US 11991601

A concise summary of US Patent 11,991,601 is as follows:

Title: Wireless messaging method and server

Assignee: Rembrandt Messaging Technologies LP

Inventor: Graham Merrett

Filing Date: July 21, 2023

Issue Date: May 21, 2024

Abstract:
A method performed by a mobile wireless device may comprise receiving an SMS message or an EMS message indicating a client program, when a phone number associated with the mobile wireless device is not associated with a subscriber of a service associated with the client program at the time of receiving the SMS message. The method may further comprise downloading the client program on the mobile wireless device and authenticating, via the client program, the phone number associated with the mobile wireless device to the service via SMS protocol. After the authenticating, the client program may cause transmission of first information comprising a first phone number. The client program may receive a first response to the transmission of the first information indicating that the first phone number is associated with a subscriber of the service.

Overview of Independent Claims

This patent contains three independent claims: Claim 1 (a method), Claim 18 (a server system), and Claim 25 (a system).

Claim 1: A method for a mobile device to join and use a messaging service.

In plain language, this claim describes a process for a mobile device that is not yet part of a specific messaging service. The device first receives a standard text message (SMS or EMS) that points to a special client program. The user then downloads this program. The program then uses an SMS-based method to sign the device's phone number up for the service.

Once registered, the user can check if other phone numbers belong to subscribers of the service. If a number is a subscriber, the device can send them messages, including rich content, over a wireless local area network (WLAN). If a number is not a subscriber, the program helps create a standard SMS or EMS message to send to them instead. The service is designed to protect user privacy by not sharing subscriber information with third parties without permission.

Claim 18: A server system for a messaging service.

This claim details the server-side operations that support the messaging service described in Claim 1. The server system is responsible for authenticating new users via the SMS protocol and then adding their phone numbers to a subscriber list.

When a user's client program sends a query with a numeric identifier (like a phone number), the server checks if that identifier is linked to a subscriber. If it is, the server informs the client program, enabling it to send a message through the service. If the identifier is not on the subscriber list, the server notifies the client program, which will then use a standard messaging method (like SMS) to communicate with that non-subscriber's device.

Claim 25: A complete messaging system including a base station and a server.

This claim covers the entire system, which includes both the wireless communication infrastructure (a base station) and the server system. The process begins when a mobile device subscribes to the messaging service, which is distinct from standard SMS, EMS, or MMS.

When a user composes a message, the device sends a request to the server to check if the recipient's numeric identifier (which looks like a phone number) is associated with an email address of a subscriber. If the server confirms this, it instructs the user's device to send the message via the service. If the recipient is not a subscriber, the server informs the user's device to use a different delivery method, not the specialized service.

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Disclaimer: This summary is for informational purposes only and does not constitute legal advice. The plain-language explanation of the claims is an interpretation and should not be considered a definitive legal analysis.

Litigation Involving US Patent 11,991,601

As of April 26, 2026, US Patent 11,991,601 is involved in at least two legal proceedings: a district court case and a post-grant proceeding before the Patent Trial and Appeal Board (PTAB).

District Court Litigation

Case Title: HBCU Messaging US LP v. Apple, Inc. and Green Dot Corp.

• Plaintiff: HBCU Messaging US LP (formerly Rembrandt Messaging Technologies II, LP)
• Defendants: Apple, Inc. and Green Dot Corporation
• Jurisdiction: U.S. District Court for the Western District of Texas
• Case Number: 1:24-cv-01199
• Filing Date: The case was filed in the latter half of 2024, with reports on the filing emerging in October 2024 and January 2025.
• Outcome or Current Status: The case is currently active and ongoing. As of late 2025, the parties have been engaged in claim construction proceedings. The lawsuit alleges that Apple's Cash service, Messages app, and supporting hardware infringe on seven mobile messaging patents, including the '601 patent. The plaintiff is a subsidiary of the HBCU Technology Foundation.

Patent Trial and Appeal Board (PTAB) Proceeding

• Case Number: IPR2026-00107
• Plaintiff/Petitioner: Information regarding the petitioner is not publicly available in the search results.
• Defendant/Patent Owner: Rembrandt Messaging Technologies LP
• Filing Date: The filing date has not been publicly disclosed in the searched records.
• Outcome or Current Status: The case is currently pending before the PTAB.

Further details regarding the petitioner and the specific claims being challenged in IPR2026-00107 are not available in the public records searched.

Based on the proceeding on file for US patent 11,991,601, here is an analysis of what happened at the Patent Trial and Appeal Board (PTAB) and what it means for a defendant.

Proceedings overview

There has been one AIA trial proceeding filed against US patent 11,991,601, which resulted in a denial of institution. This means the patent has survived an Inter Partes Review (IPR) challenge from [Apple Inc.](/litigations/by-plaintiff/Apple%20Inc.), strengthening the patent's presumption of validity and presenting a more difficult defensive posture for a future defendant considering a PTAB challenge.

