System and method for reducing call dropping rates in a multi-beam communication system

• US 6,714,780 B1
• Filed: 06/12/2001
• Issued: 03/30/2004
• Est. Priority Date: 07/21/1998
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Marsh, Gene W., Chockalingam, Ananthanarayanan, Schiff, Leonard N., Ames, William G., Determan, James T., Stewart, Richard A., Grover, Douglas, Antonio, Franklin P., Kerns, Arthur S., Bjerede, Marie M., Grob, Matthew S., Butler, Brian
• Primary Examiner(s): TRAN, CONGVAN
• Application Number:
  US09/722,001
• Time in Patent Office: 1,022 Days
• Field of Search: 455/425, 455/426, 455/429, 455/428, 455/436, 455/437, 455/424, 455/427, 455/439, 455/442, 455/12.1, 455/13.1, 455/13.3, 455/67.1, 455/423, 455/134, 455/135, 370/331, 370/332
• US Class Current: 455/425
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity
• CPC Class Codes: H04B 7/18541 for handover of resources

Abstract

A method for reducing call dropping rates in a multi-beam communication system. The multi-beam communication system includes a user terminal, a gateway, and a plurality of beam sources, where each beam source projects a plurality of beams, and where a communication link between the user terminal and the gateway is established on one or more beams. The method according to the present invention relies on a messaging protocol between the gateway and the user terminal. Based on messages sent from the user terminal to the gateway, preferably on a preselected periodic basis, the gateway can determine the more desirable beam(s) for transmitting data or information to the user terminal. The messages sent from the user terminal to the gateway contain values representing beam strengths as measured at the user terminal. The gateway uses the user terminal measured beam strengths to select the beams that should be used for transmitting data or information to the user terminal. The beams that should be used are the beams that if used will decrease the call dropping rates and provide a desired level of beam source diversity.

Claims

1. In a multi-beam communication system having a user terminal, a communication station, and a beam source, wherein the beam source projects a plurality of beams, and wherein a communication link between the user terminal and communication station is established on at least one of the plurality of beams, a method for reducing call dropping rates, comprising the steps of:

(1) receiving at the user terminal a plurality of beam identifiers transmitted from the communication station;

(2) measuring at the user terminal a beam strength of each beam identified by said plurality of beam identifiers;

(3) transmitting from the user terminal to the communication station a plurality of beam strength values, wherein each of said plurality of beam strength values is a function of a measured beam strength of a beam identified by one of said plurality of beam identifiers; and

receiving at the user terminal a handoff direction message transmitted by the communication station, wherein, based on said handoff direction message, the user terminal determines which beam or beams should be used for receiving information transmitted from the communication station;

wherein said handoff direction message comprises a beam identifier corresponding to each beam in a new active beam set, wherein said new active beam set includes beams selected by the communication station that should be used as a communication link between the communication station and the user terminal.

2. The method of claim 1, wherein upon receiving said handoff direction message, the user terminal begins receiving traffic over each beam in said new active beam set that is not in a current active beam set, wherein said current active beam set includes all beams on which a communication link between the communication station and the user terminal is already established.

3. The method of claim 2, further comprising the step of transmitting a handoff completion message from the user terminal to the communication station after the user terminal begins receiving traffic over each beam in said new active beam set that is not in said current active beam set.

4. In a multi-beam communication system having a user terminal, a communication station, and a beam source, wherein the beam source projects a plurality of beams, and wherein a communication link between the user terminal and communication station is established on at least one of the plurality of beams, a method for reducing call dropping rates, comprising the steps of:

(1) receiving at the user terminal a plurality of beam identifiers transmitted from the communication station;

(2) measuring at the user terminal a beam strength of each beam identified by said plurality of beam identifiers;

(3) transmitting from the user terminal to the communication station a plurality of beam strength values, wherein each of said plurality of beam strength values is a function of a measured beam strength of a beam identified by one of said plurality of beam identifiers; and

receiving at the user terminal a handoff direction message transmitted by the communication station, wherein, based on said handoff direction message, the user terminal determines which beam or beams should be used for receiving information transmitted from the communication station;

wherein said handoff direction message comprises a beam identifier corresponding to each beam in a new active beam set that is not in a current active beam set, wherein said current active beam set includes all beams on which a communication link between the communication station and the user terminal is already established, and said new active beam set includes beams selected by the communication station that should be used as a communication link between the communication station and the user terminal.

