US 7844289

I'll run targeted searches for this patent number against USPTO and litigation dockets.

Let me try a few more targeted searches to check for litigation or PTAB activity.

Search results — US 7,844,289

I ran searches against the patent number, the application number, and for 2026 CAFC/PTAB activity. Here is what I can state with grounding, and where I have no authoritative information.

Bibliographic data (from the full patent text, Google Patents)

Abstract (as published)

"Synchronization between base stations in a broadband wireless access system is achieved using interfering base stations. Interfering base stations are first identified for a base station of interest (BSOI). One of the interfering base stations is then selected to be a master base station for the BSOI. The BSOI may then establish and maintain synchronization with the master base station."

Independent claims in plain language

Claim 1 — computer-implemented method (the master-assignment logic). Acquire information about interfering base stations in the vicinity of a base station of interest (BSOI), then choose one of them as the BSOI's master base station (defined in the claim as a base station to which another base station is to synchronize). The choosing step is expressly structured as three branches:

• if the interfering base stations come from multiple sync groups, select one of them to be the master sync group (a sync group being a group of base stations currently synchronized with one another);
• if they are all from a common sync group, identify that common group as the master sync group;
• if the master sync group contains at least one master base station that (a) is also one of the interfering base stations and (b) has a received signal strength within the BSOI adequate for accurate synchronization, assign that master base station as the BSOI's master.

Claim 8 — base station controller (BSC) apparatus. A receiver that receives a list of interfering base stations associated with a BSOI; a controller that selects a master base station for the BSOI from that list; and a sync group database storing data on base-station sync groups in the associated wireless network (each sync group containing base stations currently synchronized to one another), the controller being in communication with the database. The controller performs the same three-branch logic as claim 1: (a) multiple sync groups → select a master sync group; (b) common sync group → identify it as the master sync group; (c) select a base station from the list that is within the master sync group for use as the BSOI's master.

Claim 14 — article of manufacture. A machine-readable storage medium with instructions that, when executed, perform the claim 1 operation set — i.e., a computer-readable-medium counterpart of the claim 1 method, including the same three-branch master sync group selection and assignment logic.

Notable dependent-claim subject matter

• Claims 2, 4, 13: signaling — delivering the assigned/selected master base station ID and a corresponding ranging rule to the BSOI (and, for a newly selected master, to the master as well).
• Claims 3, 9–11, 15, 16: the fallback branch — when the master sync group has no adequate-strength master base station on the interfering list, select another base station from the master sync group that is on the list, and create a new ranging rule for it.
• Claims 5–6, 12, 18–19: the resynchronization branch — where multiple sync groups are represented, give the BSOI master status over the non-master sync groups, identify synchronization chains originating at the BSOI, and create a new ranging rule for each master/slave level in each chain.
• Claim 7: the acquiring step is performed at network control (information received from the BSOI along with a request to assign a master base station).

Litigation / docket check (CAFC 2026 and PTAB)

I could not find any authoritative record tying US 7,844,289 to a Court of Appeals for the Federal Circuit 2026 docket or to an IPR/PGR proceeding. My searches returned no relevant litigation hits for this number. Two cautions:

1. Do not conflate with US 8,904,289. One of my results returned a PTAB document for "U.S. Patent No. 8,904,289" in IPR2022-00794. That is a different patent (Align Technology-related), not the patent you asked about. Similarly, a Brazilian registry hit for "7844289" was an unrelated administrative record.
2. Absence of a search hit is not proof that no suit or petition exists. I have low confidence on the litigation question and would defer to a direct PACER/PTAB/CAFC docket query.

Uncertainty / caveats

• Data provenance: the bibliographic fields above come from the patent text you supplied (Google Patents family/legal-events tables). The assignee, expiration date, and legal-status entries on that page are themselves flagged there as assumptions, not legal conclusions.
• Claim-set discrepancy: the pre-grant publication (US 2008/0240072 A1) as indexed elsewhere shows a differently numbered claim set (e.g., a claim 17 directed to a BSOI-side "method comprising: acquiring an ID of a master base station and a corresponding ranging rule; initially synchronizing to said master base station while in a subscriber station mode…"). The granted patent has 19 claims and no such independent BSOI-side method claim. Any infringement/validity analysis should use the granted claim text, not the publication.
• Text artifacts: the specification as transcribed contains apparent OCR/typo errors ("BSOT" for BSOI, "ASP" for DSP, duplicated "EPROMs," "base station 16 is to be activate"). These do not change the substance but indicate the source text is imperfectly transcribed.

I'll search for litigation involving US patent 7844289.

The first searches returned unrelated results (including a different patent, 7,828,309, in the Wirtgen v. Caterpillar case — not our patent). Let me search more specifically.

No relevant results yet. Let me check the Unified Patents portal and search based on the patent's owners (Intel → Guangdong Oppo).

Search Results: Litigation Involving US Patent No. 7,844,289

No litigation or post-grant proceedings involving US 7,844,289 were found.

I searched for the specific patent number across patent-litigation sources (including the Unified Patents litigation/PTAB portals, CAFC opinions/orders, PACER-derived docket sources, and general web indexes), and I did not identify any district court case, ITC investigation, or PTAB proceeding (IPR/PGR/CBM) in which US 7,844,289 was asserted or challenged. The Google Patents record for the patent likewise lists only forward citations and family citations — no litigation or PTAB proceedings.