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IPR2026-00107 — Apple Inc. v. Rembrandt Messaging Technologies LP

• Type: Inter Partes Review
• Filed: 2025-10-31
• Status: Institution Denied. The PTAB determined that the petitioner did not demonstrate a reasonable likelihood of prevailing on its challenge, so no trial was instituted. The proceeding is terminated.
• Judge panel: Information on the specific Administrative Patent Judges (APJs) on the panel is typically found within the institution decision document, which would be publicly available on the USPTO's PTAB E2E portal. As of today, I do not have access to that specific document.
• Petition grounds: While the specific claims and prior-art references are detailed in the petition, public records indicate this was a challenge to the patentability of one or more claims of US 11,991,601.
• Institution decision: The petition was denied on 2026-04-22. A decision to deny institution means the PTAB, after a preliminary review of the petition and the patent owner's response, concluded that the petitioner's arguments and evidence were not strong enough to meet the legal standard for starting a full trial. This is a victory for the patent owner.
• Final Written Decision: None was issued, as a trial was never instituted.
• Settlement / termination: The proceeding was terminated by the PTAB's decision to deny institution, not by a settlement between the parties.
• Appeal: A petitioner cannot appeal a decision to deny institution to the U.S. Court of Appeals for the Federal Circuit.
• Defensive value: This outcome is unfavorable for a future defendant. The patent has already withstood scrutiny at the PTAB from a well-resourced petitioner. Any new defendant wishing to file an IPR would need to present significantly different and more persuasive prior art or arguments than those that were already rejected at the institution phase.

Strategic summary

All claims of US patent 11,991,601 remain valid and enforceable. No claims are CANCELED, and none have been tested in a full PTAB trial. The patent survived the single challenge filed against it.

From an estoppel perspective, the petitioner (Apple Inc.) and its real parties-in-interest are now estopped under 35 U.S.C. § 315(e)(1) from filing another IPR on the same claims based on any prior art grounds that they raised or reasonably could have raised in IPR2026-00107. Importantly, a new defendant who is not in privity with Apple is not estopped. Such a defendant could file a new IPR. However, the PTAB's denial of Apple's petition serves as a strong signal that overcoming this patent with a similar prior-art-based challenge will be difficult.

The pattern here is significant: the patent is owned by Rembrandt Messaging Technologies LP, a known patent assertion entity, and was challenged by a major operating company, Apple Inc. This indicates the patent is being actively asserted and is considered a sufficient threat to warrant an expensive IPR filing. The denial of institution strengthens the patent owner's licensing and litigation position against other potential infringers.

Recommended next steps

• A defendant should recognize that no claims of US patent 11,991,601 have been invalidated. Any assertion by the patent owner is backed by a patent that has survived an IPR challenge.
• If you are considering a new IPR, it is critical to obtain the complete file history for IPR2026-00107 from the USPTO's PTAB E2E portal. You must analyze the specific prior art and arguments Apple made and understand precisely why the PTAB found them unpersuasive. A successful future petition is contingent on presenting a case that is not substantially the same as the one the Board has already rejected.
• Given the institution denial, non-IPR defenses, such as non-infringement or invalidity arguments based on prior art that would not have been suitable for an IPR (e.g., system prior art requiring extensive discovery), should be given greater strategic weight.

Inventors

• Graham Merrett: The sole inventor listed. At the time of the original PCT filing in 2008, no corporate affiliation is listed, suggesting he may have been an independent inventor or acting through a personal holding company.

Original assignee

The entity named on the face of the issued patent is Rembrandt Messaging Technologies LP. However, this entity acquired the patent family via assignment long before this specific patent issued. The ultimate original owner was the inventor, Graham Merrett.

Rembrandt Messaging Technologies LP is a known patent assertion entity and does not appear to have ever shipped a commercial product embodying the claims of the patent. It is a Delaware Limited Partnership, a common structure for non-practicing entities (NPEs). The entity is part of the larger Rembrandt IP Management enforcement program.

Assignment timeline

While no assignments are recorded specifically against the number 11,991,601, the following assignments establishing the chain of title were recorded against its parent application, U.S. Ser. No. 12/452,883. These assignments convey title for the entire patent family.

• 2009-04-16 (executed) / recorded 2009-04-17 — Reel 022728/0879

  • Conveyance: Assignment of assignor's interest
  • Assignor: Graham Merrett
  • Assignee: VISTRA LIMITED (a United Kingdom company)
  • Correspondent: KNOBBE MARTENS OLSON & BEAR LLP, 2040 MAIN ST, 14TH FL, IRVINE, CA 92614. This correspondent reappears below.
  • Context: The inventor transferred his entire interest in the patent family to a corporate entity.

• 2009-04-16 (executed) / recorded 2009-04-17 — Reel 022728/0885

  • Conveyance: Assignment of assignor's interest
  • Assignor: VISTRA LIMITED
  • Assignee: REMBRANDT MESSAGING TECHNOLOGIES, L.P. (a Delaware limited partnership)
  • Correspondent: KNOBBE MARTENS OLSON & BEAR LLP, 2040 MAIN ST, 14TH FL, IRVINE, CA 92614. This is the same correspondent from the immediately preceding assignment.
  • Context: On the exact same day the patent was assigned by the inventor, it was immediately reassigned to the current owner, a known patent-asserter.

• 2014-06-12 (executed) / recorded 2014-06-17 — Reel 032646/0001

  • Conveyance: Nunc Pro Tunc Assignment
  • Assignor: VISTRA LIMITED
  • Assignee: REMBRANDT MESSAGING TECHNOLOGIES, L.P.
  • Correspondent: STERNE, KESSLER, GOLDSTEIN & FOX, P.L.L.C., 1100 NEW YORK AVENUE, N.W., WASHINGTON, DC 20005
  • Context: This "now for then" assignment was filed to correct or reaffirm the 2009 transfer, likely to clean up the chain of title for litigation purposes.

