INTERFERENCE CANCELLATION IN A SPREAD SPECTRUM COMMUNICATION SYSTEM

• US 20090257472A1
• Filed: 06/08/2009
• Published: 10/15/2009
• 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 7,953,139 B2
• Time in Patent Office: Days
• US Class Current: 375/130
• 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 implemented in a wireless transmit receive unit (WTRU) comprising, the method comprising:

receiving a plurality of combined signals over a shared spectrum at a carrier frequency;

demodulating the plurality of combined signals to a baseband frequency;

converting the plurality of combined signals to digital samples;

filtering a plurality of pilot signals from the plurality of combined signals;

despreading the digital samples with delayed versions of the pilot signals to produce a window of despread pilot code window samples, wherein the window has evenly time spaced samples;

determining a weight for each despread pilot code window sample using a minimum mean square error algorithm;

processing each of the plurality of combined signals with the determined weights to produce weighted received signal; and

despreading the weighted received signal to recover data of the plurality of combined signals.

2. The method of claim 1, further comprising:

processing plurality of combined signals to derive a preferred weight adjustment for the received signal; and

signaling the preferred weight adjustment to a base station.

3. The method of claim 2 wherein the preferred weight adjustment includes a weight corresponding to a first antenna of the base station and a weight corresponding to a second antenna.

4. A method, implemented in a base station, the method comprising:

receiving a plurality of combined signals over a shared spectrum at a carrier frequency;

demodulating the plurality of combined signals to a baseband frequency;

converting the plurality of combined signals to digital samples;

filtering a plurality of pilot signals from the plurality of combined signals;

despreading the digital samples with delayed versions of the pilot signals to produce a window of despread pilot code window samples, wherein the window has evenly time spaced samples;

determining a weight for each despread pilot code window sample using a minimum mean square error algorithm;

processing the plurality of combined signals with the determined weights to produce a weighted received signal; and

despreading the weighted received signal to recover data of the plurality of combined signals.

5. The method of claim 4, further comprising:

receiving a preferred weight adjustment from a wireless transmit/receive unit.

6. The method of claim 5 wherein the preferred weight adjustment includes a weight corresponding to a first antenna of the base station and a weight corresponding to a second antenna.

7. A method, implemented in a wireless transmit receive unit (WTRU), the method comprising:

producing a data signal;

producing, by a plurality of mixers, a plurality of spread data signals, wherein each mixer is configured to mix the data signal with a different pseudo random chip code sequence to produce a different spread data signal;

producing, by a plurality of pilot signal generators, a plurality of spread pilot signals, wherein each pilot signal is spread with a different pseudo random chip code sequence and each pilot signal generator is associated with a different spread data signal;

producing, by a plurality of combiners, a plurality of combined signals, wherein each combined signal is produced as a result of combining one of the pilot signals with one of the spread data signals;

modulating the combined signals to a carrier frequency; and

radiating, by a plurality of antennas, the plurality of combined signals over a shared spectrum at the carrier frequency, wherein each antenna is associated with a different modulated combined signal.