Obviousness

Obviousness Analysis of US Patent 8,208,569

This analysis addresses the obviousness of US Patent 8,208,569 ("Method and apparatus for multicarrier communication") under 35 U.S.C. § 103, considering prior art references identified within the patent document itself. The patent, filed on October 8, 2010, claims priority to June 12, 2003.

I. Summary of the Invention

US 8,208,569 generally relates to multicarrier communication systems, particularly Orthogonal Frequency Division Multiplexing (OFDM) systems. The core invention, as described in the specification, is to improve the error correction rate of multicarrier signals by adjusting the two-dimensional (time and frequency) arrangement of error-correcting code blocks based on an analysis of the actual reception state of the multicarrier signal [cite: "An essence of the present invention"]. This adjustment aims to equalize the reception quality (e.g., Signal-to-Noise Ratio (SNR) or Signal-to-Interference power Ratio (SIR)) within the code blocks, thereby improving the performance of error correcting codes like turbo codes or convolutional codes [cite: "Generally, the error rate characteristic of an error correcting code...", "This embodiment analyzes SNR variation (reception state) of each symbol..."].

Independent claim 1, directed to a transmission apparatus, describes:
"1. A transmission apparatus comprising: a coding section configured to encode first data and second data; and a mapping section configured to map the encoded first data to symbols in a first part of a domain comprising a time index and a frequency index, and the encoded second data to groups of symbols in a second part of the domain, wherein: at least a part of the encoded first data is mapped to at least a part of the symbols in the first part of the domain in an increasing order according to the frequency index; at least a part of the encoded second data is mapped to at least a part of the groups of symbols in the second part of the domain and each group of the at least a part of the groups of symbols is aligned in an increasing order according to the time index; and each symbol within each of the groups of symbols is aligned along the frequency index."

Independent claim 41, also for a transmission apparatus, details a similar concept where first and second data are mapped to symbols in a time-frequency domain, with symbols mapped along frequency until a "predetermined number" is exceeded, then time index is incremented, and crucially, "the predetermined number of symbols for the encoded first data and the encoded second data is different."

II. Prior Art References

The patent's "BACKGROUND ART" section explicitly discusses "Unexamined Japanese Patent Publication No. 2000-332724" (hereafter "JP '724") [cite: "Conventionally, a technology for enhancing reception performance... in Unexamined Japanese Patent Publication No. 2000-332724."]. The "Citations" section of the patent lists numerous other prior art documents, including:

• JP2000332724A (Mitsubishi Electric Corp.): "Multi-carrier transmission system and multi-carrier modulation method". (Corresponds to JP '724 in background).
• WO2001086826A2 (Motorola, Inc.): "Method of dynamic transmit scheduling using channel quality feedback".
• US20030097623A1 (Razavilar): "Method and apparatus for performance optimization and adaptive bit loading for wireless modems with convolutional coder, FEC, CRC and ARQ".

III. Obviousness Analysis

A person having ordinary skill in the art (PHOSITA) in multicarrier communication systems at the time of the invention (priority date June 12, 2003) would have found the claimed inventions of US 8,208,569 obvious based on the combination of the identified prior art references and general knowledge in the field.

A. Combination of JP2000332724A, US20030097623A1, WO2001086826A2, and General Knowledge

1. JP2000332724A (JP '724): This reference discloses a technology for arranging spreading chips in an OFDM/CDMA system in a two-dimensional time-frequency domain to reduce inter-code interference [cite: "The technology described in this Unexamined Japanese Patent Publication No. 2000-332724 arranges spreading chips not only in the time axis direction but also in the frequency axis direction..."]. A PHOSITA would readily understand the general principle of two-dimensional (time-frequency) resource allocation in multicarrier systems and the use of different arrangement patterns (e.g., continuous in time vs. continuous in frequency) to mitigate channel impairments. While JP '724 focuses on spreading chips in CDMA, the fundamental concept of mapping communication units onto a 2D time-frequency grid to achieve specific performance characteristics in a multicarrier environment is clearly taught.

2. US20030097623A1 (Razavilar): This patent explicitly teaches methods and apparatus for "performance optimization and adaptive bit loading for wireless modems with convolutional coder, FEC, CRC and ARQ". Razavilar thus teaches the critical aspects of using Error Correcting Coding (FEC) and adaptively optimizing transmission parameters based on channel conditions. A PHOSITA would understand that optimizing FEC performance entails managing the quality of data within a code block to ensure effective decoding, and that adaptation is key to maintaining performance in varying wireless channels.

