Method and apparatus for reducing the average transmit power of a base station

• US 6,546,058 B1
• Filed: 09/29/2000
• Issued: 04/08/2003
• Est. Priority Date: 10/28/1993
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gilhousen, Klein S., Padovani, Roberto
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US09/675,306
• Time in Patent Office: 921 Days
• Field of Search: 375/267, 375/347, 375/130, 375/285, 375/346, 455/442, 455/437, 455/522, 455/436, 455/63, 455/439, 455/438, 455/562, 370/342, 370/338, 370/328, 370/331, 370/332, 370/335
• US Class Current: 375/285
• CPC Class Codes: H04B 7/0491 using two or more sectors, i.e. sector diversity
• CPC Class Codes: H04W 16/24 Cell structures
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/20 for optimising the interference level
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

A plurality of methods for achieving the soft or softer handoff process such that the performance of a system is improved. A first method is based on delaying the softer handoff process. A second method is based on reducing the power of transmissions from the sector having the weakest signal strength. A third method is based on eliminating transmissions from the sector having the weakest signal strength. A fourth method adds a new base station or sector only when the mobile unit is in need of additional power to operate properly. In all four methods, reverse link demodulation in each sector may continue with or without the transmission of the forward link. In all four methods the operation could be based on the signal strength of the reverse link signal or the forward link. It is also possible to combine two or more of these methods to create a hybrid method.

Claims

1. A method for reducing interference in a communication system having a base station comprised of multiple sectors, comprising:

communicating on a forward link and a reverse link between a mobile unit and a first sector of the base station;

receiving through a second sector of the base station a reverse link signal from the mobile unit;

measuring a signal strength of at least one of the reverse link signals and comparing the signal strength to a predefined threshold; and

delaying transmission of a forward link signal through the second sector to the mobile unit until the signal strength exceeds the predefined threshold.

2. The method of claim 1, further comprising:

combining the reverse link signal received through the second sector with the reverse link signal received through the first sector to produce an aggregate signal, independent of whether or not the transmission of the forward link signal through the second sector has begun.

3. The method of claim 2 further comprising:

determining a power control command in accordance with the aggregate signal; and

transmitting the power control command to the mobile unit.

4. The method of claim 2 further comprising:

determining a power control command in accordance with the aggregate signal; and

transmitting the power control command to the mobile unit on the forward link signal through the first sector when the transmission of the forward link signal through the second sector is delayed.

5. The method of claim 1, wherein said measuring a signal strength of at least one of the reverse link signals and comparing the signal strength to a predefined threshold comprises:

measuring a signal strength of the reverse link signal received through the second sector of the base station from the mobile unit and comparing the signal strength to a predefined threshold.

6. The method of claim 2 wherein said measuring a signal strength of at least one of the reverse link signals and comparing the signal strength to a predefined threshold:

measuring a signal strength of the aggregate reverse link signal.

7. A method for reducing interference in a communication system having a base station comprised of multiple sectors, comprising:

communicating on a forward link and a reverse link between a mobile unit and a first sector of the base station;

receiving a forward link pilot signal from a second sector of the base station;

measuring a signal strength of at least one of forward link pilot signals and comparing the signal strength to a predefined threshold; and

delaying transmission of a forward link signal through the second section to the mobile unit until the signal strength exceeds the predefined threshold.

8. The method of claim 7, wherein said measuring signal strength of at least one of forward link pilot signals and comparing the signal strength to a predefined threshold comprises:

measuring signal strength of an aggregate forward pilot link signal, the aggregate forward pilot link signal being obtained by combining the forward link pilot signal received from the second sector with a forward link pilot signal received from the first sector and comparing the signal strength to a predefined threshold.

9. The method of claim 7, wherein said measuring a signal strength of at least one of forward link pilot signals and comparing the signal strength to a predefined threshold comprises:

measuring the signal strength of the forward pilot link signal received from the second sector of the base station and comparing the signal strength to a predefined threshold.

10. The method of claim 8, further comprising:

determining a power control command in accordance with the aggregate signal; and

transmitting the power control command to the mobile unit.

