US 9900067

I'll verify the patent details and check for any 2026 CAFC activity.

Let me look for the actual claim text and any recent appellate activity.

Let me try to retrieve the actual claim language and check for assignments / later 2026 activity.

US 9,900,067 B2 — Verification Summary

Sourcing note: I could not query the USPTO PatentCenter/Public Search API directly from this environment, and I found no CAFC 2026 docket entry for this patent. The figures below are grounded in the Google Patents record for US9900067B2 (provided as authoritative), the ETRI KSP patent record (registration no. 9900067), the EPO/PISE record, and the Stanford NPE Litigation Database. Where a detail is not independently confirmed, I flag it.

Bibliographic data

Abstract (as published)

"The present invention relates to a method and apparatus for transmitting and receiving data. A data transmission method from a sender terminal to a receiver terminal in a MIMO system using a variable frequency band according to one embodiment of the present invention comprises: repeatedly generating a signal field depending on a frequency band that is applied to the transmission of a data frame; generating a data field including the data; generating a data frame including the signal field and the data field; and transmitting the data frame to the receiver terminal. The present invention is advantageous in that a signal field which is transmitted together with the data being transmitted from the sender terminal to the receiver terminal in the MIMO system can be sent more efficiently."

Independent claims — plain language

⚠️ Uncertainty flag: The full granted claim set was not available to me (the Google Patents text I received stops before the claims, and the Family has no claim listing I could retrieve verbatim). The claim text below is taken from a third-party database reproduction of the claims of the corresponding publication US 2014/0119327 A1 for application 14/147,447. These are very likely close to the granted claims but I cannot certify they are identical to the issued text. Also note the specification's "Technical Solution" section describes a transmitter-side independent claim (iteratively generating a signal field according to frequency band; generating a data field; generating a data frame; transmitting) and a receiver-side independent claim, plus corresponding device claims — so the granted set likely contains at least one transmitter-side independent claim in addition to the receiver-side claim shown below. I could not verify that from an authoritative source.

Claim 1 — receiver-side method (WLAN):
A method in which a receiver:

• receives a first signal field over an operating band using two OFDM symbols, where the operating band's bandwidth is a multiple of 20 MHz;
• receives a second signal field over that same operating band using one OFDM symbol for a MU-MIMO transmission;
• where the second signal field contains information obtained by repeating a SIG-B a predetermined number of times according to the operating bandwidth, and that number increases as bandwidth increases;
• where the first signal field carries information common to the multiple receivers targeted by the MU-MIMO transmission, while the SIG-B carries information specific to that receiver; and
• where the second signal field is received over at least one spatial stream selected from multiple spatial streams, the selected stream(s) corresponding to that receiver.

Claim 10 — receiver-side apparatus: The device counterpart of claim 1 — a reception unit that receives the two-symbol first signal field and the one-symbol second signal field for MU-MIMO, plus a data obtaining unit that recovers data using the first and second signal fields, with the same SIG-B repetition/increasing-bandwidth, common-vs-specific information, and spatial-stream-selection limitations.

Dependent claims (2–9, 11–13) add: the first signal field is received without applying MU-MIMO; the first signal field is repeated over each 20 MHz sub-band; the fields are VHT-SIG-A and VHT-SIG-B; SIG-B is 26 bits at 20 MHz, 27 bits at 40 MHz, and 29 bits above 40 MHz; a received data field includes a CRC field used to detect errors in the second signal field; and the fields are carried as a PPDU.

Note: in the claim text above, "the first signal signal includes first information…" is an apparent typographical duplication in the source, retained rather than corrected.

Corresponding subject matter in the specification

• L-STF/L-LTF/L-SIG are legacy 802.11 fields for backward compatibility; VHT-SIG-A is the common signal field (auto-detection/compatibility, iterated per 20 MHz) and VHT-SIG-B is the dedicated per-user field.
• The core teaching is that simply repeating VHT-SIG-B like VHT-SIG-A yields an SNR gain but no frequency-diversity gain; the invention applies different interleaving per stream (or CDD with per-antenna delay) so identical coded bits land on different subcarriers of different streams.
• Worked fan-out: 20/40/80/160 MHz, 1–4 streams, non-contiguous multi-channel, one-QPSK-symbol variants, and STBC/Alamouti variants (FIGS. 11–57).
• CRC handling: because VHT-SIG-B has no spare bits at 20 MHz, 4–8 reserved bits of the service field may serve as CRC covering both the SIG-B and the scrambler seed (FIGS. 49, 54), allowing PHY/MAC shutdown on error detection to save power.
• Commercial context: ETRI's project code is 10MI3500 ("IEEE 802.11 VHT 초고속 무선랜 무선전송 연구," PI Seok-Kyu Lee), i.e., this is 802.11ac VHT signaling work.

Litigation / 2026 CAFC activity

• Asserted by Sol IP, LLC in E.D. Tex.: 2:18-cv-00526 (v. AT&T Mobility LLC), 2:18-cv-00527 (v. Sprint Corporation et al.), and 2:18-cv-00528 — all listed on the Google Patents litigation panel and the Stanford NPE Litigation Database. Also an N.D. Cal. case, 5:20-cv-00399.
• No CAFC 2026 docket entry for US 9,900,067 was found. My searches returned only unrelated 2026 Federal Circuit matters (e.g., AGI SureTrack v. Farmers Edge, Ollnova v. ecobee, Ironburg v. Valve) and unrelated 2026 PTAB/IPR items. I also found no IPR/PGR against 9900067. This is a negative result from a general web search, not a complete docket check — an appeal could exist that is not indexed in the sources I could reach.

Continuation family (for context)

US 10,374,668 B2; US 10,931,337 B2; US 11,496,187 B2; US 12,074,665 B2; and US 2024/0413862 A1, plus EP 4020830 A1 — all sharing the same title/family, consistent with ETRI's continued prosecution of this disclosure.

Overall confidence: High on title, inventors, filing/issue dates, priority chain, abstract, and litigation history. Moderate on the exact granted claim wording (relied on a publication-stage claim reproduction). Low/unverified on current ownership of record and on the absence of 2026 appellate activity.

I'll search for litigation specifically involving US 9,900,067.

Let me verify the details of these cases and search for any additional litigation.

Let me pull the Stanford NPE record and details on the other identified cases.

Litigation involving US 9,900,067

Sourcing note: I searched the Stanford NPE Litigation Database, the Unified Patents litigation portal records surfaced through Google Patents, Justia/CourtListener dockets, Ex Parte's case analytics, and IP/legal trade press. I restricted hits to the literal identifier US 9,900,067 / 9900067 and discarded near-miss identifiers that returned unrelated results (e.g., WO 99/00067 — a Univ. of Iowa neural-stimulation PCT; Indian High Court cause numbers "APSWP 9900067/2001"; a Greek procurement tender no. 9900067; a Telstra parts number 9900067). Those are not this patent.

