PTAB

IPR2021-00699

ZTE Corp v. WSOU Investments LLC

Title: Method for Transmitting User Data in a Multi-Carrier Radio Communication System
Brief Description: The ’534 patent discloses a method for adaptively allocating sub-carriers in an Orthogonal Frequency Division Multiplexing (OFDM) system. The method involves a transmitter sending a threshold indication to a receiver, which then determines sub-carrier quality levels and selects a set of sub-carriers for data transmission based on both the received threshold and the measured quality levels.

Prior Art Relied Upon: Cheng (WO 2005/020489).
Core Argument for this Ground: Petitioner argued that Cheng, which seeks to improve communication efficiency in an OFDM system, anticipates or renders obvious all limitations of the challenged claims.
- Prior Art Mapping: Petitioner asserted Cheng teaches the key limitations of independent claims 1 and 6. At the receiver (terminal apparatus), Cheng’s system determines line/channel quality (e.g., Signal-to-Interferer Ratio or SIR), which constitutes the claimed “quality levels.” These quality levels, in the form of Channel Quality Indicators (CQIs), are sent back to the transmitter (base station). The transmitter sends a “request subcarrier number” to the receiver, which functions as the claimed “threshold indication.” This occurs before user data is transmitted. Finally, the receiver selects a set of sub-carriers based on both the instructed subcarrier number (the threshold) and the measured line quality (the quality levels), thereby meeting all steps of the claimed method. Dependent claims were argued to be obvious for reciting conventional features of OFDM systems also disclosed in Cheng, such as selecting sub-carriers with the highest quality first (claim 2) or identifying the receiver as a mobile terminal (claim 12).

Prior Art Relied Upon: Cheng (WO 2005/020489) and Shirali (Patent 7,697,449).
Core Argument for this Ground: Petitioner contended that claim 3, which requires the threshold to be “related to a quality level threshold,” is met by Cheng alone, or alternatively, by the combination of Cheng and Shirali.
- Prior Art Mapping: Cheng’s use of a “request transmission rate” to determine the number of subcarriers was argued to be inherently related to a reception quality threshold, as it is set with a margin to avoid quality degradation. To the extent this is not explicit, Shirali was introduced for its express disclosure of adaptively determining a data rate by comparing a signal quality measure against a signal quality threshold.
- Motivation to Combine: A POSITA would combine Shirali’s explicit use of a quality threshold with Cheng’s system to more robustly manage signal degradation from known effects like fading, a problem both references address.
- Expectation of Success: A POSITA would have a high expectation of success, as both references describe conventional OFDM systems, making the integration of a quality threshold a predictable design choice.

Prior Art Relied Upon: Cheng (WO 2005/020489) and Nishio (Application # 2006/0089102).
Core Argument for this Ground: This ground addressed claims requiring the threshold to be a “maximal number of sub-carriers” (claim 4) and for quality levels to be calculated for “groups of sub carriers” (claim 5).
- Prior Art Mapping: Petitioner argued Cheng teaches a maximal number by disclosing that all subcarriers can be selected to meet a transmission rate. Nishio was added for its teaching of arbitrarily setting the number of subcarriers to avoid the known problem of overwhelming the uplink with individual CQI reports. For claim 5, Petitioner argued Cheng’s disclosure of calculating quality for an assigned number of subcarriers inherently teaches a group. Nishio was added to explicitly disclose using “block units” (groups) of subcarriers to measure and report channel quality, for the same purpose of improving uplink efficiency.
- Motivation to Combine: A POSITA would be motivated to incorporate Nishio’s block-based grouping and reporting strategy into Cheng’s system to solve the well-known and predictable problem of excessive uplink signaling overhead caused by per-subcarrier quality reporting.
- Expectation of Success: The combination was asserted to be predictable because both references concern standard OFDM systems and address common efficiency problems.

Prior Art Relied Upon: Cheng (WO 2005/020489) and Douglas (Patent 7,075,906).
Core Argument for this Ground: This ground targets claim 11’s requirement for “detecting a specific identifier associated with the receiver” before reading the threshold indication.
- Prior Art Mapping: While Cheng was argued to teach the other elements of claim 11 (e.g., receiving and storing a threshold), Douglas was cited for its disclosure of a “unique identifier” provided for each client station during an initial hand-shaking protocol.
- Motivation to Combine: A POSITA would integrate Douglas’s hand-shaking and unique identifier system into Cheng’s framework to reliably associate quality data with a specific communication partner. This would be a predictable modification to improve system management, error detection, and overall efficiency.
- Expectation of Success: The combination would have yielded predictable results, as both references apply to standard OFDM wireless systems where identifying specific users is a fundamental requirement.

For the purposes of the IPR, Petitioner stated it adopted the Patent Owner’s constructions for all disputed terms from the parallel district court litigation.
This includes adopting the Patent Owner’s proposed structures for the various “means for” limitations in claims 6, 9, 11, 13, and 17, which identify the structure as either the “Receiver” or “Transmitter” disclosed in the specification. This strategic adoption aimed to streamline the IPR by focusing arguments on the teachings of the prior art rather than on claim scope.

Petitioner argued that discretionary denial under §314(a) based on Fintiv factors would be improper. The parallel district court trial was scheduled for June 2022, well after a Final Written Decision would issue, and court investment was minimal as claim construction had not yet occurred. Petitioner also stipulated that it would not pursue the same invalidity grounds in district court if the IPR was instituted.
Petitioner also argued against denial under §325(d), contending that the petition raised new, non-cumulative grounds. The primary prior art references (Cheng, Shirali, Nishio, and Douglas) were never cited or considered by the examiner during the original prosecution, which relied on a different reference (Nishio II).

Petitioner requested institution of an inter partes review and cancellation of claims 1-18 of the ’534 patent as unpatentable.