Method and apparatus for communications hand-off between multiple satellite systems

• US 5,920,804 A
• Filed: 04/02/1996
• Issued: 07/06/1999
• Est. Priority Date: 04/02/1996
• Status: Expired due to Term

• Current Assignee: CDC Propriete Intellectuelle
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Tayloe, Daniel Richard, Armbruster, Peter Joseph, Sowles, Kenneth Lee
• Primary Examiner(s): Tung, Bryan
• Assistant Examiner(s): Le, Vu
• Application Number:
  US08/626,589
• Time in Patent Office: 1,190 Days
• Field of Search: 455/13.2, 455/13.1, 455/12.1, 455/8, 455/427, 455/428, 455/430, 455/9-10, 455/436, 455/438-439, 455/453, 370/316, 359/172, 342/352-358, 178/2, 136/292
• US Class Current: 455/13.2
• CPC Class Codes: H04B 7/18541 for handover of resources
• CPC Class Codes: H04B 7/18584 Arrangements for data networking, i.e. for data packet routing, for congestion control data switching networks H04L12/00
• CPC Class Codes: H04B 7/195 Non-synchronous stations

Abstract

A method and apparatus for handing off communications between a primary satellite system (500) and an alternate satellite system (550) determines (602) when a hand-off condition for the primary satellite system (500) exists. An alternate satellite (552) is determined (604, 904) which has a coverage area (554) which is positioned such that the alternate satellite (552) can provide an alternate communication link (556). A hand-off between the primary satellite system (500) and the alternate satellite system (550) is then performed (606). When the hand-off condition is alleviated (610), a hand-off back to the primary satellite system (550) is performed and normal operations are resumed (600).

Claims

1. A method for a ground facility to hand-off a communication link with a primary satellite system to an alternate satellite system when the primary satellite system experiences a hand-off condition which the primary satellite system wants to alleviate by using communication services of the alternate satellite system, wherein the alternate satellite system supports an alternate communication link which can alleviate the hand-off condition, wherein the hand-off condition is that a coverage area hole exists within the primary satellite system, and wherein the ground facility is a switching gateway, prior to the hand-off to the alternate satellite system, the communication link exists between the switching gateway and a first primary satellite of the primary satellite system, and wherein during a normal hand-off within the primary satellite system, the switching gateway would acquire a second primary satellite of the primary satellite system, the method comprising the steps of:

a) detecting, by the ground facility attempting to acquire the second primary satellite and detecting that the coverage area hole exists within the primary satellite system when the attempt is unsuccessful, because the communication link cannot continue to be maintained with the primary satellite system;

b) determining that the hand-off condition exists based on the detecting step;

c) establishing the alternate communication link with the alternate satellite system; and

d) sending traffic to and receiving the traffic from the alternate satellite system over the alternate communication link.

2. A method for a ground facility to hand-off a communication link with a primary satellite system to an alternate satellite system when the primary satellite system experiences a hand-off condition which the primary satellite system wants to alleviate by using communication services of the alternate satellite system, wherein the alternate satellite system supports an alternate communication link which can alleviate the hand-off condition, wherein the hand-off condition is that a coverage area hole exists within the primary satellite system, the method comprising the steps of, wherein the ground facility is a switching gateway, prior to a hand-off to the alternate satellite system, the communication link exists between the switching gateway and a first primary satellite of the primary satellite system, during a normal hand-off within the primary satellite system, the switching gateway would switch to a second primary satellite of the primary satellite system, the method comprising the steps of:

a) detecting, by the ground facility, that the coverage area hole exists within the primary satellite system because the communication link cannot continue to be maintained with the primary satellite system based on receiving an instruction from a control facility that the switching gateway must switch to an alternate satellite of the alternate satellite system rather than to the second primary satellite;

b) determining that the hand-off condition exists based on the detecting step;

c) establishing the alternate communication link with the alternate satellite system; and

d) sending traffic to and receiving the traffic from the alternate satellite system over the alternate communication link.

