US 8514815

US Patent 8514815, titled "Training signals for selecting antennas and beams in MIMO wireless LANs," was filed on September 30, 2005, and issued on August 20, 2013. The inventors are Daqing Gu, Hongyuan Zhang, Jinyun Zhang, and Andreas F. Molisch. The current assignee is Freedom Patents LLC, though the patent document notes that listed assignees may be inaccurate and Google has not performed a legal analysis for accuracy. The original assignee was Mitsubishi Electric Research Laboratories Inc.

Abstract:
A computer-implemented method for selecting antennas in a multiple-input, multiple-output (MIMO) wireless local area network (WLAN) involves several steps. It begins with a station sending a predetermined number of sounding packets to another station for antenna selection training. The transmitting station then sends these multiple, consecutive sounding packets, each corresponding to a different subset of its available antennas. The receiving station receives these packets, estimates a channel matrix from them, and subsequently selects a subset of antennas based on this estimated channel matrix.

Independent Claims Overview:

• Claim 1: This claim describes a computer-implemented method for antenna selection in a MIMO wireless local area network. The method involves one station (the "performing" station) initiating antenna selection training by communicating to another station (the "transmitting" station) the number of sounding packets to be sent. The transmitting station then sends these specified multiple sounding packets consecutively, where each packet uses a different subset of its antennas. The performing station receives these packets, uses them to estimate the characteristics of the wireless channel (a "channel matrix"), and then selects an optimal subset of antennas based on this matrix. The total number of sounding packets used for this training is decided beforehand.

Litigation Status:
US Patent 8514815 is actively involved in litigation, primarily in the Texas Eastern District Court. The patent, along with US8374096B2 and US8284686B2, is part of a campaign by Freedom Patents LLC. For example, a case against Charter Communications (and Spectrum Gulf Coast, LLC) was dismissed with prejudice on March 8, 2024, meaning Freedom Patents LLC is permanently barred from re-filing those specific infringement claims against Charter. However, the patents remain valid and enforceable against other parties. Freedom Patents LLC has continued to file new suits as recently as April 26, 2025, against multiple defendants including Broadcom, MediaTek, Realtek Semiconductor, and Renesas Electronics, targeting devices that comply with the IEEE 802.11ax-2021 standard and implement MIMO Wi-Fi functionality. Other cases were filed in 2023 and 2024 against companies such as ASUSTek, Cisco, Deutsche Telekom (T-Mobile), HP Enterprise, Hon Hai Precision Industry (Sharp), LG Electronics, Micro-Star, Razer, Samsung, Sony, and Vantiva. These cases generally relate to the provision of devices that implement MIMO Wi-Fi capabilities. No specific CAFC dockets for 2026 directly concerning US8514815 were explicitly identified in the search results, but the ongoing district court litigation indicates active enforcement of the patent.