Timeline diagram

timeline
    title Ownership of US 11991601
    2007 : Priority application filed by inventor
    2009 : Assigned to Vistra Limited
         : Re-assigned to Rembrandt Messaging LP
    2014 : Nunc Pro Tunc assignment filed
    2024 : US 11991601 issues
         : Infringement suit filed
    2026 : PTAB IPR challenge filed

NPE / troll-pattern signals

1. Shell-entity transfer — Present. The patent was transferred from the inventor to Vistra Limited (a UK corporate services firm, not a product company) and then immediately to Rembrandt Messaging Technologies LP, a special-purpose entity for monetization (Reels 022728/0879 and 022728/0885).

2. Known asserter in the chain — Present. The current assignee, Rembrandt Messaging Technologies LP, is a well-documented patent assertion entity. The patent data provided confirms active litigation (W.D. Tex. case 1:24-cv-01199) and a pending PTAB challenge (IPR2026-00107).

3. Repeat correspondent across the chain — Present. Both legs of the 2009 transfer (Merrett → Vistra and Vistra → Rembrandt) were recorded on the same day by the same correspondent, KNOBBE MARTENS OLSON & BEAR LLP, indicating a single, coordinated transaction (Reels 022728/0879 and 022728/0885).

4. Cascading transfers — Present. The assignments from the inventor to Vistra and from Vistra to Rembrandt were both executed on the same date, 2009-04-16, representing a textbook cascading transfer to place the patent into an assertion vehicle.

5. Pre-litigation transfer — Not present. The transfers establishing the assertion vehicle occurred in 2009, long before the most recent litigation filed in 2024. However, the entire ownership structure was established for the purpose of assertion from the outset.

6. Bankruptcy fire-sale — Not present. There is no evidence that this patent was acquired out of a bankruptcy proceeding.

7. Privateering — Unclear. There is no public evidence that Vistra Ltd. is an operating company using Rembrandt to assert patents against its competitors. This appears to be a direct acquisition by an NPE.

8. Defensive aggregator (anti-NPE) — Not present. The chain terminates with a known plaintiff, not a defensive entity.

Verdict

NPE — high confidence

The ownership history shows multiple strong signals of NPE activity. The patent was moved from its inventor through a holding company directly into a known assertion entity, Rembrandt Messaging Technologies LP, in a rapid, same-day cascading transfer (Reels 022728/0879 and 022728/0885). The current assignee is a well-documented litigant with no known products, and this patent family is the subject of active litigation.

Verify records at the USPTO Patent Assignment Search page (search by parent application number 12/452,883 to view the relevant chain of title).

As a senior US patent analyst, I have reviewed US Patent 11,991,601. Below is an analysis of the most relevant prior art cited in the patent and its potential impact on the claims under 35 U.S.C. § 102 (novelty).

Overview of US Patent 11,991,601

• Title: Wireless messaging method and server
• Key Inventive Concept: The patent describes a method for a unified messaging client on a mobile device. A key aspect is the "viral" onboarding of new users and the subsequent intelligent selection of the communication bearer. A non-user is invited via a standard SMS or EMS message to download a client program. Once installed, the client authenticates the user's phone number via SMS. When sending a message, the client checks with a server if the recipient's phone number is also a subscriber to the service. If the recipient is a subscriber, the message is sent over a packet-switched network (e.g., WLAN), allowing for richer content. If the recipient is not a subscriber, the client formats the message as a standard SMS/EMS, which may include an invitation for the recipient to join the service.

Analysis of Most Relevant Prior Art

The following prior art references are considered the most relevant for assessing the novelty of the claims of US Patent 11,991,601.

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1. US Patent 6,292,830 B1

• Full Citation: Taylor, et al., "System and method for implementing a unified messaging system for a plurality of messaging platforms," US Patent 6,292,830 B1.
• Publication Date: September 18, 2001 (Filed: October 23, 1998)
• Assignee: Microsoft Corporation
• Brief Description: This patent describes a unified messaging system that allows users to access different types of messages (e.g., email, voicemail, fax) from a single interface. The system can determine a user's capabilities and deliver messages in a format they can receive. It centralizes the management of messages from various platforms.
• Potential Anticipation of Claims:
  • Claim 1: This patent is highly relevant to the concept of a unified messaging service. However, it is focused on integrating existing, different messaging platforms for a single user, rather than creating a new, homogenous messaging service that distinguishes between subscribers and non-subscribers for message routing. The '830 patent does not appear to disclose the specific onboarding method where a non-subscriber is invited via SMS to download a particular client, followed by SMS-based authentication and subsequent bearer selection based on the recipient's subscription status to that same service. Therefore, it is unlikely to anticipate the entirety of claim 1.

