Method and apparatus for transmit pre-correction in wireless communications

• US 7,046,978 B2
• Filed: 02/08/2002
• Issued: 05/16/2006
• Est. Priority Date: 02/08/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Simon, Harris S., Rao, Bhaskar D., Wengler, Michael J., Burke, Joseph P.
• Primary Examiner(s): LE, DANH C
• Application Number:
  US10/071,452
• Publication Number:
  US 20030153360A1
• Time in Patent Office: 1,558 Days
• Field of Search: 455/562.1, 455/69, 455/522, 455/67.16, 455/88, 455/272, 455/70, 455/276.1, 370/335, 370/342, 370/320, 370/441, 370/337, 370/524, 375/148
• US Class Current: 455/272
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]

Abstract

A wireless communication system includes a base station having a plurality of transmit antennas transmits pilot signals to a subscriber station. The subscriber station performs channel measurements on the signals received from the base station through at least two transmit paths and sends path characteristic information for each path to the base station. The base station uses the path characteristic information to determine how best to transmit data from the multiple transmit antennas to a single receive antenna at the subscriber station.

Through the use of pre-correction techniques, data signals are transmitted through the multiple transmit antennas such that signals received through the multiple transmit paths can be demodulated and decoded as a single signal.

Claims

1. A transmitter for transmitting a signal to a subscriber station through at least two transmit antennas, the transmitter comprising:

means for transmitting a first pilot signal through a first transmit antenna;

means for transmitting a second pilot signal through a second transmit antenna;

means for receiving channel estimate information corresponding to said first and second pilot signals;

means for generating delays and weights based on said channel estimate information, the delays corresponding to a plurality of signal paths to the subscriber station, the weights corresponding to the first and second antennas and to the plurality of signal paths;

means for applying said delays and weights to data to produce delayed, weighted data; and

means for summing the delayed, weighted data for the first and second antennas to transmit to the subscriber station, the delays causing the data transmitted on the plurality of signal paths to arrive at the subscriber station at substantially the same time, the weights causing the antennas to form a plurality of beam patterns with primary lobes along the plurality of signal paths such that a primary lobe of one beam pattern is placed nearly within a null between two lobes of another beam pattern.

2. A method for transmitting a signal to a subscriber station through at least two transmit antennas, the method comprising:

transmitting a first pilot signal through a first transmit antenna;

transmitting a second pilot signal through a second transmit antenna;

receiving channel estimate information corresponding to said first and second pilot signals;

generating delays and weights based on said channel estimate information, the delays corresponding to a plurality of signal paths to the subscriber station, the weights corresponding to the first and second antennas and to the plurality of signal paths;

applying said delays and weights to data to produce delayed, weighted data;

summing the delayed, weighted data for the first and second antennas to transmit to the subscriber station, the delays causing the data transmitted on the plurality of signal paths to arrive at the subscriber station at substantially the same time, the weights causing the antennas to form a plurality of beam patterns with primary lobes along the plurality of signal paths such that a primary lobe of one beam pattern is placed nearly within a null between two lobes of another beam pattern; and

transmitting the summed, delayed and weighted data through the first and second transmit antennas.

3. A computer readable media embodying a method for transmitting a signal to a subscriber station through at least two transmit antennas, the method comprising:

transmitting a first pilot signal through a first transmit antenna;

transmitting a second pilot signal through a second transmit antenna;

receiving channel estimate information corresponding to said first and second pilot signals;

generating delays and weights based on said channel estimate information, the delays corresponding to a plurality of signal paths to the subscriber station, the weights corresponding to the first and second antennas and to the plurality of signal paths;

applying said delays and weights to data to produce delayed, weighted data;

summing the delayed, weighted data for the first and second antennas to transmit to the subscriber station, the delays causing the data transmitted on the plurality of signal paths to arrive at the subscriber station at substantially the same time, the weights causing the antennas to form a plurality of beam patterns with primary lobes along the plurality of signal paths such that a primary lobe of one beam pattern is placed nearly within a null between two lobes of another beam pattern; and

transmitting the summed, delayed and weighted data through the first and second transmit antennas.

4. A base station apparatus comprising:

at least first and second transmit antennas;

a first mixer corresponding to a first transmit antenna, for applying a first cover code to a pilot signal to be transmitted through the first transmit antenna;

a second mixer corresponding to a second transmit antenna, for applying a second cover code to the pilot signal to be transmitted through the second transmit antenna;

receiver for receiving channel estimate information corresponding to said first and second pilot signals for at least two transmit paths per transmit antenna;

a processor for generating delays and weights based on said channel estimate information, the delays corresponding to a plurality of signal paths to the subscriber station, the weights corresponding to the first and second antennas and to the plurality of signal paths;

means for applying said delays and weights to data to produce delayed, weighted data;

a summer for combining said delayed, weighted data for the first and second antennas to transmit to the subscriber station, the delays causing the data transmitted on the plurality of signal paths to arrive at the subscriber station at substantially the same time, the weights causing the antennas to form a plurality of beam patterns with primary lobes along the plurality of signal paths such that a primary lobe of one beam pattern is placed nearly within a null between two lobes of another beam pattern; and

a transmitter for transmitting the summed, delayed, weighted data through said transmit antennas.

5. A remote station apparatus for receiving signals transmitted from at least two transmit antennas and through at least two transmit paths, the apparatus comprising:

means for determining a plurality of paths of pilot signals transmitted by the at least two transmit antennas;

at least four channel estimators, wherein each channel estimator measures channel information corresponding to a signal received through a different combination of one of the at least two transmit antennas and one of the at least two transmit paths wherein the signal transmitted through each of said at least two transmit antennas is adjusted based on said pre-correction delays and weights;

channel estimate processor for generating channel estimate information based on said measured channel information;

means for transmitting said channel information;

means for receiving data signals transmitted from the at least two transmit antennas through the plurality of paths; and

means for demodulating the received data signals from the plurality of paths as substantially a single signal received through a single path.