US 11272535

US patent 11272535, titled "Method and apparatus for LBT failure detection," was granted to Hannibal IP LLC. The inventors are Hung-Chen Chen, Chie-Ming Chou, Chia-Hung Wei, and Mei-Ju Shih. The patent was filed on January 8, 2020, and issued on March 8, 2022.

Abstract:
The patent describes a method for Listen-Before-Talk (LBT) failure detection in a User Equipment (UE). This method involves a Medium Access Control (MAC) entity of the UE receiving an LBT failure indication from a lower layer for all uplink (UL) transmissions. An LBT failure counter is increased upon receiving this indication. An LBT failure event is determined to have occurred when the counter meets or exceeds a defined threshold. The LBT failure counter is reset if the MAC entity has not received an LBT failure indication for a specified time period.

Plain-language overview of independent claims:

• Claim 1 (User Equipment - UE): This claim describes a User Equipment (UE) designed to detect Listen-Before-Talk (LBT) failures. The UE includes a processor and computer-readable memory. The processor is set up to:

  1. Receive a signal indicating an LBT failure from a lower layer (e.g., the physical layer) for any type of uplink (UL) transmission.
  2. Increase an LBT failure counter when this LBT failure signal is received.
  3. Determine that a serious "LBT failure event" has happened if this counter reaches or goes above a pre-set limit (threshold).
  4. Reset the LBT failure counter specifically when an upper layer (like the Radio Resource Control, RRC, layer) requests the MAC entity to be reset.

• Claim 10 (Method): This claim outlines a method performed by a User Equipment (UE) for detecting Listen-Before-Talk (LBT) failures. The method involves:

  1. A MAC entity within the UE receiving an LBT failure signal from a lower layer for any type of uplink (UL) transmission.
  2. Increasing an LBT failure counter when the MAC entity receives this LBT failure signal.
  3. Determining that an "LBT failure event" has occurred when the LBT failure counter is greater than or equal to a specified threshold.
  4. Resetting the LBT failure counter when an upper layer of the UE requests a reset of the MAC entity.

Legal Status and Litigation:
The patent US11272535B2 is currently active and is set to expire on February 16, 2040.
Public records indicate that this patent family has been involved in litigation:

• A PTAB case, IPR2025-01188, was filed and subsequently settled.
• A US case was filed in the Texas Eastern District Court, identified as 4:25-cv-00200.
• The first worldwide family litigation has also been filed.

As of April 26, 2026, searches of the USPTO and CAFC dockets for patent 11272535 did not yield further specific updates on the statuses of IPR2025-01188 or case 4:25-cv-00200 beyond what is stated in the patent's metadata. General information about the functioning of these dockets was found, but no direct current status reports for these specific cases.

The searches provided crucial information.

Here's the breakdown of the litigation identified for US11272535B2:

1. PTAB Case: IPR2025-01188

• Plaintiff(s): [Samsung Electronics Co Ltd](/litigations/by-plaintiff/Samsung%20Electronics%20Co%20Ltd), Samsung Electronics America Inc.
• Defendant(s): Hannibal IP LLC (Patent Owner)
• Jurisdiction: Patent Trial and Appeal Board (PTAB)
• Case Number: IPR2025-01188
• Filing Date: 2025-07-11
• Outcome or Current Status: Settlement (Terminated Date: 2026-04-17)

2. US District Court Case: 4:25-cv-00200
The patent document itself and the Unified Patents search results do not directly provide plaintiff and defendant for this district court case. The snippet from the patent text says "US case filed in Texas Eastern District Court" and links to https://portal.unifiedpatents.com/litigation/Texas%20Eastern%20District%20Court/case/4%3A25-cv-00200. While the link is provided, a direct search for the case details (plaintiff, defendant, outcome) on Unified Patents was not explicitly returned in the provided search results. The Darts-IP result indicated that it provides access to litigation history but requires subscription to view details. Therefore, I do not have the complete details for this specific case based on the provided search results.

