T-Mobile USA Inc v. Smart RF Inc

1. Case Identification

• Case #: IPR2025-00612
• Patent #: 8,078,561
• Filed: February 14, 2025
• Petitioner(s): T-Mobile USA, Inc., AT&T Mobility LLC, Cellco Partnership d/b/a Verizon Wireless, Ericsson Inc., and Nokia of America Corporation
• Patent Owner: Smart RF Inc.
• Challenged Claims: 1-22

2. Patent Overview

• Title: Nonlinear behavior models and methods for use thereof in wireless radio systems.
• Brief Description: The ’561 patent discloses behavioral models for predistortion in wide-band radio frequency transmitters. The technology aims to correct nonlinear signal distortions from power amplifiers by coupling a dynamic weak nonlinear (DWNL) module, which models memory effects, with a static strong nonlinear (SSNL) module, which models memoryless distortions.

3. Grounds for Unpatentability

Ground 1: Claims 1 and 4-6 are obvious over Lui.

• Prior Art Relied Upon: Lui (an IEEE article published in November 2005 by the inventors of the ’561 patent).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Lui discloses a behavioral model for a radio transmitter that is identical to the model claimed in the ’561 patent. Specifically, Lui teaches an "augmented Wiener model" comprising a dynamic weak nonlinear module (a "memory-effect model" with a linear FIR filter and a parallel weak nonlinear FIR filter) followed by, and coupled to, a static strong nonlinear module (a "memoryless static nonlinearity model" using AM/AM and AM/PM lookup tables). This structure, Petitioner asserted, maps directly onto the limitations of independent claim 1, which requires a first "dynamic" module coupled to a second "static" module. Dependent claims 4-6, which add details like a finite impulse response (FIR) filter and lookup tables, were also argued to be fully disclosed in Lui's model.
  • Motivation to Combine: This ground was asserted based on a single reference. Petitioner argued it would have been obvious for a person of ordinary skill in the art (POSITA) to use Lui's disclosed modules to "characterize" system properties as claimed, because Lui explicitly states its model "takes into account the dynamic properties of the transmitters" and that static nonlinearity "can be characterized by the lookup tables."

Ground 2: Claims 2, 7-10, and 15-18 are obvious over Lui.

• Prior Art Relied Upon: Lui.
• Core Argument for this Ground:
  • Prior Art Mapping: This ground targets claims directed to "Wiener" models and predistorters, where a dynamic module is followed by a static module. Petitioner argued that Lui's "augmented Wiener model" expressly teaches this arrangement. While Lui primarily describes a behavioral model, Petitioner contended it would have been obvious to a POSITA to implement this model in a predistorter, as that was the explicit purpose of such modeling in the art. Lui itself validates its model by "preceding the transmitter with its memoryless nonlinear inverse function," which describes predistortion. Independent claims 7 and 15, which recite a "predistorter" comprising a dynamic module followed by a static module, were argued to be an obvious implementation of Lui's teachings.
  • Expectation of Success: A POSITA would have had a high expectation of success in using Lui's model to build a predistorter because Lui's stated goal was to create an accurate model for RF transmitters to minimize distortion, a problem commonly solved by predistortion.

Ground 3: Claims 3, 11-14, and 19-22 are obvious over Lui in view of Ding.

• Prior Art Relied Upon: Lui and Ding (a Ph.D. thesis published in March 2004).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground targets claims directed to "Hammerstein" models and predistorters, where a static module is followed by a dynamic module (the reverse of a Wiener model). Petitioner argued it would have been obvious to modify Lui's model by reversing the order of its SSNL and DWNL modules. This modification represents one of a finite number of predictable design choices. The resulting structure would meet the limitations of independent claims 11 and 19.
  • Motivation to Combine: Petitioner asserted multiple motivations. First, a POSITA would have been motivated to try reversing the order of Lui's modules as a simple and predictable variation. Second, Ding explicitly teaches that Wiener and Hammerstein models are well-known, alternative solutions for predistortion and that a Hammerstein predistorter is the "inverse" of a Wiener system. A POSITA reading Lui, which focuses on an augmented Wiener model, would be motivated by Ding to implement the known Hammerstein alternative using Lui's improved dynamic and static modules to see if it yielded better results. Lui also cites other papers discussing Hammerstein structures, indicating awareness of this alternative in the art.
  • Expectation of Success: A POSITA would have expected success because reversing the modules was a standard, well-understood modification in the art. Ding provides an explicit roadmap, teaching a method to "first identify the Wiener system and then find the Hammerstein predistorter as its inverse."

4. Key Claim Construction Positions

• “Wiener predistorter” (Claim 15): Petitioner proposed this term be construed as "a predistorter where a dynamic module is followed by a static module," consistent with the patent's specification and the term's established meaning in the prior art.
• “Hammerstein predistorter” (Claim 19): Petitioner proposed this term be construed as "a predistorter where a static module is followed by a dynamic module," representing the inverse arrangement of the Wiener model.
• “dynamic nonlinear first order predistorter module” (Claims 15, 19): Petitioner proposed this term be construed as "a dynamic predistortion module that includes a nonlinear function with a first-power exponent," based on figures and descriptions in the ’561 patent specification.

5. Arguments Regarding Discretionary Denial

• Petitioner argued that the Board should not exercise its discretion to deny institution under 35 U.S.C. §325(d) because the primary prior art references, Lui and Ding, were never cited or considered during the original prosecution.
• Petitioner also argued against discretionary denial under 35 U.S.C. §314(a) based on the Fintiv factors. It contended that the parallel district court litigation is in its early stages with no substantive rulings issued, and the trial date is scheduled for November 2025, well after a final written decision (FWD) would issue in this inter partes review (IPR). Petitioner emphasized the strong merits of the petition and the fact that the grounds asserted have not been previously considered by any court or the Patent Office.

6. Relief Requested

• Petitioner requested the institution of an IPR and the cancellation of claims 1-22 of the ’561 patent as unpatentable under 35 U.S.C. §103.