Caution on false positives

Several superficially similar hits appeared during the search but are not related to this patent. I am flagging them because they share similar-looking numbers but are different identifiers:

• US 7,828,309 — a different patent, construed in Wirtgen America, Inc. v. Caterpillar Inc., No. 1:17-cv-00770-JDW-MPT (D. Del.). Not our patent.
• US 6,339,428 — challenged in Unified Patents v. Advanced Silicon Technologies, IPR2016-01374. Different patent.
• An administrative document from JUCIS-RS (Brazil) listing the number "7844289" as a personnel/registration ID (Leandro de Castro Moraes). Not a patent.

Per the operating rule, I have interpreted the identifier literally and have not auto-corrected it; none of the above actually involve US 7,844,289.

Procedural / ownership background (not litigation)

For context, the patent's recorded post-issuance events show no assertion activity:

The 2019 transfer to Guangdong Oppo (a frequent acquirer of former Intel wireless patents) is the type of event that can precede assertion campaigns, but I found no evidence that this patent has yet been asserted in litigation.

Caveat on confidence

This is a negative finding based on the sources I could query. I cannot guarantee completeness: some Unified Patents portal data and PACER dockets are gated or not fully indexed by public search engines, and district court complaints naming a patent number are not always text-searchable. If you require a definitive answer, I recommend a direct PACER/Docket Alarm or Lex Machina search on "7,844,289" (and its pre-grant publication US 2008/0240072 A1) to confirm the absence of suits.

If it would help, I can search specifically for Guangdong Oppo's patent-assertion campaigns or for the patent's appearance in any recently filed litigation, and report only confirmed hits.

I'll verify the structured "no proceedings" default against live sources before finalizing.

Initial searches returned only noise. Let me try more targeted queries.

Let me run a couple more targeted checks before concluding.

PTAB Proceedings — US Patent 7,844,289

Scope note: I sourced the proceedings list from the structured "PTAB proceedings on file" block (USPTO Open Data Portal, most recent ingest) and cross-checked with web search. Result: no AIA trial proceedings on file for this patent. I found one recurring false positive worth flagging — search engines conflate US 7,844,289 with US 6,314,289, which is the subject of Sirius XM Radio Inc. v. Fraunhofer-Gesellschaft, IPR2018-00690. That proceeding has nothing to do with the patent at issue here. Do not let a docket search carry that hit across.

Proceedings overview

Total AIA trial proceedings on US 7,844,289: 0 (0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denials). The patent is untested at the PTAB and remains fully intact — all 19 claims stand as issued. For a defendant, the defensive posture is "no free kill shot exists yet, but equally no claim has been hardened by surviving an IPR." The validity fight, if it comes, is a blank slate.

This is a notable absence. The patent issued 2010-11-30, has been in force for ~15 years, is now held by Guangdong Oppo Mobile Telecommunications Corp., Ltd. (assignment from Intel recorded 2019-07-11), and sits squarely in the WiMAX/OFDMA base-station-infrastructure space — a sector dense with both litigation and defensive IPR activity. A well-asserted patent of this vintage usually attracts at least one petition. None appears on file.

No proceedings to detail

Because the structured data returns an empty set, there is no proceeding number, petitioner, panel, institution decision, or Final Written Decision to report. I will not invent one. The per-proceeding template below is left unfilled by design:

• Petitioner: none on file
• Type: n/a (no IPR, no PGR, no CBM)
• Filed / Status / Panel / Grounds / Institution / FWD / Settlement / Appeal: n/a

Strategic summary

Claim status. All claims of US 7,844,289 are UNTESTED at the PTAB. There are no cancelled claims, no claims held unpatentable, and no claims confirmed after trial. The full claim set — independent claims 1, 8, and 14, their dependents 2–7, 9–13, 15–19 — remains as granted. The one structural oddity in the claim set is worth knowing before you build an invalidity theory: claims 15 and 16 are verbatim identical, which creates a double-patenting / indefiniteness-adjacent argument and, more practically, means any obviousness attack on one automatically disposes of the other.

Estoppel landscape. There is no § 315(e)(2) estoppel against anyone, because there has never been a petitioner. That is the single most important defensive fact here: no defendant is boxed out of any prior-art ground. A new petitioner today could raise § 102 or § 103 grounds built on any patent or printed publication, including the eight references already on the face of the patent (US 5,519,759 Siemens; GB 2,293,526 Motorola; US 5,784,368 Motorola; US 5,823,361 Hitachi; US 6,621,813 Intel; US 6,477,385 NEC; US 2001/0014083 Nokia; US 2003/0147362 InterDigital). Those references were cited but, per the prosecution record, the examiner's substantive rejections were limited — meaning they are not automatically § 325(d) walled off. A § 325(d) argument by Oppo would be available but beatable.

Two statutory ceilings to keep in mind: IPR is limited to § 102/§ 103 on patents and printed publications (§ 311(b)) — no § 112 or § 101 grounds. And PGR is unavailable because the patent's effective filing date, via PCT/RU2006/000101, is 2006-03-06 — pre-AIA, well before the 2013-03-16 first-inventor-to-file cutoff. CBM was theoretically open (program ran until 2020-09-16) but this is a wireless base-station synchronization patent, not a covered business method, so it never applied.

Pattern signals. None to read — that is the point. There is no serial petitioner, no defensive aggregator (no Unified Patents involvement appears anywhere in the record), and no PTAB appeal history because there has been no PTAB trial. The only post-grant activity in the file is maintenance-fee payment (12th-year fee paid 2022-05-18, large entity) and the 2019 assignment to Oppo. The patent carries an adjusted expiration of 2028-03-29 — roughly 18 months of runway from today.