⚠️ Date inconsistency — flagged per instructions: The task states the current date is April 26, 2026, and the system context I was given says 2026-09-19. Two of the cases below are reported as filed August 28, 2026 and are discussed in press dated September 2026 — i.e., after the April 26, 2026 "current date" in the prompt. I am not suppressing these; per the operating rule that search results are the current ground truth, I report them and treat the August/September 2026 dates as real. Treat the "current date" line in the prompt as unreliable.

Summary table

Case-by-case detail

1–3. The 2018 Sol IP / E.D. Tex. campaign (2:18-cv-00526 / -527 / -528).
All three were filed December 3, 2018 in the Marshall Division of E.D. Tex. before Judge Robert W. Schroeder (RWS) with Magistrate Judge Roy S. Payne (RSP). Case 2:18-cv-00526 was designated the LEAD CASE; -527 and -528 were CONSOLIDATED into it (this is stated expressly on the face of Docket No. 293). The caption in that order identifies the defendants as AT&T Mobility LLC; Cellco Partnership d/b/a Verizon Wireless; Sprint Communications Company L.P.; Sprint Solutions, Inc.; and Sprint Spectrum L.P., with Ericsson Inc. and Nokia of America Corporation as intervenors. This was a large multi-patent campaign — one docket entry notes "27 asserted patents and 497 asserted claims." The asserted patents were grouped into "LTE A," "LTE B," and "WiFi" families; US 9,900,067 is an 802.11ac/VHT Wi-Fi patent (Wi-Fi family), and Docket No. 293 shows the defendants fighting over whether the IEEE 802.11n standard could be added to their invalidity contentions against a Wi-Fi patent. The court denied that motion for leave to amend on January 7, 2020.

• Outcome: The lead case is recorded as closed on 2020-05-20. My sources do not state whether closure was by settlement, voluntary dismissal, or otherwise — I could not confirm the disposition, so I am not characterizing it as a settlement or a win for either side.
• Sources: Stanford NPE DB (https://npe.law.stanford.edu/patent/9900067); Google Patents litigation panel links (https://portal.unifiedpatents.com/litigation/Texas%20Eastern%20District%20Court/case/2%3A18-cv-00526, .../2%3A18-cv-00527, .../2%3A18-cv-00528); Docket 293 (https://law.justia.com/cases/federal/district-courts/texas/txedce/2:2018cv00526/186351/293/); status "Closed (05/20/20)" (https://ai-lab.exparte.com/case/dct/txed/2:18-cv-00526/sol-ip-llc-v-att-mobility-llc).

4. N.D. Cal. 5:20-cv-00399.
This case was surfaced on the Google Patents litigation panel for this patent. I could not confirm the defendant, the patents-in-suit, or the current status from the sources I could reach, and it did not appear in the (truncated) Stanford NPE listing I retrieved. Treat as unverified.

5–6. The 2026 Sol IP / E.D. Tex. automotive campaign (2:26-cv-00764 and 2:26-cv-00766).
Sol IP, LLC filed two suits on August 28, 2026 in E.D. Tex., both assigned to Judge James R. Gilstrap, asserting the same two patents in both cases: US 9,900,067 B2 ("Method and apparatus for transmitting and receiving data in a MIMO system") and US 10,090,894 B2 ("Method and apparatus for transceiving data in a MIMO system"). Accused technology is Wi-Fi / MIMO functionality in vehicles (802.11ac, wireless CarPlay/Android Auto, in-car hotspots). Counsel: Nelson Bumgardner Albritton and Nelson Bumgardner Conroy (Brent N. Bumgardner, John P. Murphy, Timothy E. Grochocinski, Christopher Granaghan). Both cases are recorded as Open, with no defense appearances yet at the time of the report.

• Source: https://insights.greyb.com/sol-ip-honda-volkswagen-wifi-patent-lawsuits/ (GreyB, reporting case nos. 2:26-cv-00764 and 2:26-cv-00766, filed 2026-08-28, Judge Gilstrap).
• Related context that may moot these suits: Sol IP joined Avanci's Wi-Fi 6 Vehicles pool as a licensor, and Ford/GM signed on as licensees; Chinese-language coverage of that development suggests the Honda and Volkswagen cases will likely resolve through the pool license. Source: https://ipfray.com/ford-general-motors-among-latest-licensees-to-join-avanci-wi-fi-6-vehicles-program-sol-ip-signs-up-as-licensor/.

Negative findings

• No CAFC appeal involving US 9,900,067 was located. (Same negative result as the earlier section of this analysis; still not a complete docket check.)
• No IPR, PGR, reissue, or reexamination against US 9,900,067 was located.
• No ITC (Section 337) investigation involving this patent was located. Note the ETRI v. Shenzhen Tenda E.D. Tex. suit (2:26-cv-00398) and the ETRI Wi-Fi SEP injunction case reported in February 2026 (asserting patents such as 11,664,926; 10,313,077; 10,651,992; etc.) are different patents — I checked that '067 was not among the listed patents, so I am not including them.
• No litigation found naming ETRI itself as plaintiff on the '067 patent; all identified assertions were by Sol IP, LLC.

Who is asserting it

The Stanford NPE Litigation Database categorizes Sol IP as an "Acquired patents" asserter, and IP fray describes Sol IP as managing "a portfolio of standard-essential patents (SEPs) including many originating from South Korea's Electronics and Telecommunications Research Institute (ETRI)." This is consistent with an ETRI→Sol IP transfer/licensing arrangement rather than ETRI suing directly. The current owner of record was not confirmed from an authoritative USPTO assignment record.

Confidence: High on cases 1–3 (docket-sourced) and 5–6 (trade-press sourced). Low/unverified on case 4 and on the specific disposition of the 2018 consolidated cases. If you need certified status, pull PACER for 2:18-cv-00526 and for 2:26-cv-00764/-00766.

I'll verify the structured block's negative finding against live sources before finalizing.

Let me run two more targeted queries to be thorough on the ETRI/Sol IP family and confirm no institution denial or CBM exists.

Proceedings overview

Zero AIA trial proceedings on file for US 9,900,067. The USPTO Open Data Portal structured block reports no IPR, PGR, or CBM proceedings against US 9,900,067 as of the most recent ingest, and my independent web searches (Google Patents litigation/PTAB panels, PTAB E2E–style petition documents, and general PTAB/CAFC coverage) surfaced no petition, institution decision, FWD, or appeal naming this patent. Bottom-line defensive posture: the patent has never been tested at the PTAB — it is entirely untested and un-hardened, which means there are no canceled claims to point to and no § 315(e)(2) estoppel binding anyone. That cuts both ways: a defendant has no free kill-shot, but also faces no prior-petitioner estoppel and can be the first to attack the claims on whatever art it can find.

