# US 8,787,841 B2 · Method and system for providing beamforming feedback in wireless communication systems

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 8,787,841 B2
- Document ID: US8787841B2
- Status: Granted
- Kind: B2
- Application number: 11/768,329
- Filed: 2007-06-26
- Published: 2007-12-27
- Granted: 2014-07-22
- Earliest claimed: 2006-06-27
- Assignees: QUALCOMM Incorporated
- Applicants: John W. Ketchum; Sanjiv Nanda; Arnaud Meylan; Shravan K. Surineni
- Inventors: John W. Ketchum; Sanjiv Nanda; Arnaud Meylan; Shravan K. Surineni
- Web page: https://patentgrep.com/patent/US8787841B2

## CPC

- H04B 7/0643: {Feedback on request}
- H04B 7/0617: {for beam forming}
- H04B 7/0634: {Antenna weights or vector/matrix coefficients}
- H04B 7/0636: {Feedback format}
- H04L 25/03343: {Arrangements at the transmitter end}
- H04B 7/0421: {utilizing implicit feedback, e.g. steered pilot signals}
- H04L 25/0204: {of multiple channels}
- H04L 25/0228: {with direct estimation from sounding signals}
- H04L 2025/03414: {Multicarrier}
- H04L 2025/03426: {transmission using multiple-input and multiple-output channels}
- H04L 2025/03802: {Signalling on the reverse channel}
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Techniques to support beamforming for stations in a wireless network are described. In one aspect, a station may support beamforming with implicit feedback or explicit feedback by having capabilities to transmit and receive sounding frames, respond to training request by sending a sounding frame, and respond to request for explicit feedback. In one design of explicit beamforming, the station may send a first frame with a request for explicit feedback and may also send a Null Data Packet (NDP) having at least one training field but no data field. The station may receive a second frame with the explicit feedback, which may be derived based on the NDP. The station may derive steering information (e.g., steering matrices) based on the explicit feedback and may then send a steered frame with beamforming based on the steering information. The station may also perform implicit beamforming using NDP for sounding.

## Claims

### Claim 1

An apparatus comprising:
at least one processor configured to receive a training request, to send a first sounding frame in response to the training request, to receive a request for explicit feedback for beamforming and an announcement that a Null Data Packet (NDP) will follow, to receive a second sounding frame comprising the NDP, to generate the explicit feedback based on the second sounding frame, and to send the explicit feedback in response to the request for explicit feedback; and
a memory coupled to the at least one processor.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein the at least one processor is configured to receive a steered frame sent based on the explicit feedback.

### Claim 3 (depends on 1)

The apparatus of claim 1, wherein the at least one processor is configured to receive a steered frame sent based on implicit feedback derived from the first sounding frame.

### Claim 4 (depends on 1)

The apparatus of claim 1, wherein the at least one processor is configured to receive explicit feedback derived based on the first sounding frame, to derive steering information based on the received explicit feedback, and to send a steered frame based on the steering information.

### Claim 5 (depends on 1)

The apparatus of claim 1, wherein the at least one processor is configured to receive a third sounding frame, to derive steering information based on the third sounding frame, and to send a steered frame based on the steering information.

### Claim 6 (depends on 1)

The apparatus of claim 1, wherein the first sounding frame comprises training and data fields.

### Claim 7 (depends on 1)

The apparatus of claim 1, wherein the first and second sounding frames each comprise an NDP having at least one training field but no data field.

### Claim 8 (depends on 1)

The apparatus of claim 1, wherein the first and second sounding frames each comprise a frame having training and data fields or an NDP having at least one training field but no data field.

### Claim 9 (depends on 1)

The apparatus of claim 1, wherein the explicit feedback comprises channel state information (CSI) matrices, non-compressed beamforming feedback matrices, or compressed beamforming feedback matrices.

### Claim 10 (depends on 1)

The apparatus of claim 1, wherein the first and second sounding frames comprise Physical Layer Convergence Protocol (PLCP) protocol data units (PPDUs) in IEEE 802.11.