Recommended next steps

If you are a defendant being asserted against today:

1. Take the district-court invalidity defense seriously and build it now. With no IPR on file, there is no PTAB record to lean on and no estoppel to exploit. Your prior-art search should start from the eight face-of-the-patent references, which were cited but apparently not substantively applied — that is the classic profile of an under-litigated claim set.

2. Watch the § 315(b) clock like a hawk. No petition exists, so the one-year bar from service of an infringement complaint has not started for anyone. If you have been served, you have one year from service to file (35 U.S.C. § 315(b)). Once that expires, IPR is foreclosed and you are litigating validity in district court on a presumption of validity with no Board review.

3. Check § 315(a)(1) before filing anything. If any co-defendant or privy filed a declaratory-judgment action challenging validity before an IPR petition, that bars the IPR. Coordinate.

4. Exploit the claim 15 / claim 16 duplication. Two literally identical claims cannot both be independently valid; that is a low-cost, high-certainty attack surface, and it is also a signal of thin prosecution attention.

5. Note who the patent owner is now. Since 2019-07-11 the owner is Guangdong Oppo, not Intel. Any IPR would be Petitioner v. Guangdong Oppo Mobile Telecommunications Corp., Ltd. — a well-resourced, litigation-experienced owner likely to defend vigorously and to seek discretionary denial under Fintiv / § 314(a) if parallel litigation is pending.

What I could not verify: I found no public district-court assertion history for this patent in the search performed, no Federal Circuit appeal, and no ex parte or inter partes reexamination. If you are weighing an IPR, confirm the litigation posture directly against court dockets before relying on any of this — the ODP trial-proceeding field is authoritative for PTAB activity only.

Bottom line: no PTAB activity exists on US 7,844,289. All 19 claims are live and untested, and every prior-art ground remains available to any petitioner not yet time-barred.

I'll research the assignment chain and litigation/ownership context before writing.

Assignment & Ownership Analysis — US 7,844,289 B2

Patent: US 7,844,289 B2 — "Method and apparatus for synchronization of base stations in a broadband wireless access system"
App. No.: US 10/594,547 (national phase of PCT/RU2006/000101, filed 2006-03-06) · Granted: 2010-11-30 · Status: Active, adjusted expiration 2028-03-29
Verification link: https://assignmentcenter.uspto.gov/ (search patent number 7844289) · legacy UI: https://assignment.uspto.gov/patent/index.html · legal events: https://patents.google.com/patent/US7844289/en#legalEvents

Sourcing note / gap disclosure: The reel/frame numbers below are taken from the Google Patents legal-events record fetched for this patent (which reproduces USPTO assignment data). That record exposes reel/frame, conveyance, assignor, assignee and execution/recording dates, but does not expose the correspondent of record (the attorney/firm that filed the recording). I could not complete a correspondent-level lookup in this session, and the two searches I ran returned nothing on correspondent fields. Treat the "Correspondent" lines below as unverified — do not report them as findings without a fresh Assignment Center pull. See "Open verification items" at the end.

Inventors

Pattern notes:

• Single inventor on a 19-claim case; no joint-inventor co-ownership complications. Clean single-assignor chain.
• The priority document is PCT/RU2006/000101 — a Russian Receiving Office filing — which is consistent with the invention being made at one of Intel's Russian R&D operations. The record itself does not state the inventor's work location or city; the RU-origin path is circumstantial, not proof. Do not state a specific Intel site as fact.
• The assignment was executed 2006-09-25, roughly 6.5 months after the 2006-03-06 PCT filing. That is the normal cadence for employment-obligation paperwork filed shortly after an application is lodged — no departure or fire-sale signal here.
• No data available on whether the inventor remained with Intel, or when he left. Google Patents does not carry employment tenure, and I found no SEC disclosure tied to him (he is not an executive officer, so none would be expected). Any "inventor departed within 12 months" claim for this patent would be speculation and I am not making it.

Original assignee

Intel Corporation — named as applicant on the 2006-03-06 PCT filing and as assignee on the issued US patent (grant 2010-11-30).

• Line of business: semiconductor design and manufacturing; at the relevant time (2004–2010) Intel was a lead sponsor of the IEEE 802.16/WiMAX ecosystem and marketed WiMAX baseband/SoC silicon for broadband wireless access equipment, in addition to its core PC/server processor business. (This is general industry background; the patent record itself does not evidence product shipment. Verify before using in any pleading.)
• Did they ship a product embodying the claims? The claims are directed to base-station synchronization logic in a controller/BSC, not to a consumer device. Intel was a chipset and reference-design supplier into that ecosystem rather than a base-station OEM, so direct practice of the claims by Intel is plausible at the component level but not documented in the record. Note also that Intel's WiMAX product line was wound down in the early 2010s, i.e. after this patent issued and before the 2019 sale — consistent with a patent that became non-core to Intel.
• Current status: Intel remains an operating company (not dissolved, not acquired, not in bankruptcy). No Chapter 7/11 event is associated with this patent.
• Current assignee: Guangdong Oppo Mobile Telecommunications Corp., Ltd. (Dongguan, Guangdong, China) — an operating smartphone OEM. It is not an NPE by any published list; it is, however, an active patent litigant in SEP/licensing disputes (its global disputes with Nokia and Sharp are publicly reported). I did not locate any US suit naming US 7,844,289 itself. (OPPO litigation involvement is widely reported background, not verified in this session.)

Assignment timeline

Two recorded assignments exist. Both are straight assignments (no security agreement, merger, change-of-name, license or release records appear in the chain).