No proceedings to report

• Type: N/A
• Filed: N/A
• Status: No AIA trial proceeding on file (per the canonical U.S. Open Data Portal block) — corroborated by web search.
• Judge panel: N/A
• Petition grounds: N/A
• Institution decision: N/A
• Final Written Decision: N/A — no claim of US 9,900,067 has ever been canceled, confirmed, or even challenged at the Board.
• Settlement / termination: N/A
• Appeal: No CAFC appeal from any '067 PTAB decision (there is no such decision). Note this is a negative result from general web search plus the ODP ingest, not a certified PACER/PTAB E2E docket check.
• Defensive value: The absence of PTAB activity means no petitioner has tested these claims, so the validity fight is wide open — but also unproven in your favor. The claims stand exactly as granted.

⚠️ Critical identifier trap — do not conflate US 9,900,067 with US 9,906,067

The strongest near-miss in my searches is a different patent: US 9,906,067 (Garrity Power Services LLC, "wireless power transmission / wireless battery charging") — the subject of [Samsung Electronics Co.](/litigations/by-defendant/Samsung%20Electronics%20Co.) v. Garrity Power Services LLC, IPR2021-00389, which I found as a public petition (Paul Hastings as counsel; ground 1 based on "Kasar," U.S. Pat. No. 10,404,089). That proceeding is inapposite to your patent:

• It involves US 9,906,067 (app. no. 14/754,863, filed 2015-06-30, issued 2019-09-03, "067 patent" for wireless power), not US 9,900,067 (app. no. 14/147,447, ETRI, 802.11ac/VHT MIMO).
• Different technology, different owner, different statutory posture (AIA first-to-file), different prior art.
• I found no IPR on the ETRI '067. Any search that returns IPR2021-00389 for a query about "9900067" is a digit-transposition false positive. A defendant should confirm the patent in any demand letter is the ETRI MIMO patent before assuming the Garrity IPR history applies.

Source for the Garrity petition (shown only to identify the near-miss): https://cmosedu.com/jbaker/expert_witness/2021/IPR2021_00389.pdf.

Other false positives I discarded: Greek procurement tender 9900067 (ΔΕΔΔΗΕ); Telstra parts list no. 9900067; Univ. of Iowa–derived WO 99/00067; Rajasthan/Indian cause no. APSWP 9900067/2001; VA citation no. 9900067; and NSN 9900-067 (Woodward pump governor). None is this patent.

Cross-check against the litigation posture (builds on the earlier sections)

Per the earlier litigation section, US 9,900,067 is being actively asserted by Sol IP, LLC (an ETRI-originated SEP/acquirer), including the 2018 E.D. Tex. campaign (2:18-cv-00526/-527/-528) and the 2026 E.D. Tex. automotive suits (2:26-cv-00764 v. Honda; 2:26-cv-00766 v. Volkswagen). The combination — years of assertion, multiple defendants, and still not a single IPR — is an unusual and telling signal:

• Defendants in the 2018 campaign (AT&T, Verizon/Cellco, Sprint, with Ericsson and Nokia intervening) evidently chose to litigate validity in district court rather than petition the PTAB. Whether that was a strategic choice, a time-bar problem, or a settlement-driven outcome, I could not confirm — the lead case closed 2020-05-20 without a stated disposition.
• The absence of any IPR on a patent asserted against multiple large carriers and now against two automakers is atypical and may indicate (a) settlements before institution was worth it, (b) the license/pool route (Sol IP joined Avanci's Wi-Fi 6 Vehicles pool) diverting challenges, or (c) a validity theory that defendants did not find PTAB-viable. I cannot verify which.

Strategic summary

Which claims are canceled vs. sustained vs. untested. None are canceled; none are sustained. Every claim of US 9,900,067 — including at least the receiver-side independent claim and its dependents (with the transmitter-side and device claims likely present in the granted set, per the earlier summary's flagged uncertainty about the exact granted text) — is untested. There is no FWD to cite, no IPR certificate to link, and no claim you can tell a plaintiff is dead.

Estoppel landscape. Because no IPR/PGR was ever instituted against this patent, no petitioner (and no privity chain) is bound by § 315(e)(2). That means a current defendant is not blocked by anyone else's prior art grounds — but it also means there is no roadmap of "art the Board already accepted." Any prior-art challenge is a clean slate. Conversely, if you are contemplating your own IPR, note the § 315(b) one-year bar running from service of the complaint in the 2026 automotive cases (filed 2026-08-28 per the earlier section); the window to petition is running.

Pattern signals. No petitioner has filed multiple IPRs on this patent (no petitioner has filed any). There is no defensive-aggregator (Unified Patents / RPX-type) IPR in the chain that I could find — the earlier sections note Unified Patents litigation data links only, which are not petitions. The patent owner (via Sol IP) has not pursued any PTAB appeal on this patent because there has been no PTAB proceeding to appeal.

Recommended next steps

1. Do not treat the Garrity IPR (IPR2021-00389) as relevant. If a demand letter or an opponent's invalidity narrative cites "IPR2021-00389 / the '067 IPR," verify the patent number digit-by-digit. US 9,906,067 ≠ US 9,900,067. The Garrity proceeding concerns wireless power, not 802.11ac signaling.

2. Confirm the negative with a certified docket pull. The "no PTAB activity" finding rests on (a) the canonical ODP ingest block and (b) general web search — not a PACER/PTAB E2E docket certification. Before relying on it, pull the patent's full trial-history on PTAB E2E / USPTO Patent Trial and Appeal Case Tracking System (search application 14/147,447) and the CAFC docket via CourtListener. This is the single highest-value verification step, because the whole defensive analysis turns on the absence of proceedings.

3. If you are a defendant (e.g., a 2026 Honda/VW-era target), the IPR clock is the priority. With the complaints served 2026-08-28 (per the earlier section; verify against PACER for 2:26-cv-00764/-00766), § 315(b) gives you one year from service to petition. No one has estoppel against you, and there is no institution precedent to follow — so the petition must stand on its own art. The specification's own admissions are useful targets: it repeatedly concedes that simple iteration of VHT-SIG-B like VHT-SIG-A was known and that the alleged invention is the different-interleaving-per-stream / CDD variant and the bit-allocation-by-bandwidth variant — which frames the obviousness attack.

4. If the claims survive and the patent is asserted against you, the absence of IPRs is not proof of strength. A never-challenged patent can be weak as easily as it can be strong. The realistic defenses remain (i) invalidity in district court on 802.11ac/VHT and related art, and (ii) the standard-essentiality/licensing posture, since Sol IP licenses through the Avanci Wi-Fi 6 Vehicles pool — a license may resolve the exposure more cheaply than an IPR.

5. Watch for new filings. Given the 2026 assertion activity, a first-ever IPR/PGR against this patent is plausible in the near term. If one is filed, the institution decision will arrive within ~6 months and any FWD within the 12-month statutory trial deadline from institution — milestones worth diarizing if you become a party.

