Adaptive beam forming for transmitter operation in a wireless communication system

• US 6,101,399 A
• Filed: 06/16/1995
• Issued: 08/08/2000
• Est. Priority Date: 02/22/1995
• Status: Expired due to Term

• Current Assignee: Cisco Systems, Inc.
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.), Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Jones, Vincent Knowles IV, Diggavi, Suhas Nagraj, Raleigh, Gregory Gene, Paulraj, Arogyaswami Joseph
• Primary Examiner(s): Tsang, Fan
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US08/491,044
• Time in Patent Office: 1,880 Days
• Field of Search: 455/33.1, 455/54.2, 455/54.1, 455/56.1, 455/63, 455/65, 455/67.1, 455/4, 455/115, 455/52.3, 455/226.1, 455/276.1, 455/272, 455/422, 455/440, 455/441, 455/456 , 455/457, 455/517, 455/524, 455/525, 455/561, 455/562, 379/58, 379/59, 342/350, 342/367, 342/368, 342/372, 342/373, 342/378, 395/51, 375/316, 375/347, 375/349, 375/231, 375/230, 375/232
• US Class Current: 455/561
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 84/042 Public Land Mobile systems, e.g. cellular systems
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A method for forming an adaptive phased array transmission beam pattern at a base station without any knowledge of array geometry or mobile feedback is described. The approach is immune to the problems which plague methods which attempt to identify received angles of arrival from the mobile and map this information to an optimum transmit beam pattern. In addition, this approach does not suffer the capacity penalty and mobile handset complexity increase associated with mobile feedback. Estimates of the receive vector propagation channels are used to estimate transmit vector channel covariance matrices which form objectives and constraints in quadratic optimization problems leading to optimum beam former solutions for the single user case, and multiple user case. The new invention in capable of substantial frequency re-use capacity improvement in a multiple user cellular network.

Claims

1. In a communications system including a first communications station and a second communications station, said first communications station having an antenna array for generating an antenna beam pattern used for transmission of information signals to said second communications station, a method for adaptively forming said beam pattern comprising:

estimating data transmitted from said second communications station to said first communications station based on a signal received at said first communications station;

based on said estimated transmitted data, estimating a receive channel from said second communications station to said first communications station;

computing a desired component of a statistical characterization of said received signal over time based on said receive channel estimate;

computing an undesired component of said statistical characterization of said received signal over time based on a characterization of interference taking advantage of knowledge of said estimated transmitted data and said received data;

developing a beam pattern weight vector based on said desired component and said undesired component of said statistical characterization; and

forming said beam pattern in accordance with said beam pattern weight vector.

2. The method of claim 1 wherein estimating said receive channel comprises using one or more time varying channel estimation filters.

3. The method of claim 1 wherein computing said undesired component of said statistical characterization of said received signal includes compiling an interference plus noise covariance matrix.

4. The method of claim 1 wherein computing said desired component of said statistical characterization of said received signal includes compiling an estimated receive channel covariance matrix.

5. The method of claim 4 further including forming objective and constraint functions from which said beam pattern weight vector is determined.

6. The method of claim 1 wherein said first communications station comprises a central communications station and said second communications station comprises a remote communications station.

7. In a communications system including a first communications station and a second communications station, said first communications station having an antenna array for generating an antenna beam pattern used for transmission of information signals to said second communications station, a system for adaptively forming said beam pattern comprising:

a receive processor that;

estimates data transmitted from said second communications station to said first communications station based on a signal received at said first communications station;

based on said estimated transmitted data, estimates a receive channel from said second communications station to said first communications station;

computes a desired component of a statistical characterization of said received signal over time based on said receive channel estimate; and

computes an undesired component of said statistical characterization of said received signal over time based on a characterization of interference taking advantage of knowledge of said estimated transmitted data and said received data; and

a vector processor that;

develops a beam pattern weight vector based on said statistical characterization of said desired component and said statistical characterization of said undesired component; and

forms said beam pattern in accordance with said beam pattern weight vector.

8. The system of claim 7 wherein said receive processor uses one or more time varying channel estimation filters to estimate said receive channel.

9. The system of claim 7 wherein said receive processor compiles a receive channel covariance matrix to represent said desired component of said statistical characterization of said received signal.

10. The system of claim 7 wherein said receive processor compiles an interference plus noise covariance matrix to represent said undesired component of said statistical characterization of said received signal.

11. The system of claim 7 where said vector processor forms objective and constraint functions from which said beam pattern weight is determined.

12. The system of claim 7 wherein said first communications station comprises a central communications station and said second communications station comprises a remote communications station.

13. A central communications station for adaptively forming a beam pattern to communicate with a remote communications station, comprising:

(A) a central processor;

(B) a receive processor coupled to said central processor coupled to said central processor and configured to;

estimate data transmitted from said remote communications station to said central communications station based on a signal received at said central communications station;

based on said estimated transmitted data, estimate a receive channel from said remote communications station to said central communications station;

compute a desired component of a statistical characterization of said received signal over time based on said received channel estimate; and

compute an undesired component of said statistical characterization of said received signal over time based on said receive channel estimate; and

(C) a vector processor coupled to said central processor and configured to;

develop a beam pattern weight vector based on said undesired component; and

form said beam pattern in accordance with said beam pattern weight vector.