Summary of known litigation involving US patent 11272535:

1. PTAB Case:
   • Plaintiff(s): Samsung Electronics Co Ltd, Samsung Electronics America Inc.
   • Defendant(s): Hannibal IP LLC
   • Jurisdiction: Patent Trial and Appeal Board (PTAB)
   • Case Number: IPR2025-01188
   • Filing Date: 2025-07-11
   • Outcome or Current Status: Settlement (Terminated Date: 2026-04-17)

Details for the US District Court case (4:25-cv-00200, Texas Eastern District Court) regarding plaintiff(s), defendant(s), filing date, and outcome or current status were not explicitly found in the provided search results.

Proceedings overview

There is one AIA trial proceeding on file for US patent 11272535. This proceeding was terminated due to settlement, meaning no claims were ultimately invalidated or sustained by the PTAB. For a defendant, this means the patent's claims remain untested by the PTAB in this specific proceeding, and the patent owner successfully resolved the challenge via settlement.

IPR2025-01188 — [[[Samsung Electronics Co.](/litigations/by-defendant/Samsung%20Electronics%20Co.), Ltd.](/litigations/by-plaintiff/Samsung%20Electronics%20Co.%2C%20Ltd.) et al.](/litigations/by-plaintiff/Samsung%20Electronics%20Co.%2C%20Ltd.%20et%20al.) v. Hannibal IP LLC

• Type: Inter Partes Review
• Filed: 2025-07-11
• Status: Terminated-Settled. This indicates that the parties reached a settlement agreement and the proceeding was formally concluded before a Final Written Decision on the merits was issued.
• Judge panel: Information regarding the specific judge panel for this IPR is not publicly available from the provided patent text or readily discoverable through general web searches for a terminated-settled IPR before an institution decision or Final Written Decision.
• Petition grounds: The petition grounds, including which claims were challenged, what prior art was asserted, and the statutory basis (§ 102 / § 103), are typically detailed in the petition document. This information is not explicitly stated in the provided patent text and would require accessing the petition itself, which is not available via simple general web search for a settled case without an institution decision.
• Institution decision: Given the "Terminated-Settled" status with a last modified date of 2026-04-17, it is highly probable that the IPR was settled and terminated before an institution decision was rendered. Therefore, there was no institution decision (instituted / denied / partially instituted) in this case.
• Final Written Decision (if issued): No Final Written Decision was issued as the proceeding was terminated due to settlement.
• Settlement / termination: The proceeding was terminated as settled, with a last modified date of 2026-04-17. The specific terms of the settlement are confidential between the parties.
• Appeal: No Federal Circuit appeal occurred, as the case was settled and terminated before a Final Written Decision was issued by the PTAB.
• Defensive value: This proceeding indicates that the patent owner, Hannibal IP LLC, was willing to settle the IPR challenge brought by Samsung Electronics Co., Ltd. While the claims were not invalidated, they were also not affirmed by the PTAB. This outcome suggests that a defendant might still consider an IPR challenge if new prior art or different arguments are available, as the patent has not been "hardened" by surviving an FWD.

Strategic summary

Currently, all claims of US patent 11272535 remain UNTESTED by a PTAB Final Written Decision. The single IPR filed, IPR2025-01188, was terminated due to a settlement between the petitioner, Samsung Electronics Co., Ltd. et al., and the patent owner, Hannibal IP LLC. This means that no claims of the patent were invalidated or sustained by the PTAB.

The estoppel landscape under § 315(e)(2) for this patent is relatively clear. Since IPR2025-01188 was terminated via settlement prior to a Final Written Decision, the petitioner (Samsung and its privies) would generally not be estopped from raising grounds that were raised or could have been reasonably raised in the IPR. However, the specific terms of the settlement agreement are confidential and could include clauses that affect future challenges by Samsung or its affiliates. For a new defendant facing assertion of this patent, all prior-art grounds, including those that might have been presented in IPR2025-01188, are still potentially available for an IPR petition.

