US 5566168

I'll verify the patent details against current sources, including any litigation activity.

US Patent 5,566,168 — Verification Summary

Search performed: Google Patents / FreePatentsOnline / USPTO.report / EPO Global Patent Index / UPC & general docket search for "5566168" and "CAFC 2026."

Bibliographic Data (verified against multiple sources)

The family includes EP 0662775 B1, JP 3329821 B2, KR 960701534 A, CN 1083187 C, CA 2156739 C, WO 1995019079 A1, AU 688851 B2, and others (18 countries). Source: https://patents.google.com/patent/US5566168/en and http://data.epo.org/gpi/EP0662775B1

Abstract (verbatim)

"A radio access method for facilitating communication between at least one first station and a plurality of second stations is disclosed. First, each signal intended for transmission is buffered at a first station. The signals are then divided into equal length segments. The signal segments intended for a particular one of the second stations is transmitted using a corresponding time slot in a regularly repeating time multiplex frame. The signal segments transmitted by the first station are received at at least one of the second stations and the signal segments are assembled from successive corresponding time slots to reconstruct said intended signal. A transmit frequency channel uniquely associated with the corresponding receive time slot is determined at the second station. Finally, a signal intended for transmission to the first station is buffered in the second station and compressed for transmission using the transmit frequency channel during substantially the entire time period that the second station is not receiving."

Plain-Language Overview of the Independent Claims

Claim 1 — Satellite/hub TDM downlink with inter-beam time-slot interleaving

A satellite telephone system (satellite + hubstation + PSTN + outstations), where:

• The satellite has a multi-beam antenna, multiple transmitters (one per beam), and multiple receivers that take signals from the hub and retransmit them through the beams.
• The hubstation has multiple multiplexers, each packing the signals destined for a given beam into active time slots of a TDM frame that also contains inactive time slots.
• The hub's transmitters send each TDM signal to the satellite, which retransmits it in the corresponding beam.
• The key limitation: time-slot allocating means that align the active time slots in one beam with the inactive time slots in neighboring beams. In other words, interference between adjacent beams is avoided by time reuse (staggering active sub-frames) rather than by splitting the frequency spectrum — allowing each beam to use the full bandwidth.

Dependent claims 2–6 add: (2) saturated travelling-wave-tube transmitters; (3) class-C amplifiers run at max efficiency; (4) powering those amplifiers down during inactive slots; (5) packing a beam's active slots into a contiguous subframe; (6) ensuring neighboring beams' subframes do not overlap.

Claim 7 — Full satellite/control-station architecture with paired uplink-frequency and downlink-time-slot allocation

A two-link communication satellite system spanning satellite and control (ground) station:

• Satellite side (uplink): a multi-beam antenna receives uplink signals from outstation groups in different earth regions; per-beam receivers feed transmitters that relay the signals to the control station. Separately, receivers take TDM signals from the control station, and per-beam transmitters relay them down to the outstations.
• Control-station side: receivers pick up the relayed uplink signals; transmitters send TDM signals to the satellite for downlink retransmission.
• The key limitation: time-slot and frequency allocating means that pair each outstation's uplink frequency with its downlink receive time slot, such that the allocated downlink slots and associated uplink frequencies in one beam correspond to unallocated slots and frequencies in neighboring beams. So the TDM downlink time-reuse plan automatically produces a matching FDMA uplink frequency-reuse plan, giving inter-beam/cell interference separation on both links.

Notes on the Specification's Broader Teachings (context for the claims)

The independent claims are the satellite/beam-reuse aspects of the disclosure. The specification's broader disclosure — much of which is claimed in the parent US 5,539,730 rather than here — includes:

• TDM downlink + FDMA uplink without a duplexer: the mobile receives in one downlink time slot and transmits during essentially all the remaining frame with its transmit data compressed (e.g., 511/512ths of the frame), avoiding simultaneous transmit/receive and the need for a duplex filter.
• Sub-band/orthogonality schemes for handling overlapping mobile transmissions (FIGS. 2–4), including mid-burst frequency shifting via systematic phase rotation in DSP rather than fast synthesizer switching, and alternating upper/lower half-channel on successive bursts.
• Bandwidth extension for Doppler on non-geostationary links, expanded by TDMA or by CDMA (e.g., access codes 1100/1001/1111/1010) to preserve capacity without raising peak mobile power.
• "Time reuse" 3-cell plan: in a 512-slot format, cells 1/2/3 are illuminated for the first/second/third 170 slots respectively, with mobiles replying on uplink FDMA channels 1–170 / 171–340 / 341–510; two remaining slots/frequencies reserved for paging and random access.
• Satellite payload details (FIGS. 10–11): class-C amplifiers and saturated TWTs drawing near-zero current in inactive slots, exploiting TDM's proportional current turndown versus the square-root turndown of FDMA/CDMA.

Litigation / Docket Check (CAFC 2026)

No CAFC 2026 docket activity was found for US 5,566,168, and none should be expected. Two independent reasons:

1. The patent expired 2014‑01‑11 (Google Patents legal status: "Expired – Lifetime"; anticipated expiration recorded). Note US patent term is not extendable here, and the 2014 expiry falls before the 20-year-from-filing/priority computation would otherwise apply because the priority date is 1994‑01‑11.

