Precoordination of return link for hand-off between coverage areas being traversed by a mobile transceiver platform

• US 6,885,863 B2
• Filed: 08/31/2001
• Issued: 04/26/2005
• Est. Priority Date: 08/31/2001
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Hellman, Richard A., Parkman, David S., Stephenson, Gary V
• Primary Examiner(s): Gary, Erika
• Assistant Examiner(s): SMITH, SHEILA B
• Application Number:
  US09/945,089
• Publication Number:
  US 20040092263A1
• Time in Patent Office: 1,334 Days
• Field of Search: 455/12.1, 455/13.1, 455/427, 455/428, 455/430, 455/431, 455/436, 455/437, 455/438, 455/439, 370/316
• US Class Current: 455/427
• CPC Class Codes: H04B 7/18508 with satellite system used as relay, i.e. aeronautical mobile satellite service
• CPC Class Codes: H04B 7/18541 for handover of resources
• CPC Class Codes: H04W 36/00 Hand-off or reselection arrangements
• CPC Class Codes: H04W 72/04 Wireless resource allocation
• CPC Class Codes: H04W 84/06 Airborne or Satellite Networks space-based or airborne stations H04B7/185

Abstract

A system and method for carrying out a hand-off of a satellite-based communications link with a mobile platform, such as an aircraft, leaving a first coverage region and entering a second coverage region. A land-based communications link connects ground stations in each of the coverage regions for communications with one another and also with a network operations center (NOC). As the aircraft enters an area of overlap between the two coverage regions, a sequence of communications is initiated between the ground stations and also between each of the ground stations and the aircraft to ensure that new forward link and return link assignments are received by the aircraft before the aircraft relinquishes its communications link with the first ground station to begin communicating with the second ground station. The hand-off in communications is accomplished in less than approximately 30 seconds of time after one of the ground stations detects that the aircraft has entered a pre-defined overlap area between the two coverage regions.

Claims

1. A method for coordinating a hand-off of communication from a mobile radio frequency (RE) transceiver on a mobile platform leaving a first coverage region, wherein it is in communication with a first satellite-based transponder and also with a first base station, to communicate via a second satellite-based transponder with a second base station residing within a second coverage area;

defining an overlap region between said first and second coverage areas;

using said first base station to determine when said mobile platform has entered said overlap region;

using said first base station to obtain a communication link assignment from said second base station and to relay said communication link assignment to said mobile platform via said first satellite based transponder; and

causing said mobile platform to transmit a signal to said second base station, via said second satellite-based transponder, acknowledging receipt of said communication link assignment before said first base station releases communications assets assigned to said mobile platform.

2. The method of claim 1, further comprising the step of causing said second base station to transmit a signal to said first base station informing said first base station that said hand-off is complete.

3. The method of claim 1, further comprising the step of causing said mobile platform to transmit a signal to said first base station acknowledging receipt of said communication link assignment.

4. The method of claim 1, further comprising the step of coupling said first and second base stations via a land-based communication line.

5. The method of claim 1, wherein said hand-off is completed within less than sixty seconds after said first base station requests said second base station to provide said communication link assignment.

6. The method of claim 1, wherein the step of said second base station providing said communication link assignment comprises providing a public key for decrypting subsequently transmitted encrypted information from said base station.

7. A method for coordinating a hand-off of communication from a mobile radio frequency (RE) transceiver on a mobile platform travelling within a first coverage region and communicating with a first ground based transceiver station via a first satellite transponder, to a second ground-based transceiver disposed within a second coverage area via a second satellite transponder as said mobile platform leaves said first coverage area and enters said second coverage area, said method comprising the steps of:

a) defining said first coverage area;

b) defining said second coverage area such that an area of overlap exists between said first and second coverage areas;

c) placing said first and second ground-based transceivers in communication with each other via a land-based communication line;

d) having said mobile platform periodically report its position to said first ground-based transceiver;