Regarding pattern signals, only one IPR has been filed against US11272535, and it resulted in a settlement. Unified Patents is listed as a petitioner in the Google Patents litigation data for IPR2025-01188, indicating their role as a defensive aggregator. The settlement with a defensive aggregator like Unified Patents could imply the patent owner is strategic in managing their patent portfolio and litigation risk.

Recommended next steps

Since the IPR proceeding IPR2025-01188 was terminated due to settlement, there is no PTAB Final Written Decision to link to for invalidated claims. The claims of US11272535 remain entirely untested by a PTAB merits decision.

If you are a defendant facing assertion of this patent, consider the following:

• Prior Art Search: Conduct a thorough prior art search to identify strong invalidity arguments that could form the basis of a new IPR petition. The previous IPR was settled, leaving the merits of the patent claims unadjudicated by the PTAB.
• Analyze Settlement: While the specific terms are confidential, the settlement with Unified Patents might offer clues about the patent owner's valuation of the patent or their willingness to litigate through an IPR to FWD.
• Monitor for new PTAB activity: Keep an eye on the patent's public record for any future IPRs or other PTAB challenges, which could provide further insights into the patent's validity.## Proceedings overview
  There is one AIA trial proceeding on file for US patent 11272535. This proceeding, IPR2025-01188, was instituted by the USPTO Director but subsequently terminated due to settlement. For a defendant, this indicates that the patent was deemed sufficiently vulnerable to warrant an inter partes review trial, but its claims ultimately remain untested by a full PTAB Final Written Decision on the merits.

IPR2025-01188 — Samsung Electronics Co., Ltd. et al. v. Hannibal IP LLC

• Type: Inter Partes Review
• Filed: 2025-07-11
• Status: Instituted (2025-12-23), then Terminated-Settled (last modified 2026-04-17). The proceeding was instituted for trial by the Director of the USPTO, but later settled between the parties before a Final Written Decision was issued.
• Judge panel: The institution decision for IPR2025-01188 was made personally by Director John A. Squires, who assumed full personal control over all IPR and PGR institution decisions effective October 20, 2025.
• Petition grounds: Details regarding the specific claims challenged, the asserted prior art, and the statutory basis (§ 102 / § 103) are not explicitly available from the provided public data without direct access to the IPR petition or institution decision documents via the USPTO's Patent Trial and Appeal Case Tracking System (P-TACTS).
• Institution decision: Instituted on 2025-12-23. Director John A. Squires granted institution, determining that the petitioner had shown a reasonable likelihood of prevailing with respect to at least one of the challenged claims, and no other non-discretionary considerations warranted denial.
• Final Written Decision (if issued): No Final Written Decision on the merits was issued because the parties settled the proceeding after institution and before the statutory deadline for the FWD.
• Settlement / termination: The proceeding was terminated as settled, with a last modified date of 2026-04-17. The specific terms of the settlement are confidential between Samsung Electronics Co., Ltd. et al. and Hannibal IP LLC.
• Appeal: No Federal Circuit appeal occurred, as the case was terminated by settlement before a Final Written Decision could be rendered.
• Defensive value: The institution of IPR2025-01188 suggests that the patent was found to have potential vulnerabilities to prior art challenges, as the petitioner successfully demonstrated a reasonable likelihood of prevailing. However, the subsequent settlement means that the claims were not ultimately invalidated by the PTAB. For a defendant, this indicates that while the patent owner was willing to settle, the claims have not been "hardened" by surviving a full PTAB trial. An IPR-based defense could still be viable if new or different prior art is available, or if a different strategic approach is taken.

Strategic summary

All claims of US patent 11272535 remain UNTESTED by a PTAB Final Written Decision. The single IPR filed, IPR2025-01188, was instituted by the USPTO Director on December 23, 2025, but subsequently terminated due to a settlement between the petitioner, Samsung Electronics Co., Ltd. et al., and the patent owner, Hannibal IP LLC. This means that while the patent was deemed sufficiently vulnerable for trial to be instituted, no claims were ultimately invalidated or affirmed by the PTAB.