Confidence: High that there is no AIA trial proceeding on US 9,900,067 as of the sources reachable here (the canonical ODP block is consistent with independent search). Moderate on completeness, because I could not run a certified PTAB E2E/PACER docket check and cannot exclude an unindexed or very recent filing. All statements about the Garrity IPR2021-00389 and the Wilus/Samsung WiFi IPRs are included only to identify them as different patents; I did not verify their outcomes and they are not asserted here to apply to the ETRI '067.

I'll research the assignment record for US 9,900,067, starting with the USPTO Assignment Center and cross-referencing NPE directories.

Let me dig into the specific assignment records and the Sol IP / ETRI transfer.

Key finding emerging. Let me verify the inventor-to-ETRI assignment record and the alleged ETRI→Sol IP transfer.

Assignment & Ownership Analysis — US 9,900,067 B2

⚠️ Sourcing limitation (read first): My research tools ran out of steps before I could pull the Assignment Center interface directly. I was not able to retrieve the reel/frame-level records for this patent (or for application 14/147,447 / PCT/KR2011/001742). I am therefore not going to invent reel/frame numbers. What follows distinguishes (a) facts I could ground in court filings, NPE directories, and the patent face, from (b) items that require a live Assignment Center pull. Where a section cannot be completed for lack of a reel/frame, I say so rather than guess.

Inventors

• All three are named on the '067 patent with ETRI as assignee, which matches the ETRI KSP record for this registration ("Project Code 10MI3500, IEEE 802.11 VHT 초고속 무선랜 무선전송 연구," PI 이석규 / Seok-Kyu Lee). Source: https://ksp.etri.re.kr/ksp/patent/read?id=PR20100299USa.
• Unusual patterns: None found. I located no evidence of inventors leaving ETRI within 12 months of filing, no evidence of a competing spinoff, and no inventor-side assignments beyond the expected employee→institute assignment. I could not positively confirm each inventor's continued tenure (that is a personnel question, not a USPTO record), so treat "no departure" as an absence of evidence, not a verified negative.
• Note the inventors are all ETRI Daejeon; this is a normal government-research-institute inventor set — not a pattern (like the pro se / serial-inventor / address-of-convenience patterns) that usually flags a fire-sale.

Original assignee

• Entity on the issued patent: Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea.
• Primary line of business: ETRI is South Korea's largest government-funded electronics/telecommunications research institute (a national R&D lab, not a consumer-product manufacturer). Its output is research, standards contributions, and patent licensing.
• Did it ship a product embodying the claims? No — ETRI is a research institute. The '067 disclosure is 802.11ac "VHT" signaling work (VHT-SIG-A / VHT-SIG-B), i.e., it fed the IEEE 802.11ac standard rather than an ETRI-branded WLAN product. This matters for the NPE analysis below: the original assignee is a non-practicing research institution, which is itself an important fact.
• Current status: Operating (active as of 2026; still executing Wi-Fi SEP assertion campaigns — e.g., the reported ETRI v. Shenzhen Tenda E.D. Tex. suit 2:26-cv-00398 and the Feb-2026 ETRI Wi-Fi SEP injunction matter — on other patents).

Assignment timeline

Bottom line: I could not complete a reel/frame-level timeline. What I can state on the record:

• The patent issued to ETRI on 2018-02-20, and Google Patents' current-assignee field still lists ETRI. On the face of the record I could reach, ETRI — not Sol IP — is the owner of record.
• The only downstream transaction I could document is not a recorded assignment at all. In IPR2020-00242 (a different ETRI patent, US 10,080,204), Sol IP stated on 2019-12-31 that "ETRI transferred to exclusive licensee Sol IP, LLC, all substantial rights … and retained no substantial rights for itself." That is a transfer-of-all-substantial-rights via exclusive license, and Sol IP filed its notices as "Exclusive Licensee," with ETRI still captioned as "Patent Owner."
• Critically, contemporaneous analysis (Mondaq, 2021-04-02, reporting on Sol IP v. Qualcomm, 6:21-cv-00270) states plainly: "Currently available USPTO assignment records do not reflect ownership by Sol IP of any US patents, including the more than two dozen asserted assets." Source: https://www.mondaq.com/unitedstates/patent/1053522/.

Consequence: For the '067 patent I have no evidence of any recorded assignment after issuance, and direct evidence that the ETRI→Sol IP relationship was structured as an unrecorded exclusive license (or a license-plus-all-substantial-rights transfer) that does not appear as a change of owner in the Assignment Center. I therefore cannot supply executed/recorded dates, reels/frames, or the recording correspondent.

Items I could NOT verify and will not fabricate:

• The original inventor→ETRI assignment reel/frame for 14/147,447 (or for parent 13/434,681 / PCT/KR2011/001742), and its correspondent of record.
• Any ETRI→Sol IP recordation (execution date, reel/frame, correspondent). Based on the Mondaq source, I do not believe one exists.
• Any change-of-name, security interest, merger, or release on this patent.

To close these three gaps, pull: https://assignmentcenter.uspto.gov/ and https://assignment.uspto.gov/patent/index.html, searching by patent number 9900067 and by application 14147447.

*(Note: generic searches did surface ETRI assignment documents with correspondents such as Paul J. Farrell / Farrell IP Law, Rabin & Berdo PC, Staas & Halsey LLP (J. Randall Reckers), and William, Park & ... — but those were all for different ETRI patents/applications. I am deliberately not attributing any of them to the '067 filing.)*

Timeline diagram

timeline
    title Ownership of US 9900067
    2010 : Priority filings in Korea
    2011 : PCT filed by ETRI
    2014 : US continuation filed by ETRI
    2015 : Sol IP LLC formed in Virginia
    2018 : Patent issued to ETRI
         : Sol IP sues ATT Sprint Verizon
    2026 : Sol IP sues Honda and Volkswagen

NPE / troll-pattern signals

Verdict

NPE — high confidence.

Justification: Two strong signals are present. First, a known, repeat patent asserter controls enforcement — Sol IP, LLC, per Sol IP v. AT&T, E.D. Tex. 2:18-cv-00526/-527/-528 (filed 2018-12-03) and the 2026 E.D. Tex. 2:26-cv-00764/-00766 suits against Honda and Volkswagen, with Sol IP classified under "Acquired patents" in the Stanford NPE database. Second, the asserting entity is a licensing-only shell-style vehicle — Sol IP, LLC, a Virginia LLC formed Jan 2015 (member Choongsoo Park), holding no products and only an exclusive license with "all substantial rights" from ETRI, which it asserted in IPR2020-00242 on 2019-12-31. The original assignee, ETRI, is itself a non-practicing research institute, so there is no operating-company-asserts-competitor reading available.

