Method and apparatus for mitigating interference between base stations in a wideband CDMA system

• US 6,385,264 B1
• Filed: 06/08/1999
• Issued: 05/07/2002
• Est. Priority Date: 06/08/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Agrawal, Avneesh, Terasawa, Daisuke
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Tran, Khai
• Application Number:
  US09/328,119
• Time in Patent Office: 1,064 Days
• Field of Search: 375/371, 375/146, 375/296, 375/295, 375/220, 375/149, 375/130, 375/367, 375/141, 370/342, 370/335, 370/321
• US Class Current: 375/371
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 2201/70706 with means for reducing the peak-to-average power ratio
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04L 7/041 using special codes as synchronising signal
• CPC Class Codes: H04W 56/0085 detecting a given structure in the signal

Abstract

A method for mitigating the effect of interference between a first base station and a second base station, the first base station and second base stations both sharing a same primary synchronization code. The method includes generating a primary synchronization channel having the primary synchronization code. In a W-CDMA system, all base stations share this primary synchronization code, causing code timing collisions. The present invention includes rotating the primary synchronization channel in phase according to a phase rotation sequence before transmitting the primary synchronization channel. By rotating the primary synchronization channel in phase according to the phase rotation sequence, the interference can be reduced. The phase rotation sequence may be pseudorandom in phase. The phase rotation sequence may include changing phase once per slot, or alternately once per frame. The phase rotation sequence may also be based at least in part on a secondary synchronization code.

Claims

1. A method for mitigating the effect of interference between a first base station and a second base station, said first base station and second base stations both sharing a same primary synchronization code, the method comprising the steps of:

generating a primary synchronization channel having said primary synchronization code;

rotating said primary synchronization channel in phase according to a phase rotation sequence; and

transmitting said primary synchronization channel.

2. The method of claim 1 wherein said phase rotation sequence is pseudorandom.

3. The method of claim 2 wherein said phase rotation sequence includes changing phase once per slot.

4. The method of claim 2 wherein said phase rotation sequence includes changing phase once per frame.

5. The method of claim 3 wherein said phase rotation sequence includes changing phase by integer multiples of π

/2 radians.

6. The method of claim 4 wherein said phase rotation sequence includes changing phase by integer multiples of π

/2 radians.

7. The method of claim 2 further comprising the step of generating a secondary synchronization channel having a secondary synchronization code, said phase rotation sequence being based at least in part on said secondary synchronization code.

8. The method of claim 7 further comprising the step of:

combining said primary synchronization channel and said secondary synchronization channel to produce a synchronization channel;

wherein said step of rotating said primary synchronization channel in phase comprises rotating said primary synchronization channel before said combining step.

9. The method of claim 7 further comprising the step of:

combining said primary synchronization channel and said secondary synchronization channel to produce a synchronization channel;

wherein said step of rotating said primary synchronization channel in phase comprises rotating said synchronization channel in phase.

10. The method of claim 7 further comprising the steps of:

generating a dedicated channel;

combining said primary synchronization channel and said secondary synchronization channel to produce a synchronization channel; and

combining said synchronization channel and said dedicated channel to produce a downlink channel;

wherein said step of rotating said primary synchronization channel in phase comprises rotating said downlink channel in phase.

11. An apparatus for mitigating the effect of interference between a first base station and a second base station, said first base station and second base stations both sharing a same primary synchronization code, the apparatus comprising:

a primary synchronization channel generator for generating a primary synchronization channel having said primary synchronization code;

a phase rotator, coupled to said primary synchronization channel generator, for rotating said primary synchronization channel in phase according to a phase rotation sequence; and

a transmitter, coupled to said phase rotator, for transmitting said primary synchronization channel.

12. The apparatus of claim 11 wherein said phase rotation sequence is pseudorandom.

13. The apparatus of claim 12 wherein said phase rotation sequence includes changing phase once per slot.

14. The apparatus of claim 12 wherein said phase rotation sequence includes changing phase once per frame.

15. The apparatus of claim 13 wherein said phase rotation sequence includes changing phase by integer multiples of π

/2 radians.

16. The apparatus of claim 14 wherein said phase rotation sequence includes changing phase by integer multiples of π

/2 radians.

17. The apparatus of claim 12 further comprising a secondary synchronization channel generator for generating a secondary synchronization channel having a secondary synchronization code, said phase rotation sequence being based at least in part on said secondary synchronization code.

18. The apparatus of claim 17 further comprising:

a first combiner for combining said primary synchronization channel and said secondary synchronization channel to produce a synchronization channel;

wherein said phase rotator is coupled between an output of said primary synchronization channel generator and an input of said first combiner.

19. The apparatus of claim 17 further comprising:

a first combiner for combining said primary synchronization channel and said secondary synchronization channel to produce a synchronization channel;

wherein said phase rotator is coupled to an output of said first combiner.

20. The apparatus of claim 17 further comprising:

a first combiner for combining said primary synchronization channel and said secondary synchronization channel to produce a synchronization channel; and

a second combiner for combining said synchronization channel and a dedicated channel to produce a downlink channel;

wherein said phase rotator is coupled to an output of said second combiner.