2. Search results returned several unrelated "5566168" hits that must not be conflated with this patent. Specifically:

   • JP Patent 5566168 — a Japanese GNSS receiver/velocity-correction patent (application 2010‑086116, filed 2010‑04‑02, published 2011‑10‑27). This is a completely different, unrelated patent sharing the same numeric string. (J‑GLOBAL)
   • UPC case 1568/2025 — the "1568" here is a UPC case number for Ericsson v. Transsion (patents at issue: EP 2 712 236 B1, EP 3 836 631 B1, EP 3 245 744 B1), not US 5,566,168 and not a CAFC matter. (unifiedpatentcourt.org orders, 13 May 2026 / 27 May 2026 / 15 June 2026)
   • Ericsson's active 2026 controversies (e.g., the LDPC/'893 patent ITC/PTAB proceedings at ptacts.uspto.gov) involve entirely different patents.

Uncertainty disclosure: I cannot claim to have exhaustively queried the CAFC's own docket system (I relied on web search, not a direct CAFC PACER/CM-ECF query), so I state with moderate-but-not-absolute confidence that no 2026 CAFC case names this patent. However, given the 2014 expiration and the fact that the patent is long past any damages window, a 2026 CAFC appeal involving it is effectively implausible.

Corroborating Sources

• https://patents.google.com/patent/US5566168/en
• https://www.freepatentsonline.com/5566168.html
• https://uspto.report/patent/grant/5566168
• http://data.epo.org/gpi/EP0662775B1 (family/assignee confirmation)
• https://patents.google.com/patent/[US5539730A](/patent/US5539730A) (parent, same title)

I'll search for litigation involving US patent 5566168 specifically.

Let me search more specifically for litigation involving this patent.

Let me check specific patent litigation databases and searches for this exact patent number.

Litigation Search: US Patent No. 5,566,168

Bottom Line

No litigation specifically involving U.S. Patent No. 5,566,168 was identified in the sources searched. I could not find any district court case, Federal Circuit appeal, or PTAB proceeding in which US 5,566,168 was a patent-in-suit, an asserted patent, or a challenged patent.

What I Searched and What I Found

I ran targeted queries against patent-litigation resources (including the Unified Patents portal, PACER/Federal Circuit opinion repositories such as CourtListener, and general web indices), using the exact number "5566168" and "5,566,168."

Key caution — several near-miss patents that must NOT be confused with 5,566,168:

Note: The apparent "hits" on "5566168" were almost all citation/prior-art references (e.g., international search reports listing "US 5566168 A") or the unrelated Japanese patent — not litigation records.

Case Table

Important Caveats

1. Confidence level: Moderate that no litigation exists. Absence of results across the resources I could query does not prove the patent has never been litigated. The patent is a divisional of US 08/179,954 (issued as US 5,539,730) and is assigned to Ericsson Inc. (originally Ericsson GE Mobile Communications Inc.). Ericsson is a prolific litigant, so an assertion of this or its sibling patent could exist in a record I did not surface.

2. Most-likely confusion risk: If anyone reports "the '616 patent" in an Ericsson or cochlear-implant context, verify whether it is US 5,609,616 (cochlear implants — Alfred E. Mann v. Cochlear) or US 5,566,168 (this one). These are frequently conflated because of the shared "616" suffix.

3. Recommended next steps to confirm: Query the USPTO Patent Center "Litigation" / assignment records, Darts-IP, Lex Machina, or RPX Insight using the exact patent number 5,566,168, and check the patent's transaction history for any recorded licenses or assignments that might hint at assertion activity.

If you can point me to a specific index or docket you believe contains a case, I can drill into that record directly.

I'll start by verifying the ODP-provided default against public sources, since the task directs me to flag any proceedings the ODP hasn't indexed.

The first pass found no trial proceedings. Let me run targeted confirmatory searches on the patent's litigation/PTAB footprint and Unified Patents' portal.

Let me do a final check for litigation or Federal Circuit activity that could have spawned (or resulted from) an AIA trial.

PTAB / AIA Trial Analysis — U.S. Patent No. 5,566,168

Patent: TDMA/FDMA/CDMA hybrid radio access methods
Inventor: Paul W. Dent
Original assignee: Ericsson GE Mobile Communications Inc. (current: Ericsson Inc.)
App. No.: 08/475,303 · Filed: 1995-06-07 (divisional of 08/179,954, filed 1994-01-11)
Priority: 1994-01-11 · Granted: 1996-10-15 · Claims: 7
Status: Expired – Lifetime (anticipated expiration 2014-01-11)

Proceedings overview

There are zero AIA trial proceedings on file against US 5,566,168 — no IPRs, no PGRs, no CBM reviews — so there is no breakdown by status to report; the patent has never been tested at the PTAB, and the bottom line is not "hardened" but "abandoned": it expired 2014-01-11, meaning any demand letter citing these claims today is asserting a dead patent against conduct that predates the § 286 damages window.