5. The method of claim 4, wherein upon receiving said handoff direction message, the user terminal begins to receive traffic on a beam identified by a beam identifier in said handoff direction message.

6. The method of claim 5, further comprising the step of transmitting a handoff completion message from the user terminal to the communication station.

7. In a multi-beam communication system having a user terminal, a communication station, and a beam source, wherein the beam source projects a plurality of beams, and wherein a communication link between the user terminal and communication station is established on at least one of the plurality of beams, a method for reducing call dropping rates, comprising the steps of:

(1) receiving at the user terminal a plurality of beam identifiers transmitted from the communication station;

(2) measuring at the user terminal a beam strength of each beam identified by said plurality of beam identifiers;

(3) transmitting from the user terminal to the communication station a plurality of beam strength values, wherein each of said plurality of beam strength values is a function of a measured beam strength of a beam identified by one of said plurality of beam identifiers; and

receiving at the user terminal a handoff direction message transmitted by the communication station, wherein, based on said handoff direction message, the user terminal determines which beam or beams should be used for receiving information transmitted from the communication station;

wherein said handoff direction message comprises a beam identifier corresponding to each beam in a current active beam set that is not in a new active beam set, wherein said new active beam set includes beams selected by the communication station that should be used as a communication link between the communication station and the user terminal, and said current active beam set includes all beams on which a communication link between the communication station and the user terminal is already established.

8. The method of claim 7, wherein, after receiving said handoff direction message, the user terminal stops receiving traffic on a beam identified by a beam identifier in said hand off direction message.

9. In a multi-beam communication system having a user terminal, a communication station, and a plurality of beam sources, wherein each beam source projects a plurality of beams, and wherein a communication link between the user terminal and the communication station is established on one or more beams, a method for reducing call dropping rates, comprising the steps of:

(1) transmitting from the communication station to the user terminal a plurality of beam identifiers, wherein said plurality of beam identifiers identifies a plurality of beams and a plurality of beam sources currently in use by the communication station;

(2) receiving at the communication station a plurality of beam strength values transmitted by the user terminal, wherein each of said plurality of beam strength values is a function of a measured beam strength of a beam identified by one of said plurality of beam identifiers;

(3) determining at the communication station a new active beam set based on said plurality of beam strength values, wherein said new active beam set includes one or more beams that should be used as a communication link between the communication station and the user terminal, comprising the steps of

(a) selecting a first beam having the strongest beam strength based on said plurality of beam strength values, wherein said first beam is projected by a first beam source; and

(a) including said first beam in said new active beam set; and

(4) transmitting traffic from the communication station to the user terminal on said beams within said new active beam set;

(5) selecting a first subset of beam strength values from said plurality of beam strength values, wherein said first subset of beam strength values includes each of said plurality of beam strength values that correspond to a beam projected by a beam source other than said first beam source;

(6) selecting a second beam having the strongest beam strength based on said first subset of beam strength values; and

(7) including said second beam in said new active beam set if the strength of said first beam minus the strength of said second beam is less than or equal to a first threshold amount, wherein said first threshold amount is greater than or equal to zero.

10. The method of claim 9, wherein the step of determining at the communication station a new active beam set further comprises the steps of:

(8) selecting a second subset of beam strength values from said first subset, wherein each beam strength value within said second subset of beam strength values corresponds to an active beam, wherein an active beam is a beam over which information is currently being transmitted between the user terminal and the communication station;

(9) selecting a third beam having the strongest beam strength based on said second subset of beam strength values; and

(10) including said third beam in said new active beam set if the strength of said first beam minus the strength of said third beam is less than or equal to a second threshold amount.