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2. US Patent 7,058,393 B2

• Full Citation: Gallant, "System for providing a calling-party-pays-for-data service on a wireless network," US Patent 7,058,393 B2.
• Publication Date: June 6, 2006 (Filed: May 23, 2002)
• Assignee: Verizon Laboratories Inc.
• Brief Description: This patent discloses a system for sending data to a wireless device where the sending party can pay for the data transmission. It involves a server that can determine if a recipient is eligible to receive the data and can manage the billing. It discusses sending a notification (like an SMS) to a user to inform them of available data to download.
• Potential Anticipation of Claims:
  • Claims 1, 10, 11: The '393 patent discusses using SMS as a trigger or notification for a data service, which is a component of the '601 patent's onboarding process. However, the context is different. The '393 patent is focused on a "calling-party-pays" model for data services in general, not specifically for establishing a new messaging client and ecosystem. It does not appear to describe the client-side logic of checking the recipient's subscription status to a specific messaging service to decide between a packet-switched message and a standard SMS. The inclusion of an invitation or a URL in the message (relevant to claims 10 and 11) is for a different purpose than the viral onboarding of the '601 patent. Thus, it is unlikely to anticipate these claims.

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3. US Patent Application Publication 2006/0292994 A1

• Full Citation: Pousti, "Method and System for Multi-Modal Communication," US 2006/0292994 A1.
• Publication Date: December 28, 2006 (Filed: August 29, 2005)
• Brief Description: This patent application describes a multi-modal communication system where a user can send a message from one device, and it can be received on a different type of device in a different format. It discusses the ability to check the "presence" and capabilities of a recipient to determine the best way to deliver a message. This includes determining if a user is online and what type of client they are using.
• Potential Anticipation of Claims:
  • Claim 1, 9: The concept of checking a user's presence and capabilities is very close to the idea of checking if a user is a "subscriber" and "active" as recited in the '601 patent. However, this application seems to focus on interoperability between different known client types (e.g., IM client, email client) rather than a single, specific client ecosystem. The crucial step of inviting a non-user via SMS to download and install this specific client, and then using that client to make the subscriber/non-subscriber distinction, does not appear to be explicitly disclosed. Therefore, while it describes a system with similar goals, it is unlikely to anticipate the specific method claimed.

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4. US Patent 6,836,664 B1

• Full Citation: Vataja, et al., "Method and arrangement for transmitting a message," US Patent 6,836,664 B1.
• Publication Date: December 28, 2004 (Filed: November 12, 1999)
• Assignee: Nokia Mobile Phones Ltd.
• Brief Description: This patent discloses a method for sending messages where the sending device first checks the capabilities of the receiving device. It describes sending a query to a server or the recipient's device to determine what kind of message it can handle (e.g., SMS, EMS, a specific application data). Based on the response, the sending device formats and sends the message accordingly.
• Potential Anticipation of Claims:
  • Claim 1: This reference is highly relevant as it describes a "check-before-sending" mechanism. It teaches querying a recipient's capabilities. However, it does not seem to link this capability check to a specific, downloadable client that forms a closed ecosystem of "subscribers." The '664 patent is more about general interoperability. The novel aspect of the '601 patent lies in the context of this check: not just "can you receive a picture message?" but "are you a subscriber to this specific service?" and the viral loop of inviting non-subscribers. For this reason, the '664 patent is unlikely to be a direct anticipation of claim 1.

Summary of Analysis

The prior art cited against US Patent 11,991,601 discloses several key components of the claimed invention in isolation, such as unified messaging, bearer selection based on device capabilities, and using SMS as a notification mechanism. However, none of the analyzed references appear to disclose the complete combination of elements as claimed, particularly the specific onboarding process and the subsequent intelligent routing performed by the downloaded client based on a binary "subscriber vs. non-subscriber" status within its own ecosystem. The novelty of the '601 patent appears to reside in this specific, integrated system for viral expansion of a messaging service and the dual-mode messaging logic embedded within the client. Therefore, under 35 U.S.C. § 102, the independent claims of US Patent 11,991,601 are likely to be considered novel over the cited prior art.

Obviousness Analysis of U.S. Patent No. 11,991,601

Prepared for: Internal Review
Date: May 13, 2026
Analyst: Senior Patent Analyst

I. Introduction

This report provides an analysis of the obviousness of the claims of U.S. Patent No. 11,991,601 ("the '601 patent") under 35 U.S.C. § 103. The '601 patent, titled "Wireless messaging method and server," was granted on May 21, 2024, and is assigned to Rembrandt Messaging Technologies LP. The analysis is based on the prior art references cited within the patent's file history.

The invention claimed in the '601 patent generally relates to a method and system for unified messaging on a mobile wireless device. A key feature of the claimed invention is the automatic selection of a communication bearer (packet-switched or SMS) based on whether the recipient is a subscriber to a particular messaging service. This functionality aims to provide a seamless user experience, allowing for the transmission of rich media to fellow subscribers while gracefully degrading to standard SMS for non-subscribers.

II. Legal Standard for Obviousness

Under 35 U.S.C. § 103, a patent claim is invalid as obvious if the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art (a "PHOSITA"). An obviousness rejection typically requires a finding that a PHOSITA would have been motivated to combine the teachings of multiple prior art references to arrive at the claimed invention, with a reasonable expectation of success.

III. Analysis of Independent Claim 1

Independent claim 1 of the '601 patent recites a method performed by a mobile wireless device, comprising the steps of:

1. Receiving an SMS or EMS message indicating a client program when the device's phone number is not associated with a subscriber of the service.
2. Downloading the client program.
3. Authenticating the phone number to the service via SMS protocol.
4. Transmitting first information with a first phone number.
5. Receiving a first response indicating the first phone number is a subscriber.
6. Transmitting first message content to the first phone number's device via a WLAN based on the first response.
7. Transmitting second information with a second phone number that is not a subscriber.
8. Inserting second message content into a message for delivery to the second phone number's device via SMS or EMS.
9. The service restricts third-party access to subscriber information without consent.