3. WO2001086826A2 (Motorola): This reference describes a "method of dynamic transmit scheduling using channel quality feedback". This directly teaches the motivation and mechanism for adaptively changing transmission parameters, including how data is scheduled or arranged, based on feedback regarding the actual reception state or channel quality.

4. General Knowledge: It was well-known in the art that the performance of error correcting codes (like those mentioned in US 8,208,569, e.g., turbo codes and convolutional codes [cite: "Normally in a multicarrier communication, multicarrier signal is subjected to error correcting coding processing such as turbo coding and convolutional coding..."]) is significantly affected by the variation in reception quality (e.g., SNR) within a code block. A larger variation typically leads to worse error rates, even if the average reception quality is the same [cite: "Generally, the error rate characteristic of an error correcting code... decreases as the variation of reception quality... decreases, while the error rate increases as the variation of quality increases..."]. Furthermore, different types of channel impairments (e.g., fast fading due to high mobility causing time-axis variation, or frequency-selective fading due to multipaths causing frequency-axis variation [cite: "A mobile communication system using OFDM signals is affected by the SNR variation in the time axis direction... and affected by the SNR variation in the frequency axis direction..."]) benefit from different diversity techniques (time diversity vs. frequency diversity), which are achieved through different data interleaving or mapping patterns across the time-frequency domain. The concept of encoding "first data" and "second data" (as in Claim 1 and 41) could represent different data streams for different users or different types of data with varying quality of service requirements, which are common scenarios in adaptive wireless communication.

B. Motivation for Combination

A PHOSITA would be motivated to combine the teachings of these prior art references to overcome known challenges in multicarrier communication, specifically the deterioration of FEC performance due to varying channel conditions.

1. Applying 2D Mapping to FEC Code Blocks: Recognizing the benefits of 2D data arrangement in multicarrier systems from JP '724 (e.g., for mitigating channel impairments), a PHOSITA would naturally extend this concept from CDMA spreading chips to error-corrected code blocks in general multicarrier systems. This is a logical design choice for enhancing the robustness of coded data.
2. Adaptive Optimization for FEC: Given Razavilar's teachings on optimizing FEC performance and using adaptive techniques in wireless modems, and the general understanding that FEC performance is sensitive to quality variations within a code block, a PHOSITA would be motivated to adaptively adjust the 2D mapping of these code blocks. The goal would be to minimize quality variations within blocks to maximize the error correction capability, directly addressing the problem US 8,208,569 purports to solve.
3. Utilizing Channel Feedback for Adaptation: Motorola's disclosure of "dynamic transmit scheduling using channel quality feedback" provides the explicit mechanism and motivation for how such adaptive adjustment would be implemented. A PHOSITA would find it obvious to use channel quality feedback (e.g., Doppler frequency, delay profile, SIR, as discussed in US 8,208,569 [cite: "In the analysis step, the reception state is analyzed based on Doppler frequency and delay profile...", "the reception state is preferably analyzed based on a ratio of signal power to interference power for each symbol..."]) to dynamically select appropriate 2D mapping patterns for FEC code blocks.
4. Selecting Specific Mapping Patterns: The specific mapping patterns described in Claim 1 and Claim 41 (e.g., mapping along frequency for first data, and time-grouped with frequency alignment within groups for second data; or using different "predetermined numbers" for frequency-axis mapping for different data) represent known and straightforward techniques for distributing symbols in a 2D time-frequency grid. A PHOSITA would routinely select and apply such patterns to achieve desired diversity gains (time, frequency, or a combination) depending on the assessed channel characteristics and the type of data being transmitted. For instance, arranging data primarily along the frequency axis might be favored when time variations are dominant, while distributing data across both axes in specific blocks could offer resilience against both time and frequency selective fading. The decision to use different patterns for "first data" and "second data" (as claimed) would be an obvious design choice to accommodate different link conditions, different users (as illustrated in Embodiment 4 of US 8,208,569), or different quality of service requirements.

Therefore, combining the general concept of 2D data arrangement in multicarrier systems (JP '724), the principle of adaptive FEC optimization (Razavilar), and the use of channel quality feedback for dynamic scheduling (Motorola), along with the PHOSITA's knowledge of error correction coding and common 2D mapping techniques, would have rendered the claimed subject matter of US 8,208,569 obvious. The claimed specific mapping patterns are merely implementations of well-known strategies for interleaving and resource allocation in a 2D time-frequency domain for improved communication performance.