### Claim 11

A method for wireless communication comprising:
receiving, at an apparatus, a training request;
sending a first sounding frame in response to the training request;
receiving a request for explicit feedback for beamforming and an announcement that a Null Data Packet (NDP) will follow;
receiving a second sounding frame comprising the NDP;
generating the explicit feedback based on the second sounding frame; and
sending, by the apparatus, the explicit feedback in response to the request for explicit feedback.

### Claim 12 (depends on 11)

The method of claim 11, further comprising:
receiving a steered frame sent based on either the explicit feedback or implicit feedback derived from the first sounding frame.

### Claim 13 (depends on 11)

The method of claim 11, further comprising:
receiving explicit feedback derived based on the first sounding frame;
deriving steering information based on the received explicit feedback; and
sending a steered frame based on the steering information.

### Claim 14 (depends on 11)

The method of claim 11, further comprising:
receiving a third sounding frame;
deriving steering information based on the third sounding frame; and
sending a steered frame based on the steering information.

### Claim 15

An apparatus comprising:
means for receiving a training request;
means for sending a first sounding frame in response to the training request;
means for receiving a request for explicit feedback for beamforming and an announcement that a Null Data Packet (NDP) will follow;
means for receiving a second sounding frame comprising the NDP;
means for generating the explicit feedback based on the second sounding frame; and
means for sending the explicit feedback in response to the request for explicit feedback.

### Claim 16 (depends on 15)

The apparatus of claim 15, further comprising: means for receiving a steered frame sent based on either the explicit feedback or implicit feedback derived from the first sounding frame.

### Claim 17 (depends on 15)

The apparatus of claim 15, further comprising:
means for receiving explicit feedback derived based on the first sounding frame;
means for deriving steering information based on the received explicit feedback; and
means for sending a steered frame based on the steering information.

### Claim 18 (depends on 15)

The apparatus of claim 15, further comprising:
means for receiving a third sounding frame;
means for deriving steering information based on the third sounding frame; and
means for sending a steered frame based on the steering information.

### Claim 19

A non-transitory processor-readable medium including instructions stored thereon, comprising:
a first instruction set for receiving, at an apparatus, a training request;
a second instruction set for sending a first sounding frame in response to the training request;
a third instruction set for receiving a request for explicit feedback for beamforming and an announcement that a Null Data Packet (NDP) will follow;
a fourth instruction set for receiving a second sounding frame comprising the NDP;
a fifth instruction set for generating the explicit feedback based on the second sounding frame; and
a sixth instruction set for sending, to the apparatus, the explicit feedback in response to the request for explicit feedback.

### Claim 20

An apparatus comprising:
at least one processor configured to send a first frame with a request for explicit feedback, to send a Null Data Packet (NDP) having at least one training field but no data field, to receive a second frame with the explicit feedback derived based on the NDP, to send a third frame with a reverse direction grant within a short interframe space (SIFS) time of the NDP, and to receive the second frame after the third frame,
wherein the at least one processor is further configured to include, in the first frame or the third frame, an announcement that the NDP will follow; and
a memory coupled to the at least one processor.

### Claim 21 (depends on 20)

The apparatus of claim 20, wherein the at least one processor is configured to derive steering information based on the explicit feedback and to send a steered frame based on the steering information.

### Claim 22 (depends on 20)

The apparatus of claim 20, wherein the first frame comprises a Request to Send (RTS) frame, and wherein the at least one processor is configured to receive a Clear to Send (CTS) frame and to send the NDP within a short interframe space (SIFS) time of the CTS frame.

### Claim 23

A method for wireless communication comprising:
sending a first frame with a request for explicit feedback;
sending a Null Data Packet (NDP) having at least one training field but no data field;
receiving a second frame with the explicit feedback derived based on the NDP; and
sending a third frame with a reverse direction grant within a short interframe space (SIFS) time of the NDP, wherein the second frame is received after the third frame; and further comprising:
including, in the first frame or the third frame, an announcement that the NDP will follow.

