Prior art

Analysis of Prior Art for U.S. Patent No. 7,154,961

The following analysis details the most relevant prior art references cited during the prosecution of U.S. Patent No. 7,154,961 ("the '961 patent"). The analysis focuses on the potential for these references to anticipate the independent claims of the '961 patent under 35 U.S.C. § 102, based on their disclosures relative to the '961 patent's priority date of October 18, 2002.

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Key Prior Art References and Potential Anticipation

The core invention of the '961 patent is the use of different modulation schemes (constellation rearrangements) for an initial transmission and subsequent ARQ retransmissions, where these transmissions are sent over different diversity branches to improve reliability at the receiver.

1. WO2002067491A1 ("'491 application")

• Full Citation: WO2002067491A1, "Hybrid arq method with single constellation rearrangement", Matsushita Electric Industrial Co., Ltd.
• Publication Date: August 29, 2002 (Prior art to the '961 patent).
• Description: This international application, from the same original assignee as the '961 patent, discloses a method for Hybrid Automatic Repeat Request (HARQ) where the signal constellation mapping is changed for retransmissions. The stated goal is to average the reliability of the bits mapped to a modulation symbol. For example, a first transmission uses a standard 16-QAM mapping, and if a retransmission is requested, a different 16-QAM mapping is used for the subsequent transmission. This change in mapping helps to ensure that bits that were in low-reliability positions in the first transmission are moved to high-reliability positions in the retransmission, improving the overall decoding performance after the receiver combines the two attempts.
• Potential Anticipation of Claim(s): High potential to anticipate the core method, but may lack a key element.
  • The '491 application clearly discloses the central concept of using a first modulation scheme for a first transmission and a second, different modulation scheme for an ARQ retransmission to improve bit reliability. This appears to anticipate the majority of the steps in Claim 1 and the dependent claims that focus on averaging bit reliabilities (like Claim 2).
  • However, the '961 patent claims specify that the first and second transmissions are performed over a first diversity branch and a second diversity branch, respectively. If the '491 application only describes constellation rearrangement for retransmissions over a single channel or does not explicitly teach sending the differently-modulated signals over distinct diversity branches, it would not fully anticipate the claimed combination. The invention of the '961 patent can be seen as the specific application of the '491 method in a transmit diversity context.

2. EP0735701A2 ("'701 patent")

• Full Citation: EP0735701A2, "Switched antenna diversity transmission method and system using ARQ techniques", AT&T IPM Corp.
• Publication Date: October 2, 1996 (Prior art to the '961 patent).
• Description: The '701 patent describes a system that combines switched antenna diversity with an ARQ protocol. In this system, if a data packet transmitted from a first antenna is not received correctly, the receiver sends a retransmission request. The transmitter then re-sends the packet from a different antenna. This process leverages spatial diversity to overcome localized fading or interference that may have affected the first transmission path.
• Potential Anticipation of Claim(s): Partial anticipation; likely does not anticipate the key inventive step.
  • This reference clearly teaches using ARQ in combination with transmit diversity, specifically sending an initial transmission on a first diversity branch (antenna 1) and a retransmission on a second diversity branch (antenna 2). This anticipates the "diversity branch" and "ARQ re-transmission" elements of Claim 1 and Claim 11.
  • However, the '701 patent does not appear to teach or suggest using different modulation schemes or constellation rearrangements for the initial transmission and the retransmission. It focuses on changing the physical transmission path (the antenna), not the signal's modulation characteristics. Therefore, it would not anticipate the complete combination of elements claimed in the '961 patent.

3. US 6,769,085 B2 ("'085 patent")

• Full Citation: US 6,769,085 B2, "Method for modifying a bit sequence in an ARQ restransmission, receiver and transmitter therefor", Matsushita Electric Industrial Co., Ltd.
• Filing Date: November 16, 2001 (Prior art to the '961 patent).
• Description: This patent, also from Matsushita, discloses a method for modifying a bit sequence during an ARQ retransmission. The modification is achieved by inverting or reordering (interleaving) the bits of the data packet before it is modulated and re-sent. This modification effectively changes the mapping of bits to modulation symbols between the first and second transmissions. The transmitter described includes components for performing this bit modification.
• Potential Anticipation of Claim(s): High potential to anticipate claims related to implementation.
  • This reference directly teaches the methods described in Claim 5 (obtaining different modulation schemes by interleaving or inverting bits) and the transmitter structure of Claim 11 (a transmitter with an "interleaver or inverter to obtain different modulation schemes").
  • Similar to the '491 application, the key question for full anticipation of Claim 1 and Claim 11 is whether the '085 patent explicitly teaches sending the initial transmission and the modified (interleaved/inverted) retransmission over separate and distinct diversity branches as part of a combined diversity scheme. If it does not, it anticipates the method of creating different modulations but not the full claimed method of applying it across diversity branches.

4. US 6,356,528 B1 ("'528 patent")

• Full Citation: US 6,356,528 B1, "Interleaver and deinterleaver for use in a diversity transmission communication system", Qualcomm Incorporated.
• Filing Date: April 15, 1999 (Prior art to the '961 patent).
• Description: The '528 patent describes the use of an interleaver in a communication system that employs transmit diversity. The system transmits data over multiple antennas. Interleaving is used to reorder symbols before transmission to mitigate the effects of burst errors. The receiver performs the corresponding de-interleaving.
• Potential Anticipation of Claim(s): Partial anticipation; likely does not anticipate the ARQ-based scheme.
  • This patent links the concepts of "interleaving" and "diversity transmission," which are elements of claims in the '961 patent (specifically Claim 5 and Claim 11).
  • However, the context in the '528 patent is typically for a single, initial transmission spread across multiple antennas (e.g., space-time coding) rather than for an ARQ retransmission scheme where the modulation property is deliberately changed in response to a repeat request. It lacks the crucial element of using different modulation schemes for a first transmission and a subsequent second transmission based on a repeat request.

Summary of Prior Art Analysis

The cited prior art establishes that the individual components of the '961 invention were known before its priority date. Specifically:

• Using different antennas for ARQ retransmissions (diversity) was known ('701 patent).
• Changing the signal constellation (modulation scheme) for ARQ retransmissions was known ('491 application).
• Implementing this change via bit interleaving or inverting was known ('085 patent).

The novelty of the '961 patent, as allowed by the examiner, appears to reside in the specific combination of these known techniques: applying constellation rearrangement to an ARQ retransmission scheme and transmitting the original and rearranged signals over separate diversity branches. While references like the '491 application and '085 patent are very close, they may not explicitly disclose this combined diversity and constellation rearrangement strategy for ARQ, which forms the basis of the independent claims of the '961 patent.