Emergency handoff method of redirecting calls in a satellite communication system

• US 5,826,190 A
• Filed: 02/18/1997
• Issued: 10/20/1998
• Est. Priority Date: 01/04/1995
• Status: Expired due to Term

• Current Assignee: CDC Propriete Intellectuelle
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Krutz, Michael William, Tayloe, Daniel Richard, Bakke, Bradley B.
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US08/801,322
• Time in Patent Office: 609 Days
• Field of Search: 455/13.2, 455/12.1, 455/13.1, 455/33.1, 455/33.2, 455/34.2, 455/57.1, 455/56.1, 455/422, 455/427, 455/428, 455/429, 455/436, 455/437, 455/438, 455/439
• US Class Current: 455/428
• CPC Class Codes: H04B 7/18541 for handover of resources

Abstract

An emergency handoff method (50) reroutes or redirects communications from one channel in a cell (105) to another channel in the same cell (105) or a different cell (107). Handoff is initiated by a subscriber unit (SU) (100) when the SU (100) determines that an emergency handoff is needed. Once a new channel is needed, the SU (100) chooses a new, available channel to transfer its communication. After selecting an available channel, the SU (100) acquires the available channel. The servicing satellite which is providing the available channel then makes the constellation of satellites reroute or redirect the call data or the communication packets across the new channel to the SU (100).

Claims

1. A method of handing-off a call from a current channel to one of a plurality of available channels in a satellite cellular communication system, the call being between a first subscriber unit (SU) and a second SU, the current channel being projected onto earth by a first satellite, the available channels being projected onto earth by a second satellite, a third satellite servicing the second SU, the method comprising the steps of:

a) the first SU determining that an emergency handoff is needed, wherein synchronization is not lost;

b) the first SU acquiring an available channel from the available channels and providing a logical channel number to the second satellite;

c) the second satellite creating a new logical channel number;

d) the second satellite receiving a pathend from the first satellite;

e) the second satellite transmitting the new logical channel number to the pathend, the pathend being the third satellite;

f) the third satellite rerouting the call from the first satellite to the second satellite; and

g) the third satellite rerouting the call from the first satellite to the second satellite so that the second satellite can redirect the call to the available channel.

2. A method as recited in claim 1, wherein step (c) further comprises the step of the second satellite transmitting the new logical channel number to the first SU.

3. A method of handing-off a call from a current channel to one of a plurality of available channels in a satellite cellular communication system, the call being between a first subscriber unit (SU) and a second SU, the current channel being projected onto earth by a first satellite, the available channels being projected onto earth by a second satellite, a third satellite servicing the second SU, the method comprising the steps of:

(a) the first SU determining that an emergency handoff is needed, wherein synchronization is not lost;

(b) the first SU identifying an available cell from a list of available cells;

(c) the first SU acquiring an available channel from the available cell;

(d) the second satellite creating a new logical channel number;

(e) the second satellite receiving a pathend from the first satellite;

(f) the second satellite transmitting the new logical channel number to the pathend, the pathend being the third satellite;

(g) the third satellite rerouting the call from the first satellite to the second satellite; and

(h) the second satellite redirecting the call to the available channel.

4. A method of handing-off a call from a current channel to one of a plurality of available channels in a satellite cellular communication system, the call being between a first subscriber unit (SU) and a second SU, the current channel being projected onto earth by a first satellite, the available channels being projected onto earth by the first and a second satellite, a third satellite servicing the second SU, the method comprising the steps of:

(a) the first SU determining that an emergency handoff is needed, wherein synchronization is not lost;

(b) the first SU identifying an available cell from a list of available cells;

(c) the first SU acquiring an available channel from the available cell;

(d) the first SU providing a logical channel number to one of the first and second satellites;

(e) the first satellite rerouting the call to the available channel if the logical channel number matches a logical channel number of the first satellite;

(f) the third satellite rerouting the call from the first satellite to the second satellite if the logical channel number does not match a logical channel of the second satellite; and

(g) the second satellite redirecting the call to the available channel if the logical channel number does not match the logical channel of the second satellite.

5. A method of handing-off a call from a current channel to one of a plurality of available channels in a satellite cellular communication system, the call being between a first subscriber unit (SU) and a second SU, the current channel being projected onto earth by a first satellite, the available channels being projected onto earth by a second satellite, the second satellite servicing the second SU, the method comprising the steps of:

(a) the first SU determining that an emergency handoff is needed, wherein synchronization is not lost;

(b) the first SU acquiring an available channel from the available channels;

(c) the second satellite determining whether it handled the call before the first SU acquired the available channel;

(d) the second satellite requesting and receiving a pathend from the first satellite;

(e) the second satellite determining that the pathend is the second satellite; and

(f) the second satellite rerouting the call to the available channel.