Obviousness

Obviousness Analysis of US Patent 7949068 under 35 U.S.C. § 103

This analysis identifies combinations of prior art references that would render the independent claims of US Patent 7949068 (US7949068B2) obvious to a person having ordinary skill in the art (PHOSITA) as of the patent's priority date of April 26, 2005. The PHOSITA in the field of this patent would possess knowledge of wireless communication systems, including MIMO (Multiple-Input Multiple-Output) technology, OFDM (Orthogonal Frequency Division Multiplexing), antenna diversity techniques (such as cyclic delay diversity), and various linear algebra operations (e.g., matrix multiplication, unitary matrices) applied in signal processing for communication.

The core of US7949068 involves a system and method for transmitter diversity expansion where K base data streams are used to generate N-K extension data streams, which are then transmitted along with the K base data streams from a total of N antennas. The generation of these N-K extension streams involves cyclic shifting and combining the original K data streams using a unitary matrix. A key advantage cited by the patent is that this process is "seamless to the receiver," meaning the receiver does not need special decoding circuitry.

Combination 1: US7539463B2 in view of US6801579B1 and common knowledge of unitary matrices

This combination primarily addresses independent claims 1, 9, and 17, and their dependent claims related to cyclic shifting and combining with a unitary matrix.

Primary Reference: US7539463B2 (Intel Corporation) – "Techniques to enhance diversity for a wireless system"

• Priority Date: March 30, 2005 (predates US7949068B2's priority date of April 26, 2005).
• Teachings: This patent describes techniques to enhance diversity for wireless systems. Specifically, its abstract states: "A channel estimation field having a first portion and a second portion is transmitted. The first portion of the channel estimation field may be cyclic delayed and combined across multiple transmit antennas."
  • This reference directly teaches the concept of taking signals ("channel estimation field," which is a form of data stream) and processing them by applying "cyclic delayed" versions that are then "combined across multiple transmit antennas." This implicitly teaches a transmit processor configured to generate processed data streams from original data streams, where the processing involves cyclic shifting and combining, and transmitting these from multiple antennas.
  • It covers the generation of "extension data streams" (the cyclic delayed and combined portions) based on "base data streams" (the original channel estimation field or input signals) and their transmission from "multiple transmit antennas."

Secondary Reference: US6801579B1 (Lucent Technologies Inc.) – "Method and wireless communication using unitary space-time signal constellations"

• Priority Date: March 9, 2000 (predates US7949068B2's priority date).
• Teachings: This patent discloses methods for wireless communication using unitary space-time signal constellations. Its abstract states: "A unitary space-time code matrix is generated based on a selected constellation... A wireless signal based on the unitary space-time code matrix is transmitted from an antenna array."
  • This reference explicitly teaches the use of a "unitary space-time code matrix" in the context of transmitting signals from an "antenna array." This directly teaches the "unitary matrix" and "matrix multiplication" elements found in claims 1, 9, and 17 of US7949068B2.

Motivation to Combine and Obviousness:

A PHOSITA, seeking to enhance transmitter diversity and reliability in wireless communication systems (a well-known objective, particularly with the advent of standards like IEEE 802.11n which was considering MIMO as noted in US7949068B2's background), would have been motivated to combine the teachings of US7539463B2 and US6801579B1.