e) using said first ground-based transceiver to determine when said mobile platform has entered said area of overlap and to request from said second ground-based transceiver a hand-off of communication with said mobile transceiver from said first ground-based transceiver to said second ground-based transceiver;

f) using said second ground-based transceiver to transmit transponder assignment information concerning said second satellite transponder to said first ground-based transceiver;

g) using said first ground-based transceiver to transmit said assignment information to said mobile platform via said first satellite transponder;

h) using said second ground-based transceiver to poll said mobile platform to verify a presence of said mobile platform within said area of overlap; and

i) using said mobile transceiver to transmit an acknowledgement to said second ground-based transceiver via said second satellite-based transponder, to acknowledge receipt of said assignment information in response to said poll, whereafter said mobile platform communicates with said second ground-based transceiver rather than said first ground-based transceiver.

8. The method of claim 7, further comprising the step of:

after receiving said assignment information from said first ground-based transceiver, causing said mobile transceiver to transmit a signal acknowledging reception of said assignment information back to said first ground-based transceiver.

9. The method of claim 7, further comprising the step of:

after receiving said acknowledgement from said mobile transceiver at said second ground-based transceiver, using said second ground-based transceiver to inform said first ground-based transceiver that said hand-off is complete.

10. The method of claim 9, further comprising the step of having said first ground-based transceiver transmit an acknowledgement signal to said second ground-based transceiver acknowledging that said second ground-based transceiver has taken over communication with said mobile transceiver.

11. The method of claim 7, wherein step f) comprises the step of transmitting a public key to said mobile transceiver;

and

wherein said public key enables said mobile transceiver to decrypt subsequently encrypted data transmitted from said second ground-based transceiver via said second satellite-based transponder.

12. A method for coordinating a hand-off of communication from a mobile radio frequency (RE) transceiver on a mobile platform from a first base station to a second base station as said mobile platform travels from a first coverage region into a second coverage region, the method comprising the steps of:

defining an area of overlap between said first and second coverage areas;

when said mobile platform enters said overlap area, causing said second base station to transmit, via a land based communications line coupling said base stations, a new communication link assignment to said first base station;

using said first base station to relay said new communication link assignment, via a first satellite-based transponder orbiting within said first coverage area, to said mobile RF transceiver; and

causing said mobile transceiver to transmit an acknowledgement signal, via a second satellite-based transponder orbiting within said second coverage area, to said first base station, that said mobile platform has received said new communications link assignment.

13. The method of claim 12, further comprising the step of causing said mobile platform to periodically report its position to said first base station.

14. The method of claim 12, further comprising the step of causing said mobile RF transceiver to transmit an acknowledgement signal to said second base station acknowledging reception of said new communications link assignment.

15. The method of claim 14, further comprising the step of causing said second base station to transmit a return acknowledgement signal to said first base station after receiving said acknowledgement signal from said mobile RF transceiver.

16. The method of claim 15, further comprising the step of causing said first base station to transmit a reply acknowledgement to said second base station acknowledging that said hand-off is complete.

17. A system for enabling a hand-off of communications from a mobile platform communicating with a first base station in a first coverage region via a first satellite based transponder, to a second base station in a second coverage region via a second satellite based transponder, comprising:

a radio frequency (RF) transceiver disposed on said mobile platform;

a first base station having an RF transceiver and being located in said first coverage region;

a second base station having an RF transceiver and being located in said second coverage region;

a land based communications line coupling said first and second base stations;

a network operations center (NOC) in communications with each of said base stations via said land based communications line; and

wherein said NOC coordinates a hand-off of communications between said mobile platform and said first base station to said second base station by;

detecting when said mobile platform enters a region of overlap between said coverage regions;

causing said second base station to transmit transponder related assignment information to said first base station;

causing said first base station to relay said assignment information to said mobile platform via said first satellite-based transponder;

causing said second base station to poll said mobile platform;

causing said mobile platform to respond to said poll via said second satellite-based transponder, to acknowledge receipt of said assignment information; and

causing said second base station to inform said first base station that a communications link with said mobile platform has been established.