IV. Potential Obviousness Combinations

A thorough review of the prior art would be necessary to construct a definitive obviousness argument. However, based on the general knowledge in the field of mobile messaging at the time of the invention (with a priority date of July 24, 2007), a person of ordinary skill in the art would have been familiar with several key technologies that, when combined, would render the claims of the '601 patent obvious.

A potential combination of prior art could involve:

• A primary reference disclosing an over-the-top (OTT) messaging application that uses a packet-switched network (like the internet) for communication between its users. Examples from that era include early versions of instant messaging clients that were being adapted for mobile use.
• A secondary reference teaching the use of SMS for service invitation and user authentication. It was common practice for services to send an SMS with a download link and to use SMS for verifying a user's phone number.
• A tertiary reference or general knowledge regarding the use of contact lists or address books on mobile devices to check for the presence of other users of the same service. This was a fundamental feature of many social and communication applications.

Motivation to Combine:

A PHOSITA at the time would have been motivated to combine these elements for several compelling business and technical reasons:

1. User Growth and Network Effects: The primary motivation would be to grow the user base of the messaging service. By integrating an SMS-based invitation and fallback mechanism, the service could virally expand. When a user tried to message a non-user, the system would automatically send an SMS invitation, turning a failed communication attempt into a marketing opportunity. This leverages the powerful network effects inherent in communication platforms.

2. Improved User Experience: A seamless experience is crucial for application adoption. A user should not have to manually check if a contact is a subscriber before sending a message. The automatic bearer selection described in the '601 patent—sending a rich message if possible and an SMS otherwise—provides a frictionless user interface. This was a logical and desirable feature for any messaging application competing for users.

3. Cost and Efficiency: Packet-switched data was becoming increasingly cheaper and more prevalent than SMS, especially for rich media. For the service provider and the user, it was economically advantageous to use data networks whenever possible. The motivation to check for subscriber status first and then select the bearer is directly tied to optimizing for cost and message capability.

Example Combination:

Let's assume a hypothetical prior art reference, "InstantMsg," which discloses a mobile instant messaging application that allows users to send text and pictures over a GPRS or Wi-Fi connection to other "InstantMsg" users. The users are identified by their phone numbers.

Another hypothetical reference, "MobileAuth," teaches a method for a web service to authenticate new users by sending a verification code via SMS to the user's mobile number.

A PHOSITA would find it obvious to combine "InstantMsg" and "MobileAuth." To expand the "InstantMsg" user base, the developer would naturally look for ways to handle communication attempts to non-users. The most straightforward solution would be to send them a standard SMS. To make this process intelligent, the "InstantMsg" client would first query a server (as taught by the concept of a centralized user database in "InstantMsg") to see if the recipient's phone number is on the subscriber list. If not, it would fall back to sending an SMS. The SMS could also contain a link to download the "InstantMsg" client, directly applying the invitation concept. The authentication method from "MobileAuth" would then be the obvious choice to register the new user, as it was a well-understood and secure method at the time for tying a service account to a specific phone number. The privacy aspect (restricting third-party access) was also a standard and expected feature for any service handling user data and contact information.

V. Conclusion

The claims of U.S. Patent No. 11,991,601 appear to be vulnerable to an obviousness challenge under 35 U.S.C. § 103. The core inventive concept—dynamically selecting a messaging bearer based on the recipient's subscription status—represents a logical and predictable combination of known technologies in the mobile messaging space as of the 2007 priority date. A person of ordinary skill in the art would have been motivated to combine existing over-the-top messaging clients with standard SMS invitation and authentication techniques to achieve the user growth, seamless experience, and cost benefits that such a combination would provide. The individual elements of the claims were present in the prior art, and the motivation to combine them would have been readily apparent to a skilled practitioner in the field.

Based on a technical analysis of US Patent 11,991,601, here are the details regarding its term, related applications, and patent family.

Patent Term and Expiration

• Patent Term Adjustment (PTA) / Patent Term Extension (PTE): The provided record for US Patent 11,991,601 does not indicate any Patent Term Adjustment (PTA) or Patent Term Extension (PTE). The patent's term is determined by its priority filings.

• Projected Expiration Date: The anticipated expiration date for US Patent 11,991,601 is July 18, 2028. This date is calculated as 20 years from the filing date of the earliest relevant international application, PCT/AU2008/001043, which was filed on July 18, 2008. This expiration date is noted in the "Legal events" section of the patent record (Source: https://patents.google.com/patent/[US11991601](/patent/US11991601)/en).

Continuation and Divisional History

US Patent 11,991,601 is part of a long and complex chain of continuation applications. The patent itself is a continuation of a prior application, which is a continuation of another, and so on. This history demonstrates a strategy of continuing to pursue claims related to the original invention.

The direct parent of this patent is:

• U.S. Application No. 18/207,802, filed on June 9, 2023 (now US Patent 11,871,306).

This chain of applications traces back through more than a dozen predecessor applications to PCT Application No. PCT/AU2008/001043, which claims priority from Australian Patent Application No. 2007903979, filed on July 24, 2007. The full lineage is detailed in the "CROSS-REFERENCE TO RELATED APPLICATIONS" section of the patent's description.

No divisional applications are explicitly identified in the provided documentation for this specific patent. The prosecution strategy appears to have relied on filing a series of continuation applications.

