Obviousness

Obviousness Analysis of US Patent 9,191,180 under 35 U.S.C. § 103

This analysis will assess the obviousness of US Patent 9,191,180 by identifying potential combinations of prior art references and articulating the motivation a Person Having Ordinary Skill in the Art (PHOSITA) would have had to combine them. The effective filing date of US 9,191,180 is March 21, 2012.

Legal Standard for Obviousness

Under 35 U.S.C. § 103, a patent claim is obvious if "the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains." The Supreme Court in KSR International Co. v. Teleflex Inc. emphasized that obviousness can be established by combining or modifying prior art teachings where there is some teaching, suggestion, or motivation to do so. This motivation can come from the knowledge of those skilled in the art, from the prior art references themselves, or from the nature of the problem to be solved.

Prior Art References

The patent itself lists prior art keywords as "subframe," "serving cell," "data," "grant," and "harq."

1. US 9,137,804 B2 (Kim et al.) ("Kim '804"): Published on December 27, 2012 (though its PCT application, WO2011/115480 A2, was filed March 18, 2011, and claims priority to a US provisional application filed March 18, 2010), this patent explicitly discusses "Systems and Methods for supporting carrier aggregation with different TDD configurations." It addresses HARQ feedback mechanisms for both simultaneous and non-simultaneous DL/UL transceiving in such a scenario. Kim '804 illustrates an example where a Primary Cell (PCELL) has TDD configuration 1 and a Secondary Cell (SCELL) has TDD configuration 0, highlighting the challenge of HARQ feedback when PCELL subframes are downlink and lack UL resources. It also details that HARQ feedback may be transmitted via PUCCH or PUSCH.
2. "HARQ For Dynamic Change of the TTD UL/DL Configuration in LTE TDD Systems" (Mohanty et al.) ("Mohanty"): This article discusses HARQ in the context of dynamic TDD UL/DL configuration changes in LTE TDD systems. It highlights identifying different TDD UL/DL configurations for adjacent radio frames and discusses controlling the number of HARQ processes for PDSCH/PUSCH prior to reconfiguration. It also mentions sending an UL grant for PUSCH retransmission based on UL grant timing of the current configuration, potentially using DCI.
3. WO 2015/048404 A1 (Qualcomm Inc.) ("Qualcomm '404"): Published April 2, 2015 (International Filing Date: September 26, 2014), this patent application focuses on "REDUCED DELAY HARQ PROCESS TIMELINE FOR FDD-TDD CARRIER AGGREGATION." It describes methods for multi-carrier scheduling, including minimizing HARQ delay in networks using one or more TDD component carriers and one or more FDD component carriers. It also mentions determining the number of HARQ processes for a TDD component carrier based on its DL/UL configuration and that scheduling may involve overwriting certain HARQ transfers.
4. "Dynamic Uplink - Downlink Configuration in TD- LTE with HARQ Feedback" (Sharma et al.) ("Sharma"): This academic paper, while potentially published after the effective filing date (exact date not provided, but references include 2012-2016), discusses HARQ reference configurations for each serving cell in carrier aggregation for better effectiveness. It states that the HARQ reference configuration should not depend on the actual UL-DL configuration, making it robust against reconfiguration errors. It also notes that an UL subframe in the downlink HARQ reference configuration cannot be used for PDSCH transmissions because no UL HARQ acknowledgment timing is defined.
5. "HARQ Timing (Multiplexed Mode)" (Keysight) ("Keysight"): This document provides a timing diagram for LTE TDD uplink HARQ processes, noting that the number of UL HARQ processes depends on the UL/DL configuration. It explains that the eNB sends ACK/NACK after certain subframes, and based on this response, the UE sends new data or retransmits. It further details how PHICH can carry multiple HARQ ACK/NACKs depending on the UL/DL configuration.

Obviousness Combinations

The core inventive concept of US 9,191,180 lies in performing synchronous HARQ in a TDD-based carrier aggregation system where different UL-DL configurations are used across serving cells.

Combination 1: Kim '804 + Keysight + PHOSITA Common Knowledge

• Kim '804 clearly discloses the concept of carrier aggregation with different TDD UL-DL configurations for different serving cells (e.g., PCELL with TDD configuration 1 and SCELL with TDD configuration 0). It explicitly raises the problem of HARQ feedback mechanisms in such a scenario, noting that directly applying a standard HARQ feedback timetable can lead to issues where UL resources for feedback are unavailable in a particular cell. Kim '804 even suggests "smart scheduling" to avoid scheduling DL resources that would require HARQ feedback in an unavailable UL subframe.

• Keysight describes the fundamental principles of TDD uplink HARQ processes, including the dependence of the number of HARQ processes on the UL/DL configuration and the mechanism of ACK/NACK feedback leading to retransmission or new data transmission. It also explains how PHICH can carry multiple HARQ ACK/NACKs.

• Motivation to Combine: A PHOSITA, aware of the challenges identified in Kim '804 regarding HARQ feedback in carrier aggregation with different TDD UL-DL configurations, and possessing the general knowledge of TDD HARQ timing as described in Keysight, would have been motivated to find solutions for maintaining reliable HARQ operation. The problem itself—ensuring proper HARQ timing and feedback across cells with asynchronous UL/DL structures—would drive a PHOSITA to explore adaptations of existing HARQ mechanisms.

