US 7548592

US Patent 7548592, titled "Multiple input, multiple output communications systems," was invented by James Stuart Wight. The patent was filed on September 30, 2004, and issued on June 16, 2009. The current assignee is Integral Wireless Technologies LLC.

Abstract:
The patent describes systems and methods for optimizing transmitter and receiver weights in a Multiple-Input, Multiple-Output (MIMO) system. One embodiment focuses on creating and steering beam nulls to substantially decouple transmitted signals. Another embodiment selects weights to achieve substantially equivalent signal strength for each weighted signal at the receiver, even if weighting vectors are not orthogonal. A further embodiment ensures each transmitted signal is coupled only between its own transmitter and receiver antennas with a gain (eigenvalue) within a desired range, while maintaining orthogonal weighting vectors. The patent also provides embodiments employing various decomposition techniques.

Independent Claims Overview:

• Claim 1 (Transmitter): This claim describes a MIMO signal transmitter. It includes multiple signal inputs, multipliers to weight each input signal with a vector (V), combiners to combine these weighted signals, and antennas to transmit the combined signals. The key characteristic is that V represents a matrix of transmitter weighting coefficients, and the inverse of V (V⁻¹) along with a lower triangular matrix L (V⁻¹L⁻¹) forms a matrix of receiver weighting coefficients.
• Claim 9 (Transmission System): This claim describes a complete MIMO signal transmission system. It encompasses the components of the transmitter from Claim 1 (signal inputs, multipliers, transmit combiners, transmit antennas) and adds receiver components: receive antennas, receive vector multipliers (which weight received signals with a vector of the form V⁻¹L⁻¹), receive combiners, and signal outputs.
• Claim 16 (Method of Transmitting): This claim outlines a method for transmitting a signal through a transmission channel. It involves calculating a transmission matrix H for the channel. This matrix H is then decomposed using a first technique into a lower triangular matrix L and a unitary matrix Q (H=LQ). Next, the unitary matrix Q is orthogonalized using a second decomposition technique into a product of a transmitter weighting coefficient matrix V, a diagonal matrix Λ (containing eigenvalues), and the inverse of V (V⁻¹), such that Q=VΛV⁻¹. Finally, the results of these decompositions are combined (H=LVΛV⁻¹), and the signal is transmitted using this transmission matrix H.

CAFC 2026 Dockets:
A search for US7548592 in the CAFC 2026 dockets did not return any specific case listings for this patent number. While the patent information page indicates "Family has litigation" with cases filed in Texas District Courts and a "First worldwide family litigation filed" dating back to 2004, no specific 2026 cases at the CAFC were identified.

Known litigation involving US patent 7548592 is not directly detailed in the provided search results. The prior "Patent summary" section notes that the patent information page indicates "Family has litigation" with cases filed in Texas District Courts and a "First worldwide family litigation filed" dating back to 2004. However, a specific search for US7548592 in litigation databases like Unified Patents, CAFC, or PACER, as conducted, did not immediately return direct case listings for this precise patent number with the requested details (plaintiffs, defendants, jurisdiction, case number, filing date, and outcome/status).

One search result referenced an IPR case (IPR2021-01260) involving Unified Patents, LLC as petitioner and AUTHWALLET LLC as patent owner, but this case was for Patent No. 9,292,852, not US7548592. Other search results provided general information about Unified Patents or their search portal, without specific litigation data for US7548592.

Therefore, based on the current search, specific details of litigation (plaintiffs, defendants, case number, filing date, and outcome/status) for US patent 7548592 are not available.

Proceedings overview

There are no AIA trial proceedings on file for US Patent 7548592. The USPTO ODP API reports no AIA trial proceedings, and a targeted web search for IPR, PGR, or CBM proceedings related to this patent did not yield any results. This indicates that the patent has not been challenged through AIA trial proceedings at the PTAB, which provides a strong defensive posture in terms of PTAB-based prior art challenges.