Patent Family Members

US Patent 11,991,601 belongs to a large family of related patents and patent applications filed in the United States and other countries, all stemming from the original 2007 Australian priority document.

Selected U.S. Family Members (Granted Patents):

• US 8,401,576
• US 8,918,127
• US 10,893,395
• US 11,044,584
• US 11,218,847
• US 11,425,541
• US 11,432,115
• US 11,445,338
• US 11,533,587
• US 11,653,183
• US 11,812,345
• US 11,871,306
• US 11,991,600

International Family Members:

The patent family also includes filings in other jurisdictions, including:

• Australia (AU): AU2008201643B1
• Europe (EP): EP2177072B3
• World Intellectual Property Organization (WO): WO2009012516A1

This extensive patent family indicates a broad strategy to protect the invention in multiple key markets. The full list of 26 family applications can be found in the "Family Applications" section of the patent record (Source: https://patents.google.com/patent/US11991601/en).

Defensive Disclosure and Prior Art Generation

RE: U.S. Patent 11,991,601 “Wireless messaging method and server”
Publication Date: May 13, 2026

This document serves as a defensive publication of derivative concepts and technical variations related to the art described in U.S. Patent 11,991,601 (hereafter 'the '601 patent'). The purpose is to place these concepts into the public domain, thereby establishing them as prior art to preclude future patenting of these or similar obvious variations by third parties. The disclosures herein build upon the core method of dynamic bearer selection for messaging based on recipient subscriber status, as outlined in the claims of the '601 patent.

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Section 1: Derivative Works Based on Core Method (Claim 1)

The core method involves a mobile device downloading a client, authenticating via SMS, and then dynamically selecting between a packet-switched bearer (e.g., WLAN) for fellow subscribers and a circuit-switched bearer (SMS/EMS) for non-subscribers.

1.1. Material & Component Substitution

Derivative 1.1.1: USSD-Based Authentication and Status Check

• Enabling Description: The authentication process, instead of using the SMS protocol, utilizes Unstructured Supplementary Service Data (USSD). When the client program is first launched, it generates a unique device identifier and sends a USSD message (e.g., *123*<auth_identifier>#) to a service number. The messaging server receives this request in real-time via the mobile network's HLR/VLR, authenticates the device's phone number (MSISDN) instantly, and adds it to the subscriber list. Subsequent checks for a recipient's status are also performed via a USSD query, which provides a synchronous, low-latency response indicating subscriber status without consuming the user's SMS inbox. This is more efficient for machine-to-machine checks than the store-and-forward nature of SMS.
• Mermaid Diagram:

  sequenceDiagram
      participant Client as Mobile Client
      participant MSC as Mobile Switching Center
      participant Server as Messaging Server
      Client->>MSC: Initiate USSD Session (*123*AuthID#)
      MSC->>Server: Forward USSD Request (MSISDN, AuthID)
      Server->>Server: Validate AuthID, Add MSISDN to Subscribers
      Server-->>MSC: USSD Response (Success)
      MSC-->>Client: Display/Process USSD Response
      Client->>MSC: Initiate USSD Query (*124*RecipientMSISDN#)
      MSC->>Server: Forward USSD Query
      Server->>Server: Check Subscriber List for RecipientMSISDN
      Server-->>MSC: USSD Response (Is_Subscriber: true/false)
      MSC-->>Client: Process Response to Select Bearer
  

Derivative 1.1.2: Data Transport Using Protocol Buffers over QUIC

• Enabling Description: The message content sent over the packet-switched bearer is not formatted as an XML ASCII string but is instead serialized using Google's Protocol Buffers (Protobuf). This provides a more compact and efficient binary format, reducing latency and bandwidth consumption. The transport protocol used is QUIC (Quick UDP Internet Connections) instead of TCP. This further reduces connection establishment latency and provides multiplexing without head-of-line blocking, making it superior for real-time messaging, especially on mobile networks with frequent connection interruptions. The fallback to SMS/EMS for non-subscribers remains unchanged.
• Mermaid Diagram:

  graph TD
      A[Message Content Generation] --> B{Serialize with Protobuf};
      B --> C[Establish QUIC Session];
      C --> D[Transmit Protobuf Datagrams];
      D --> E[Recipient Client];
      E --> F{Deserialize Protobuf};
      F --> G[Display Message];
  

1.2. Operational Parameter Expansion

Derivative 1.2.1: High-Frequency M2M Communication in Vehicular Networks

• Enabling Description: The messaging method is applied to a Vehicle-to-Everything (V2X) network at an industrial scale. Each vehicle acts as a "mobile wireless device." The "client program" is embedded in the vehicle's Telematics Control Unit (TCU). Vehicles subscribe to a central traffic management service. When a vehicle needs to send a critical safety message (e.g., "hard braking event"), it queries the recipient vehicle's status. If the recipient is a subscriber with an active 5G URLLC (Ultra-Reliable Low-Latency Communication) connection (the packet-switched bearer), the message is sent as a rich data packet containing precise GPS coordinates, deceleration curves, and LIDAR point-cloud data. If the recipient vehicle is not a subscriber or is only reachable via a legacy DSRC (Dedicated Short-Range Communications) or C-V2X on a 4G network (the "SMS bearer" equivalent), the TCU formats a basic, standardized safety message with only the event type and location.
• Mermaid Diagram:

  stateDiagram-v2
      state "Vehicle A (Sender)" as A
      state "Vehicle B (Recipient)" as B
      [*] --> A
      A --> CheckRecipient: Hard Braking Event
      state CheckRecipient <<fork>>
          CheckRecipient --> Subscriber: If B is on 5G URLLC
          CheckRecipient --> NonSubscriber: If B is on legacy DSRC/4G
      Subscriber --> SendRichData: Send full sensor data via 5G
      NonSubscriber --> SendBasicAlert: Send standardized alert via DSRC
      SendRichData --> B
      SendBasicAlert --> B
      B --> [*]
  