Important caveat that refines (and partly corrects) the earlier sections of this analysis: the "Patent summary" section flagged a possible later assignment from ETRI to Sol IP. The stronger evidence now indicates no assignment was recorded — Mondaq reports USPTO assignment records reflect no Sol IP ownership of any US patent, and Sol IP litigates as exclusive licensee with ETRI still the owner of record. So the correct characterization is "unrecorded exclusive license / all-substantial-rights transfer," not "assignment." That distinction matters for standing and for any future ownership diligence.

Verify at: https://assignmentcenter.uspto.gov/ — search patent 9900067 and application 14147447 to obtain the exact reels/frames and correspondent that I was unable to pull here.

I'll search for the USPTO record and prior-art citations for US 9,900,067 specifically.

Let me dig into the specific citation lists for this patent.

Prior Art Analysis — US 9,900,067 B2 ("9900067")

⚠️ Headline sourcing limitation (read first)

I could not retrieve the face-of-patent "References Cited" (56) list for US 9,900,067 B2 from the sources reachable in this environment. The Google Patents text supplied to me as authoritative is truncated — it ends mid-sentence in the "MODE FOR INVENTION" section and contains no "Patent Citations" (backward) list. My four targeted searches (Google Patents citation URL, "References Cited," the application number 14/147,447, and inventor/inventor-name queries) returned mostly near-miss identifiers and unrelated documents — which I discarded per the literal-ID rule:

• Telstra part no. 9900067 (cast-iron pit crossbars) — not this patent.
• Greek procurement tender 9900067 (ΔΕΔΔΗΕ access-control purchase) — not this patent.
• NIEHS histology animal ID "HISTO: 9900067" (acrylonitrile study) — not this patent.
• Swiss/Dutch CH 9900067 W (CH 37298, aircraft door hinge) — not this patent.
• Indian High Court cause number APSWP 9900067/2001 — not this patent.

Consequence: I cannot present a verbatim, claim-by-claim table of the exact references cited on the '067 front page. Per the operating rule against fabrication, I will not invent a citation list. Instead, below I (A) report the one citation-data point I did confirm, and (B) give the technically on-point 802.11ac/VHT-SIG prior art I actually located, clearly labeled as candidate prior art in the same field — not certified as cited on the face of '067 — with a § 102 analysis and the priority-date caveat that governs whether each could even qualify.

Also noted: the task header says current date April 26, 2026, while the system context says 2026-09-19. This is the same inconsistency the prior "Litigation" section already flagged; I treat the later date as ground truth and do not let it affect the patent-art analysis (which is date-insensitive here).

A. Citation data I could confirm

Note the distinction: "Cited By 6" is forward art (later patents that cite '067 as background), not the prior art examined against '067. Do not conflate the two.

B. Candidate prior art in the same field (technically on-point; on-face citation unverified)

The '067 claims (per the earlier summary section) are directed to a receiver that gets (i) a two-OFDM-symbol first signal field (VHT‑SIG‑A) over a bandwidth that is a multiple of 20 MHz, (ii) a one-OFDM-symbol second signal field (VHT‑SIG‑B) whose content is the SIG‑B repeated a bandwidth-dependent number of times, (iii) common-vs-user-specific split between SIG‑A and SIG‑B, and (iv) SIG‑B carried on a selected spatial stream. The references below are the art that was in the air in this exact window (2009–2011 802.11ac drafting).

B1. Qualcomm — "Format of VHT‑SIG‑B and service fields in IEEE 802.11ac"

• Family: US 13/160,343 (filed 2011‑06‑14) → pub. US 2014/0198877 A1 (2014‑07‑17); WO 2011/159562; EP 2 577 927 (Qualcomm; inventors Van Nee, Van Zelst, Merlin, Sampath); priority US 61/354,930 (2010‑06‑15) and related US 201113149411 (2011‑05‑31).
• Where I found it: the RVO/EPO listing of granted EP patents (https://www.rvo.nl/.../IE_53_2015.pdf, entry "EP2577927 … Format of VHT‑SIG‑B and service fields in IEEE 802.11AC, Qualcomm") and FreePatentsOnline for US 2014/0198877 (https://www.freepatentsonline.com/y2014/0198877.html).
• Substance (highly material): express disclosure of the VHT‑SIG‑B bit budget by bandwidth — "twenty signal bits and six tail bits … if a transmission bandwidth is 20 MHz"; "one reserved bit and six tail bits … repeat the set … if 40 MHz"; "three reserved bits and six tail bits … repeat the set three times … if 80 MHz"; "160 MHz … repeat the group"; plus "copy the VHT‑SIG‑B onto a number of space-time streams that is the same as a number of space-time streams in the DATA field."
• § 102 potential: Claim 1 (SIG‑B content obtained by repeating a bandwidth‑dependent number of times; carried on the receiver's spatial streams) and dependent claim(s) reciting 26/27/29‑bit SIG‑B allocations. Caveat: priority 2010‑06‑15 is after '067's earliest priority (2010‑03‑12), so this is § 102 art only to '067 claims whose effective filing date is later than June 2010 (see §D).

B2. Qualcomm — "Constructing VHT‑SIG fields for reduced PAPR"

• Family: US 2012/0039198 A1 (pub. 2012‑02‑16; filed 2011‑08‑10; priority US 61/372,790, 2010‑08‑11); WO 2012/021624 A1; CA 2806235; JP 6325029 B2. Inventors Yang, Jones, Van Zelst, Sampath, Van Nee.
• Where found: FreePatentsOnline (/y2012/0039198.html), CA 2806235C PDF, and JP 6325029B2 (SumoBrain).
• Substance: construction/scrambling of the VHT‑SIG field (SIG‑A and SIG‑B) within the preamble; "example VHT‑SIG field values."
• § 102 potential: general § 102(a) art for the VHT‑SIG‑A/SIG‑B framework, but does not itself appear to disclose the bandwidth-scaled SIG‑B repetition or stream selection → weak standalone anticipation; better as § 103 background. Same June–August 2010 date problem.

B3. Qualcomm — "Method and apparatus for saving power by using signal field of preamble"

• US 2012/0182980 A1 (pub. 2012‑07‑19). Found at FreePatentsOnline.
• Substance: computes a CRC over the SIG field bits at the receiver and "may stop a decoding process if it fails to correctly decode" the VHT‑SIG‑A/VHT‑SIG field — i.e., power saving by early abort.
• § 102 potential: squarely relevant to the dependent claim reciting a CRC field used to detect errors in the second signal field and to the spec's teaching that "when an error of the scrambler seed is detected, the operation of PHY and MAC layers can be stopped … reducing power consumption." Date caveat applies (priority ~ Dec 2010/Jan 2011).

B4. Broadcom — "Group ID Concept for Downlink MU‑MIMO Transmission"

• IEEE 802.11‑10/0073r2, Joonsuk Kim et al., 2010‑03‑15. Found as an "Other Reference" cited on the face of Qualcomm's JP 6325029 B2.
• Substance: the Group ID by which a user determines which stream(s) to demodulate in DL MU‑MIMO — i.e., the common-vs-user-specific information split and the spatial-stream-selection concept.
• § 102 potential: the concept maps onto claim 1's "information common to the multiple receivers" and "at least one spatial stream … corresponding to the receiver." Date is three days after '067's earliest priority (2010‑03‑12) → § 102/§ 103 art only for later-effective-date claims.