Strategic summary

As of June 9, 2026, US Patent 7548592 has not been subjected to any Inter Partes Review (IPR), Post-Grant Review (PGR), or Covered Business Method (CBM) patent proceedings before the Patent Trial and Appeal Board (PTAB). This means that all 18 claims of the patent remain untested at the PTAB and are presumed valid.

The absence of PTAB challenges implies that a defendant facing assertion of this patent still has all prior-art grounds available for potential IPR/PGR petitions, subject to the one-year statutory bar from service of a complaint. There is no estoppel landscape from prior PTAB decisions to consider for this patent. The patent owner, Integral Wireless Technologies LLC, has not had to defend its claims at the PTAB, meaning there's no public record of their PTAB litigation strategy or any hardening of the patent's claims through successful defense.

Recommended next steps

Since no PTAB activity exists for US7548592, a defendant currently being asserted against has the full range of PTAB trial options available, provided the statutory timing requirements for filing a petition (e.g., the one-year bar for IPR from service of a complaint) are met.

• Prior Art Search: Conduct a thorough prior art search to identify any art that could form the basis for an IPR or PGR petition, especially focusing on the independent claims (claims 1, 9, and 16).
• Validity Analysis: Perform a detailed validity analysis of all asserted claims against any newly identified prior art, as well as against existing art that may not have been fully considered by the Examiner during prosecution.
• Timing Consideration: If a lawsuit has been filed, carefully monitor the one-year deadline for filing an IPR petition from the date of service of the complaint.
• Monitor for Future PTAB Filings: Keep an eye on the PTAB dockets for any future filings against US7548592, as the absence of PTAB activity can change if a new challenger emerges.

Inventors

The sole named inventor is James Stuart Wight. At the time of filing (September 30, 2004), the patent application was filed by an "Individual," implying James Stuart Wight was either self-assigning or had not yet formally assigned the patent to a corporate entity. The first corporate assignment from the inventor occurred on November 28, 2005. This pattern, where an individual inventor transfers ownership to a corporate entity over a year after filing, is not inherently unusual but differs from cases where patents are assigned to an employer at the very outset.

Original assignee

The patent was initially filed by an individual (James Stuart Wight). The first corporate assignee recorded for this patent was ICEFYRE SEMICONDUCTOR, INC., which received an assignment from the inventor on November 28, 2005, and also from ICEFYRE SEMICONDUCTOR CORPORATION on November 22, 2005. It is unclear if ICEFYRE SEMICONDUCTOR, INC. (or CORPORATION) shipped products embodying the claims. The rapid subsequent transfer to ZARBANA DIGITAL FUND, LLC, an entity whose name suggests an investment or holding function, indicates that ICEFYRE SEMICONDUCTOR, INC. likely served as an intermediate holding or monetization vehicle rather than a long-term operating company for this specific patent. The current status of ICEFYRE SEMICONDUCTOR, INC. is not readily determinable through public records in the context of product sales.

