Interference cancellation in a spread spectrum communication system

• US 20050025224A1
• Filed: 08/23/2004
• Published: 02/03/2005
• Est. Priority Date: 09/10/1999
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Reznik, Alexander, Mesecher, David K., Cheung, Gary, Grieco, Donald
• Granted Patent: US 6,985,515 B2
• Time in Patent Office: Days
• US Class Current: 375/147
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 7/0613 using simultaneous transmission H04B7/0686 takes precedence
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/0678 using different spreading codes between antennas code allocation H04J13/16
• CPC Class Codes: H04B 7/0845 per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch rake receivers as such H04B1/7115
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04B 7/0857 using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• CPC Class Codes: H04B 7/0891 Space-time diversity rake receivers H04B1/7115; space-time decoding H04L1/0631
• CPC Class Codes: H04J 13/0003 Code application, i.e. aspects relating to how codes are applied to form multiplexed channels

Abstract

A code division multiple access communication system transmits a pilot and traffic signal over a shared spectrum. The pilot and traffic signal have an associated code and are received over the shared spectrum. The received signals are sampled and the samples are delayed to produce a window. A weighted value for each despread pilot code window sample is determined using an adaptive algorithm. Each window sample is despread with a traffic code. Each despread traffic code window sample is weighted according to a weight corresponding to its respective pilot code sample.

Claims

1. A method for receiving a traffic signal in a code division multiple access communication system, the system transmitting a traffic signal over a shared spectrum, traffic signal having an associated code, the method comprising:

receiving signals over the shared spectrum;

sampling the received signals to produce samples;

delaying the samples to produce a window, the window having evenly time spaced samples;

despreading the samples and determining a weight for each despread window sample using an adaptive algorithm, the adaptive algorithm providing a determination of an optimum weight for each of a plurality of despread components;

despreading each window sample with a traffic code;

weighting each despread traffic code window sample with a weight corresponding to a weight of its respective pilot signal; and

combining the weighted despread traffic code window sample as data of the traffic signal.

2. The method of claim 1 comprising the despreading including using the window sample and a delayed version of the window sample obtained by said delaying the samples.

3. The method of claim 1 comprising:

the system transmitting a reference signal and the traffic signal over a shared spectrum, the reference signal having an associated reference code; and

despreading each window sample with the reference code so that the determining of the weight for each window provides an optimum weight for each of a plurality of despread components with the reference signal.

4. The method of claim 3 wherein the reference signal includes a pilot signal and the reference code includes a pilot code.

5. The method of claim 3 wherein the adaptive algorithm comprises comparing a combination of the despread reference code window samples with an ideal value to produce an error signal and using the error signal to determine the weight for each despread reference code window sample.

6. The method of claim 1 comprising:

the system transmitting a pilot signal and the traffic signal over a shared spectrum, the pilot signal having an associated pilot code; and

despreading each window sample with the pilot code so that the determining of the weight for each window provides an optimum weight for each of a plurality of despread components with the pilot signal, wherein the adaptive algorithm comprises comparing a combination of the despread pilot code window samples with an ideal value to produce an error signal and using the error signal to determine the weight for each despread pilot code window sample.

7. The method of claim 6 wherein the ideal value is 1+j.

8. The method of claim 1 wherein the adaptive algorithm is a minimum mean square error algorithm.

9. The method of claim 1 wherein the adaptive algorithm is a least mean square error algorithm.

10. The method of claim 1 comprising the evenly spaced samples evenly spaced at half chip intervals.

11. A user equipment for use in code division multiple access communication system, the system having a base station transmitting traffic signal over a shared spectrum, the traffic signal having an associated code, the user equipment comprising:

means for receiving signals over the shared spectrum;

means for sampling the received signals to produce samples;

means for delaying the samples to produce a window, the window having evenly time spaced samples;

means for despreading the samples;

means for determining a weight for each despread window sample using an adaptive algorithm, the adaptive algorithm providing a determination of an optimum weight for each of a plurality of despread components;

means for despreading each window sample with a traffic code;

means for weighting each despread traffic code window sample with a weight corresponding to a weight of its respective pilot signal; and

means for combining the weighted despread traffic code window sample as data of the traffic signal.

12. The user equipment of claim 11 comprising the despreading including using the window sample and a delayed version of the window sample obtained by said delaying the samples.

13. The user equipment of claim 11 wherein:

the base station transmits a reference and traffic signal over the shared spectrum, the reference and traffic signal having an associated reference code, the despread window including the reference code; and

the means for determining the weight of each window sample provides an optimum weight for each of a plurality of despread components with the reference signal.

14. The user equipment of claim 13 wherein the reference signal includes a pilot signal and the reference code includes a pilot code.

15. The user equipment of claim 13 wherein the adaptive algorithm comprises comparing a combination of the despread reference code window samples with an ideal value to produce an error signal and using the error signal to determine the weight for each despread reference code window sample.

16. The user equipment of claim 11 wherein:

the base station transmits a pilot and traffic signal over the shared spectrum, the pilot and traffic signal having an associated pilot code, the despread window including the pilot code; and

the means for determining the weight of each window sample provides an optimum weight for each of a plurality of despread components with the pilot signal, wherein the adaptive algorithm comprises comparing a combination of the despread pilot code window samples with an ideal value to produce an error signal and using the error signal to determine the weight for each despread pilot code window sample.

17. The user equipment of claim 16 wherein the ideal value is 1+j.

18. The user equipment of claim 11 wherein the adaptive algorithm is a minimum mean square error algorithm.

19. The user equipment of claim 11 wherein the adaptive algorithm is a least mean square error algorithm.

20. The user equipment of claim 11 wherein the evenly spaced samples are evenly spaced at half chip intervals.