Adaptive pilot insertion for a MIMO-OFDM system

• US 8,000,221 B2
• Filed: 07/20/2004
• Issued: 08/16/2011
• Est. Priority Date: 07/20/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Walton, Jay Rodney, Wallace, Mark S.
• Primary Examiner(s): Lai; Andrew
• Application Number:
  US10/896,277
• Publication Number:
  US 20060018287A1
• Time in Patent Office: 2,583 Days
• Field of Search: 370/203, 370/204, 370/208
• US Class Current: 370/204
• CPC Class Codes: H04B 7/0413 MIMO systems
• 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 1/06 using space diversity
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/261 Details of reference signals

Abstract

A transmitting entity transmits a “base” pilot in each protocol data unit (PDU). A receiving entity is able to derive a sufficiently accurate channel response estimate of a MIMO channel with the base pilot under nominal (or most) channel conditions. The transmitting entity selectively transmits an additional pilot if and as needed, e.g., based on channel conditions and/or other factors. The additional pilot may be adaptively inserted in almost any symbol period in the PDU. The receiving entity is able to derive an improved channel response estimate with the additional pilot. The transmitting entity sends signaling to indicate that additional pilot is being sent. This signaling may be embedded within pilot symbols sent on a set of pilot subbands used for a carrier pilot that is transmitted across most of the PDU. The signaling indicates whether additional pilot is being sent and possibly other pertinent information.

Claims

1. A method of transmitting signaling in a multiple-input multiple-output (MIMO) communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

selecting a signaling value from among a plurality of signaling values;

selecting a set of pilot symbols from among a plurality of sets of pilot symbols, wherein each of the plurality of sets of pilot symbols corresponds to a different one of the plurality of signaling values, and wherein the selected set of pilot symbols corresponds to the selected signaling value, and

multiplexing the selected set of pilot symbols on a first set of frequency subbands used for a carrier pilot, wherein the plurality of signaling values includes a signaling value that indicates that one or more additional pilot symbols for deriving an improved channel response estimation are being transmitted on a second set of frequency subbands.

2. The method of claim 1, wherein the carrier pilot is suitable for use by a receiving entity to track a phase of a carrier signal used by a transmitting entity.

3. The method of claim 1, wherein the selected set of pilot symbols is transmitted on the first set of frequency subbands and the additional pilot symbols are concurrently transmitted on the second set of frequency subbands in a symbol period.

4. The method of claim 1, wherein the plurality of signaling values further include another signaling value indicating data symbols are being transmitted on the second set of frequency subbands.

5. The method of claim 1, wherein a selected signaling value indicates a type of an additional pilot being transmitted.

6. The method of claim 1, wherein a selected signaling value indicates a mode of transmission for an additional pilot being transmitted.

7. An apparatus in a multiple-input multiple-output (MIMO) communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

a controller configured to select a signaling value from among a plurality of signaling values;

a processor configured to select a set of pilot symbols from among a plurality of sets of pilot symbols, wherein each of the plurality of sets of pilot symbols corresponds to a different one of the plurality of signaling values, and wherein the selected set of pilot symbols corresponds to the selected signaling value; and

a multiplexer configured to multiplex the selected set of pilot symbols on a first set of frequency subbands used for a carrier pilot, wherein the plurality of signaling values includes a signaling value that indicates the presence or absence of one or more additional pilot symbols for deriving an improved channel response estimation being transmitted on a second set of frequency subbands.

8. The apparatus of claim 7, wherein the selected set of pilot symbols is transmitted on the first set of frequency subbands and the additional pilot symbols are concurrently transmitted on the second set of frequency subbands in a symbol period.

9. An apparatus in a multiple-input multiple-output (MIMO) communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

means for selecting a signaling value from among a plurality of signaling values;

means for selecting a set of pilot symbols from among a plurality of sets of pilot symbols wherein each of the plurality of sets of pilot symbols corresponds to a different one of the plurality of signaling values, and wherein the selected set of pilot symbols corresponds to the selected signaling value; and

means for multiplexing the selected set of pilot symbols on a first set of frequency subbands used for carrier pilot, wherein the plurality of signaling values includes a signaling value that indicates the presence or absence of one or more additional pilot symbols for deriving an improved channel response estimation being transmitted on a second set of frequency subbands.

10. The apparatus of claim 9, wherein the selected set of pilot symbols is transmitted on the first set of frequency subbands and the additional pilot symbols are concurrently transmitted on the second set of frequency subbands in a symbol period.

11. A machine-readable medium encoded with instructions for transmitting signaling in a multiple-input multiple-output (MIMO) communication system utilizing orthogonal frequency division multiplexing (OFDM), the instructions comprising code for:

selecting a signaling value from among a plurality of signaling values;

selecting a set of pilot symbols from among a plurality of sets of pilot symbols, wherein each of the plurality of sets of pilot symbols corresponds to a different one of the plurality of signaling values, and wherein the selected set of pilot symbols corresponds to the selected signaling value; and

multiplexing the selected set of pilot symbols on a first set of frequency subbands used for a carrier pilot, wherein the plurality of signaling values includes a signaling value that indicates the presence or absence of one or more additional pilot symbols for deriving an improved channel response estimation being transmitted on a second set of frequency subbands.

12. The machine-readable medium of claim 11, wherein the carrier pilot is suitable for use by a receiving entity to track a phase of a carrier signal used by a transmitting entity.

13. The machine-readable medium of claim 11, wherein the selected set of pilot symbols is transmitted on the first set of frequency subbands and the additional pilot symbols are concurrently transmitted on the second set of frequency subbands in a symbol period.

14. The machine-readable medium of claim 11, wherein the plurality of signaling values further include another signaling value indicating data symbols are being transmitted on the second set of frequency subbands.

15. The machine-readable medium of claim 11, wherein a selected signaling value indicates a type of an additional pilot being transmitted.

16. The machine-readable medium of claim 11, wherein a selected signaling value indicates a mode of transmission for an additional pilot being transmitted.