1. Combining and Cyclic Shifting: US7539463B2 teaches "cyclic delayed and combined across multiple transmit antennas" to enhance diversity. A PHOSITA would understand that this combining operation could be represented or implemented using matrix algebra.
2. Incorporating Unitary Matrices: US6801579B1 teaches the benefits and application of "unitary space-time code matrices" for transmission from antenna arrays to achieve improved signal characteristics. It was well-known in the art that unitary matrices offer desirable properties (e.g., preserving signal energy, facilitating orthogonal transformations) in wireless communications for robust transmission and diversity.
3. Synergistic Combination: A PHOSITA would recognize that applying a unitary matrix (as taught by Lucent) during or after the cyclic delay and combining process (as taught by Intel) would provide a powerful way to further optimize the spatial characteristics of the transmitted signals, enhance diversity, and potentially improve receiver performance. For instance, a unitary matrix could be used to perform the combining function itself, or to further process the cyclically-shifted signals before transmission. Such a combination would have a reasonable expectation of success as both techniques were established in the field for improving wireless communication.
4. Receiver Transparency: The patent US7949068B2 emphasizes "seamless to the receiver." While neither US7539463B2 nor US6801579B1 explicitly state this exact advantage in combination, the general aim of diversity techniques is often to improve signal quality without requiring complex modifications at the receiver beyond standard MIMO decoding capabilities. If the unitary matrix (e.g., a Walsh-Hadamard matrix as mentioned in US7949068B2) is applied in a structured way, the receiver could often decode the individual streams without a priori knowledge of complex channel state information or specific decoding algorithms beyond typical MIMO reception. This would be a design choice a PHOSITA would explore.

Specific Claim Elements Rendered Obvious:

• "a transmit processor configured to generate a set of one or more extension data streams based on a set of base data streams" (Claim 1): Taught by US7539463B2, which describes processing input signals ("channel estimation field") to produce "cyclic delayed and combined" versions ("extension data streams").
• "wherein at least one data stream of the set of one or more extension data streams is the product of a matrix multiplication of the set of base data streams with a unitary matrix" (Claim 1): Taught by combining US7539463B2's combining operation with US6801579B1's explicit teaching of using a "unitary space-time code matrix" for transmission. A PHOSITA would understand that the combining operation in US7539463B2 could be implemented via matrix multiplication, and that using a unitary matrix for this purpose, as taught by US6801579B1, would be a beneficial design choice.
• "wherein the transmit processor is communicatively coupled to a set of base antennas and a set of one or more expansion antennas, wherein each base antenna is configured to transmit a corresponding one of the base data streams, and wherein each expansion antenna is configured to transmit a corresponding one of the extension data streams" (Claim 1): US7539463B2 teaches "multiple transmit antennas." The concept of dedicating individual antennas for distinct (original or derived) data streams is fundamental to multi-antenna systems and would be an obvious architectural choice for a PHOSITA maximizing diversity and utilization of available antennas, including the "systematic mapping" described in US7949068B2 where K original streams are sent to K antennas and also processed for N-K extension streams.
• Dependent claims 2, 10, 18 (cyclically-shifted combination): Directly taught by US7539463B2's "cyclic delayed and combined" teaching.
• Dependent claims 3, 5, 11, 13, 19, 21 (order of operations - cyclic shift before combining/combining with cyclically shifted streams): Both orders (cyclic shift then combine, or combine then cyclic shift) are permutations of linear operations that a PHOSITA would routinely consider and explore in signal processing, as described in US7949068B2's FIGS. 5 and 6. The choice between them would be a matter of design and optimization for specific system requirements, without introducing non-obviousness.
• Dependent claims 6, 14, 22 (unitary matrix is Fourier Transform or Walsh matrix): US7949068B2 itself notes that the combining matrix "may be a fast Fourier transform matrix" or have a "Walsh-Hadamard construct." These are well-known examples of unitary matrices used in signal processing and communications for orthogonal transformations and spreading. A PHOSITA, when implementing a unitary matrix function as taught by US6801579B1, would obviously select from such known and advantageous matrix types.
• Dependent claims 7, 8, 15, 16, 24, 25 (quantity of base data streams vs. extension data streams): These relate to the number of input streams K and the number of extension streams N-K. These are design choices for multi-antenna systems, where the ratio of input to output streams is adjusted based on desired diversity gain, data rate, and available antenna elements, as widely understood by a PHOSITA in the field.

Therefore, the claims of US7949068B2 would have been obvious to a PHOSITA based on the combination of US7539463B2, US6801579B1, and the general knowledge prevalent in the field of wireless communications.