B5. Qualcomm — "802.11ac Preamble"

• IEEE 802.11‑10/0876r0, Hemanth Sampath et al., 2010‑07‑13. Found in the EP 2 800 326 A3 search report (cited "Y" against claims 1–9 alongside WO 03/034674).
• Substance: 802.11ac preamble structure — legacy-compatible L‑SIG/L‑STF/L‑LTF followed by VHT‑SIG‑A/VHT‑SIG‑B; general 802.11ac frame layout.
• § 102 potential: § 102(a) background for claims 1 and 13 ("carried as a PPDU" / backward-compatible preamble); likely anticipates only the preamble-format elements, not the repetition logic.

B6. Lanante et al. — "IEEE 802.11ac Preamble with Legacy 802.11a/n Backward Compatibility"

• IEEE 802.11‑yy/0847r0, 2009‑07‑14 (slides 1–18). Cited as an "Other Reference" on JP 6325029 B2.
• Substance: designing the ac preamble so 802.11a/n devices still detect it. Pre-dates '067's priority (2009‑07‑14 < 2010‑03‑12) → clean § 102(a) art for dependent claim 2/3 ("first signal field received without applying MU‑MIMO" / "repeated over each 20 MHz sub-band") and the auto-detection/backward-compat limitation.

B7. Narasimhamurthy, Banavar & Tepedelenlioğlu — OFDM Systems for Wireless Communications

• Morgan & Claypool Publishers, 2010‑03‑10, pp. 32 et seq. (ISBN 1598297015). Cited "Y"/"A" in the EP 2 800 326 A3 report.
• Substance: textbook OFDM background (subcarrier/interleaving, diversity). § 102 potential: background (§ 102(b) printed publication); supports obviousness of interleaving/precoding, but a textbook is not a § 102 anticipation of the claimed SIG‑B repetition.

B8. WO 03/034674 A1 (Ericsson / van Nigtevecht et al.), 2003‑04‑24

• Cited "X" in the Qualcomm EP 2 800 326 A3 search report (relev. claims 1–9).
• Substance: OFDM preamble/signaling techniques. § 102 potential: only if a claim read on generic OFDM signaling; on its face it does not disclose MU‑MIMO SIG‑B repetition → more likely § 103 background.

C. Which claims each candidate touches under § 102

No candidate I found reads on all elements of claim 1 and claim 10 simultaneously with clean dated status, so at this stage this is a § 103-combination picture, not a clean § 102 single-reference knockout — subject to the priority-date throttle below.

D. The decisive date problem (why § 102 "anticipation" is fragile here)

'067's earliest priority is 2010‑03‑12 (KR 10‑2010‑0022122); the PCT was filed 2011‑03‑11, and the asserted claims are continuation claims of US 13/434,681. That means:

• For any '067 claim whose subject matter is supported by the 2010‑03‑12 disclosure, § 102 art must pre-date 2010‑03‑12. Under that date, B4 (2010‑03‑15), B1 (2010‑06‑15), B2 (2010‑08‑11), B3, B5 (2010‑07‑13) all post-date it and drop out; only B6 (2009‑07‑14) and B7 (2010‑03‑10) remain comfortably pre-critical-date.
• But '067's VHT‑SIG‑B bit-allocation / repetition-by-bandwidth subject matter (the FIGS. 45–48 material, the 26/27/29-bit allocation) appears to ride on the later Korean applications — 10‑2010‑0065898 (2010‑07‑08), ‑0066458 (2010‑07‑09), ‑0068167 (2010‑07‑14), ‑0072506 (2010‑07‑27). If those claims do not get the March 12 date (a standard § 112 written-description support question), the effective date slips to July 2010, which re-admits B1 (June 15) and B4 (March 15) — and potentially makes B1 a genuine § 102 reference.

Practical takeaway: whether the Qualcomm VHT‑SIG‑B-format reference (B1) anticipates the claim-1 repetition limitation turns entirely on the priority/§ 112-support determination for the SIG‑B repetition subject matter. This is exactly the kind of issue that would have been litigated in Sol IP v. AT&T/Sprint (E.D. Tex. 2:18‑cv‑00526/‑527/‑528) and is worth pulling from the invalidity contentions if you can access PACER.

E. How to obtain the authoritative face-citation list (so this can be closed out)

1. USPTO PatentCenter / PAIR for application 14/147,447 → "References Cited" (56) and the PTO‑892/1449 forms — the definitive list.
2. Google Patents → US9900067B2 → "Patent Citations" table (the sections that were truncated in the text I received).
3. WIPO Patentscope / EP Register for the parent PCT/KR2011/001742 → the ISR (PCT/ISA/210) "Documents Considered Relevant," which is the search-examiner's own prior-art list and the best proxy for what the family's examiners treated as art.
4. The related EP family member (EP 4020830 A1, same title) → its EPO search report lists cited art with X/Y/A categories.

Everything in Section B should be re-checked against items 1–4 before being called "cited by '067." Section B is technically sound as prior art in the field, but I have not verified that any particular reference appears on the '067 face.

F. Confidence and flags

Two explicit flags carried forward: (1) the prompt/system date contradiction (Apr 26 vs. Sep 19, 2026) noted earlier; and (2) the fact that no CAFC/IPR activity was located in the earlier sections is a general-search negative result, not a complete docket check — and it bears on prior art only indirectly (a PTAB IPR, if one existed, would carry the petitioner's own art list, which is another route to the definitive references).

I'll ground this analysis in verified prior-art references rather than relying on memory. Let me search for the specific prior art relevant to this patent's claims (VHT-SIG-B repetition, interleaving per stream, common vs. dedicated signal fields).

I found several highly probative references. Let me pin down the bibliographic details (dates, assignees) of the closest ones, since priority dates determine whether they're §102/§103 prior art.

Obviousness Analysis — U.S. Patent No. 9,900,067 B2

Grounded in: the authoritative Google Patents record for US9900067B2 (provided), the EPO search report / PISE record for the family (EP 4 020 830 A1), the IEEE 802.11ac-2013 text, and the prior-art references located and verified below.

Sourcing caveats (read first):

• The task says "use the results from the Prior Art section of this page." No such section was supplied in this prompt — there was no prior-art list attached other than the Google Patents "Prior art keywords" (bits, field, indicator, sig, vht) and the patent's own Background. I therefore built the prior-art basis from (i) the references the examiner/EPO actually cited on this family, and (ii) references I verified by search. I flag every date I could not confirm.
• The granted claim text I am working from was carried over from the earlier "Patent summary" section (a publication-stage reproduction of US 2014/0119327 A1) and is not certified to be the issued text. If the issued claims differ, the mappings below shift. I flag this again in §3.
• Date discipline matters enormously here. US 9,900,067 carries an earliest priority of 2010-03-12 (KR 10-2010-0022122). Under pre-AIA §102/§103, most of the technically closest references I found (Qualcomm's June 2010 VHT-SIG-B work) postdate that date and are therefore not §102(a)/(b) art and not §102(e) art (their §102(e) dates are also after March 2010). This materially weakens the obviousness case unless the claims lose the March 12, 2010 priority — which is a live question (§7).

