# US 2014/0153662 A1 · Downlink transmit beamforming

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- Number: US 2014/0153662 A1
- Document ID: US20140153662A1
- Status: Published application
- Kind: A1
- Application number: 14/175,381
- Filed: 2014-02-07
- Published: 2014-06-05
- Earliest claimed: 2004-12-30
- Assignees: Intel Corporation
- Inventors: Xintian E. Lin; Qinghua Li
- Web page: https://patentgrep.com/patent/US20140153662A1

## CPC

- H04B 7/0413: MIMO systems
- H04B 7/0617: {for beam forming}
- H04L 1/0681: {adapting space time parameters, i.e. modifying the space time matrix}
- H04B 7/0643: {Feedback on request}
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A wireless network access point can operate as a closed loop MIMO device when communicating with a station that is operating as an open loop MIMO device. Transmit/receive chains in the access point are calibrated to support aggregate channel reciprocity.

## Claims

### Claim 1

A method comprising:
calibrating a plurality of transmit/receive chains in a wireless network access point device, wherein calibrating comprises adjusting gain values to make transmitter gain to receiver gain ratios substantially equal;
receiving a packet from a station having a first antenna and a second antenna;
determining a downlink beamforming matrix; and
transmitting two data streams to the station.