Obviousness

US Patent 11777776, concerning header repetition in packet-based Orthogonal Frequency Division Multiplexing (OFDM) systems, would likely be found obvious under 35 U.S.C. § 103 when considering a combination of readily available prior art references, particularly those explicitly cited or discussed in the patent's background. A Person Having Ordinary Skill in the Art (PHOSITA) in wireless communication systems would have been motivated to combine these references to achieve robust and flexible header decoding in environments with varying channel conditions or device capabilities.

The core of the claimed invention, as captured in independent claims 1 and 7, involves:

1. A wireless communication device or method for receiving and decoding a wireless packet through a communication channel.
2. The wireless packet can be in a first format (header on a single OFDM symbol) or a second format (header on a first OFDM symbol, followed by a repetition of that header on a second OFDM symbol).
3. The device or method distinguishes the second packet format from the first by detecting the repeated second header field.

The following combination of prior art references would render these claims obvious:

Prior Art References

1. ITU-T Recommendation G.9960: Next generation wire-line based home networking transceivers—Foundation (January 2009): This standard, published prior to the priority date of US11777776 (August 21, 2009), describes packet-based OFDM transmission where the header can be carried over one (D=1) or two (D=2) OFDM symbols, with multiple header information blocks repeated over the frequency band within each symbol. It highlights the importance of reliable header decoding.
2. ITU Temporary Document ITU-T SG-15/Q4 09CC-046, "G.hn: PHY-Frame Header Extension" (August 2009): This document, also prior to the priority date, explicitly discusses the expansion of D to 2.
3. ITU Temporary Document ITU-T SG15/Q4 09XC-100, "G.hn: Using Two Symbols for the Header of PHY Frame on Coax" (July 2009): This document, prior to the priority date, specifically addresses the use of two OFDM symbols for the PHY frame header. The patent's own description and FIG. 1 clarify that when D=2, the second instance of the header block is a copy or repetition of the prior block.
4. US 2005/0243774 A1 to Sandhu et al. (Atheros Communications, Inc.) (Published November 3, 2005): This patent application, titled "Repetition coding for a wireless system," teaches the use of repetition coding to enhance reliability in wireless communication systems.
5. US 2006/0050705 A1 to Yu (LG Electronics Inc.) (Published March 9, 2006): This patent application, titled "Distinguishing between protocol packets in a wireless communication system," teaches methods for a receiver to distinguish between different protocol packets in a wireless communication system.

Obviousness Analysis

Motivation to Combine:
The background section of US11777776 explicitly articulates the problems that would motivate a PHOSITA to combine these references. It states that "The default value of D is 1, but expanding it to 2 in some cases is under discussion" for G.9960, and points out that "the level of frequency diversity is different depending on the bandplan, hence providing different header decodability if D is fixed to 1." It further notes that "If D is fixed to 2, then it increases reliability for the narrowband devices, but may also unnecessarily increase overhead for the wide-band devices." This clearly establishes the need for a system that can accommodate different header repetition schemes (D=1 or D=2) to balance reliability and efficiency across various network conditions and device types within a single domain.

A PHOSITA would recognize that these challenges, identified within the context of wireline G.hn, are equally (if not more) pertinent to wireless communication systems due to the inherently less stable nature of wireless channels.

Application to Claims:

• Wireless Communication Device/Method and Packet Formats (Claims 1 & 7, Body Part 1):
  The G.9960 standard, along with the two G.hn temporary documents, clearly teaches the fundamental concept of packet-based OFDM headers being carried over either one (D=1) or two (D=2) OFDM symbols, where the two-symbol case involves repetition of the header information for diversity and reliability. The patent's own description confirms that the "second header field being a repetition of the first header field" is intrinsic to the D=2 scenario. While G.9960 primarily focuses on wireline, the patent itself broadly applies its concepts to "wireless home networks, wireless corporate networks". The application of repetition coding for reliability in wireless systems is a well-known technique, as evidenced by US 2005/0243774 A1. Therefore, a PHOSITA would find it obvious to apply the D=1/D=2 header repetition scheme, including the repetition of header fields, to a wireless OFDM communication system.

• Distinguishing Packet Formats by Detecting Repetition (Claims 1 & 7, Body Part 2):
  Given the explicit discussion in G.hn about having both D=1 and D=2 options, and the patent's stated goal that "a receiving node in the domain should be able to decode packets sent by the transmitter without knowing D a priori", a PHOSITA would be motivated to devise a mechanism for the receiver to determine the value of D. The general concept of distinguishing between different packet formats in a wireless system is known in the art, as taught by US 2006/0050705 A1.

  The method described in the patent—where a receiver "starts processing the header by decoding one OFDM header symbol. If the receiver decodes it successfully, then the receiver knows how many more OFDM symbols (D−1) are carrying header information... If the receiver fails... then the receiver can try to decode two OFDM header symbols, and so on"—represents an obvious and logical implementation for a PHOSITA. This progressive decoding strategy inherently allows the receiver to "detect" the presence of the second header field (i.e., the repeated header) when attempting to gain enough diversity to successfully decode the header. If the first attempt (D=1) fails, the subsequent successful decoding using two symbols (D=2, with repetition) constitutes the act of "detecting, from the received wireless packet, the second header field which repeats the first header field" to distinguish the packet format.

Conclusion

Based on the combination of ITU-T G.9960 and its associated temporary documents, US 2005/0243774 A1, and US 2006/0050705 A1, a PHOSITA would have been motivated to implement a wireless OFDM communication system with flexible header repetition (D=1 or D=2). The method of distinguishing these formats by attempting to decode with D=1 and then, if necessary, utilizing the repeated header in a D=2 decoding attempt, represents an obvious solution to a known problem of balancing reliability and overhead in varied communication environments.