1. Legal framework applied

• The '067 patent issued from a continuation (14/147,447, filed 2014-01-03) claiming benefit back to a pre-March 16, 2013 PCT/KR2011/001742 (2011-03-11). Assuming the claims are supported by the earliest Korean priority document, the pre-AIA statute governs (35 U.S.C. §§ 102/103 as in force before the AIA), including pre-AIA §102(e) — a US patent/application is prior art as of its effective US filing date (including a provisional it supports, In re Giacomini).
• Obviousness is evaluated under Graham v. John Deere (scope/content of art; differences; PHOSITA level; secondary considerations), with the KSR Int'l v. Teleflex flexibility: a combination is obvious where (a) the elements were known in the art, (b) there was a known problem for which a known solution existed, (c) the combination is a predictable use of prior-art elements, or (d) it is a "simple substitution" / "obvious to try" with a finite number of identified, predictable solutions.

2. Person of ordinary skill in the art (PHOSITA)

A PHOSITA here is an engineer with an M.S. (or equivalent experience) in EE/communications plus 2–4 years designing OFDM/MIMO WLAN PHYs, familiar with IEEE 802.11a/n and with the ongoing IEEE 802.11ac (TGac) draft work, including VHT-SIG-A/VHT-SIG-B preamble design, spatial-stream allocation, precoding/beamforming, and per-20 MHz sub-channel duplication. The '067 specification itself confirms this frame of reference by expressly invoking 802.11n tone counts (52 tones at 20 MHz / 108 at 40 MHz) and 802.11ac.

3. The claims under analysis (as carried over)

⚠️ Note the mismatch worth flagging explicitly: the specification's asserted point of novelty is different interleaving per stream / CDD to obtain frequency diversity and reducing SIG-B from two symbols to one. The claims as reproduced are directed instead to bandwidth-dependent repetition of SIG-B. That gap matters: it makes the claims broad enough to read onto the ordinary 802.11ac SIG-B construction, which is where the best (if date-limited) prior art sits.

4. Prior-art landscape with qualification

Key structural observation: the four elements E1, E2, E4 and much of E5 are pervasively present in date-qualified art (LG family; Broadcom family; the Marvell 802.11ac proposals read with 802.11n). E3 — the bandwidth-scaled repetition of SIG-B — is explicit only in the post-dated Qualcomm '574 and the 802.11ac-2013 standard, and is implicit in the earlier art through the known per-20 MHz duplication of the legacy/VHT-SIG-A field.

5. Obviousness grounds

Ground 1 — Fischer/Broadcom distributed-SIG family + IEEE 802.11n (+ Marvell 11-09/1174) → claim 1

Teaches/maps:

• E1/E4: first SIG field in the legacy portion, omni-directional, common to the multi-user packet (Broadcom US 9,553,649, claim 1 and Figs. 16A/26).
• E2/E4: second SIG field in the VHT portion, beamformed/precoded, providing SIG-B info (MCS, packet length) to specific devices.
• E5: second field transmitted via beamforming/steering → the per-stream nature.
• E3: per-20 MHz duplication of signaling fields in a channel-bonded 40/80 MHz PPDU is the established 802.11n behavior (legacy L-SIG/HT-SIG are duplicated across each 20 MHz sub-channel), and Fischer itself describes legacy vs. VHT portions in a bonded bandwidth. Marvell 11-09/1174 and 11-10/0070 address exactly how the 802.11ac preamble signals scale with bandwidth.

Motivation (KSR): A PHOSITA designing the VHT preamble knows 802.11n duplicates legacy signaling per 20 MHz for backward compatibility, and knows that a field decoded after VHT-LTF no longer needs that duplication but does need sufficient processing/frequency diversity at wider bandwidths. Applying the known per-20 MHz duplication/repetition structure to the second SIG field so that it grows with bandwidth is a predictable use of a known technique, with the recognized benefit (SNR averaging across replicated soft values). Fischer supplies both halves (two-tier SIG fields; beamformed second field), so the combination is a design-level, not inventive, step.

Weakness: the Broadcom art does not expressly recite bandwidth-scaled one-symbol repetition of SIG-B; a Patent Owner would argue E3 is only obvious with hindsight from the June-2010 Qualcomm proposal.

Ground 2 — LG control-information family (US 8,675,597 / US 8,718,173 prov. Feb 2010 / US 2016/0191292) + IEEE 802.11n/802.11ac framework → claim 1

This is the strongest date-qualified ground because one reference alone maps most elements:

E3 is supplied by the same design logic: because L-SIG/VHT-SIG-A are already replicated per 20 MHz (D2), and because the LG art expressly teaches that the number of OFDM symbols for the public field (2) exceeds that for the STA-specific field (1), the remaining step — scaling the content of the one-symbol STA-specific field with bandwidth — is the natural, expected completion of the same scheme. A PHOSITA motivated to keep SIG-B decodable with adequate processing gain would repeat its bit block in step with the number of 20 MHz sub-channels (2× at 40 MHz, 4× at 80 MHz, 8× at 160 MHz) — a finite, predictable set of solutions ("obvious to try," KSR).

Motivation: (a) same field of endeavor, same problem (reliable per-user signaling in MU-MIMO VHT WLAN); (b) both references expressly address the public/private signaling split and spatial-stream allocation; (c) the 802.11ac framework document (Marvell 11-09/1174 / 11-10/0070) frames the very design space. Combining them is a combination of prior-art elements according to known methods to yield predictable results.

Ground 3 — LG/802.11n combination + Marvell proposals to reach D2–D6

• D3 (VHT-SIG-A/VHT-SIG-B naming) and D6 (PPDU): explicit in both the LG and Broadcom families.
• D5 (CRC in the data field for the SIG field): expressly disclosed in LG's VHT-SIG-B/service-field and in Qualcomm '574 claims 10/21/72/90/118 ("the data portion comprises another field used for scrambler initialization, wherein the other field comprises a CRC … associated with the field indicating the length of the useful data"). If Qualcomm qualifies (see §7), D5 is squarely met.
• D4 (26/27/29 bits): the 26-bit @20 MHz value is date-qualified (LG US 8,675,597: "the number of information bits of the VHTSIG-B is 26"). The 27/29-bit values are, to my verified sources, a June-2010 Qualcomm contribution → date-problematic unless priority slips.

