Pilots for MIMO communication systems

• US 9,312,935 B2
• Filed: 06/08/2011
• Issued: 04/12/2016
• Est. Priority Date: 10/25/2002
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ketchum, John W., Wallace, Mark S., Walton, J. Rodney, Howard, Steven J.
• Primary Examiner(s): Burd, Kevin M
• Application Number:
  US13/155,916
• Publication Number:
  US 20110235744A1
• Time in Patent Office: 1,770 Days
• Field of Search: 375/259, 375/260, 375/267, 375/219, 375/295, 375/299, 375/347
• US Class Current: 1/1
• CPC Class Codes: H04B 7/0421 utilizing implicit feedback, e.g. steered pilot signals
• CPC Class Codes: H04B 7/043 using best eigenmode, e.g. beam forming or beam steering
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0684 using different training sequences per antenna
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• 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: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0017 where the mode-switching is based on Quality of Service requirement
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals
• CPC Class Codes: H04L 2027/0089 In-band signals
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 5/0023 : Time-frequency-space
• CPC Class Codes: H04L 5/0026 : Division using four or more dimensions
• CPC Class Codes: H04L 5/0048 : Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/005 : of common pilots, i.e. pilots destined for multiple users or terminals
• CPC Class Codes: H04L 5/006 : Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04W 16/28 : using beam steering
• CPC Class Codes: H04W 28/20 : Negotiating bandwidth
• CPC Class Codes: H04W 52/50 : at the moment of starting communication in a multiple access environment

Abstract

Pilots suitable for use in MIMO systems and capable of supporting various functions are described. The various types of pilot include—a beacon pilot, a MIMO pilot, a steered reference or steered pilot, and a carrier pilot. The beacon pilot is transmitted from all transmit antennas and may be used for timing and frequency acquisition. The MIMO pilot is transmitted from all transmit antennas but is covered with different orthogonal codes assigned to the transmit antennas. The MIMO pilot may be used for channel estimation. The steered reference is transmitted on specific eigenmodes of a MIMO channel and is user terminal specific. The steered reference may be used for channel estimation. The carrier pilot may be transmitted on designated subbands/antennas and may be used for phase tracking of a carrier signal. Various pilot transmission schemes may be devised based on different combinations of these various types of pilot.

Claims

1. In a user terminal for use in a wireless communication system supporting multiple-input multiple-output (MIMO) communications, a method comprising:

receiving a first pilot of a first type including information to facilitate system timing and frequency acquisition from an access point including a plurality of antennas;

receiving a second pilot of a second type different from the first type including information to facilitate channel estimation between said user terminal and the access point; and

generating a channel estimate from information in said second pilot,

wherein the first pilot is neither beamformed nor spatially multiplexed and the second pilot is one of beamformed using signal processing or spatially multiplexed, and

wherein the second pilot includes a steered pilot transmitted on specific eigenmodes of a MIMO channel for a specific user terminal.

2. The method of claim 1, wherein the second pilot includes user specific information.

3. The method of claim 1, further comprising:

receiving a third pilot including user specific information and a first cover code from a first one of said plurality of antennas at the access point; and

receiving a fourth pilot including user specific information and a second cover code from a second one of said plurality of antennas at the access point,

wherein the first and second cover codes are orthogonal cover codes.

4. The method of claim 3, wherein the orthogonal cover codes comprise Walsh codes.

5. The method of claim 3, further comprising generating a MIMO channel estimate from information in the third and fourth pilots.

6. The method of claim 3, wherein the third and fourth pilots comprise MIMO pilots.

7. The method of claim 6, wherein each of the MIMO pilots includes a pilot that was transmitted from each of the plurality of antennas at the access point with different orthogonal codes.

8. The method of claim 1, wherein the first pilot comprises a beacon pilot.

9. The method of claim 8, wherein the beacon pilot includes a specific set of pilot symbols that was transmitted from each of the plurality of antennas at the access point.

10. The method of claim 1, wherein the second pilot comprises a steered pilot.

11. In an access point including a plurality of antennas for use in a wireless communications system supporting multiple-input multiple-output (MIMO) communications, a method comprising:

generating a plurality of pilots, said plurality of pilots including;

a first pilot of a first type including information to facilitate system timing and frequency acquisition, and

a second pilot of a second type different from the first type including information to facilitate channel estimation between said access point and at least one user terminal; and

transmitting said plurality of pilots to said at least one user terminal,

wherein the first pilot is neither beamformed nor spatially multiplexed and the second pilot is one of beamformed using signal processing or spatially multiplexed, and

wherein the second pilot includes a steered pilot transmitted on specific eigenmodes of a MIMO channel for a specific user terminal.