11. The method of claim 8, wherein said transmitting the power control command to the mobile unit comprises:

transmitting the power control command to the mobile unit on the forward link through the first sector when the transmission of the forward link signal through the second sector is delayed.

12. A method for reducing interference in a communication system, comprising:

communicating between a mobile unit and a first sector on a forward link and a reverse link;

measuring a signal strength of the reverse link at each of the first sector and at least a second sector;

summing the measured signal strengths in decreasing order of magnitudes until a desired signal strength is reached;

determining each of the at least second sector whose measured signal strength was utilized in the summation; and

initiating transmission of a forward link signal through each of the determined at least second sector.

13. The method of claim 12, wherein the measuring a signal strength of the reverse link at each of the first sector and at least a second sector comprises:

measuring a signal strength of the reverse link at each of the first sector and at least a second sector, wherein the first sector and the at least second sector comprise a base station.

14. The method of claim 12 wherein the measuring a signal strength of the reverse link at each of the first sector and at least a second sector comprises:

measuring a signal strength of the reverse link at each of the first sector and at least a second sector, wherein the first sector and the at least second sector comprise different base stations.

15. A method for reducing interference in a communication system, comprising:

communicating between a mobile unit and a first sector on a forward link and a reverse link;

measuring a signal strength of forward links transmitted by the first sector and at least one second sector at a remote unit;

summing the measured signal strengths in decreasing order of magnitudes until a desired signal strength is reached;

determining each of the at least second sector whose measured signal strength was utilized in the summation; and

initiating transmission of a forward link signal through each of the determined at least second sector.

16. The method of claim 15, wherein the measuring a signal strength of forward links transmitted by the first sector and at least one second sector at a remote unit comprises:

measuring a signal strength of forward links transmitted by the first sector and at least one second sector at a remote unit, wherein the first sector and the at least second sector comprise a base station.

17. The method of claim 15, wherein the measuring a signal strength of forward links transmitted by the first sector and at least one second sector at a remote unit comprises:

measuring a signal strength of forward links transmitted by the first sector and at least one second sector at a remote unit, wherein the first sector and the at least second sector comprise different base stations.

18. A method for reducing interference in a communication system, comprising:

communicating between a mobile unit and at least two sectors on forward links and a reverse link;

measuring a signal strength of the reverse link at each of the at least two sectors;

summing the measured signal strengths in decreasing order of magnitudes until a desired signal strength is reached;

determining each of the at least two sectors whose measured signal strength was not utilized in the summation; and

ceasing transmission of a forward link signal through each of the determined at least two second sectors.

19. The method of claim 18, wherein the measuring a signal strength of the reverse link at each of the at least two sectors comprises:

measuring a signal strength of the reverse link at each of the at least two sectors, wherein the at least two sectors comprise a base station.

20. The method of claim 18, wherein the measuring a signal strength of the reverse link at each of the at least two sectors comprises:

measuring a signal strength of the reverse link at each of the at least two sectors, wherein the at least two sectors comprise different base stations.

21. A method for reducing interference in a communication system having a base station comprised of multiple sectors, comprising:

communicating between a mobile unit and at least two sectors on forward links and a reverse link;

measuring a signal strength of each of the forward link transmitted by the at least two sectors at the mobile unit;

summing the measured signal strengths in decreasing order of magnitudes until a desired signal strength is reached;

determining each of the at least two sectors whose measured signal strength was not utilized in the summation; and

ceasing transmission of a forward link signal through each of the determined at least two second sectors.

22. The method of claim 21, wherein the measuring a signal strength of each of the forward link transmitted by the at least two sectors at a remote unit comprises:

measuring a signal strength of each of the forward link transmitted by the at least one two sectors at a remote unit, wherein the at least two sectors comprise a base station.

23. The method of claim 21, wherein the measuring a signal strength of each of the forward link transmitted by the at least two sectors at a remote unit comprises:

measuring a signal strength of each of the forward links transmitted by the at least two sectors at a remote unit, wherein the at least two sectors comprise different base stations.