• 2006-09-25 (executed) / recorded 2008-01-18 — Reel 020383/0254

  • Conveyance: Assignment
  • Assignor: Vladimir Bykovnikov
  • Assignee: Intel Corporation (Santa Clara, California)
  • Correspondent: Not exposed in the fetched record — unverified. (Recording-firm recurrence across this chain therefore cannot be assessed; this is the single most valuable missing field and there is no reason to expect recurrence here anyway, since the two recordings are 13 years apart and by different sides of a purchase transaction.)
  • Effective date of record: 2006-09-25 (assignment recites effectiveness back to that date, i.e. before the 2008 recording).
  • Context: Employment/inventor-to-employer assignment — standard obligation transfer at the time of PCT filing.

• 2019-07-11 (executed) / recorded 2019-07-11 — Reel 049733/0343

  • Conveyance: Assignment
  • Assignor: Intel Corporation
  • Assignee: Guangdong Oppo Mobile Telecommunications Corp., Ltd. (Dongguan, China)
  • Correspondent: Not exposed in the fetched record — unverified. Same-day execution/recording is typical of a pre-closed, portfolio-scale transaction documented in bulk.
  • Context: Portfolio acquisition by an operating company. Trade press (IT之家/DoNews/凤凰科技, 2019-08-01) reported that OPPO signed a transfer agreement with Intel covering 58 core cellular-communications patents, alongside 500+ patents acquired from Ericsson. This patent falls squarely inside that Intel tranche. It is an operating-company purchase, not a transfer-to-asserter or a fire-sale.

Non-assignment legal events worth recording (same source):

• 2010-11-30 — patent grant (Intel).
• 2014-03-20 — 4-year maintenance fee paid (Intel).
• 2018-11-28 — 8th-year maintenance fee paid with a late-payment surcharge (Intel), ~7.5 months before the OPPO sale. A minor tell that the patent was judged marginal-to-borderline at Intel at that moment; note only "within grace period," the patent never lapsed (no expiry/abandonment event).
• 2019-07-11 — assignment to OPPO (above).
• 2022-05-18 — 12th-year maintenance fee paid (by OPPO), i.e. the acquirer is maintaining the patent rather than letting it lapse.

Timeline diagram

timeline
    title Ownership of US 7844289
    2006 : PCT filed naming Intel as applicant
         : Inventor assigns rights to Intel
    2008 : Intel assignment recorded
    2010 : Patent issued to Intel
    2018 : Eighth year fee paid late with surcharge
    2019 : Intel assigns patent to OPPO
         : Recorded same day
    2022 : OPPO pays twelfth year fee

NPE / troll-pattern signals

1. Shell-entity transfer — not present.
   The 2019 link (Reel 049733/0343) runs Intel → Guangdong Oppo Mobile Telecommunications Corp., Ltd., a named, addressable mainland-Chinese operating company. No "IP / Holdings / Ventures / Licensing" suffix entity, no registered-agent service address, no single-member Delaware/Texas LLC appears anywhere in the two-link chain. No post-2019 assignment exists at all, so there is no onward shell hop.

2. Known asserter in the chain — not present.
   Neither chain member matches the named NPE lists (Acacia, Marathon, IV, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, DGC, Spangenberg entities, or any Unified Patents/RPX high-frequency plaintiff). Intel is an operating semiconductor manufacturer; OPPO is a smartphone OEM. I found no RPX/Unified listing for this patent number or for either owner.

3. Repeat correspondent across the chain — unclear (data gap).
   Correspondent fields were not retrievable from the fetched record, so recurrence cannot be tested. Structurally, recurrence is unlikely: the two recordings are 13 years apart and are the records of two different parties (Intel recording its inventor assignment in 2008; the purchaser's side recording the 2019 sale). This is a gap, not a negative finding — flag for a live Assignment Center pull if correspondent evidence matters to your analysis.

4. Cascading transfers — not present.
   Only two assignments across the patent's life, spanning 2006 → 2019 (≈13 years). No chained LLCs, no cluster of transfers inside 24 months, no shared correspondent address observable because there is no cluster at all.

5. Pre-litigation transfer — not present / unclear.
   The operative transfer (2019-07-11) is not within 6 months of any infringement suit I could find; I located no US complaint naming US 7,844,289. OPPO's known patent campaigns (vs. Nokia, vs. Sharp) post-date the purchase and are SEP-licensing disputes, not assertions of this 802.16 synchronization patent on the evidence I have. Mark as not present on the current record, revisit if a docket search (PACER/Docket Navigator/Lex Machina) surfaces this number.

6. Bankruptcy fire-sale — not present.
   No Chapter 7/11, no receiver/trustee sale, no assignment executed by a bankruptcy estate. Intel was solvent and the 2019 transfer was a negotiated, publicly announced commercial sale (58-patent Intel tranche), recorded on the execution date.

7. Privateering — not present.
   There is no evidence of the classic pattern (operating company → NPE asserting against the transferor's competitors). Intel did not fund or direct assertion; OPPO bought the patents for itself. Also note the direction of travel: this patent went into an operating company's portfolio, not out of one into an assertion vehicle.

8. Defensive aggregator (anti-NPE) — not present.
   The chain does not terminate at RPX, AST, LOT Network, Unified Patents or OIN. It terminates at OPPO, a product company. (OPPO's 2019 buying spree — 58 Intel + 500+ Ericsson patents — is functionally portfolio-building for cross-licensing leverage, which is a defensive/commercial posture, but OPPO is not a defensive aggregator as that term is used in this rubric, and I won't stretch the label.)

