Obviousness

Obviousness Analysis under 35 U.S.C. § 103 for US Patent 7,924,802

This analysis will identify potential combinations of prior art references that could render the claims of US Patent 7,924,802 obvious to a Person Having Ordinary Skill in the Art (PHOSITA) at the time of the invention (priority date January 23, 2008). The obviousness determination considers the scope and content of the prior art, differences between the prior art and the claims, the level of ordinary skill in the art, and any secondary considerations of non-obviousness.

The core of US 7,924,802 involves transmitting multiple, non-overlapping frequency-shifted signals simultaneously using a single power amplifier and antenna, often for improved data throughput or reliability. The patent also describes receiving such signals and, in some embodiments, employing OFDM with Alamouti coding.

Prior Art Landscape:

The patent itself identifies typical prior art approaches to improving information capacity in wireless communication systems as "maximizing the bandwidth around the center frequency to increase the amount of information that may be modulated onto the carrier frequency." It also discusses limitations related to allowable output power and the need for improvements in wireless communication systems.

The classifications associated with US7924802B2 provide insight into the relevant technical fields:

• H04L27/2601: Multicarrier modulation systems (e.g., OFDM).
• H04B1/0067: Adapting radio receivers, transmitters, and transceivers for operation on two or more bands with one or more circuit blocks in common for different bands.
• H04B1/0483: Transmitters with multiple parallel paths.
• H04L1/0668: Space-time coding, specifically orthogonal systems using Alamouti codes.

Given these classifications and the patent's own description of prior art, a PHOSITA would be familiar with:

• Basic wireless transmitter and receiver architectures (e.g., DAC, filter, mixer, power amplifier, antenna, LNA, down-converter, ADC).
• Up-conversion and down-conversion techniques.
• The concept of transmitting signals at different center frequencies.
• The use of power amplifiers with specific bandwidths.
• Techniques for increasing data throughput (e.g., maximizing bandwidth).
• Diversity reception and coding schemes like OFDM and Alamouti codes for improving reliability and throughput.
• Wireless protocols such as UWB (WiMedia), WLAN (802.11g), and cellular standards.

Potential Obviousness Combinations:

Combination 1: Basic Simultaneous Multi-Frequency Transmission with Shared PA/Antenna (Claims 1, 3, 4, 10, 17)

• Starting Point: A conventional wireless transmitter (e.g., as depicted in FIG. 1 of US 7,924,802) capable of up-converting and transmitting a signal at a single center frequency.
• Additional Prior Art (Hypothetical): A reference disclosing the desire or known technique for transmitting multiple, distinct data streams or even redundant data streams for reliability over a wireless channel. This could be motivated by a need for increased data throughput or improved reliability/range, as articulated in the '802 patent's background. Furthermore, a general understanding of frequency division multiplexing (FDM) in communication systems is well-established prior art.
• Motivation to Combine: A PHOSITA, faced with the desire to increase data throughput or reliability in a wireless communication system while potentially constrained by power limits at any single frequency, would be motivated to transmit multiple information streams simultaneously at different carrier frequencies. The motivation to use a single power amplifier and antenna, as claimed in the '802 patent (Claims 3, 4, 10, 17), would stem from cost, size, and complexity reduction. It is a common engineering goal to consolidate hardware where possible. If a power amplifier with sufficient bandwidth to cover the desired multiple frequency ranges is available (as explicitly stated in claims 4 and 17), then using a single wideband PA for multiple, non-overlapping up-converted signals would be an obvious design choice to simplify the RF front-end and reduce costs compared to using multiple PAs and antennas. The "frequency difference between the first center frequency and the second center frequency is greater than the sum of one-half the first frequency range and one-half the second frequency range" (Claim 2, 10, 17) is an obvious design choice to prevent inter-signal interference and distortion.

Combination 2: Frequency Hopping/Changing of Simultaneous Multi-Frequency Signals (Claims 5, 11, 12, 18, 19, 20)

• Starting Point: The system described in Combination 1, allowing for simultaneous transmission of multiple, non-overlapping signals.
• Additional Prior Art (Hypothetical): References disclosing frequency hopping or dynamic frequency allocation in wireless communication systems. Frequency hopping spread spectrum (FHSS) has been a known technique for security, interference avoidance, and sharing spectrum for decades. Adaptive frequency management is also common to optimize spectrum usage.
• Motivation to Combine: A PHOSITA would be motivated to combine simultaneous multi-frequency transmission with frequency hopping/changing to further enhance system performance. This could be to:
  • Mitigate interference: If certain frequency bands experience temporary interference, hopping to different, clearer bands could maintain communication quality.
  • Avoid detection/intercept: As in traditional FHSS, this adds a layer of security.
  • Optimize channel conditions: Dynamically moving signals to frequency bands with better propagation characteristics or less fading.
  • Load balancing: Distributing traffic across a wider range of spectrum to accommodate more users or higher data rates.
    The concurrent changing of frequencies (Claims 5, 12, 19) would be a logical extension for maintaining the non-overlapping nature of the signals as they hop, or for coordinated spectrum management. The requirement that the center frequencies change by at least their respective frequency ranges (Claim 5, 11) is an obvious engineering consideration to ensure that the hopped signals occupy entirely new spectral locations and do not interfere with previous transmissions or residual energy.

