beam allocation table.

2. The method as claimed in claim 1, wherein said method further comprises the steps of:

measuring average received signal power, when a beam does not exist at said location;

comparing said avenge received signal power to a second threshold;

assigning a single polarization beam to said location when said average received signal power is greater than said second threshold;

assigning a dual polarization beam to said location when said average received signal power is not greater than said second threshold; and

updating said beam allocation table.

3. The method as claimed in claim 2, wherein said method further comprises the steps of:

lowering said second threshold, when the number of available dual polarization channels is less than a first limit; and

raising said second threshold when the number of available single polarization channels is less than a second limit.

4. A method of operating a subscriber unit (SU) in a dual-polarization reception system, said method comprising the steps of:

acquiring a signal from a satellite via a broadcast channel;

determining a location for said subscriber unit, said SU self-determining said location;

determining from a beam allocation table a beam assignment at said location;

measuring co-polarized signal power and cross-polarized signal power at said location;

determining whether said measured co-polarized signal power and said measured cross-polarized signal power are consistent with said beam assignment;

modifying said beam assignment, when said measured co-polarized signal power or said measured cross-polarized signal power is not consistent with said beam assignment; and

updating said beam allocation table.

5. The method as claimed in claim 4, wherein said method further comprises the step of transmitting beam assignment modifications to a satellite.

6. The method as claimed in claim 4, wherein said method further comprises the step of reporting said measured co-polarized signal power and said measured cross-polarized signal power to a system control center.

7. The mcthod as claimed in claim 4, wherein said method further comprises the step of storing said measured co-polarized signal power and said measured cross-polarized signal power in a history file for said location.