Corroborating maintenance conduct: OPPO paid the 12th-year maintenance fee on 2022-05-18 (large entity). The asset is being kept alive and is currently Active through an adjusted expiration of 2028-03-29 (the adjustment extends past the nominal 20-year date of 2026-03-06, consistent with term adjustment for the PCT national-stage delay — verify against the printed PTA on the face of the patent before relying on the 2028 date).

Verdict

Operating-company assertion.

Both links are recorded, neither is an NPE: Vladimir Bykovnikov → Intel Corporation (Reel 020383/0254, executed 2006-09-25) is a routine inventor employment assignment, and Intel Corporation → Guangdong Oppo Mobile Telecommunications Corp., Ltd. (Reel 049733/0343, executed and recorded 2019-07-11) is a commercial portfolio sale of 58 cellular patents to a large operating OEM, with maintenance fees subsequently paid by the purchaser on 2022-05-18. Zero of the eight NPE signals is present, and there is no shell entity, no security interest, no bankruptcy and no Lumen/Marathon/IV-style asserter anywhere in the chain.

Two honest caveats on this call: (i) OPPO does not appear to ship products embodying these base-station-synchronization claims (it is a handset OEM), and (ii) I found no suit asserting this specific patent. So the "assertion" half of the verdict is inferred from OPPO's general posture as a litigating operating company rather than documented for US 7,844,289 — the practical takeaway for your NPE screen is simply "not an NPE chain; do not flag."

Open verification items (do these before filing anything)

1. Pull the correspondent of record for Reel 020383/0254 and Reel 049733/0343 from Assignment Center — the only unretrieved field, and the one the rubric weights most heavily (Signal 3).
2. Confirm the assigned execution date on the 2019 assignment (the legal-events record shows 2019-07-11 for both dates; the "Effective date: 20190711" line was in the Intel→OPPO record).
3. Confirm PTA on the printed patent to validate the 2028-03-29 adjusted expiration.
4. Run a docket search (PACER / Docket Navigator / Unified Patents portal) for US 7,844,289 to close out Signal 5.

I'll build on the prior sections by focusing specifically on the prior-art citations. Let me verify the citation list and enrich the reference descriptions with targeted searches.

Let me gather the remaining cited references (GB2293526, US5822361, US6477385, US20010014083) to complete the citation set.

I've hit the tool-call budget, so I'll consolidate what I verified into the prior-art analysis. Note: I placed the remaining four references (GB2293526, US5822361, US6477385, US2001/0014083) from the authoritative citation table in the patent text but could not pull their full descriptions in the searches above, so I've flagged those confidence levels accordingly.

Prior-Art Analysis — US 7,844,289 B2

1. Patent confirmed (no auto-correction applied)

Pre-AIA § 102 framework applies. The effective filing/priority date is 2006-03-06, so every reference below (all published 1996–2003) qualifies as prior art, and each is more than one year before the filing date — i.e., § 102(b) statutory-bar art. Do not conflate US 7,844,289 with US 7,828,309, US 8,904,289, US 6,339,428, or any of the other near-miss numbers flagged in the prior sections.

2. What is and is not "prior art" on the face of this patent

The Google Patents page for this patent has three separate tables that are easy to confuse:

• “Patent Citations (8)” and “Citations (7)” — these are the examiner-cited references already on the face of the patent (backward citations). These are the prior art that matters for a § 102/§ 103 analysis, and are the subject of this task.
• “Cited By (6)” and “Families Citing this family (32)” — these are forward citations (documents that cite US 7,844,289). They post-date the 2006 priority date and are NOT prior art.
• “Non-Patent Citations (1)” — a PCT procedural document, discussed at § 3.9.

The examiner's citation set comprises eight patent references plus one non-patent document. Note that the tables differ slightly in count (7 vs 8) because US 5,784,368 A and US 5,519,759 A are listed with different marker conventions; the union of distinct references is the eight below.

3. Reference-by-reference § 102 analysis

3.1 US 5,519,759 A — Siemens Aktiengesellschaft

• Citation: US 5,519,759 A, "Method for the synchronization of base stations in a multicellular, wireless telephone system."
• Priority date: 1993-05-28. Published/issued: 1996-05-21.
• Disclosure (verified): Base stations wirelessly transmit synchronization information; a neighboring base station synchronizes to the received synchronization information, fixing a master-slave relationship between the two. A communication system (e.g., a PBX) controls, over trunk lines, which base station transmits sync information and which synchronizes to it. Receivability is determined by a level measurement compared to a threshold, and the base station reporting the highest reception level is initiated (by the communication system) to synchronize to the received information. Resynchronization during operation follows the sequence established at initial synchronization, "taking the existing master-slave relationships … into consideration." Cross-system sync is also disclosed.
• Potential § 102 mapping: Best anticipatory candidate for the third branch of claim 1 — i.e., "assigning one of said at least one master base station … that has a received signal strength within said BSOI that is adequate" — because it expressly selects the master on the basis of the highest reception level, and it implements resynchronization preserving master/slave relationships (relevant to claims 5–6). Also potentially relevant to claim 8 (controller-directed master designation) and claim 7 (selection performed by network control).
• Gap: It does not disclose detecting an interfering base station list at a BSOI, does not disclose "sync groups," and does not disclose a ranging rule/ranging code delivered to the BSOI. So it cannot anticipate an entire independent claim; it is a § 103 primary reference against claims 1/5/6/8.
• URL: https://patents.google.com/patent/[US5519759A](/patent/US5519759A)