1.3. Cross-Domain Application

Derivative 1.3.1: Aerospace - Satellite Constellation Tasking

• Enabling Description: The method is used for communication between a ground station and a constellation of Earth observation satellites. The "client" is on the ground station. When a new imaging task is submitted, the ground station must command a specific satellite. It first checks the satellite's status with a constellation management server. If the satellite is capable and has an active high-bandwidth Ka-band link (the packet-switched bearer), the server sends a detailed command packet including precise orbital adjustments, sensor calibration settings, and a complex imaging schedule. If the satellite is in a power-saving mode or only has a low-bandwidth S-band telemetry link available (the SMS bearer equivalent), the ground station sends a highly compressed, essential command (e.g., "Image_Grid_XYZ_Now") which the satellite's onboard system expands using pre-stored parameters.
• Mermaid Diagram:

  sequenceDiagram
      participant GroundStation
      participant ConstellationManager
      participant Satellite
      GroundStation->>ConstellationManager: Query Satellite Status (ID: Sat-01)
      ConstellationManager-->>GroundStation: Response (Status: Active, Link: Ka-Band)
      GroundStation->>Satellite: Send Detailed Tasking Packet (Ka-Band)
      alt Satellite S-Band Only
          GroundStation->>ConstellationManager: Query Satellite Status (ID: Sat-02)
          ConstellationManager-->>GroundStation: Response (Status: Low Power, Link: S-Band)
          GroundStation->>Satellite: Send Compressed Command (S-Band)
      end
  

Derivative 1.3.2: AgTech - Smart Irrigation System

• Enabling Description: The system manages communication between a central farm server and various irrigation controllers in fields. The farm server checks if a specific controller is a "subscriber" to the farm's private LoRaWAN network (the packet-switched bearer). If so, it sends a detailed irrigation schedule with variable flow rates based on real-time soil moisture sensor data. If a controller is older or in a location only covered by public cellular IoT networks like NB-IoT or LTE-M (the SMS bearer equivalent), the server sends a simple on/off command with a fixed duration, which is less efficient but ensures basic functionality. The authentication is done when a new controller is installed, sending its hardware ID via an NB-IoT message to register with the server.
• Mermaid Diagram:

  graph TD
      subgraph Farm Server
          A[New Schedule] --> B{Check Controller Status};
      end
      subgraph Field Controller
          C[Controller X]
          D[Controller Y]
      end
      B -- LoRaWAN Subscriber --> E[Format Rich LoRaWAN Packet];
      E --> C;
      B -- NB-IoT Only --> F[Format Simple NB-IoT SMS];
      F --> D;
      C --> G[Execute Variable Flow Schedule];
      D --> H[Execute Simple On/Off];
  

1.4. Integration with Emerging Tech

Derivative 1.4.1: AI-Optimized Predictive Bearer Selection

• Enabling Description: The client program integrates a lightweight, on-device machine learning model. Instead of querying the server for every message, the model predicts the recipient's subscriber status and likely network availability based on historical communication patterns, time of day, user location (with consent), and current network performance telemetry. The model outputs a probability score for packet-switched success. If the score is above a configurable threshold (e.g., 95%), the client sends the message via the packet-switched bearer without a preliminary check, reducing latency. If the score is low, it defaults to SMS. The model is continuously updated (federated learning) based on the actual success/failure of message deliveries, improving its accuracy over time.
• Mermaid Diagram:

  flowchart LR
      A[Compose Message] --> B[Input to ML Model: Recipient, Time, Location];
      B --> C{Predict PS_Success_Prob};
      C -- Prob > 0.95 --> D[Send via Packet-Switched];
      C -- Prob <= 0.95 --> E[Send via SMS Bearer];
      D --> F{Delivery Success?};
      E --> F;
      F -- Yes/No --> G[Update On-Device ML Model];
  

Derivative 1.4.2: Blockchain-Managed Decentralized Subscriber List

• Enabling Description: The subscriber list is not maintained by a central server but on a permissioned blockchain (e.g., Hyperledger Fabric). When a user authenticates, a transaction is written to the distributed ledger, mapping their phone number's hash to their public key and subscriber status. To check a recipient's status, the client program queries a node of the blockchain. This provides a tamper-proof, decentralized, and auditable record of subscribers, removing the single point of failure and control of a central server. Messages on the packet-switched bearer can be encrypted using the recipient's public key retrieved from the ledger.
• Mermaid Diagram:

  sequenceDiagram
      participant ClientA as Sending Client
      participant BlockchainNode
      participant ClientB as Receiving Client
      ClientA->>BlockchainNode: Query hash(ClientB_PhoneNumber)
      BlockchainNode-->>ClientA: Return Record {is_subscriber: true, pub_key: '...'}
      ClientA->>ClientA: Encrypt message with ClientB_pub_key
      ClientA->>ClientB: Send encrypted packet-switched message
  

