Method and apparatus for call recovery in a wireless communication system

• US 20020077104A1
• Filed: 12/15/2000
• Published: 06/20/2002
• Est. Priority Date: 12/05/2000
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wang, Jun, Chen, Tao
• Granted Patent: US 7,945,266 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04W 36/005 involving radio access media independent information, e.g. MIH [Media independent Hand-off]
• CPC Class Codes: H04W 36/0061 of neighbour cell information
• CPC Class Codes: H04W 76/19 Connection re-establishment

Abstract

A method and apparatus for call recovery in a wireless communication system (10). When the communication link between a mobile station (38) and a base station (32) is in trouble, the mobile station and the infrastructure prearrange potential rescue base stations (34). The source cell base station contacts all recovery-capable neighbors as potential rescuers. Each rescue base station is instructed to use a default channel for rescue transmissions. The rescue transmission is considered a call recovery operation. The mobile station establishes a soft hand-off with rescue base station, wherein the FL uses the default channel and an alternate channel. Once hand-off is complete the rescue base station discontinues use of the default channel. In one embodiment, the source cell base station provides the mobile station with the list of recovery-capable neighbors as overhead during transmissions and prior to development of the communication link problem.

Claims

1. In a wireless communication system having a plurality of base stations, each of the plurality of base stations having a neighbor set comprising neighboring base stations, each of the neighboring base stations having a default channel, a method comprising:

transmitting default channel information to a mobile station;

detecting occurrence of a call recovery trigger; and

instructing all base stations in the neighbor set to transmit on respective default channels.

2. The method of claim 1, wherein the call recovery trigger occurs when the FL signal quality is below a predetermined threshold.

3. The method of claim 1, wherein the call recovery trigger occurs when:

acknowledging a first message from the mobile station; and

receiving the first message from the mobile station a predetermined number of times subsequent to acknowledging the first message.

4. The method of claim 1, further comprising:

establishing soft hand-off with the neighbor set wherein each of the neighbor set transmits on an alternate channel.

5. The method of claim 4, further comprising:

receiving a hand-off complete message from the mobile station.

6. The method of claim 1, further comprising:

determining an active set of the mobile station.

7. The method of claim 6, further comprising:

receiving a pilot signal measurement message from the mobile station, the pilot signal measurement message including signal strength measurements for a set of base stations; and

assigning the set of base stations to the active set.

8. The method of claim 6, wherein at least one base station in the neighbor set has acquired a signal from the mobile station, the method further comprising:

assigning the at least one base station to the active set.

9. The method of claim 1, wherein a first neighbor in the neighbor set has a plurality of default channels.

10. The method of claim 9, wherein the mobile station uses a deterministic function to determine one of the plurality of default channels to use for call recovery.

11. The method of claim 10, wherein the deterministic function is a hash function.

12. The method as in claim 10, wherein a first identifier is associated with the mobile station, the method further comprising:

transmitting the first identifier to the first neighbor; and

instructing the first neighbor to use the deterministic function to determine one of the plurality of default channels to use for call recovery.

15. The apparatus of claim 14, wherein the predetermine power control instruction is based on the transmit power level prior to the call recovery.

16. The apparatus of claim 14, wherein the predetermine power control instruction is based on the transmit power level prior to the call recovery.

17. The apparatus of claim 15, wherein the predetermine power control instruction is based on the transmit power level prior to the call recovery.

19. The computer program of claim 18, wherein the special event is a Global Positioning System (GPS) search operation.

20. The computer program of claim 19, wherein the special event is a candidate frequency search operation.

13. A wireless apparatus, comprising:

an antenna;

a processor coupled to the antenna;

transmit circuitry coupled to the antenna and the processor;

receiver circuitry coupled to the antenna and the processor;

a first set of computer readable instructions executable by the processor to receive a list of neighbors for a base station, the list including default channel assignments for each of the neighbors;

a second set of computer readable instructions executable by the processor to identify a call recovery trigger and disable a transmit circuitry in response; and

a third set of computer readable instructions executable by the processor to establish hand-off with at least one of the neighbors.

14. A wireless apparatus, comprising:

a transmitter circuit;

a recovery adjust unit operative subsequent to a call recovery operation to generate a predetermined power control instruction; and

a power adjust unit coupled to the recovery adjust unit and the transmitter circuit, the power adjust unit operative to adjust the transmitter circuit in response to the power control instruction.

18. A computer program embodied on a computer-readable medium containing computer-executable instructions, the program comprising:

A first set of instructions operative to identify a special event;

A second set of instructions operative to disable call recovery during the special event; and

A third set of instructions operative to notify a wireless communication system of the special event.