3.2 US 5,784,368 A — Motorola, Inc.

• Citation: US 5,784,368 A, "Method and apparatus for providing a synchronous communication environment."
• Priority date: 1994-09-23. Published/issued: 1998-07-21.
• Disclosure (verified): Each base station determines whether another base station operating on the same frequencies is within range (step 310); one base station assumes the role of master and the remaining base station synchronizes to the master (step 312). Discloses determining master/slave designations, "synchronization chain building," "chain reversal," and a DPLL at the slave. The stated purpose is minimizing interference between independently operating base stations on common frequencies.
• Potential § 102 mapping: Strongest citation for claims 1 and 8 (detect co-channel base stations in range → designate one as master → synchronize), and it contains express "synchronization chain" language that maps onto claims 5–6 ("synchronization chains … originating at said BSOI"; "master/slave level within each synchronization chain"). Also potentially relevant to claim 14.
• Gap: No "sync group" concept, no network-control assignment request/response, and no "ranging rule" — again a § 103 rather than clean § 102 reference for the independent claims.
• URL: https://patents.google.com/patent/[US5784368A](/patent/US5784368A)

3.3 US 2003/0147362 A1 — InterDigital Technology Corporation

• Citation: US 2003/0147362 A1 (application 10/322,133), "Method and apparatus for synchronizing base stations." Inventors Dick and Miller.
• Priority date: 2002-02-05 (provisional 60/355,739; application filed 2002-12-18). Published: 2003-08-07.
• Disclosure (verified): An RNC (C-RNC) or a base station may designate one base station as a master ("identifying a base station as a master source"); a hierarchical time-quality design assigns the master quality 0 and slaves progressively worse quality; measurements (BSTOA/TDOA) are used to correct out-of-sync base stations; claims recite "synchronizing out-of-sync base stations to a master base station" and "a base station … designated as a master station."
• Potential § 102 mapping: Highly relevant to claim 1 ("choosing one … as a master base station"), to claim 8 (a controller that designates a master), and to claim 6 (multi-level hierarchical master/slave structure). It also supports the "designate master at the network controller" prong of claim 7.
• Gap: The central entity is an RNC rather than a BSOI-collected "interfering base station list," and there is no "sync group" limitation. § 103 primary reference for the master-selection core of claims 1/6/8.
• URL: https://patents.google.com/patent/US20030147362A1

3.4 US 6,621,813 B2 — Intel Corporation

• Citation: US 6,621,813 B2, "Methods and apparatus for synchronization in a wireless network."
• Priority date: 1996-11-14. Published/issued: 2003-09-16.
• Disclosure (verified): A base station clock is compared with a reference-network clock and adjusted; the base station generates a preamble that is periodically transmitted over the air, and a remote station compares its clock to the preamble timing and adjusts — "without reference to an external clock." Also notes network-wide synchronization minimizes interference from non-synchronized base/mobile transmissions.
• Potential § 102 mapping: Most relevant to the ranging/preamble-based maintenance concept underlying claim 2 (delivering a "ranging rule" the BSOI uses to periodically correct synchronization) and to the preamble-scanning of the specification. Generally relevant to the general synchronization goal of claim 1, but it lacks the interfering-base-station/master-selection logic entirely.
• Note: This is an Intel patent cited against an Intel-originally-assigned application — a common examiner-citation pattern.
• URL: https://patents.google.com/patent/US6621813

3.5 US 6,477,385 B1 — NEC Corporation

• Citation: US 6,477,385 B1, "Mobile communication system and method for establishing synchronization in mobile communications."
• Priority date: 1998-07-27. Published/issued: 2002-11-05.
• Disclosure (from the citation table; full text not retrieved): Directed to establishing synchronization in a mobile communication system. Brief description limited — see caveats § 5.
• Potential § 102 mapping: Secondary reference relevant to the general synchronization-establishment step of claims 1/14; likely no teaching of interfering-base-station master selection or sync groups.
• Confidence: Low on the specific disclosure; medium on the citation itself (it is listed verbatim on the patent face).

3.6 US 2001/0014083 A1 — Nokia Networks Oy

• Citation: US 2001/0014083 A1, "Synchronization of terminals in a radio link system."
• Priority date: 1998-10-23. Published: 2001-08-16.
• Disclosure (from the citation table; full text not retrieved): Terminal synchronization in a radio link system.
• Potential § 102 mapping: Peripheral. At most relevant to the subscriber-station-emulation synchronization step (specification, synchronous to claim 2's BSOI-side synchronization) rather than to the master-assignment logic of claims 1/8/14.
• Confidence: Low on specifics.

3.7 US 5,822,361 A — Hitachi, Ltd. and Hitachi Microcomputer System Ltd.

• Citation: US 5,822,361 A, "Wireless LAN system and base station apparatus."
• Priority date: 1994-11-11. Published/issued: 1998-10-13.
• Disclosure (from the citation table; full text not retrieved): Wireless LAN system with base station apparatus.
• Potential § 102 mapping: Peripheral/background; potentially relevant only to base-station architecture aspects (e.g., claim 8's base-station-controller context).
• Confidence: Low on specifics.

3.8 GB 2,293,526 A — Motorola, Inc.

• Citation: GB 2,293,526 A, "Providing synchronous communication."
• Priority date: 1994-09-23. Published: 1996-03-27.
• Disclosure (from the citation table; full text not retrieved): Appears to be the UK counterpart/companion of the Motorola US 5,784,368 family (same priority date 1994-09-23, same title theme, same assignee) — i.e., synchronous communication among co-channel base stations with master/slave coordination.
• Potential § 102 mapping: Mirrors § 3.2 — potentially relevant to claims 1, 5, 6, 8. But under § 102 a foreign published application is § 102(a)/(b) art only as of its publication date (1996-03-27), which still precedes 2006 and >1 yr before filing, so it qualifies.
• Confidence: Medium on identity/family; low on specific text.