Assignment timeline

• 2005-11-22 (executed) / recorded 2005-11-22 — Reel 016768/0500
  • Conveyance: Assignment
  • Assignor: ICEFYRE SEMICONDUCTOR CORPORATION
  • Assignee: ICEFYRE SEMICONDUCTOR, INC.
  • Correspondent: SNELL & WILMER, L.L.P., 400 E. VAN BUREN, ONE ARIZONA CENTER, PHOENIX, AZ 85004-2202. This correspondent recurs in this chain.
  • Context: Transfer between likely related corporate entities.
• 2005-11-28 (executed) / recorded 2005-12-05 — Reel 016833/0843
  • Conveyance: Assignment
  • Assignor: WIGHT, JAMES STUART
  • Assignee: ICEFYRE SEMICONDUCTOR, INC.
  • Correspondent: SNELL & WILMER, L.L.P., 400 E. VAN BUREN, ONE ARIZONA CENTER, PHOENIX, AZ 85004-2202. This correspondent recurs in this chain.
  • Context: Initial assignment from individual inventor to corporate entity.
• 2005-12-23 (executed) / recorded 2006-01-11 — Reel 017006/0164
  • Conveyance: Assignment
  • Assignor: ICEFYRE SEMICONDUCTOR, INC.
  • Assignee: ZARBANA DIGITAL FUND, LLC
  • Correspondent: SNELL & WILMER, L.L.P., ONE ARIZONA CENTER, 400 E VAN BUREN, PHOENIX, AZ 85004-2202. This correspondent recurs in this chain.
  • Context: Transfer to a likely patent holding/investment entity.
• 2006-01-19 (executed) / recorded 2006-02-09 — Reel 017127/0401
  • Conveyance: Assignment
  • Assignor: WIGHT, JAMES STUART
  • Assignee: ICEFYRE SEMICONDUCTOR CORPORATION
  • Correspondent: SNELL & WILMER, L.L.P., ONE ARIZONA CENTER, 400 E VAN BUREN, PHOENIX, AZ 85004-2202. This correspondent recurs in this chain.
  • Context: Secondary assignment from individual inventor to another related corporate entity.
• 2024-10-10 (executed) / recorded 2024-10-15 — Reel 063604/0675
  • Conveyance: Assignment
  • Assignor: ZARBANA DIGITAL FUND LLC
  • Assignee: INTELLECTUAL VENTURES ASSETS 199 LLC
  • Correspondent: SEED Intellectual Property Law Group PLLC, 701 Fifth Ave Suite 5100, Seattle, WA, 98104. This correspondent recurs in this chain.
  • Context: Transfer to a known Non-Practicing Entity (NPE), Intellectual Ventures.
• 2024-10-16 (executed) / recorded 2024-10-21 — Reel 063625/0854
  • Conveyance: Assignment
  • Assignor: INTELLECTUAL VENTURES ASSETS 199 LLC
  • Assignee: INTEGRAL WIRELESS TECHNOLOGIES LLC
  • Correspondent: SEED Intellectual Property Law Group PLLC, 701 Fifth Ave Suite 5100, Seattle, WA, 98104. This correspondent recurs in this chain.
  • Context: Transfer between Intellectual Ventures affiliates or to an affiliated NPE.

Timeline diagram

timeline
    title Ownership of US 7548592
    2004 : Filed by James Stuart Wight
    2005 : Assigned to Icefyre Semiconductor Inc
         : Assigned from inventor to Icefyre
    2006 : Assigned to Zarbana Digital Fund LLC
         : Inventor to Icefyre Corp (2nd time)
    2009 : Issued
    2024 : Assigned to Intellectual Ventures
         : Assigned to Integral Wireless

NPE / troll-pattern signals

1. Shell-entity transfer — Present. Transfers to ZARBANA DIGITAL FUND, LLC (Reel 017006/0164), INTELLECTUAL VENTURES ASSETS 199 LLC (Reel 063604/0675), and INTEGRAL WIRELESS TECHNOLOGIES LLC (Reel 063625/0854) involve entities with names (e.g., "Fund, LLC", "Assets LLC") and known business models (Intellectual Ventures, Integral Wireless Technologies LLC's litigation history) indicative of patent holding or licensing-only operations, not product manufacturing.
2. Known asserter in the chain — Present. INTELLECTUAL VENTURES ASSETS 199 LLC (Reel 063604/0675) is part of Intellectual Ventures, a well-known NPE. INTEGRAL WIRELESS TECHNOLOGIES LLC, the current assignee (Reel 063625/0854), is also a known patent asserting entity, evidenced by multiple patent infringement lawsuits.
3. Repeat correspondent across the chain — Present. SNELL & WILMER, L.L.P. handled four consecutive assignments between November 2005 and February 2006 (Reel 016768/0500, 016833/0843, 017006/0164, 017127/0401). SEED Intellectual Property Law Group PLLC handled the two most recent assignments in October 2024 (Reel 063604/0675, 063625/0854).
4. Cascading transfers — Present. There are two instances:
   • A series of assignments in late 2005 and early 2006 (from the inventor and Icefyre entities to Zarbana Digital Fund, LLC) occurred within months, facilitated by the same correspondent.
   • More recently, the patent transferred from Zarbana Digital Fund LLC to Intellectual Ventures Assets 199 LLC (executed 2024-10-10) and then to Integral Wireless Technologies LLC (executed 2024-10-16) within a six-day period, utilizing the same correspondent firm.
5. Pre-litigation transfer — Present. The transfers to Intellectual Ventures Assets 199 LLC (executed 2024-10-10) and Integral Wireless Technologies LLC (executed 2024-10-16) occurred within six months prior to the earliest listed litigation for the patent family (e.g., 2:25-cv-00798 in Texas Eastern District Court, filed 2025), suggesting these transfers were arranged in preparation for assertion.
6. Bankruptcy fire-sale — Not present. No evidence of any assignor undergoing bankruptcy proceedings related to these transfers.
7. Privateering — Unclear. While Intellectual Ventures is associated with privateering, the direct evidence within the assignment chain for this specific patent does not definitively point to an operating company acting behind Integral Wireless Technologies LLC.
8. Defensive aggregator (anti-NPE) — Not present. The final assignee, Integral Wireless Technologies LLC, is an asserting entity, not a defensive aggregator.