### Claim 24 (depends on 23)

The method of claim 23, further comprising:
deriving steering information based on the explicit feedback; and
sending a steered frame based on the steering information.

### Claim 25 (depends on 23)

The method of claim 23, further comprising:
receiving a Clear to Send (CTS) frame in response to a Request to Send (RTS) frame sent as the first frame, and wherein the NDP is sent within a short interframe space (SIFS) time of the CTS frame.

### Claim 26

An apparatus comprising:
at least one processor configured to receive a Null Data Packet (NDP) having at least one training field but no data field, to derive steering information based on the NDP, to send a steered frame based on the steering information, to send a reverse direction grant in a first frame, to receive a second frame after the first frame, wherein the second frame includes an announcement that the NDP will follow, and to receive the NDP after the second frame; and
a memory coupled to the at least one processor.

### Claim 27 (depends on 26)

The apparatus of claim 26, wherein the at least one processor is configured to send the first frame with a training request and to receive the NDP in response to the training request.

### Claim 28 (depends on 26)

The apparatus of claim 26, wherein the second frame includes an indication that another frame will follow, and wherein the at least one processor is configured to receive a third frame after the second frame, the third frame including an indication that no other frame will follow.

### Claim 29 (depends on 26)

The apparatus of claim 26, wherein the at least one processor is configured to send a Request to Send (RTS) frame, to receive a Clear to Send (CTS) frame in response to the RTS frame, and to send the first frame after the CTS frame.

### Claim 30

A method for wireless communication comprising:
receiving a Null Data Packet (NDP) having at least one training field but no data field;
deriving steering information based on the NDP;
sending a steered frame based on the steering information;
sending a reverse direction grant in the first frame; and
receiving a second frame after the first frame, wherein the second frame includes an announcement that the NDP will follow, and wherein the NDP is received after the second frame.

### Claim 31 (depends on 30)

The method of claim 30, further comprising:
sending the first frame with a training request, and wherein the NDP is received in response to the training request.

### Claim 32

An apparatus comprising:
at least one processor configured to send a first frame with a training request and an announcement that a first Null Data Packet (NDP) will follow, to send the first NDP having at least one training field but no data field, and to receive a second NDP in response to the training request, wherein the at least one processor is configured to derive steering information based on the second NDP and to send a steered frame based on the steering information; and
a memory coupled to the at least one processor.

### Claim 33 (depends on 32)

The apparatus of claim 32, wherein the at least one processor is configured to receive a steered frame based on steering information derived from the first NDP.

### Claim 34 (depends on 32)

The apparatus of claim 32, wherein the at least one processor is configured to send a Request to Send (RTS) frame, to receive a Clear to Send (CTS) frame in response to the RTS frame, and to send the first frame after the CTS frame.

### Claim 35

A method for wireless communication comprising:
sending a first frame with a training request and an announcement that a first Null Data Packet (NDP) will follow;
sending the first NDP having at least one training field but no data field;
receiving a second NDP in response to the training request;
deriving, at an apparatus, steering information based on the second NDP; and
sending, by the apparatus, a steered frame based on the steering information.

### Claim 36 (depends on 35)

The method of claim 35, further comprising:
receiving a steered frame based on steering information derived from the first NDP.

### Claim 37

An apparatus comprising:
at least one processor configured to send a first frame with a request for explicit feedback for calibration, wherein the first frame includes a training request and an announcement that a Null Data Packet (NDP) will follow, to send the NDP having at least one training field but no data field, to receive a second frame with the explicit feedback to receive a sounding frame, wherein the sounding frame is sent in response to the training request, to derive a channel estimate based on the sounding frame, and to perform calibration based on the channel estimate and the explicit feedback; and
a memory coupled to the at least one processor.

### Claim 38 (depends on 37)

The apparatus of claim 37, wherein the sounding frame comprises an NDP.

### Claim 39 (depends on 37)

The apparatus of claim 37, wherein the sounding frame comprises training and data fields.