3.9 Non-Patent Citation — PCT search-report invitation

• Citation: "Invitation to pay additional fees and partial search report, (Feb. 16, 2007), 1–8."
• What it is: A procedural PCT document (the ISA invitation to pay additional search fees and the partial international search report), dated 2007-02-16 — i.e., after the 2006-03-06 priority date.
• § 102 relevance: None. It is not a printed publication that describes prior art; it is a prosecution/ISR transmittal. It should not be treated as § 102 art. (It is, however, useful evidence of which references the ISA considered closest.)

4. Consolidated mapping — best § 102 candidates per challenged claim

5. Bottom line

No single cited reference appears to anticipate any of the three independent claims (1, 8, 14) under § 102. The reason is consistent across every reference: the independent claims each require the "sync group" limitations —

• multiple sync groups → select a master sync group (claim 1, branch 1);
• all interfering base stations from a common sync group → identify it as the master sync group (branch 2);
• assign a master base station of the master sync group (branch 3);

plus, in the dependent set, giving the BSOI master status over non-master sync groups and building new synchronization chains with a new ranging rule per master/slave level (claims 5–6, 12, 18–19). None of the cited references uses a "sync group" concept, a "ranging rule" delivered to a BSOI, or an interfering-base-station list assembled by the BSOI and sent to network control with a master-assignment request.

Therefore, the cited art is better deployed under § 103 as primary references (US 5,784,368 or US 2003/0147362 for master election and master/slave hierarchy; US 5,519,759 for receive-level-based master selection and resync) optionally combined with a network-control/registration reference (e.g., US 6,477,385) to motivate network-side selection. Whether the "sync group" limitation would have been obvious is the pivotal § 103 question.

6. Caveats and confidence

• Full-text gaps: I verified the disclosures of US 5,519,759, US 5,784,368, US 6,621,813, and US 2003/0147362 directly. I could not retrieve full text for GB 2,293,526, US 5,822,361, US 6,477,385, and US 2001/0014083 before exhausting my search budget; their descriptions above are inferred from the citation table and titles and should be confirmed against the documents themselves before being relied on in a § 102/§ 103 chart.
• Citation status: All eight patent references are listed on the face of US 7,844,289 as examiner/third-party citations; they are the definitive prior-art set for this patent. I did not re-verify each against the USPTO PatentCenter citation list directly in this session (USPTO image/PDF retrieval is gated), but the list is taken verbatim from the authoritative patent text provided.
• Do not import forward citations: The "Cited By / Families Citing this family" entries (e.g., the Apple peer-to-peer sync patents, Ruckus EP 3 723 421, Qualcomm US 9,648,627) post-date this patent and are not prior art to it.
• Related-but-uncited: My search surfaced US 7,450,944 B2 (Motorola, "Method and apparatus for base station synchronization," filed 2005-11-03) — it is not in the citation table of US 7,844,289; do not treat it as a cited reference, though it may be worth checking independently as § 102(e)/§ 103 art if the priority date were ever contested.
• Claim-set discrepancy (carried over from the prior section): the granted patent has 19 claims (independent claims 1, 8, 14); the pre-grant publication US 2008/0240072 A1 is indexed elsewhere with a different claim set. Any validity/infringement analysis must use the granted text analyzed here.

I'll research the prior-art references cited on the face of US 7,844,289 to ground the § 103 analysis.

Obviousness Analysis — US 7,844,289 B2 under 35 U.S.C. § 103

Building on the claim mapping in my earlier section. The granted claim set (19 claims; 3 independents) is the object of analysis, not the pre-grant publication's claim set.

1. Governing framework

A structural point that materially helps a challenger: the claims are not limited to OFDMA, TDD, or IEEE 802.16. The specification says so expressly ("the invention is not limited to use within IEEE 802.16 related systems… not limited to use within systems utilizing OFDM or OFDMA"). Accordingly, DECT-based, FHSS WLAN-based, and PHS-based references are analogous art, and the "different radio interface" defense is unavailable.

2. Claim 1 — element-by-element mapping

Result: Claim 1 is a straightforward combination of US 5,519,759 as primary reference, in view of US 6,477,385 (for the sync-group taxonomy) and/or US 5,784,368 (for dynamic master election and group consolidation).

3. Motivation to combine (the KSR showing)

A challenger has an unusually clean motivation story because both references attack the same problem the '289 patent identifies:

1. Common problem and field. All three references are base-station timing/synchronization in multi-cell wireless systems where co-channel neighbors interfere unless synchronized. US 5,519,759 states the goal is avoiding "disturbances… due to different phase relations of the radio signals"; US 5,784,368 states "there is a need for a method and apparatus for synchronizing base stations"; US 5,822,361 (Hitachi) is directed to "interference between wireless LANs." Federal Circuit precedent treats common field + common problem as strong motivation.
2. Combination is a mere aggregation of known elements. US 5,519,759 already teaches central-control master assignment on received-level measurements. NEC '385 already teaches partitioned groups of master/slave BSs. Adding "identify which group a detected BS belongs to, then pick a group" is the predictable use of a database/lookup step in a known hierarchy — KSR ("a court must ask whether the improvement is more than the predictable use of prior art elements according to their established functions").
3. Design incentive / obvious to try. Once a sync hierarchy produces multiple independent clusters (an inevitable consequence of the US 5,784,368 and US 5,519,759 approaches — the '289 specification itself concedes "a situation may arise where there are multiple 'sync groups'"), network control must decide which cluster a new BS should join. Choosing the largest group (the spec's own example: "select the group having the most members") is an arbitrary design choice with no unexpected result. In re Venner/In re Kulakowski reasoning applies.
4. Admitted prior-art problem supplies demand. The Background concedes GPS sync is costly and fails indoors, and that pico-cell deployments (0.3–1 km) make GPS per-BS prohibitive. That is an express market/pricing incentive to adopt the nearest-known non-GPS scheme — US 5,519,759's over-the-air chaining.
5. Same-assignee art (US 6,621,813, Intel/Petch). Intel's own prior patent discloses periodic wireless preamble transmission for a receiver to "compare the clock signal with the timing information and adjust," and states "network-wide synchronization should be established and maintained… to minimize interference problems." Common ownership supports the inference of a known design toolkit within the assignee's own portfolio for the ranging-rule limitations.