11. The method of claim 10, wherein said second threshold amount is greater than or equal to said first threshold amount.

12. In a multi-beam communication system having a user terminal, a communication station, and a beam source, wherein the beam source projects a plurality of beams, and wherein a communication link between the user terminal and communication station is established on at least one beam, a system within the user terminal for reducing call dropping rates, comprising:

(a) means for receiving a plurality of beam identifiers transmitted from the communication station, wherein said beam identifiers identify a plurality of beams currently in use by the communication station;

(b) means for measuring a beam strength of each beam identified by said plurality of beam identifiers; and

(c) first transmitting means for transmitting to the communication station a plurality of beam strength values, wherein each of said plurality of beam strength values is a function of a measured beam strength of a beam identified by one of said plurality of beam identifiers; and

(d) receiving means for receiving a handoff direction message transmitted by the communication station, and means for determining which beam or beams should be used for receiving information transmitted from the communication station based on said handoff direction message;

wherein said handoff direction message comprises a beam identifier corresponding to each beam in a current active beam set that is not in a new active beam set, wherein said new active beam set includes beams selected by the communication station that should be used as a communication link between the communication station and the user terminal, and said current active beam set includes all beams on which a communication link between the communication station and the user terminal is already established.

13. The system of claim 12, wherein, after receiving said handoff direction message, the user terminal stops receiving traffic on a beam identified by a beam identifier in said hand off direction message.

14. In a multi-beam communication system having a user terminal, a communication station, and a beam source, wherein the beam source projects a plurality of beams, and wherein a communication link between the user terminal and communication station is established on at least one beam, a system within the user terminal for reducing call dropping rates, comprising:

(a) means for receiving a plurality of beam identifiers transmitted from the communication station, wherein said beam identifiers identify a plurality of beams currently in use by the communication station,

(b) means for measuring a beam strength of each beam identified by said plurality of beam identifiers; and

(c) first transmitting means for transmitting to the communication station a plurality of beam strength values, wherein each of said plurality of beam strength values is a function of a measured beam strength of a beam identified by one of said plurality of beam identifiers;

(d) means for receiving beam strength adjustment values transmitted by the communication station; and

(e) adjusting means for adjusting said plurality of beam strength values according to said received beam strength adjustment values, wherein said adjusting means adjusts said plurality of beam strength values according to said received beam strength adjustment values prior to said first transmitting means transmitting said plurality of beam strength values to the communication station, whereby the communication station will receive adjusted beam strength values.

15. In a multi-beam communication system having a user terminal, a communication station, and a plurality of beam sources, wherein each beam source projects a plurality of beams, and wherein a communication link between the user terminal and communication station is established on one or more beams, a system within the communication station for reducing call dropping rates, comprising:

(a) means for identifying a plurality of beams currently in use by the communication station,

(b) means for transmitting to the user terminal a plurality of beam identifiers, wherein each beam identifier identifies one of said beams currently in use by the communication station;

(c) means for receiving a plurality of beam strength values transmitted by the user terminal, wherein each of said plurality of beam strength values is a function of a measured beam strength of a beam identified by one of said plurality of beam identifiers;

(d) means for determining a new active beam set based on said plurality of beam strength values, wherein said new active beam set includes one or more beams that should be used as a communication link between the communication station and the user terminal, wherein said means for determining a new active beam set comprises;

(1) means for selecting a first beam having the strongest beam strength based on said plurality of beam strength values, wherein said first beam is projected by a first beam source;

(2) means for including said first beam in said new active beam set;

(3) means for selecting a first subset of beam strength values from said plurality of beam strength values, wherein said first subset of beam strength values includes each of said plurality of beam strength values that correspond to a beam projected by a beam source other than said first beam source;

(4) means for selecting a second beam having the strongest beam strength based on said first subset of beam strength values; and

(5) means for including said second beam in said new active beam set, wherein said means for including said second beam in said new active beam set includes said second beam in said new active beam set if the strength of said first beam minus the strength of said second beam is less than or equal to a first threshold amount, wherein said first threshold amount is greater than or equal to zero; and

(e) means for transmitting traffic to the user terminal on said beams within said new active beam set.

