Obviousness

US patent 11716171B2 relates to a base wireless communication terminal and a method for efficiently managing simultaneous multi-user uplink data transmissions. The core inventive concept, as described in the "Technical Solution" and "Abstract" of the patent, involves a base wireless communication terminal (e.g., an Access Point or AP) that transmits a trigger frame for multi-user uplink transmission, receives multi-user uplink data, and then transmits a block ACK through the allocated resources. A key feature of the invention is that the transmission of the block ACK in each resource is terminated at the same time, achieved by either padding the block ACK or inserting duplicated ACK information.

Based on the provided patent text, a person having ordinary skill in the art (PHOSITA) would have found the claimed invention obvious under 35 U.S.C. § 103 by combining the general understanding of multi-user communication and acknowledgment mechanisms in wireless local area networks (WLANs) with the patent's own disclosure regarding frame length alignment.

Elements of the Invention to be Analyzed for Obviousness:

1. Base wireless communication terminal (AP) managing multi-user uplink transmission: The patent describes this as a fundamental aspect of next-generation WLANs (IEEE 802.11 standards). [cite: "BACKGROUND ART", FIG. 8, FIG. 9]
2. Transmission of a trigger frame: The patent states that in non-legacy WLAN systems, multi-user uplink transmission may be initiated by a trigger frame from the AP, which can also include NAV setting information. [cite: FIG. 16]
3. Reception of multi-user uplink data: This is inherent to the multi-user uplink transmission scenario. [cite: FIG. 9]
4. Transmission of a block ACK in response: The patent describes transmitting a multiplexed group ACK (which may have a block ACK format) from the AP to acknowledge received uplink data from multiple stations. [cite: FIG. 9, FIG. 10, FIG. 17]
5. Critical Feature: Simultaneous termination of block ACK transmission in each resource: This is the central feature.
6. Methods for simultaneous termination: Padding the block ACK or inserting duplicated ACK information. [cite: FIG. 19]

Combination of Prior Art References for Obviousness:

For the purpose of an obviousness analysis, the patent's "BACKGROUND ART" and "Detailed Description" sections provide ample disclosure of existing technologies and identified problems.

Prior Art Reference 1 (P1): General understanding of Multi-User Uplink and Block ACKs in IEEE 802.11 standards.

• The "BACKGROUND ART" section details the evolution of IEEE 802.11 standards (802.11n, 802.11ac), highlighting the introduction of technologies like MIMO and multi-user MIMO to achieve higher throughput in high-density environments. This context clearly establishes that multi-user communication, including uplink, was a known and evolving area. [cite: "BACKGROUND ART"]
• The patent also describes the use of ACK frames (FIG. 7) and explicitly illustrates the structure of a "multiplexed group ACK" which "may have a frame format of a block ACK (BA)" (FIG. 17). This indicates that block ACKs for multiple users were a known concept or a straightforward extension of existing 802.11 block ACK mechanisms. [cite: FIG. 7, FIG. 17]

Prior Art Reference 2 (P2): The patent's own disclosure of the problem of differing block ACK lengths and a solution using padding for uplink data frames.

• The patent explicitly identifies the problem that the claimed invention seeks to solve. FIG. 18 notes that "at least some information of the multiplexed group ACKs transmitted on each channel may have different lengths" due to varying numbers of STAs. It further states that "the multiplexed group ACKs transmitted on each channel should have the same length based on the value of a PPDU length field included in the L-SIG." [cite: FIG. 18]
• FIG. 21 further elaborates on the problem, explaining that if Block ACKs (M-BAs) of different lengths are transmitted, it can lead to premature channel access by other terminals, causing interference or disadvantageous competition for the AP. To mitigate this, the patent explicitly states that the AP "may set the lengths of multiplexed block ACKs transmitted through a plurality of channels to be the same" and "may perform padding on the multiplexed block ACKs transmitted through at least one channel to match the termination points." [cite: FIG. 21]
• Crucially, FIG. 9 (S250) of the patent, in the context of multi-user uplink data transmission, already discloses the concept of padding to achieve simultaneous termination: "the STAs using the channel in which the air time is short may perform zero padding until the uplink data transmission of a channel having the longest air time is completed, to wait for ACK reception (S 250 )." [cite: FIG. 9] This teaches that padding data frames to achieve simultaneous termination across multiple resources is a known technique within the scope of multi-user wireless communication as described by the inventors.

Motivation for a PHOSITA to Combine P1 and P2:

A PHOSITA, building upon the established knowledge of multi-user uplink communication and block ACKs (P1), would clearly recognize the problems associated with variable-length block ACK transmissions across different resources, as explicitly detailed within the patent itself (FIG. 18 and FIG. 21). The stated issues include inconsistency with common preamble information (L-SIG/HE-SIG-A requiring uniform PPDU length) and detrimental effects on channel access by other terminals, leading to reduced spectral efficiency. [cite: FIG. 18, FIG. 21]

Given that the patent itself (P2) already presents padding as a solution to ensure simultaneous termination for uplink data frames (S250 in FIG. 9) for a similar purpose (e.g., waiting for ACK reception or ensuring coordinated timing), it would be an obvious design choice for a PHOSITA to apply this same, known padding technique to the downlink block ACK frames to address the analogous and explicitly identified problems with their variable lengths. Padding is a common, well-understood technique in digital communications for aligning frame lengths or filling unused space. Extending this established technique from data frames to acknowledgment frames to resolve known timing and synchronization issues in a multi-user environment would not require any inventive leap.

The alternative method of "inserting duplicated ACK information" instead of simple padding (e.g., zero padding) to match termination points would also be obvious. If padding with arbitrary data is known, then padding with meaningful, albeit redundant, information would be a straightforward design optimization to ensure data integrity or provide additional robustness, especially given that the block ACK information field can contain repeated data for multiple STAs or TIDs (FIG. 17). [cite: FIG. 17]

Conclusion:

The combination of the general understanding of multi-user uplink and Block ACK mechanisms in IEEE 802.11 standards (P1) with the patent's own disclosure of the problems arising from variable-length block ACKs and the previously taught solution of padding for uplink data frames to achieve simultaneous termination (P2) would render the claims of US11716171B2 obvious. The motivation to combine these references is directly derived from the patent's explicit problem statement and the clear applicability of a known length-alignment technique to solve a similar timing/synchronization problem in an analogous context.