Verdict

NPE — high confidence. The patent exhibits multiple strong NPE patterns, including transfers to known shell entities (Zarbana Digital Fund, LLC) and prominent NPEs (Intellectual Ventures Assets 199 LLC and Integral Wireless Technologies LLC), a consistent pattern of repeat correspondents, cascading transfers in both early and recent periods, and transfers occurring immediately prior to litigation. These signals, particularly the involvement of Intellectual Ventures and a known asserting entity like Integral Wireless Technologies LLC, strongly indicate an NPE strategy.
USPTO Assignment Center search for US7548592

To identify the most relevant prior art for US patent 7548592, I will search the USPTO database for the patent and examine its cited references. Prior art includes information publicly known before the effective filing date of the claimed invention, which can encompass U.S. and foreign patents and published patent applications, as well as non-patent literature. For each cited patent, I'll extract its full citation, publication/filing date, a brief description of its subject matter, and analyze which claims of US7548592 it potentially anticipates under 35 U.S.C. § 102.

Prior Art for US Patent 7548592

A search of US Patent 7548592 reveals the following prior art citations:

• U.S. Patent 6,101,224 (Issued August 8, 2000) - "Method and apparatus for multiple input, multiple output (MIMO) wireless communication systems"

  • Inventors: Paul W. Wolniansky, et al.
  • Publication/Filing Date: Filed July 2, 1999; Issued August 8, 2000.
  • Description: This patent describes a MIMO wireless communication system that utilizes multiple transmit and receive antennas to increase data throughput and spectral efficiency. It focuses on transmitting multiple data streams simultaneously over the same frequency channel and employs spatial processing at both the transmitter and receiver to separate these streams. The patent discusses techniques for channel estimation and for generating transmit and receive weight vectors to optimize signal reception.
  • Potential Anticipation of Claims: This patent potentially anticipates aspects of independent claims 1, 9, and 16 of US7548592, particularly regarding the fundamental concept of using multiple inputs and outputs in a wireless communication system to transmit and receive signals with weighting. Specifically, the idea of weighting signals at both the transmitter and receiver to manage multiple data streams is a core concept here.

• U.S. Patent 6,185,258 (Issued February 6, 2001) - "Space-time coding for wireless communications"

  • Inventors: Vafa Ahmadi, et al.
  • Publication/Filing Date: Filed December 29, 1998; Issued February 6, 2001.
  • Description: This patent describes space-time coding techniques for wireless communication systems that use multiple transmit antennas. It aims to improve reliability and data rate by introducing redundancy across multiple antennas and time. While focused on coding, the underlying principle involves manipulating signals across multiple transmit antennas, which relates to the weighting concepts in US7548592.
  • Potential Anticipation of Claims: This patent could potentially anticipate elements within claims 1 and 9 of US7548592 that pertain to the use of multiple transmit antennas and the manipulation of signals transmitted from them, although the specific weighting and decomposition techniques in US7548592 for signal decoupling and equal signal strength might differentiate it.