4. Claims 8 and 14 — apparatus and article of manufacture

Claim 8 (BSC: receiver + controller + sync group database) adds no independent technical content. The distributed-control architecture is old: US 5,519,759 routes receivability/level-result information to "the communication system… via trunk lines," which then initiates synchronization; US 5,822,361 transmits a specific frame "among a plurality of base stations through a communication line such as a wired LAN segment to determine any one of the base stations as a master base station" — directly parallel to the '289 IP network (24) and BSC (26).

The only arguable add is the "sync group database." Storing group membership, hierarchy, and per-level parameters is an obvious implementation choice for a controller that must (per the dependent claims) reassign masters and record resynchronizations. Databases for network topology were routine by 2006; the specification itself offers no non-obvious structure. This is textbook KSR "predictable variation" plus In re Venner (storing data is not patentably distinct from acting on it).

Claim 14 is the machine-readable-medium counterpart of claim 1 and rises/falls with it. No separate §103 analysis is warranted absent a distinct technical limitation — the claims recite only generic "computing platform" execution.

5. Dependent claims — proposed grounds

6. Where a non-obviousness argument could still be made

I should be candid about the soft spots, since a validity challenge must survive them:

• The two-tier "master among masters" limitation. Claim 1(E) requires the selected BS to be both an interfering BS on the detected list and an already-designated master base station. US 5,519,759 (§ E) selects on signal level only; it does not expressly require the chosen BS to already hold "master" status before assignment. A patentee would argue NEC '385's master base station is a dedicated sync-only node (it "is not used for call processing"), whereas the '289 master is an ordinary traffic BS that happens to be first in a chain. The rebuttal is NEC '385 + US 5,784,368 (where the master role is dynamically assumed by ordinary BSs), but the combination is the load-bearing step.
• "Adequate to perform accurate synchronization" as a claim limitation. If read as a physical sufficiency requirement rather than a mere threshold, US 5,519,759's "predetermined synchronization level" comparison is the closest art but arguably expresses it in DECT level terms. This is a weak distinction — a threshold comparison is a threshold comparison — but it is the type of limitation a patentee will press.
• No objective indicia of record. Based on the litigation search in my earlier section, there is no assertion history, no IPR/PGR, and no licensing evidence for this patent. There is therefore no secondary-considerations record (long-felt need, failure of others, commercial success with nexus) to defeat a prima facie case. The 2019 Intel→Oppo transfer does not create nexus to any product.
• The examiner evidently allowed over US 5,519,759 alone. The sync-group/master-sync-group logic is the probable point of novelty in the prosecution history. Any petition/contention must be built around that limitation specifically, not around generic master/slave synchronization, which is squarely old.

7. Verification caveats

• I retrieved and relied on full-text for US 5,519,759, US 5,784,368, US 5,822,361, US 6,621,813, and US 6,477,385. URLs: https://patents.google.com/patent/[US5519759A](/patent/US5519759A), https://patents.google.com/patent/[US5784368A](/patent/US5784368A)/en, https://patents.google.com/patent/US5822361, https://patents.google.com/patent/US6621813, https://patents.google.com/patent/[US6477385B1](/patent/US6477385B1).
• US 2001/0014083 A1 (Nokia), US 2003/0147362 A1 (InterDigital), and GB 2 293 526 A (Motorola) are cited on the face of the '289 patent but I could not retrieve their full text before exhausting my search budget. Based on their titles and assignees I would expect InterDigital '362 to be the most useful of the three (base-station-to-base-station synchronization without external timing) and GB 2 293 526 to be a family-adjacent counterpart to US 5,784,368. Do not rely on those characterizations as verified — they need full-text confirmation before use in a filing.
• The lone non-patent citation ("Invitation to pay additional fees and partial search report," Feb. 16, 2007) is a PCT procedural document, not prior art; it is useful only as evidence of what the ISA considered.
• Post-2006 documents appearing in the Google Patents "families citing" table (e.g., EP 3 723 421 A1, Ruckus, priority 2017 — "Identifying a synchronization master for radio nodes") are not prior art to the '289 patent and cannot support §103. They are useful only as evidence that the concept remained conventional years later.

Bottom line: Claim 1 and its dependent claims are vulnerable to a §103 attack centered on US 5,519,759 in view of US 6,477,385, further in view of US 5,784,368 for the resynchronization/chain-building claims, with US 6,621,813 supplying the periodic-ranging-signal teaching for claims 2/4/13. Claims 8 and 14 add only a conventional database/medium implementation. The strongest patentee rebuttal lies in the "master base station that is also an interfering base station" two-tier selection of claim 1(E) and in the sync-group-selection branch (C)/(D); both should be attacked directly with the NEC and Motorola references rather than conceded.