Ground 4 (conditional) — Qualcomm '574 (Van Nee et al.) + Sampath 11-10/0876 → claims 1 and dependents (near-anticipatory)

If the granted claims are not entitled to 2010-03-12 (see §7), Qualcomm '574 becomes devastating:

• E1: VHT-SIG-A = two OFDM symbols (Fig. 3, ¶[0057]).
• E2: VHT-SIG-B = one OFDM symbol, MU-specific, spatially multiplexed for different STAs (¶[0058], ¶[0061]).
• E3 literally: "determining a bandwidth … generating a block of bits … and repeating the block of bits a number of times according to the determined bandwidth" — 27×2 @40, 29×4 @80, 29×8 @160 (claim 85 / ¶¶[0070]–[0075], Fig. 9).
• E4: 20 information bits = 16-bit length + 4-bit MCS (user-specific); VHT-SIG-A carries the group/spatial-stream allocation.
• E5: VHT-SIG-B "may be spatially multiplexed for different STAs"; preamble carries a spatial-stream allocation field (¶¶[0059]–[0061]).
• D4: 26 precoded bits @20 MHz (claim 3); 27 @40; 29 @80 (claims 87/88).
• D5: CRC in the Service field (claims 10/21).
• D2: option of duplicating subcarriers in all 20 MHz subchannels just like VHT-SIG-A (¶[0065]).

Practically the whole claim set would be obvious over this one reference plus the background 802.11ac/802.11n knowledge — the only residual dispute would be the precise "number increases as bandwidth increases" wording, which '574 discloses numerically.

6. Why a PHOSITA would combine (motivation, consolidated)

1. Common field of endeavor & same problem — reliable, low-overhead per-user signaling in an MU-MIMO VHT WLAN; all references are 802.11 WLAN PHY/preamble documents.
2. Known technique, predictable result — per-20 MHz duplication of signaling is the 802.11n/802.11ac legacy mechanism; extending it to the dedicated field to grow processing gain with bandwidth does not change the principle of operation.
3. Recognized design tension drives the modification — the specification itself concedes the prior-art baseline: the common field "is transmitted through a simple iterative structure to [obtain] an SNR gain and a frequency diversity gain," while the dedicated field "cannot obtain both … although such a simple iterative structure … is used." A PHOSITA starting from that concession has an express incentive to fix the dedicated field by the same mechanism.
4. Finite, predictable options — with 20/40/80/160 MHz the repetition factor is a small integer set (1/2/4/8); KSR treats this as "obvious to try."
5. Industry convergence as objective evidence of predictability — IEEE 802.11ac-2013 §22.3.8.3.6/Table 22-14 ultimately standardized VHT-SIG-B as one symbol, 26/27/29 bits — exactly the claim D4 values. (The standard itself postdates the priority, so it proves predictability, not §102 art.)

7. The pivotal issue: effective priority date (this drives everything)

The entire strength of the invalidity case hinges on whether the granted claims (not the spec) are supported by the March 12, 2010 Korean application. If they are, the June–July 2010 Qualcomm/802.11ac-draft material is not prior art and Grounds 1–2 (weaker, element-E3-reliant) are the only options. If the claims instead take the July 8/9/14/27, 2010 Korean dates (because the 26/27/29-bit / repeated-block subject matter was added after March 12), then Qualcomm '574 (2010-06-02) and Sampath 11-10/0876 (2010-07-13) qualify, and the case becomes strong.

I cannot resolve this from the material available: Google Patents flags its priority date as "an assumption," and I did not retrieve the KR 10-2010-0022122 text, the parent 13/434,681 claims, or the prosecution file. This is the single most important thing to pull from PAIR/Global Dossier before asserting invalidity.

8. Rebuttals / why the claims might still survive

• Priority preservation: if the March 12, 2010 KR filing already disclosed VHT-SIG-B repetition and the 26/27/29-bit structure, all of the Qualcomm art is removed and the remaining grounds rest on combining Broadcom/LG with the general per-20 MHz duplication idea — a weaker, more hindsight-flavored case for the specific E3 wording.
• Different invention, narrower claims: the specification's actual contribution (per-stream interleaving or CDD to convert SIG-B repetition into frequency diversity, and collapsing two SIG-B symbols to one) is not squarely taught by the pre-March-2010 art. If the issued claims recite the per-stream-differential-interleaving/CDD limitation (the earlier summary could not confirm this), invalidity becomes substantially harder.
• Secondary considerations: the commercial and standards uptake (802.11ac adopted the VHT-SIG-B framework; the patent was asserted against AT&T/Verizon/Sprint and later against Honda/VW, and Sol IP joined Avanci's Wi-Fi 6 Vehicles pool as a licensor) is potentially probative of non-obviousness and copying/industry adoption — but settlement/licensing history is not automatically a "nexus," and no court has ruled on validity of '067 (see the prior Litigation summary). No IPR/PGR against '067 was found.
• Teaching away: one could argue the art taught away from reusing the VHT-SIG-A iterative structure on SIG-B, since the common-field iteration was understood to give SNR gain without frequency-diversity gain for a beamformed field. This is a real, if modest, counter-argument.

9. Conclusion

• If the claims keep the 2010-03-12 priority date: the strongest available §103 case is Broadcom's distributed-SIG-field family (2009 provisionals; US 8,599,804 / US 9,553,649) and/or the LG control-information family (Feb 2010 provisionals; US 8,675,597 / US 8,718,173 / US 2016/0191292), each combined with IEEE 802.11n and the Marvell 802.11ac preamble proposals (11-09/1174; 11-10/0070), to supply the per-20 MHz repeat-and-scale- with-bandwidth (E3) limitation. This is a plausible but contestable prima facie case — E1/E2/E4/E5 and D1/D2/D3/D6 are well covered; E3 and D4 (27/29 bits) are the weak links and would be attacked as hindsight.
• If the claims fall back to July 2010 (or later): US 8,867,574 B2 / US 2011/0299468 A1 (Qualcomm, Van Nee et al.) alone, optionally with Sampath 11-10/0876, renders claim 1 and most dependents (incl. the 26/27/29-bit and CRC-in-service-field dependents) obvious, bordering on anticipatory.

Confidence: High on the substance and dating of the LG, Broadcom, Qualcomm, and Marvell references and on the 802.11ac-2013 SIG-B values. Moderate on the claim-to-reference mapping, because the granted claim text was not independently verified. Low on the critical priority-determination question and on the exact priority/filing dates of US 2014/0198877 / US 9,246,649 (flagged as unverified).

Recommended next steps to firm this up: (1) pull the certified issued claims of 9,900,067 and the parent 13/434,681 claims; (2) pull the KR 10-2010-0022122 (and KR 10-2010-0065898/0066458/0068167/0072506) specifications to fix the effective priority date; (3) confirm the §102(e) dates (provisional support) for the Broadcom and LG references; (4) confirm the priority/filing dates of US 9,246,649 / US 2014/0198877.