  Specifically, independent Claim 1, which involves receiving an UL grant for a second serving cell via a first serving cell, sending UL data in the first subframe of the second serving cell, receiving ACK/NACK via the first serving cell, and retransmitting in a second subframe of the second serving cell if NACK, all while using different UL-DL configurations, would be obvious. Kim '804 already discusses HARQ feedback mechanisms in carrier aggregation with different TDD configurations and shows PCELL being used for SCELL feedback concerns. The idea of an HARQ process involving initial transmission and retransmission in response to an ACK/NACK is fundamental to HARQ, as explained in Keysight. The adjustment of timing or process allocation to accommodate different UL-DL configurations, as presented in the problem statement of Kim '804, would be a natural engineering solution for a PHOSITA.

Combination 2: Kim '804 + Mohanty + PHOSITA Common Knowledge

• Kim '804 again establishes the context of carrier aggregation with differing TDD UL-DL configurations and the problem of HARQ feedback.

• Mohanty specifically addresses HARQ in the context of dynamic changes in TDD UL/DL configurations. It discusses identifying different UL/DL configurations for adjacent radio frames and controlling the number of HARQ processes. Crucially, it also mentions sending an UL grant for PUSCH retransmission based on UL grant timing, potentially using DCI (Downlink Control Information).

• Motivation to Combine: Given Kim '804's disclosure of the difficulties in managing HARQ across cells with static but different TDD UL-DL configurations, a PHOSITA would be motivated to look at solutions for managing HARQ in scenarios involving TDD configuration differences, including dynamic changes. Mohanty's teachings on controlling HARQ processes and using UL grants with DCI for retransmission in dynamic TDD environments would directly inform a PHOSITA's approach to solving the problems raised in Kim '804.

  This combination renders independent Claim 12 obvious. Claim 12 focuses on the retransmission information being included in a second uplink grant for a second subframe, where the subframe receiving this grant does not include PHICH resources. Mohanty teaches sending UL grants for PUSCH retransmission based on current UL grant timing using DCI. Kim '804 identifies the problem of PCELL subframes lacking UL resources for HARQ feedback from SCELL, implying the need for alternative feedback mechanisms or scheduling adjustments. A PHOSITA would recognize that if PHICH resources are unavailable (as described in Kim '804's problem scenario), including retransmission information directly in an UL grant (as suggested by Mohanty for DCI) would be an effective alternative to manage HARQ, rather than relying on a PHICH. This is a logical adaptation to solve the identified problem of scarce or misaligned UL feedback resources.

Combination 3: Kim '804 + Sharma + Keysight + PHOSITA Common Knowledge

• Kim '804 establishes the multi-cell TDD environment with different UL-DL configurations.

• Sharma discusses HARQ reference configurations for each serving cell in carrier aggregation and states that these configurations should be robust against UL-DL reconfiguration errors. It also points out that an UL subframe in a downlink HARQ reference configuration might not be usable for PDSCH transmission due to undefined UL HARQ acknowledgment timing.

• Keysight provides the basic understanding of HARQ timing and the dependence of HARQ processes on UL/DL configuration.

• Motivation to Combine: Facing the challenges of different UL-DL configurations and potential HARQ timing conflicts (as presented in Kim '804 and implied by Sharma's discussion of reference configurations), a PHOSITA would be motivated to harmonize or adapt HARQ processes across these cells. Sharma's concept of an HARQ reference configuration per serving cell, designed for robustness, directly addresses the underlying problem of managing HARQ in such complex scenarios. Combining this with the fundamental HARQ mechanisms from Keysight and the carrier aggregation context from Kim '804 would lead to the adaptations claimed in US 9,191,180.

  This combination makes independent Claim 11 obvious. Claim 11, similar to Claim 1, involves receiving a grant for a first subframe of a second serving cell via a first serving cell, sending data, and receiving an ACK/NACK, with different UL-DL configurations. It adds that either the first or second UL-DL configuration may have the "same regression period of an HARQ process" or the "same DL-UL switch-point periodicity." Sharma's discussion of HARQ reference configurations for each serving cell and their robustness against configuration changes implies a desire for stable and predictable HARQ timing (i.e., consistent regression periods or switch-point periodicity) even when underlying UL-DL configurations differ. A PHOSITA would understand the benefit of such consistency for efficient HARQ operation across aggregated carriers, especially when combining the known HARQ operations from Keysight and the multi-cell, differing TDD configurations from Kim '804. This would motivate a PHOSITA to design the system to achieve such consistent periodicity where possible or to define HARQ processes with a consistent regression period despite differing UL-DL configurations.

Conclusion

The claims of US Patent 9,191,180 would likely be found obvious over combinations of the identified prior art references. The references collectively disclose the essential elements of carrier aggregation, TDD systems, differing UL-DL configurations across cells, and the general principles of HARQ and its timing. The problems inherent in integrating HARQ into such a complex environment (e.g., ensuring timely ACK/NACK feedback, managing HARQ processes across disparate timing structures, and conveying retransmission information efficiently) would have provided ample motivation for a PHOSITA to combine and adapt the known teachings to arrive at the claimed inventions.