### Claim 40 (depends on 37)

The apparatus of claim 37, wherein the at least one processor is configured to send a third frame with a training request after the NDP, and wherein the sounding frame is sent in response to the training request.

### Claim 41

A method for wireless communication comprising:
sending a first frame with a request for explicit feedback for calibration, wherein the first frame includes a training request and an announcement that a Null Data Packet (NDP) will follow;
sending the NDP having at least one training field but no data field;
receiving a second frame, at an apparatus, with the explicit feedback;
receiving a sounding frame, wherein the sounding frame is sent in response to the training request;
deriving a channel estimate, at the apparatus, based on the sounding frame; and
performing calibration based on the channel estimate and the explicit feedback.

### Claim 42 (depends on 41)

The method of claim 41, further comprising:
sending a third frame with a training request after the NDP, and wherein the sounding frame is sent in response to the training request.

### Claim 43

A non-transitory computer-readable medium having instructions stored thereon, comprising:
instructions for receiving, at an apparatus, a training request;
instructions for sending a first sounding frame in response to the training request;
instructions for receiving a request for explicit feedback for beamforming and an announcement that a Null Data Packet (NDP) will follow;
instructions for receiving a second sounding frame comprising the NDP;
instructions for generating the explicit feedback based on the second sounding frame; and
instructions for sending, by the apparatus, the explicit feedback in response to the request for explicit feedback.

### Claim 44

A non-transitory computer-readable medium having instructions stored thereon, comprising:
instructions for sending a first frame with a request for explicit feedback;
instructions for sending a Null Data Packet (NDP) having at least one training field but no data field;
instructions for receiving a second frame with the explicit feedback derived based on the NDP; and
instructions for sending a third frame with a reverse direction grant within a short interframe space (SIFS) time of the NDP,
wherein the instructions further comprise instructions for including, in the first frame or the third frame, an announcement that the NDP will follow.

### Claim 45 (depends on 44)

The non-transitory computer-readable medium of claim 44, further comprising: instructions for deriving steering information based on the explicit feedback; and instructions for sending a steered frame based on the steering information.

### Claim 46

A non-transitory computer-readable medium having instructions stored thereon, comprising:
instructions for receiving a Null Data Packet (NDP) having at least one training field but no data field;
instructions for deriving steering information based on the NDP;
instructions for sending a steered frame based on the steering information;
instructions for sending a reverse direction grant in a first frame; and
instructions for receiving a second frame after the first frame, wherein the second frame includes an announcement that the NDP will follow, and wherein the NDP is received after the second frame.

### Claim 47 (depends on 46)

The non-transitory computer-readable medium of claim 46, further comprising: instructions for sending a first frame with a training request, and wherein the NDP is received in response to the training request.

### Claim 48

A non-transitory computer-readable medium having instructions stored thereon, comprising:
instructions for sending a first frame with a training request and an announcement that a first Null Data Packet (NDP) will follow;
instructions for sending the first NDP having at least one training field but no data field;
instructions for receiving a second NDP in response to the training request;
instructions for deriving, at an apparatus, steering information based on the second NDP; and
instructions for sending, by the apparatus, a steered frame based on the derived steering information.

### Claim 49 (depends on 48)

The non-transitory computer-readable medium of claim 48, further comprising: instructions for receiving a steered frame based on steering information derived from the first NDP.

### Claim 50

A non-transitory computer-readable medium having instructions stored thereon, comprising:
instructions for sending a first frame with a request for explicit feedback for calibration, wherein the first frame includes a training request and an announcement that a Null Data Packet (NDP) will follow;
instructions for sending the NDP having at least one training field but no data field;
instructions for receiving, at an apparatus, a second frame with the explicit feedback;
instructions for receiving a sounding frame, wherein the sounding frame is sent in response tot eh training request;
instructions for deriving, at the apparatus, a channel estimate based on the sounding frame; and
instructions for performing calibration based on the channel estimate and the explicit feedback.