16. The system of claim 15, wherein said means for determining a new active beam set further comprises:

(6) means for selecting a second subset of beam strength values from said first subset, wherein each beam strength value within said second subset of beam strength values corresponds to an active beam, wherein an active beam is a beam over which information is currently being transmitted between the user terminal and the communication station;

(7) means for selecting a third beam having the strongest beam strength based on said second subset of beam strength values; and

(8) means for including said third beam in said new active beam set, wherein said means for including said third beam in said new active beam set includes said third beam in said new active beam set if the strength of said first beam minus the strength of said third beam is less than or equal to a second threshold amount.

17. The system of claim 16, wherein said second threshold amount is greater than or equal to said first threshold amount.

18. In a multi-beam communication system having a user terminal, a communication station, and a plurality of beam sources, wherein each beam source projects a plurality of beams, and wherein a communication link between the user terminal and communication station is established on one or more beams, a system within the communication station for reducing call dropping rates, comprising:

a computer useable medium; and

computer program logic stored on said computer useable medium, said computer program logic comprising;

(a) means for enabling the communication station to identify a plurality of beams currently in use by the communication station;

(b) means for enabling the communication station to transmit to the user terminal a plurality of beam identifiers, wherein each beam identifier identifies one of said beams currently in use by the communication station;

(c) means for enabling the communication station to receive a plurality of beam strength values transmitted from the user terminal, wherein each of said plurality of beam strength values is a function of a measured beam strength of a beam identified by one of said plurality of beam identifiers;

(d) means for enabling the communication station to determine, based on said plurality of beam strength values, a new active beam set, wherein said new active beam set includes one or more beams that should be used as a communication link between the communication station and the user terminal, wherein said means for enabling the communication station to determine, based on said plurality of beam strength values, a new active beam set comprises;

(1) means for enabling the communication station to select a first beam having the strongest beam strength based on said plurality of beam strength values, wherein said first beam is projected by a first beam source; and

(2) means for enabling the communication station to include said first beam in said new active beam set;

(3) means for enabling the communication station to transmit traffic to the user terminal on said beams within said new active beam set;

(4) means for enabling the communication station to select a first subset of beam strength values from said plurality of beam strength values, wherein said first subset of beam strength values includes each of said plurality of beam strength values that correspond to a beam projected by a beam source other than said first beam source;

(5) means for enabling the communication station to select a second beam having the strongest beam strength based on said first subset of beam strength values; and

(6) means for enabling the communication station to include said second beam in said new active beam set, wherein the communication station includes said second beam in said new active beam set if the strength of said first beam minus the strength of said second beam is less than or equal to a first threshold amount, wherein said first threshold amount is greater than or equal to zero.

19. The system of claim 18, wherein said means for enabling the communication station to determine, based on said plurality of beam strength values, a new active beam set further comprises:

(7) means for enabling the communication station to select a second subset of beam strength values from said first subset, wherein each beam strength value within said second subset of beam strength values corresponds to an active beam, wherein an active beam is a beam over which information is currently being transmitted between the user terminal and the communication station;

(8) means for enabling the communication station to select a third beam having the strongest beam strength based on said second subset of beam strength values; and

(9) means for enabling the communication station to include said third beam in said new active beam set, wherein the communication station includes said third beam in said new active beam set if the strength of said first beam minus the strength of said third beam is less than or equal to a second threshold amount.

20. The system of claim 19, wherein said second threshold amount is greater than or equal to said first threshold amount.