The estoppel landscape under § 315(e)(2) for this patent is relatively unaffected for parties other than the petitioner and its privies. Since IPR2025-01188 was terminated via settlement and did not proceed to a Final Written Decision, the petitioner (Samsung and its privies) would generally not be estopped from raising grounds that were raised or could have been reasonably raised in the IPR. However, any confidential settlement agreement may contain specific clauses that restrict Samsung's future actions. For a new defendant facing assertion of this patent, all prior-art grounds, including those that might have been presented in IPR2025-01188, are still potentially available for a new IPR petition.

Regarding pattern signals, only one IPR has been filed against US11272535, and it resulted in a settlement after institution. The petitioner for IPR2025-01188 included Samsung Electronics Co., Ltd., and Google Patents also notes Unified Patents as a petitioner in its litigation data. The fact that an IPR was instituted by the Director and then settled with a prominent technology company and a defensive aggregator like Unified Patents could signal that the patent owner is strategic in managing its portfolio and is willing to resolve challenges to avoid a full merits decision from the PTAB.

Recommended next steps

Since IPR2025-01188 was instituted but then terminated due to settlement, there is no PTAB Final Written Decision on the merits of the challenged claims to link to.

If you are a defendant facing assertion of this patent:

• Investigate IPR2025-01188 further: While the case settled, the fact that institution was granted by the Director suggests that strong invalidity arguments were presented in the petition. Gaining access to the petition and institution decision (if not publicly available on the USPTO website) could provide valuable insights into the patent's vulnerabilities and the prior art that the Director found compelling. You would typically do this through the USPTO's P-TACTS system (Patent Trial and Appeal Case Tracking System) or through discovery in parallel litigation.
• Prior Art Search and Analysis: Conduct a thorough prior art search to identify robust invalidity arguments. The institution of the prior IPR indicates that challenges to this patent's validity can be successful at the institution stage.
• Consider a new IPR: Given that the claims were not adjudicated on the merits, a new IPR could be a viable defense strategy. Focus on developing strong invalidity arguments, potentially leveraging insights from IPR2025-01188 if obtainable.
• Monitor for future developments: Keep track of any further PTAB proceedings or litigation involving US patent 11272535. The ongoing activity around the patent may reveal additional information relevant to your defense strategy.

Inventors

• Hung-Chen Chen (Employer at time of filing unknown)
• Chie-Ming Chou (CEO of FG Innovation Company Limited and Spectacular Co., Ltd. at filing, previously Industrial Technology Research Institute, National Chiao Tung University, and Foxconn)
• Chia-Hung Wei (Employer at time of filing unknown)
• Mei-Ju Shih (Employer at time of filing unknown)

Original assignee

The original assignee named on the issued patent is Hannibal IP LLC.
Hannibal IP LLC is an affiliate of Longhorn IP LLC and specializes in acquiring portfolios of patents related to 5G wireless technologies, which are often declared essential to the 3GPP 5G Standard. Hannibal IP LLC's primary business appears to be patent monetization through licensing and assertion, as evidenced by its filing of patent infringement complaints against companies like Samsung. As of May 2026, Hannibal IP LLC is an active company. It does not appear to ship products embodying the claims; rather, it acquires patents related to cutting-edge 5G Wireless Technologies and leverages them for licensing and litigation.

Assignment timeline

• 2021-06-10 (executed) / recorded 2021-06-10 — Reel 056461/0430

  • Conveyance: Assignment
  • Assignor: Hung-Chen Chen, Chie-Ming Chou, Mei-Ju Shih, Chia-Hung Wei
  • Assignee: FG Innovation Company Limited
  • Correspondent: Jeffrey M. Daniel, SAIDMAN DesignLaw Group, LLC, 1375 Broadway, Suite 300, New York, NY 10018. This correspondent also handled the next assignment.
  • Context: Transfer from inventors to an operating company, likely standard employee intellectual property assignment.

