Obviousness

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.