3. A method for a ground facility to hand-off a communication link with a primary satellite system to an alternate satellite system when the primary satellite system experiences a hand-off condition which the primary satellite system wants to alleviate by using communication services of the alternate satellite system, wherein the alternate satellite system supports an alternate communication link which can alleviate the hand-off condition, wherein the hand-off condition is that a coverage area hole exists within the primary satellite system, wherein the ground facility is a communication unit (CU), prior to a hand-off to the alternate satellite system, the communication link exists between the CU and the primary satellite system through a first channel provided by the primary satellite system, during a normal hand-off within the primary satellite system, the CU would hand-off to a second channel of the primary satellite system, the method comprising the steps of:

a) detecting, by the ground facility, that the coverage area hole exists within the primary satellite system because the communication link cannot continue to be maintained with the primary satellite system based on attempting to hand-off to the second channel provided by the primary satellite system;

b) determining that the hand-off condition exists based on the detecting step;

c) establishing the alternate communication link with the alternate satellite system; and

d) sending traffic to and receiving the traffic from the alternate satellite system over the alternate communication link.

4. A method for a ground facility to hand-off a communication link with a primary satellite system to an alternate satellite system when the primary satellite system experiences a hand-off condition which the primary satellite system wants to alleviate by using communication services of the alternate satellite system, wherein the alternate satellite system supports an alternate communication link which can alleviate the hand-off condition, wherein the hand-off condition is that a coverage area hole exists within the primary satellite system, wherein the ground facility is a communication unit (CU), prior to a hand-off to the alternate satellite system, the communication link exists between the CU and the primary satellite system through a first channel provided by the primary satellite system, during a normal hand-off within the primary satellite system, the CU would hand-off to a second channel of the primary satellite system, the method comprising the steps of:

a) detecting, by the ground facility, that the coverage area hole exists within the primary satellite system because the communication link cannot continue to be maintained with the primary satellite system based on receiving an instruction from a switching gateway that the CU must switch to an alternate channel of the alternate satellite system rather than to the second channel;

b) determining that the hand-off condition exists based on the detecting step;

c) establishing the alternate communication link with the alternate satellite system; and

d) sending traffic to and receiving the traffic from the alternate satellite system over the alternate communication link.

5. A method for handing-off a communication link with a ground facility from a primary satellite system to an alternate satellite system, the method comprising the steps of:

a) detecting, by a control facility, that a hand-off condition exists when a need to hand-off from the primary satellite system to the alternate satellite system arises;

b) predicting, by the control facility, a hand-off time when the primary satellite system should hand-off to the alternate satellite system;

c) generating, by the control facility, a first instruction which instructs a primary satellite of the primary satellite system to hand-off the communication link to an alternate satellite of the alternate satellite system at the hand-off time rather than to hand-off the communication link within the primary satellite system, wherein after hand-off, the first instruction will cause the primary satellite to send traffic to and receive the traffic from the alternate satellite;

d) sending, by the control facility, the first instruction to the primary satellite prior to the hand-off time;

e) receiving, by the primary satellite, the first instruction to hand-off the communication link to the alternate satellite;

f) establishing, by the primary satellite, a cross-link with the alternate satellite as a result of the first instruction;

g) receiving, by the alternate satellite, a second instruction to provide the communication services to the ground facility using an alternate communication link with the ground facility;

h) establishing, by the ground facility, the alternate communication link with the alternate satellite;

j) sending, by the ground facility, traffic to and receiving traffic from the alternate satellite system over the alternate communication link;

k) discontinuing, by the primary satellite, sending and receiving the traffic through the communication link between the primary satellite and the ground facility;

l) sending and receiving, by the primary satellite, the ground facility traffic through the alternate satellite over the cross-link;

m) routing, by the alternate satellite, the traffic from the ground facility destined for the primary satellite system through the cross-link; and

n) routing, by the alternate satellite, the traffic from the primary satellite destined for the ground facility through the alternate communication link.