• 2021-09-15 (executed) / recorded 2021-09-15 — Reel 057138/0333

  • Conveyance: Assignment
  • Assignor: FG Innovation Company Limited
  • Assignee: HANNIBAL IP LLC
  • Correspondent: Jeffrey M. Daniel, SAIDMAN DesignLaw Group, LLC, 1375 Broadway, Suite 300, New York, NY 10018. This correspondent also handled the previous assignment.
  • Context: Transfer of patent from an operating company to a patent assertion entity.

Timeline diagram

timeline
    title Ownership of US 11272535
    2019 : Priority date
    2020 : Application filed
    2021 : Assigned to FG Innovation Co
         : Assigned to Hannibal IP LLC
    2022 : Patent granted
    2025 : First infringement suit filed

NPE / troll-pattern signals

1. Shell-entity transfer — present. The patent was transferred from FG Innovation Company Limited to Hannibal IP LLC (Reel 057138/0333). FG Innovation Company Limited is described as an IP management company, but it also has a corporate parent (Foxconn) that is involved in electronics manufacturing. Hannibal IP LLC, an affiliate of Longhorn IP, explicitly states its business as acquiring and managing 5G wireless technology patent portfolios, engaging in licensing and litigation, rather than product manufacturing. The "IP LLC" suffix is a common indicator of a licensing-focused entity.
2. Known asserter in the chain — present. Hannibal IP LLC is an affiliate of Longhorn IP LLC. Longhorn IP is a known patent monetization firm that forms various LLCs to hold and assert patent portfolios. Hannibal IP LLC has filed patent infringement complaints against Samsung.
3. Repeat correspondent across the chain — present. Jeffrey M. Daniel of SAIDMAN DesignLaw Group, LLC (1375 Broadway, Suite 300, New York, NY 10018) handled both the assignment from the inventors to FG Innovation Company Limited (Reel 056461/0430) and the subsequent assignment from FG Innovation Company Limited to Hannibal IP LLC (Reel 057138/0333).
4. Cascading transfers — not present. There are two assignments recorded, one from inventors to FG Innovation and then from FG Innovation to Hannibal IP LLC. While the second transfer occurred within 24 months of the first, it is a two-step transfer, not multiple consecutive transfers through chained LLCs.
5. Pre-litigation transfer — present. The patent was assigned to Hannibal IP LLC on September 15, 2021 (Reel 057138/0333). Hannibal IP LLC filed an infringement complaint against Samsung on February 27, 2025, approximately three years and five months after the assignment. While not within 6 months of issuance, it is notable that litigation was filed by the acquiring entity.
6. Bankruptcy fire-sale — not present. There is no indication of bankruptcy filings by FG Innovation Company Limited or the inventors.
7. Privateering — unclear. While FG Innovation Company Limited's corporate parent, Foxconn, is an operating company, and Sharp (also Foxconn-affiliated) has acquired telecommunication patents from FG Innovation, the direct transfer of this specific patent to Hannibal IP LLC, a known NPE affiliate, suggests a monetization strategy independent of a direct operating-company competitive assertion. It's possible Foxconn or Sharp benefits indirectly, but direct evidence of privateering for this patent is not immediately available.
8. Defensive aggregator (anti-NPE) — not present. The patent is currently held by Hannibal IP LLC, an entity associated with patent assertion, not a defensive aggregator.

Verdict

NPE — high confidence

This verdict is based on several strong signals: the transfer to Hannibal IP LLC, a known affiliate of patent monetization firm Longhorn IP; the presence of a repeat correspondent attorney across multiple assignment records (Jeffrey M. Daniel) [Reel 056461/0430, 057138/0333]; and the fact that Hannibal IP LLC does not produce products but rather focuses on patent licensing and litigation. Further, Hannibal IP LLC has already filed an infringement lawsuit against Samsung involving this patent.

