Prior art

The following is an analysis of the most relevant prior art for US patent 8514815, based on the provided patent text and search results. The patent's priority date is September 30, 2005.

Most Relevant Prior Art for US Patent 8514815

US patent 8514815 claims a computer-implemented method for selecting antennas in a MIMO WLAN, involving sending a number of sounding packets for training, transmitting multiple consecutively transmitted sounding packets, receiving these packets (each corresponding to a different antenna subset), estimating a channel matrix, and selecting an antenna subset. The method primarily operates at the MAC layer without requiring PHY layer modification, and the sounding packets can include data.

The most directly relevant prior art cited in US8514815 itself is:

• U.S. patent application Ser. No. 11/127,006, "Training Frames for MIMO Stations," filed by Andreas Molisch, Jianxuan Du and Daqing Gu on May 11, 2005.
  • Full Citation: US 7,486,720 B2 (granted Feb. 3, 2009) or US 2006/0067277 A1 (published Mar. 30, 2006). The snippet specifically references the application number and filing date.
  • Publication/Filing Date: Filed May 11, 2005.
  • Brief Description: This patent application describes a training method where a long sequence of training frames is transmitted from a receive station to a transmit station, and in response, the transmit station transmits a short sequence of training frames. This enables both stations to perform channel estimation and antenna selection.
  • Potential Anticipated Claim(s) under 35 U.S.C. § 102: This reference explicitly discloses "channel estimation and antenna selection" using "training frames for MIMO stations." It potentially anticipates the core concept of estimating a channel matrix and selecting antennas (claim 1, and by extension claims 2, 3, 6, 7, 8, 17, 18, 19, 20, 21), particularly the general idea of using training frames for this purpose. The distinction might lie in the specific "consecutively transmitted sounding packets, each corresponding to a different subset of the set of antennas" operating at the MAC layer without PHY layer modification, which is emphasized in 8514815 as an improvement.

Other prior art documents cited in US8514815 that provide relevant background include:

• IEEE 802.11n standard (also known as WiFi)

  • Brief Description: This standard specifies a Link Adaptation Control (LAC) frame defined at the MAC layer for supporting MIMO training requests and exchange of link adaptation information. It also defines components like the MAC header, LAC mask, MCS feedback field, and FCS.
  • Potential Anticipated Claim(s) under 35 U.S.C. § 102: This reference provides the foundational MAC layer structure and protocols for MIMO WLANs. It anticipates the general use of LAC frames, MAC headers, and MCS feedback in WLANs (claims 9, 10, 11). However, it does not explicitly describe the novel use of consecutive sounding packets for antenna selection as claimed in US8514815.

• IEEE 802.11-04/0889r7, "TGn Sync Proposal Technical Specification"

  • Brief Description: This document describes the control frame in detail, which includes the MAC header, LAC mask, MCS feedback field, and FCS.
  • Potential Anticipated Claim(s) under 35 U.S.C. § 102: Similar to the IEEE 802.11n standard, this document establishes the prior art for the structure of control frames in WLANs, thus potentially anticipating elements related to the LAC frame structure (claims 9, 10, 11).

• Sudarshan, P., Mehta, N. B., Molisch, A. F., Zhang, J., "Spatial Multiplexing and Channel Statistics-Based RF Pre-Processing for Antenna Selection," Globecom, November 2004.

  • Brief Description: This publication describes that antenna selection for beamforming, where magnitudes of elements in the selection matrix are zero or one, can be implemented in the RF domain using phase-shifters, switches, and linear combiners.
  • Potential Anticipated Claim(s) under 35 U.S.C. § 102: This reference provides background on the physical implementation of antenna selection and beamforming. It does not appear to directly anticipate the method of using consecutive sounding packets at the MAC layer for channel estimation and antenna selection but rather the hardware aspects of selection.

It is crucial to note that while these references provide a foundation for the technology, the novelty of US8514815 lies in the specific method of "rapidly send[ing] consecutively multiple training frames, designated as sounding packets... Each sounding packet conforms to a conventional PHY layer design and is for a different subset of all of the available antennas so that characteristics of the entire channel can be estimated by the receiver of the sounding packets" and that "the entire training method operates at the MAC layer." The prior art would need to demonstrate this specific combination and its MAC layer operation to anticipate the claims of US8514815.