1.5. The "Inverse" or Failure Mode

Derivative 1.5.1: Graceful Degradation to Ad-Hoc Mesh Network

• Enabling Description: When the client program cannot connect to the central messaging server to verify a recipient's status (due to a server outage or lack of internet), it enters a "degraded" mode. In this mode, it uses local peer-to-peer networking technologies like Wi-Fi Aware or Bluetooth Mesh to discover other clients in the vicinity. It broadcasts a Bloom filter containing the hashes of its intended recipients' phone numbers. Nearby clients check this filter against their own number's hash. If there's a match, the recipient's client responds, and a direct device-to-device link is established for packet-switched messaging, bypassing both the server and the cellular network. If no peer is found after a timeout, the client falls back to sending a standard SMS.
• Mermaid Diagram:

  stateDiagram-v2
      state "Online" as Online
      state "Degraded" as Degraded
      state "P2P Discovery" as P2P
      state "SMS Fallback" as SMS
      [*] --> Online
      Online --> Degraded: Server Unreachable
      Degraded --> P2P: Initiate P2P Broadcast
      P2P --> Degraded: Peer Found, Direct Connection
      P2P --> SMS: Timeout, No Peer Found
      Degraded --> Online: Server Reachable Again
      SMS --> Online: Server Reachable Again
  

---

Section 2: Combination with Open-Source Standards

Combination 2.1: Integration with RCS Universal Profile

• Enabling Description: The subscriber check mechanism of the '601 patent is implemented as a proprietary capability extension within the open Rich Communication Services (RCS) standard. A standard RCS client, upon initiating a chat with a contact, performs the standard SIP OPTIONS query to determine RCS capabilities. In addition, it performs a background HTTPS query to the '601 patent's server to check for "premium subscriber" status. If the recipient is a premium subscriber, the client enables an extension in the application/vnd.gsma.rcs-ft-http+xml message body, allowing it to send proprietary, interactive objects (e.g., polls, payment requests) that are rendered by the recipient's client. If the recipient is only a standard RCS user, these options are disabled, and only standard RCS features (chat, file transfer) are used. If the user has no RCS capabilities, the client falls back to SMS as per the standard.
• Mermaid Diagram:

  sequenceDiagram
      participant SenderClient
      participant RCSServer
      participant ProprietaryServer
      participant RecipientClient
      SenderClient->>RCSServer: SIP OPTIONS for Recipient
      RCSServer-->>SenderClient: Standard RCS Capabilities
      SenderClient->>ProprietaryServer: HTTPS GET /status?id=Recipient
      ProprietaryServer-->>SenderClient: {is_premium: true}
      SenderClient->>RecipientClient: RCS Message with Proprietary Payload
  

Combination 2.2: Federation via XMPP (Jabber) with SMS Gateway

• Enabling Description: The packet-switched messaging backbone is implemented using the open and federated XMPP (Extensible Messaging and Presence Protocol) standard. Each user's identifier is their phone number mapped to a JID (Jabber ID), e.g., +15551234567@messaging.com. When a user sends a message, the client first attempts to resolve the recipient's JID via standard XMPP server-to-server federation. If the recipient's server is found and the user is online, the message is delivered via XMPP. If the JID is not resolvable or the user is offline (as per XMPP presence), the sender's XMPP server (acting as the "message server" from the '601 patent) forwards the message to an integrated SMS gateway, which then delivers the content as a standard SMS to the recipient's phone number. The initial authentication is also handled by the XMPP server, which sends an SMS with a one-time code to verify ownership of the phone number before creating the JID.

• Mermaid Diagram:

  graph TD
      ClientA[Client A] --> ServerA[Server A (XMPP)];
      ServerA --> B{Recipient JID Resolvable?};
      B -- Yes --> ServerB[Recipient Server B (XMPP)];
      ServerB --> ClientB[Client B];
      B -- No --> SMSGW[SMS Gateway];
      SMSGW --> C[Deliver as SMS to Phone Number];
  

Combination 2.3: End-to-End Encryption using the Signal Protocol

• Enabling Description: The method from the '601 patent is combined with the open-source Signal Protocol for end-to-end encryption. The message server, in addition to storing subscriber status, also acts as a key distribution server, storing users' public pre-keys, as is standard in Signal Protocol implementations. When a client checks a recipient's status and confirms they are a subscriber, it also fetches the recipient's public key bundle from the server. It then establishes an encrypted session using Signal's Double Ratchet Algorithm and sends the message payload over the packet-switched bearer. The server only sees encrypted blobs and cannot read the message content. If the recipient is not a subscriber, the client falls back to sending the message as a standard, unencrypted SMS or EMS message, explicitly warning the user that the communication is not secure.
• Mermaid Diagram:

  sequenceDiagram
      participant ClientA
      participant Server
      participant ClientB
      ClientA->>Server: Get status & key bundle for ClientB
      alt Subscriber
          Server-->>ClientA: {is_subscriber: true, keys: [...]}
          ClientA->>ClientA: Establish Signal Protocol Session
          ClientA->>ClientB: Send E2E Encrypted Message
      else Not a Subscriber
          Server-->>ClientA: {is_subscriber: false}
          ClientA->>ClientA: Display "Unsecure SMS" Warning
          ClientA->>ClientB: Send Plaintext SMS Message
      end