Method for autonomous handoff in a wireless communication system

• US 6,337,983 B1
• Filed: 01/29/2001
• Issued: 01/08/2002
• Est. Priority Date: 06/21/2000
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Love, Robert T., Bonta, Jeffrey D., Dillon, Matthew J.
• Primary Examiner(s): Maung, Nay
• Assistant Examiner(s): Vuong, Quochien B.
• Application Number:
  US09/772,226
• Time in Patent Office: 344 Days
• Field of Search: 455/436, 455/437, 455/438, 455/439, 455/442, 455/443, 455/444, 370/335, 370/336
• US Class Current: 455/437
• CPC Class Codes: H04W 28/26 Resource reservation
• CPC Class Codes: H04W 36/0055 Transmission or use of information for re-establishing the radio link
• CPC Class Codes: H04W 36/08 Reselecting an access point

Abstract

A method and apparatus for handoff to a rescue channel is introduced without the need to send and receive handoff control messages. In the preferred embodiment of the present invention, coordination of the rescue procedure at the infrastructure and mobile station is provided first by disabling the mobile transmitter followed by subsequent detection of signal loss and frame erasures at the serving cells, then by enabling the mobile transmitter followed by subsequent detection of signal by a rescue cell, and finally by enabling the rescue cell channel transmitter followed by subsequent detection and reception of signal and frames by the mobile.

Claims

1. A method for a mobile unit to perform autonomous handoff within a communication system, the method comprising the steps of:

determining that a poor communication exists between the mobile unit and a base station;

de-keying a transmitter to break communication with the base station, causing a rescue base station to set up receiver resources to listen for the mobile unit; and

after a predetermined period of time, reactivating the transmitter causing the rescue base station to enable its transmitter to communicate to the mobile unit.

2. The method of claim 1 wherein the step of determining that the poor communication exists between the mobile and the base station comprises the step of detecting that a predetermined amount of bad frames has been received from the base station.

3. The method of claim 1 further comprising the step of assigning receiver resources to communicate with the rescue base station.

4. The method of claim 1 wherein the step of de-keying the transmitter to break communication comprises the step of turning off the transmitter to break communication.

5. A method for a mobile unit to perform autonomous handoff within a communication system, the method comprising the steps of:

communicating with a first base station;

receiving an active set of base stations from the first base station;

determining that a poor communication exists between the mobile and the first base station;

de-keying a transmitter to break communication with the first base station;

after a predetermined period of time, adding a second base station to the active set of base stations without being instructed to do so by any base station; and

receiving transmission from the second base station.

6. The method of claim 5 wherein the step of determining that poor communication exists comprises the step of determining that a predetermined amount of bad frames has been received.

7. A method for autonomous handoff, the method comprising the steps of:

detecting that communication with a first base station has been lost;

de-keying a transmitter in response to the detection that communication with the first base station has been lost;

determining a list of candidate base stations for autonomous handoff;

re-keying the transmitter to send a message to the first base station in order to facilitate the autonomous handoff to a second base station.

8. The method of claim 7 wherein the step of re-keying the transmitter comprises the step of re-keying the transmitter at a full power level.

9. The method of claim 7 wherein the step of detecting that communication with the first base station has been lost comprises the step of detecting that a predetermined amount of bad frames has been received from the first base station.

10. The method of claim 7 wherein the step of de-keying the transmitter in response to the detection that communication with the first base station has been lost comprises the step of turning off the transmitter in response to the detection that communication with the first base station has been lost.

11. A method for autonomous handoff within a communication system, the method comprising the steps of:

determining that a first mobile unit has lost communication;

determining that a second mobile unit has lost communication;

determining that a similar base station needs to rescue both the first and the second mobile unit;

communicating with the first mobile unit on a rescue channel;

forcing a handover of the first mobile unit to a second channel served by the similar base station based on the determination that the similar base station needs to rescue both the first and the second mobile unit; and

communicating with the second mobile unit on the rescue channel after the forced handover.