12. The method of claim 11, further comprising:

receiving a channel estimate from said at least one user terminal based on information in the second pilot.

13. The method of claim 11, further comprising:

generating a third pilot including information specific to said at least one user terminal and a first cover code;

generating a fourth pilot including information specific to said at least one user terminal and a second cover code, wherein the first cover code is orthogonal to the second cover code;

transmitting the third pilot from one of said plurality of antennas; and

transmitting the fourth pilot from a different one of said plurality of antennas.

14. A user terminal for use in a wireless communication system supporting multiple-input multiple output (MIMO) communications, comprising:

a receiver;

a processor operative to;

process a first pilot of a first type including information to facilitate system timing and frequency acquisition received from an access point including a plurality of antennas,

process a second pilot of a second type different from the first type including information to facilitate channel estimation between said user terminal and the access point, and

generate a channel estimate from information in said second pilot,

wherein the first pilot is neither beamformed nor spatially multiplexed and the second pilot is one of beamformed using signal processing or spatially multiplexed, and

wherein the second pilot includes a steered pilot transmitted on specific eigenmodes of a MIMO channel for a specific user terminal.

15. In a user terminal for use in a wireless communication system supporting multiple-input multiple-output (MIMO) communications, a method comprising:

receiving a first pilot of a first type including information to facilitate system timing and frequency acquisition from an access point including a plurality of antennas;

receiving a second pilot of a second type different from the first type including information to facilitate channel estimation between said user terminal and the access point; and

generating a channel estimate from information in said second pilot,

wherein the second pilot comprises a steered pilot, and wherein the steered pilot includes a pilot that was transmitted on specific eigenmodes of a MIMO channel for a specific user terminal.

16. In a user terminal for use in a wireless communication system supporting multiple-input multiple-output (MIMO) communications, a method comprising:

receiving a first pilot of a first type including information to facilitate system timing and frequency acquisition from an access point including a plurality of antennas;

receiving a second pilot of a second type different from the first type including information to facilitate channel estimation between said user terminal and the access point; and

generating a channel estimate from information in said second pilot,

wherein the information to facilitate channel estimation at least includes a steering vector and a pilot signal, and

wherein the second pilot includes a steered pilot transmitted on specific eigenmodes of a MIMO channel for a specific user terminal.

17. An access point for use in a wireless communications system supporting multiple-input multiple-output (MIMO) communications, comprising:

a plurality of antennas;

a processor operative to;

generate a plurality of pilots, said plurality of pilots including;

a first pilot of a first type including information to facilitate system timing and frequency acquisition, and

a second pilot of a second type different from the first type including information to facilitate channel estimation between said access point and at least one user terminal; and

transmit said plurality of pilots to said at least one user terminal,

wherein the first pilot is neither beamformed nor spatially multiplexed and the second pilot is one of beamformed using signal processing or spatially multiplexed, and

wherein the second pilot includes a steered pilot transmitted on specific eigenmodes of a MIMO channel for a specific user terminal.

18. A user terminal for use in a wireless communication system supporting multiple-input multiple-output (MIMO) communications, comprising:

a receiver;

a processor operative to;

receive a first pilot of a first type including information to facilitate system timing and frequency acquisition from an access point including a plurality of antennas;

receive a second pilot of a second type different from the first type including information to facilitate channel estimation between said user terminal and the access point; and

generate a channel estimate from information in said second pilot,

wherein the second pilot comprises a steered pilot, and wherein the steered pilot includes a pilot that was transmitted on specific eigenmodes of a MIMO channel for a specific user terminal.

19. A user terminal for use in a wireless communication system supporting multiple-input multiple-output (MIMO) communications, comprising:

a receiver;

a processor operative to;

receive a first pilot of a first type including information to facilitate system timing and frequency acquisition from an access point including a plurality of antennas;

receive a second pilot of a second type different from the first type including information to facilitate channel estimation between said user terminal and the access point; and

generate a channel estimate from information in said second pilot,

wherein the information to facilitate channel estimation at least includes a steering vector and a pilot signal, and

wherein the second pilot includes a steered pilot transmitted on specific eigenmodes of a MIMO channel for a specific user terminal.