Method for controlling transmission during handoff in a communication system

• US 5,491,717 A
• Filed: 10/18/1993
• Issued: 02/13/1996
• Est. Priority Date: 10/18/1993
• Status: Expired due to Term

• Current Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Hall, Scott M.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US08/137,334
• Time in Patent Office: 848 Days
• Field of Search: 455/33.1, 455/33.2, 455/53.1, 455/54.1, 455/54.2, 455/56.1, 455/67.1, 455/67.3, 379/58-60, 370/18
• US Class Current: 370/332
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 52/04 TPC
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

Transmission is controlled using the present method after a handoff procedure has been entered between a subscriber unit and target transceivers. During this process, a communication link between the subscriber and at least one other transceiver is maintained. A quality factor of a signal from the subscriber is received by the target transceiver. If the quality factor meets a quality threshold, then a transmission from the target transceiver is activated. If the target transceiver is active and the quality factor drops below the quality threshold, then the transmission from the target transceiver is terminated.

Claims

1. A method of controlling transmission during simultaneous handoff in a communication system, said method comprising the steps of:

A) measuring a quality factor of a signal from said subscriber received by said target transceiver;

B) increasing a transmission power from said target transceiver to said subscriber if said transmission power is below a normal power level and said quality factor meets a quality threshold; and

C) reducing said transmission power from said target transceiver to said subscriber to a power level below said normal power level if said transmission power is at said normal power level and said quality factor fails to meet said quality threshold.

2. The method of claim 1 further comprising the step of repeating said steps A through C until said handoff procedure is terminated.

3. The method of claim 1 wherein said quality factor is a received signal quality factor and said quality threshold is a received signal quality threshold.

4. The method of claim 1 wherein said communication system is a code division multiple access (CDMA) communication system.

5. The method of claim 4 wherein said CDMA communication system is a direct sequence (DS) CDMA communication system.

6. The method of claim 1 further comprising the step of reducing a transmission power from a source transceiver to said subscriber if said quality factor of said signal received from said subscriber by said source transceiver fails to meet said quality threshold.

7. The method of claim 6 further comprising the step of increasing said transmission power from said source transceiver to said subscriber if said quality factor of said signal received from said subscriber by said source transceiver fails to meet said quality threshold.

8. The method of claim 1 further comprising the steps of:

terminating a transmission from a source transceiver to said subscriber if said quality factor of said signal received from said subscriber by said source transceiver fails to meet said threshold and said transmission from said target transceiver is activated; and

designating said target transceiver as a new source transceiver.

9. The method of claim 1 wherein said quality factor comprises one of a reverse power control signal, a signal-to-noise ratio (E_b /N_o), a frame error/erasure rate (FER), a subscriber'"'"'s pilot strength message, and a subscriber'"'"'s received signal strength message.

10. The method of claim 1 further comprising the step of continuing to receive said signal from said subscriber at said target transceiver.

11. A method of controlling transmission during handoff in a communication system, said method comprises the steps of:

A) measuring a first quality factor and a second quality factor of a signal transmitted by said subscriber at said first and second transceivers, respectively;

B) comparing said first and second quality factors to determine a quality factor difference;

C) increasing a transmission power, from one of said first and second transceivers having a worse quality factor, to a normal power level if said transmission power is below said normal power level and said quality factor difference meets a transmit threshold; and

D) reducing said transmission power, when said transmission power is at, or exceeds, said normal power level, from said one of said first and second transceivers having said worse quality factor, to a power level below said normal power level, if said quality factor difference fails to meet said transmit threshold.

12. The method of claim 11 wherein said steps A through D are repeated until said handoff procedure is terminated.

13. The method of claim 11 wherein said communication system is a code division multiple access (CDMA) communication system.

14. The method of claim 13 wherein said CDMA communication system is a direct sequence (DS) CDMA communication system.

15. The method of claim 11 wherein said step of terminating said transmission from said one of said first and second transceivers having said worst quality factor is prevented if said quality factor from a remaining one of said first and second transceivers does not meet a handoff threshold.

16. The method of claim 11 wherein said quality factor comprises one of a reverse power control signal, a signal-to-noise ratio (E_b /N_o), a frame error/erasure rate (FER), a subscriber'"'"'s pilot strength message, and a subscriber'"'"'s received signal strength message.

17. The method of claim 11 wherein said quality factor is a received signal quality factor and said quality threshold is a received signal quality threshold.

18. A method of controlling transmission during handoff in a communication system, said method comprising the steps of:

A) measuring a first handoff quality factor of a transmission between a source transceiver and a subscriber and a second handoff quality factor of a signal between a target transceiver said subscriber;

B) allocating resources at said target transceiver for communication with said subscriber unit if said second handoff quality factor meets a handoff threshold of said first handoff quality factor;

C) measuring a first received signal quality factor of said signal between said subscriber and said source transceiver and a second received quality factor of said signal between said subscriber and said target transceiver;

D) increasing a transmission power from said target transceiver to said subscriber if said transmission power from said target transceiver is below a normal power level and said second received signal quality factor meets a received signal quality threshold of said first received signal factor;

E) reducing a transmission power from said source transceiver to said subscriber if said transmission power from said source transceiver is at, or exceeds, a normal power level and said first received signal quality factor is worse than said second received signal quality factor and fails to meet said received signal quality threshold of said second received signal quality factor; and

F) de-allocating resources at said source transceiver for communication with said subscriber unit if said first handoff quality factor fails to meet said handoff threshold of said second handoff quality factor.

19. The method of claim 18 wherein said communication system is a code division multiple access (CDMA) communication system.

20. The method of claim 19 wherein said CDMA communication system is a direct sequence (DS) CDMA communication system.

21. The method of claim 18 wherein said first and second received signal quality factors each comprise one of a reverse power control signal, a signal-to-noise ratio (E_b /N_o), a frame error/erasure rate (FER), a subscriber'"'"'s pilot strength message, and a subscriber'"'"'s received signal strength message.

22. The method of claim 18 wherein said first and second handoff quality factors measured at said subscriber each comprise a first transceiver'"'"'s transmission received signal level or a difference between said first and a second transceiver'"'"'s transmission received signal levels.

23. A method of controlling transmission during handoff in a communication system, said method comprising the steps of:

A) measuring a first handoff quality factor of a transmission between a source transceiver and a subscriber, a second handoff quality factor of a signal between a first target transceiver said subscriber, and a third handoff quality factor of a signal between a second target transceiver and said subscriber;

B) allocating resources at said first or second target transceivers for communication with said subscriber unit if said second or third handoff quality factors, respectively, meet a handoff threshold of said first handoff quality factor;

C) measuring a first received signal quality factor of said signal between said subscriber and said source transceiver, a second received quality factor of said signal between said subscriber and said first target transceiver, and a third received quality factor of said signal between said subscriber and said second target transceiver;

D) increasing a transmission power from said first or second target transceiver to said subscriber if said transmission power from said first or second target transceivers, respectively, are below a normal power level and said second or third received signal quality factors, respectively, meet a received signal quality threshold of said first received signal factor;

E) reducing a transmission power from said source transceiver to said subscriber if said transmission power from said source transceiver is at;

or exceeds, said normal power level and said first received signal quality factor is worse than said second or third received signal quality factor and fails to meet said received signal quality threshold of said same second or third received signal quality factor; and

F) de-allocating resources at said source transceiver for communication with said subscriber unit if said first handoff quality factor fails to meet said handoff threshold of said same second or third handoff quality factor.