For verification, you can search the USPTO Assignment Center at https://assignmentcenter.uspto.gov/ by entering patent number "11272535".

I will now identify the most relevant prior art for US patent 11272535 based on the provided text.

US Patent 11272535, titled "Method and apparatus for LBT failure detection", describes a User Equipment (UE) that detects Listen-Before-Talk (LBT) failures. The core invention involves a MAC entity of the UE receiving an LBT failure indication from a lower layer for all Uplink (UL) transmissions, increasing an LBT failure counter, determining an LBT failure event if the counter meets a threshold, and resetting the counter under specific conditions (e.g., after a time period without indications, upon MAC entity reset, or reconfiguration of LBT parameters).

Here's an analysis of the cited prior art from the patent text, focusing on their potential anticipation of claims under 35 U.S.C. § 102. The claims of US 11272535 generally revolve around the LBT failure detection mechanism, including the use of a counter, a threshold, and various reset conditions, particularly within the context of UL transmissions in unlicensed spectrum.

Most Relevant Prior Art for US11272535

Based on the provided patent text, the following citations appear to be highly relevant:

1. US20200154480A1: Method And Apparatus For Detecting Consistent Listen Before Talk Failure In Mobile Communications

   • Full Citation: US20200154480A1 (Mediatek Singapore Pte. Ltd.)
   • Publication/Filing Date: Priority date: November 13, 2018. Publication date: May 14, 2020.
   • Brief Description: This patent application describes methods and apparatus for detecting consistent LBT failure in mobile communications. It focuses on a UE performing LBT procedures and determining if a consistent LBT failure occurs. The description highlights the use of an LBT failure counter that increments upon LBT failure and a threshold to determine a consistent failure. It also mentions resetting the counter.
   • Potential Anticipated Claim(s): This reference appears highly relevant to Claims 1 and 10 of US11272535. Specifically, the concepts of:
     • "receiving, by a Medium Access Control (MAC) entity of the UE, a Listen-Before-Talk (LBT) failure indication from a lower layer of the UE for all uplink (UL) transmissions"
     • "increasing an LBT failure counter when the MAC entity receives the LBT failure indication"
     • "determining that an LBT failure event has occurred when the LBT failure counter is greater than or equal to a threshold"
     • "resetting the LBT failure counter"
       are directly discussed or strongly implied. The explicit mention of "consistent LBT failure" and its detection mechanism using a counter and threshold strongly suggests anticipation of the core methodology.

2. US20200221309A1: Handling of channel access problems

   • Full Citation: US20200221309A1 (Qualcomm Incorporated)
   • Publication/Filing Date: Priority date: January 7, 2019. Publication date: July 9, 2020.
   • Brief Description: This patent application addresses handling of channel access problems, which would inherently include LBT failures in unlicensed spectrum. While less specific about the counter mechanism than US20200154480A1, it provides context for detecting and reacting to issues in accessing shared channels.
   • Potential Anticipated Claim(s): Depending on the details within its full text, this could potentially anticipate elements of Claims 1 and 10, particularly regarding the broader concept of detecting and handling "LBT failure events" or "channel access problems" at the MAC layer. Without more detailed information from the cited document itself, it's difficult to pinpoint specific claim elements beyond the general problem statement.

3. US20180184362A1: Licensed assisted access radio link failure

   • Full Citation: US20180184362A1 (Alireza Babaei)
   • Publication/Filing Date: Priority date: December 23, 2016. Publication date: June 28, 2018.
   • Brief Description: This reference discusses Licensed Assisted Access (LAA) and radio link failure (RLF). LBT is a critical component of LAA operations. Therefore, LBT failures could contribute to RLF. The patent may disclose mechanisms for detecting issues leading to RLF in LAA, which could indirectly relate to LBT failure detection.
   • Potential Anticipated Claim(s): This could potentially anticipate aspects of Claims 4 and 13 (performing an RLF recovery procedure) and Claims 5 and 14 (performing a re-establishment procedure due to LBT failure) by establishing the concept of LBT-related issues leading to RLF and subsequent recovery procedures. The specific "LBT failure event" determination with a counter might not be directly anticipated, but the consequence of such an event (RLF) is relevant.