Combination 3: Protocol-Specific and Data Redundancy Aspects (Claims 6, 7, 8, 13, 21, 22)

• Starting Point: The simultaneous multi-frequency transmission system from Combination 1.
• Additional Prior Art (Hypothetical):
  • References discussing the use of different wireless protocols (e.g., UWB, WLAN, cellular) in the same device or environment. Multimode devices are a long-standing trend in wireless communications.
  • References on error correction coding, diversity techniques (frequency diversity), or retransmission strategies to improve reliability. Sending the "same data transmitted across two different frequencies" (Claim 7) or "from the same data stream using coding or data mapping" (Claim 8, 22) is a fundamental concept of frequency diversity and robust data transmission.
• Motivation to Combine:
  • Multiple Protocols (Claims 6, 13, 21): A PHOSITA would be motivated to transmit information using different wireless protocols simultaneously (e.g., one for short-range high bandwidth, another for long-range lower bandwidth, or supporting legacy devices) to enhance flexibility and interoperability. This is a common design goal in multi-standard wireless devices.
  • Data Redundancy/Reliability (Claims 7, 8, 22): Transmitting the same data or coded versions of the same data over different frequencies is a classic form of frequency diversity. A PHOSITA would be motivated to employ such a technique to combat frequency-selective fading, improve signal-to-noise ratio (SNR), and increase the reliability or range of data transmission, especially in challenging wireless environments. This directly addresses the '802 patent's stated problem of "limiting the reliability, the range, and the effective throughput of data transmission."

Combination 4: OFDM and Alamouti Coding Integration (Claims 9, 23, and receiver claims 14, 15, 16, 24, 25 in conjunction with FIGS. 10 & 11)

• Starting Point: The simultaneous multi-frequency transmission system.
• Additional Prior Art (Hypothetical):
  • Extensive prior art exists for Orthogonal Frequency Division Multiplexing (OFDM) as a multicarrier modulation technique to achieve high data rates and spectral efficiency, particularly in mitigating multipath fading.
  • Alamouti codes are a well-known space-time block coding (STBC) scheme used in Multiple-Input Multiple-Output (MIMO) systems to achieve transmit diversity, improving reliability without requiring additional bandwidth.
• Motivation to Combine: The '802 patent specifically mentions OFDM and Alamouti codes (FIG. 10). A PHOSITA would be motivated to combine the simultaneous transmission across different frequency ranges with OFDM and Alamouti coding to achieve significant benefits:
  • OFDM (Claims 9, 23): Using OFDM in each of the simultaneously transmitted frequency ranges would naturally enhance the spectral efficiency and robustness against frequency-selective fading for each individual stream.
  • Alamouti Code (FIG. 10 & 11, implicitly supported by claims 9, 23 for multiple symbols): While Alamouti codes are typically associated with spatial diversity (multiple antennas), the patent adapts this concept by transmitting the coded symbols over different frequency ranges simultaneously, using a single physical antenna (FIG. 10 shows a single antenna 1009 for the Alamouti encoded streams). This represents a form of frequency diversity enabled by the multi-frequency transmission. A PHOSITA seeking to improve reliability and performance in a single-antenna, multi-frequency transmission system would be motivated to explore how transmit diversity techniques like Alamouti codes could be adapted to leverage the available frequency diversity. The equations provided in FIG. 11 for decoding Alamouti-like symbols further demonstrate this application. The concept of transmitting different symbols in different time slots and across different frequency ranges (Claim 9, 23) is a direct consequence of implementing space-time coding like Alamouti, where symbols are spread across time and "transmit paths" (here, different frequencies).

Conclusion on Obviousness:

The independent claims of US 7,924,802 appear to combine well-known concepts in wireless communications. The motivation for these combinations stems from common engineering goals: increasing data throughput, enhancing reliability and range, and reducing cost/complexity.

1. Simultaneous Multi-Frequency Transmission: Transmitting multiple signals at distinct, non-overlapping frequencies to either increase aggregate data rate or provide frequency diversity for reliability is a straightforward application of frequency division multiplexing. The use of a single wideband power amplifier and antenna would be an obvious cost and size reduction measure if such a PA is available and its bandwidth is sufficient, as explicitly claimed.
2. Frequency Agility: Incorporating frequency hopping or dynamic frequency changing into such a multi-frequency system would be obvious for interference avoidance, security, or channel optimization, drawing from established FHSS and adaptive spectrum management techniques.
3. Protocol and Redundancy: Transmitting different data streams or redundant data streams encoded with different protocols or for diversity is a known strategy in multimode and robust wireless communication.
4. OFDM and Alamouti Coding: The application of OFDM to each frequency channel for spectral efficiency and robustness is standard. The adaptation of Alamouti-like coding for frequency diversity across simultaneously transmitted frequency bands, while potentially clever, leverages a known coding scheme for a known benefit (diversity) in a context (frequency) analogous to its original spatial diversity application.

Therefore, a PHOSITA would likely find the claimed inventions to be obvious combinations of existing technologies, driven by clear motivations to improve performance, reliability, and cost-effectiveness in wireless communication systems. The specific parameters, such as the non-overlapping frequency ranges and the power amplifier bandwidth, are engineering design choices that flow logically from the desired functionality.