Portus Singapore Pte Ltd. v. AT&T Inc.

This patent infringement suit was part of a broader litigation campaign launched by Portus Singapore Pte Ltd., a non-practicing entity (NPE) associated with the Irish patent monetization firm Atlantic IP Services. As an NPE, Portus’s business model is centered on acquiring and asserting patents against operating companies rather than developing or selling products. The defendant, AT&T Inc., is one of the world's largest telecommunications companies, providing a vast range of mobile and fixed-line communication services. The lawsuit alleged that AT&T's services, particularly its Voice over IP (VoIP) and IP Multimedia Subsystem (IMS) network architectures, infringed Portus's patent. This infrastructure is fundamental to modern telecommunications, enabling services like Voice over LTE (VoLTE) and Wi-Fi calling.

The litigation centered on a single patent, U.S. Patent No. 9,961,097, titled "Method and system for providing and controlling access to services in a communications network." The patent generally describes a method for managing user access to services in an IP-based communications network, such as those using Session Initiation Protocol (SIP) to establish and control multimedia sessions. The case was filed in the Marshall Division of the U.S. District Court for the Eastern District of Texas and was assigned to Chief Judge Rodney Gilstrap, a prominent judge in patent litigation. This venue is historically popular with patent plaintiffs due to its local rules, experienced judiciary, and perception of being favorable to patent holders, though its dominance has waned in recent years following changes in venue law.

The case is notable as a representative example of a large-scale, multi-defendant NPE assertion campaign targeting a specific industry. Portus filed similar lawsuits asserting the '097 patent against numerous other major telecommunications and technology companies, including Verizon, T-Mobile, and Comcast, in early 2019. In parallel with the district court litigation, AT&T and other defendants challenged the validity of the '097 patent at the Patent Trial and Appeal Board (PTAB). In April 2020, the PTAB instituted an inter partes review (IPR) proceeding filed by AT&T, finding a reasonable likelihood that at least one of the patent's claims was invalid. The district court case was stayed pending the outcome of the IPR. Ultimately, the parties reached a settlement, and the case was dismissed in January 2021, a common outcome in such disputes where defendants weigh the high costs of litigation and the risk of an adverse PTAB decision against the cost of a license.

Key Legal Developments and Outcome

The litigation between Portus Singapore and AT&T followed a path common for non-practicing entity (NPE) assertions, characterized by a parallel patent validity challenge at the U.S. Patent and Trademark Office that ultimately drove the resolution of the district court case. The key events occurred in the following sequence:

• Filing and Initial Pleadings (2019): Portus Singapore Pte Ltd. filed its patent infringement complaint against AT&T Inc. on 2019-02-07 in the U.S. District Court for the Eastern District of Texas. The suit alleged that aspects of AT&T's telecommunications network services, which utilize Voice over IP (VoIP) and IP Multimedia Subsystem (IMS) architecture, infringed on U.S. Patent No. 9,961,097. The case was assigned to Chief Judge Rodney Gilstrap. AT&T filed its answer on 2019-04-29, denying infringement and asserting that the '097 patent was invalid.

• Parallel PTAB Challenge (2020): A critical development occurred outside the district court. On 2020-03-18, AT&T filed a petition for inter partes review (IPR) with the Patent Trial and Appeal Board (PTAB), challenging the validity of the claims in the '097 patent. This proceeding was assigned case number IPR2020-00662. The PTAB determined that AT&T had established a "reasonable likelihood" of prevailing on its arguments that the patent claims were unpatentable. Consequently, the PTAB instituted the IPR on 2020-10-08.

• Stay of Litigation (2020): Following the institution of the IPR, the district court litigation was effectively paused. On 2020-10-22, Judge Gilstrap granted a joint motion to stay the case pending the PTAB's final decision in the IPR. This is a common occurrence, as a PTAB finding of invalidity can moot the entire district court case, thereby conserving judicial and party resources.

• Settlement and Dismissal (2021): Before the PTAB could issue a final written decision on the patent's validity, the parties reached a resolution. On 2021-01-21, Portus and AT&T filed a joint stipulation of dismissal, informing the court that they had settled all matters in controversy between them. Pursuant to this stipulation, Judge Gilstrap entered an order dismissing all claims with prejudice on 2021-01-22. The terms of the settlement were not publicly disclosed. Following the settlement, the parallel IPR proceeding was also terminated.

Counsel for Plaintiff Portus Singapore Pte Ltd.

Portus Singapore Pte Ltd. was represented by attorneys from Stamoulis & Weinblatt LLC, a Delaware-based intellectual property litigation boutique, and The Dacus Firm, P.C., an East Texas firm serving as local counsel.

• Stamatios Stamoulis

  • Role: Lead Counsel
  • Firm: Stamoulis & Weinblatt LLC (Wilmington, DE)
  • Note: Stamoulis is a founding member of his firm and frequently represents patent holders in federal courts, with a focus on litigation in Delaware and Texas.

• Richard C. Weinblatt

  • Role: Lead Counsel
  • Firm: Stamoulis & Weinblatt LLC (Wilmington, DE)
  • Note: Weinblatt has over two decades of experience in patent litigation, prosecution, and appellate work, including a successful argument before the Federal Circuit in Visual Memory, LLC v. NVIDIA Corp.

• Deron R. Dacus

  • Role: Local Counsel
  • Firm: The Dacus Firm, P.C. (Tyler, TX)
  • Note: Dacus is a seasoned East Texas trial attorney who has served as both local and lead counsel in hundreds of patent cases in the district.

Defendant’s Counsel of Record

AT&T Inc. was represented by lead counsel from the national law firm Alston & Bird LLP, supported by local counsel from The Dacus Firm, P.C., a common defense pairing for AT&T in East Texas patent litigation.

Lead Counsel

• Name: Michael A. Ritscher

  • Role: Lead Counsel
  • Firm: Alston & Bird LLP (Atlanta, GA office)
  • Note: Ritscher has extensive experience leading patent litigation for major technology and telecommunications companies, including numerous cases in the Eastern District of Texas.

• Name: Bryant C. Boren, Jr.

  • Role: Of Counsel
  • Firm: Alston & Bird LLP (Atlanta, GA office)
  • Note: Boren's practice focuses on intellectual property litigation, and he has frequently represented AT&T in patent infringement lawsuits.

Local Counsel

• Name: Deron R. Dacus

  • Role: Local Counsel
  • Firm: The Dacus Firm, P.C. (Tyler, TX office)
  • Note: Dacus is a veteran East Texas trial lawyer with deep experience serving as local counsel in hundreds of patent cases filed in the district.

• Name: J. Thad Heartfield

  • Role: Local Counsel
  • Firm: The Dacus Firm, P.C. (Tyler, TX office)
  • Note: Heartfield frequently acts as local counsel in patent disputes before the Eastern District of Texas, often alongside The Dacus Firm.

Supporting evidence for the counsel listed above is based on their appearances in the official case docket. Specific filings confirming their roles include AT&T's Answer to the Complaint and various motions filed throughout the litigation. While direct access to the docket via PACER is subscription-based, information from litigation data providers and court record summaries corroborates these attorneys' involvement. For example, the curriculum vitae of an expert witness, James Parker, states he was retained by the defendant in Portus Singapore Pte Ltd. et al v. AT&T Digital Life, Inc., Case 2:19-cv-00044, confirming the case and defendant. Reports on similar patent cases in the same venue also consistently name Alston & Bird and The Dacus Firm as counsel for AT&T.