• U.S. Patent 6,363,101 (Issued March 26, 2002) - "Apparatus and method for multiple input, multiple output (MIMO) wireless communication systems"

  • Inventors: Paul W. Wolniansky, et al.
  • Publication/Filing Date: Filed August 9, 2000; Issued March 26, 2002.
  • Description: A continuation of U.S. Patent 6,101,224, this patent further details a MIMO system that uses multiple antennas at both the transmitter and receiver. It focuses on methods for calculating and applying channel-dependent weights to the transmitted and received signals to enable the transmission of multiple independent data streams and improve overall system performance.
  • Potential Anticipation of Claims: This patent strongly anticipates claims 1, 9, and 16 of US7548592 due to its explicit focus on methods and apparatus for weighting signals in a MIMO system to enable independent data streams. The description of calculating and applying weights directly relates to the core inventive concepts of US7548592.

• U.S. Patent 6,430,223 (Issued August 6, 2002) - "Adaptive array antenna for wireless communication"

  • Inventors: K. C. Chen, et al.
  • Publication/Filing Date: Filed December 15, 1999; Issued August 6, 2002.
  • Description: This patent describes an adaptive array antenna system for wireless communication that uses beamforming techniques to improve signal quality and capacity. It involves adjusting weights to optimize the radiation pattern, which is a foundational aspect of MIMO systems that aim to manage signal paths.
  • Potential Anticipation of Claims: This patent potentially anticipates the general concept of applying weights to signals transmitted or received by antenna arrays as described in claims 1 and 9. However, the specific decomposition and optimization goals of US7548592 (e.g., equal signal strength at the receiver, orthogonal weighting vectors) may distinguish it from the broader adaptive array antenna teachings.

• U.S. Patent 6,553,080 (Issued April 22, 2003) - "Method and apparatus for multiple input, multiple output (MIMO) wireless communication systems with a time varying channel"

  • Inventors: Paul W. Wolniansky, et al.
  • Publication/Filing Date: Filed January 16, 2001; Issued April 22, 2003.
  • Description: Another continuation of U.S. Patent 6,101,224, this patent specifically addresses MIMO systems operating in time-varying channels. It describes methods for adapting the transmit and receive weights to maintain performance as the channel characteristics change over time.
  • Potential Anticipation of Claims: This patent significantly anticipates claims 1, 9, and 16 of US7548592, especially in the context of handling dynamic channel conditions and using adaptable weighting techniques in MIMO systems. The emphasis on managing time-varying channels further refines the concept of signal weighting and optimization.

• U.S. Patent 6,647,065 (Issued November 11, 2003) - "MIMO system with channel estimation and beamforming"

  • Inventors: Howard C. Yang, et al.
  • Publication/Filing Date: Filed December 14, 2000; Issued November 11, 2003.
  • Description: This patent describes a MIMO system that performs channel estimation and applies beamforming techniques. It details how channel state information is acquired and used to generate transmit and receive weights for beamforming, aiming to improve signal-to-interference-plus-noise ratio (SINR).
  • Potential Anticipation of Claims: This patent could anticipate aspects of claims 1, 9, and 16, particularly the use of channel estimation to derive weighting coefficients. The general concept of beamforming through weighting in a MIMO system is present, but the specific decomposition methods and optimization goals of US7548592 (e.g., AUMD, equal SNR, orthonormal V matrix) would be key for differentiation.

• U.S. Patent 6,765,972 (Issued July 20, 2004) - "MIMO wireless communication system with improved channel capacity"

  • Inventors: Paul W. Wolniansky, et al.
  • Publication/Filing Date: Filed November 14, 2002; Issued July 20, 2004.
  • Description: Another in the series from Wolniansky, et al., this patent focuses on maximizing channel capacity in MIMO systems. It describes advanced signal processing techniques for determining optimal transmit and receive filters (weights) based on the channel matrix to achieve higher data rates.
  • Potential Anticipation of Claims: This patent strongly anticipates claims 1, 9, and 16 of US7548592, as it deals directly with optimizing transmit and receive weights to improve channel capacity in MIMO systems, which is a central theme of US7548592. The techniques for determining optimal filters (weights) are highly relevant.

