Interference cancellation in a spread spectrum communication system

• US 20060093020A1
• Filed: 12/13/2005
• Published: 05/04/2006
• 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 7,545,846 B2
• Time in Patent Office: Days
• US Class Current: 375/148
• 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 code division multiple access (CDMA) communication system, comprising:

a transmitter comprising;

a data signal generator for producing a data signal;

a plurality of mixers for producing a plurality of spread data signals, each mixer for mixing said data signal with a different pseudo random chip code sequence to produce a different spread data signal;

a plurality of pilot signal generators for producing a plurality of spread pilot signals, each pilot signal spread with a different pseudo random chip code sequence, each pilot signal generator associated with one of said different spread data signals;

a plurality of combiners, each combiner for combining one of said pilot signals with one of said spread data signals to produce a combined signal;

a modulator to modulate said combined signals to a carrier frequency; and

an array of antennas for radiating said combined signals at the carrier frequency over a shared spectrum, each antenna associated with a different modulated combined signal; and

a receiver comprising;

an antenna for receiving said combined signals radiated over the shared spectrum at the carrier frequency;

a demodulator for demodulating the received combined signals to a baseband frequency;

an analog to digital converter for converting the combined signals to digital samples;

a filtering device to process the pilot signals of the combined signals;

a first plurality of despreaders for despreading the samples with delayed versions of the pilot codes to produce a window of despread pilot code window samples, the window having evenly time spaced samples;

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

an adaptive filter for processing the received signal with the determined weights to produce a weighted received signal; and

a despreader for despreading the weighted received signal to recover the data of the received signals.

2. The CDMA system of claim 1, wherein the transmitter antenna array comprises three or four antennas.

3. A code division multiple access (CDMA) communication system, comprising:

a transmitter comprising;

a plurality of data signal generators for producing a set of data signals;

a plurality of sets of mixers for producing a plurality of spread data signals, each mixer in each set of mixers for mixing one of said data signals in each set of data signals with a different pseudo random chip code sequence to produce a plurality of sets of spread data signals;

a plurality of pilot signal generators, each pilot signal generator associated with one of said sets of spread data signals and producing a pilot signal spread with a different pseudo random chip code sequence;

a plurality of combiners, each combiner for combining one of said pilot signals with one of said sets of spread data signals to produce a plurality of combined signals;

a modulator to modulate said plurality of combined signals to a carrier frequency; and

an array of antennas for radiating said plurality of combined signals at carrier frequency over a shared spectrum, each antenna associated with a different modulated combined signal; and

a receiver comprising;

an antenna for receiving said combined signals radiated over the shared spectrum at the carrier frequency;

a demodulator for demodulating the received combined signals to a baseband frequency;

an analog to digital converter for converting the combined signals to digital samples;

a filtering device to process the pilot signals of the combined signals;

a first plurality of despreaders for despreading the samples with delayed versions of the pilot codes to produce a window of despread pilot code window samples, the window having evenly time spaced samples;

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

an adaptive filter for processing the received signal with the determined weights to produce a weighted received signal; and

a despreader for despreading the weighted received signal to recover the data of the received signals.