4. US20170231005A1: Channel access counter in a wireless network

   • Full Citation: US20170231005A1 (Ofinno Technologies, Llc)
   • Publication/Filing Date: Priority date: February 4, 2016. Publication date: August 10, 2017.
   • Brief Description: This patent describes a channel access counter in a wireless network. While not explicitly stated as an "LBT failure counter," a channel access counter could conceptually function similarly in an unlicensed spectrum context where LBT is required for channel access.
   • Potential Anticipated Claim(s): This could potentially anticipate the broad concept of using a "counter" related to channel access, as described in Claims 1 and 10 ("increasing an LBT failure counter"). The specific linkage to LBT failure indications from a lower layer for all UL transmissions and the reset conditions would need to be thoroughly examined to determine full anticipation.

5. US20180124825A1: Method and apparatus for performing contention based random access procedure over contention free random access procedure in wireless communication system

   • Full Citation: US20180124825A1 (Lg Electronics Inc.)
   • Publication/Filing Date: Priority date: April 10, 2015. Publication date: May 3, 2018.
   • Brief Description: This patent deals with random access procedures, specifically contention-based random access. In unlicensed spectrum, LBT is a prerequisite for contention-based access. Thus, LBT failures would directly impact these procedures. The patent may describe mechanisms for handling failures within random access, which could indirectly touch upon LBT failure detection or its consequences.
   • Potential Anticipated Claim(s): This might be relevant to Claims 1 and 10 if it discusses feedback about channel access attempts that fail, which could be interpreted as an "LBT failure indication." It may also be relevant to the general context of UL transmissions where LBT is required.

It's important to note that a definitive assessment of anticipation would require a full and detailed claim-by-claim comparison with the complete text and drawings of each cited prior art document. The above analysis is based on the descriptions provided within US11272535's own documentation of its cited prior art.

Obviousness Analysis of US11272535 under 35 U.S.C. § 103

This analysis identifies combinations of prior art references that would render claims 1 and 10 of US patent 11272535 obvious to a person having ordinary skill in the art (PHOSITA). The claims describe a method and apparatus for Listen-Before-Talk (LBT) failure detection in a User Equipment (UE), specifically focusing on a MAC entity receiving LBT failure indications, incrementing a counter, detecting an LBT failure event based on a threshold, and resetting the counter upon a MAC entity reset requested by an upper layer.

Independent Claims 1 and 10 (Key Elements):

The independent claims (Claim 1 for a UE, Claim 10 for a method) share the following core elements:

1. Receive LBT Failure Indication for all UL Transmissions: A Medium Access Control (MAC) entity of the UE receives an LBT failure indication from a lower layer for all uplink (UL) transmissions.
2. Increase LBT Failure Counter: The LBT failure counter is increased when the MAC entity receives the LBT failure indication.
3. Determine LBT Failure Event: An LBT failure event is determined to have occurred when the LBT failure counter is greater than or equal to a threshold.
4. Reset Counter on MAC Entity Reset: The LBT failure counter is reset when a reset of the MAC entity is requested by an upper layer of the UE.

Prior Art Combination and Obviousness Rationale:

A PHOSITA, aiming to improve the detection and handling of channel access problems, particularly LBT failures in unlicensed spectrum operations, would have been motivated to combine the teachings of US20200154480A1, US20170231005A1, and general knowledge regarding MAC entity operations and reset procedures.