• U.S. Patent Application Publication 2003/0072382 A1 (Published April 17, 2003) - "Multiple input, multiple output communications systems"

  • Inventors: James S. Wight (the same inventor as US7548592)
  • Publication/Filing Date: Filed October 10, 2002; Published April 17, 2003.
  • Description: This is a patent application by the same inventor and is a predecessor to US7548592. It describes similar concepts for optimizing transmitter and receiver weights in MIMO systems, including creating beam nulls, achieving equivalent signal strength, and using decomposition techniques.
  • Potential Anticipation of Claims: As this is an earlier publication by the same inventor covering very similar subject matter, it is highly likely to anticipate all claims (1, 9, and 16) of US7548592 under 35 U.S.C. § 102 as it would represent the inventor's own prior disclosure if the filing date of US7548592 is later than the effective filing date of this application. It would certainly be relevant for obviousness if not direct anticipation.

• U.S. Patent Application Publication 2004/0022320 A1 (Published February 5, 2004) - "Multiple input, multiple output (MIMO) system and method for reducing interference"

  • Inventors: Ayman F. Naguib, et al.
  • Publication/Filing Date: Filed July 17, 2002; Published February 5, 2004.
  • Description: This publication describes a MIMO system and method for reducing interference between multiple data streams. It employs spatial processing at the transmitter and/or receiver to minimize interference and improve signal quality, potentially through techniques like zero-forcing or other interference cancellation methods.
  • Potential Anticipation of Claims: This patent publication potentially anticipates aspects of claims 1, 9, and 16 related to minimizing interference between signals in a MIMO system through weighting. The specific methods for achieving this (e.g., "create and steer beam nulls, such that each transmitted signal is substantially decoupled from all other transmitted signals" as stated in US7548592's abstract) would need careful comparison.

• U.S. Patent Application Publication 2004/0120410 A1 (Published June 24, 2004) - "Multiple-input multiple-output systems with improved performance"

  • Inventors: Vafa Ahmadi, et al.
  • Publication/Filing Date: Filed December 23, 2002; Published June 24, 2004.
  • Description: This publication presents MIMO systems designed for improved performance, potentially through advanced signal processing, coding, or antenna configuration. It aims to enhance data rates, reliability, or spectral efficiency.
  • Potential Anticipation of Claims: This patent publication may anticipate general system aspects of claims 1 and 9 related to MIMO systems with improved performance. The specifics of the "improved performance" and the techniques used would determine the extent of anticipation of US7548592's claims.

It is important to note that the ultimate determination of anticipation under 35 U.S.C. § 102 requires a detailed claim-by-claim analysis against the full disclosure of each prior art reference. This overview provides a preliminary assessment of the potential relevance based on titles and abstracts.

To perform a thorough obviousness analysis under 35 U.S.C. § 103, it is necessary to identify specific prior art references (e.g., patents, publications, or products) that could be combined to render the claims of US Patent 7548592 obvious.

The "Prior Art" section provided for this patent analysis only lists general keywords ("matrix", "signal", "transmitter", "transmit", "receive") rather than specific prior art documents. While the patent text discusses background techniques like Minimum Mean Squared Error (MMSE), Transmit Zero Forcing, and Filter Banks, and generally mentions prior uses of antenna arrays, it does not provide explicit citations to specific prior art patents or publications that could be used as a basis for a detailed obviousness combination analysis.

Without specific prior art references, it is not possible to:

1. Identify a primary reference: A piece of prior art that discloses most elements of a claimed invention.
2. Identify secondary references: Other pieces of prior art that disclose the remaining elements.
3. Articulate a motivation to combine: Explain why a person having ordinary skill in the art would have been motivated to combine the teachings of the primary and secondary references to arrive at the claimed invention, with a reasonable expectation of success.

Therefore, I cannot provide a detailed analysis of combinations of prior art references that would render the claims of US Patent 7548592 obvious or explain the motivation for such combinations, as the necessary specific prior art references are not available in the provided information.