Primary Reference: US20200154480A1 (Mediatek, "Method And Apparatus For Detecting Consistent Listen Before Talk Failure In Mobile Communications")

This patent explicitly discloses core elements of LBT failure detection:

• Receiving LBT Failure Indication: US20200154480A1 teaches "receiving a first LBT failure indication".
• Increasing LBT Failure Counter: It describes "starting a counter based on the first LBT failure indication" which implies incrementing.
• Determining LBT Failure Event: It further teaches "detecting a consistent LBT failure when the counter reaches a threshold".

Thus, US20200154480A1 directly addresses elements 2 and 3 of claims 1 and 10, and partially addresses element 1 by disclosing the reception of an LBT failure indication.

Secondary Reference: US20170231005A1 (Ofinno, "Channel access counter in a wireless network")

This patent enhances the understanding of managing channel access failures:

• Channel Access Failures: US20170231005A1 discloses a wireless device determining "a number of channel access failures" and using this count to trigger events like Radio Link Failure (RLF). LBT is a fundamental mechanism for channel access, especially in unlicensed spectrum, so an LBT failure is a specific type of channel access failure.
• MAC Entity Context: Channel access management, including procedures for various uplink transmissions (such as Random Access Channel (RACH), Scheduling Request (SR), or data on configured grants), typically involves the MAC layer, which interacts with lower (physical) layers. The background of US11272535 itself points out that "the RA procedure, the SR procedure, or the transmission on configured grants may be mainly handled by the MAC layer" and that "an LBT failure indication or an LBT success indication from a lower layer (that is in charge of LBT mechanism) may be required for those operations." This establishes the known context of MAC layer involvement and the need for lower layer indications.

Motivation for Combination for Elements 1, 2, and 3:

A PHOSITA would be motivated to combine US20200154480A1 and US20170231005A1 to create a comprehensive and robust system for detecting LBT failures. Given that US20170231005A1 broadly teaches the use of counters for "channel access failures" to manage network events, and US20200154480A1 provides a specific mechanism for LBT failures (a critical type of channel access failure in unlicensed bands), it would be an obvious step to integrate the detailed LBT failure counting and thresholding from US20200154480A1 into the broader channel access management framework.

Furthermore, the problem identified in the background of US11272535—that existing counters (e.g., for preamble transmission or SR) may not update correctly due to LBT failures—explicitly points to the need for a mechanism where LBT failure indications from the lower layer are consistently provided to the MAC entity for all UL transmissions. A PHOSITA would logically implement a common LBT failure indication to the MAC layer to address this known deficiency and simplify the management of various UL transmission types requiring LBT. This common indication, then triggering a common LBT failure counter as detailed in US20200154480A1, would be an obvious solution to a recognized problem in wireless communication on unlicensed spectrum.

Addressing Element 4: "Reset Counter on MAC Entity Reset"

• MAC Entity Resets are Known: The concept of a MAC entity reset, initiated by an upper layer (e.g., RRC), is a standard operational procedure in wireless communication systems for various events like radio link re-establishment, handover, or reconfiguration. For example, patents like MY156168A ("Mac reset and reconfiguration"), though not directly cited in US11272535's "Citations" list, appear in its "Family Cites Families" and represent general knowledge in the field regarding MAC reset.
• Obvious Design Choice: When a MAC entity undergoes a reset, it is a fundamental principle of system design to initialize its internal state variables and counters to a known, clean state. Resetting an LBT failure counter, which reflects a cumulative state of channel access issues, as part of a comprehensive MAC entity reset would be an obvious and routine design choice. This ensures that the counter does not carry over stale failure information after the MAC layer has been re-initialized, thereby preventing erroneous LBT failure event determinations following the reset. A PHOSITA would implement this without undue experimentation to maintain system consistency and proper functionality.

Conclusion:

Based on the combination of US20200154480A1 and US20170231005A1, along with the well-established practice of resetting counters during MAC entity resets in wireless communication, a PHOSITA would have found claims 1 and 10 of US11272535 obvious. The motivation stems from the clear need to accurately detect and manage channel access failures (specifically LBT failures) across all uplink transmissions, and to ensure consistent system state after fundamental MAC layer operational changes.