I need to flag the evidentiary basis for that conclusion plainly, because the two sources disagree in a way that matters:

1. The structured "PTAB proceedings on file" block in this prompt is empty. The prompt states the USPTO Open Data Portal returns no AIA trial proceedings for this patent as of the most recent ingest. That is the canonical list, and it is nil.
2. My independent web searches surfaced nothing to contradict it. Targeted queries on the patent number plus "IPR," "inter partes review," "post-grant review," "covered business method," and "PTAB" returned only the patent's own family/publication records (Google Patents, FreePatentsOnline, USPTO.report), foreign search reports citing the patent as prior art, and unrelated patents that happen to bear the number "5566168" (e.g., a Japanese national patent 5566168 on a GNSS receiver, and an SEC filing identifier). No petition, institution decision, FWD, or appeal docket appeared.

Caveat, stated honestly: I could not complete a live query against PTAB E2E / the PTAB API before exhausting my search budget, so I am relying on the ODP block (authoritative and nil) plus negative web results. I found no proceeding number to report, and I will not invent one. If you need a belt-and-suspenders confirmation, the direct check is the PTAB Patent Trial and Appeal Board End-to-End system (https://ptacts.uspto.gov) and the USPTO Patent Center "Proceedings" tab for application 08/475,303.

No proceeding sections follow, because there are no proceedings to detail. Each of the requested fields (petitioner, panel, grounds, institution decision, FWD, settlement, appeal) would require fabrication. I'm not doing that.

Strategic summary

Claim status. All seven claims — independent claims 1 and 7, and dependent claims 2–6 — are UNTESTED at the PTAB. None is canceled by any AIA trial, because no AIA trial was ever instituted. The "CANCELED vs. SUSTAINED vs. UNTESTED" ledger comes back entirely in the third column. The claims as issued are:

• Claim 1 — satellite + hubstation system: multiple-beam antenna, multiple transmitters per beam, multiple receivers, hubstation multiplexing into active TDM slots, and time-slot allocating means so each beam's active slots coincide with neighboring beams' inactive slots.
• Claims 2–6 — dependents of claim 1 (saturated TWTs; class C amplifiers; power-down during inactive slots; active slots packed into a subframe; non-overlapping neighboring-beam subframes).
• Claim 7 — system claim covering the satellite uplink/downlink relay plus hubstation time-slot and frequency allocating means, with the beam-to-beam slot/frequency complementarity limitation.

The closest thing to validity testing on this family is prosecution and foreign counterpart examination, not PTAB. Note the EP family member EP0662775B1 and the JP member JP3329821B2 were granted, and the Chinese counterpart CN1083187C survived — but foreign grants carry no estoppel and no preclusive effect here. The WO/ISA search reports in the record cite EP 0 662 775 A1 (Ericsson GE Mobile Inc.) — i.e., the family's own sibling — as the closest art, which is a hint that the art landscape closest to these claims is internal to the patentee, not third-party.

Estoppel landscape: there is none to navigate. Because no IPR was ever instituted, § 315(e)(2) estoppel has never attached to anyone. No petitioner, real party in interest, or privy is barred from raising any ground. A defendant today has the full invalidity menu: § 102/§ 103 on patents and printed publications (IPR-eligible), plus § 101 eligibility and § 112 written-description/enablement/indefiniteness defenses, which are not IPR-eligible anyway and are always available in district court. In other words, this patent gives a defendant maximum freedom of action — the opposite of the hardened-patent scenario. Contrast that with the family history: the parent US 5,539,730 (issued from 08/179,954) and this divisional US 5,566,168 both went their whole lives without a single AIA challenge.

Pattern signals: the absence is the real story. Well-asserted patents attract IPRs — that's the empirical rule, and it's why the task frames a clean PTAB record as itself a signal. Here the signal cuts against the patentee for a mundane and decisive reason: the patent expired 2014-01-11. The AIA IPR regime opened for business on 2012-09-16, leaving only ~16 months in which an IPR against this patent could even have been worth filing, and the patent was a 1994-priority, hub-and-satellite architecture claim set tied to 1990s satellite systems (Iridium/Inmarsat-era design) rather than a 2010s smartphone/NPE assertion target. There is no serial petitioner, no defensive aggregator (Unified Patents or RPX) in the chain, and no patent-owner appeal activity, because there is no trial history at all. Unified Patents appears in the search landscape only in the generic sense that its portal indexes Ericsson patents; it has not run a contest against this one.

Recommended next steps

If you are a defendant facing assertion of US 5,566,168 — lead with expiration, not with PTAB. There is no FWD to link to and no canceled claim to quote; the strongest defensive fact is the patent's own record:

• The patent is Expired – Lifetime with an anticipated expiration of 2014-01-11 (20 years from the 1994-01-11 parent filing date under the URAA term rule; the alternative 17-years-from-issue date, 2013-10-15, is earlier). Source: https://patents.google.com/patent/US5566168/en and the USPTO Patent Center record for 08/475,303.
• Consequence under 35 U.S.C. § 286: no recovery for infringement more than six years before the complaint is filed. A complaint filed today (2026-09-28) reaches back only to 2020-09-28 — after the patent expired. All accused conduct necessarily ceased on or before 2014-01-11. Absent a previously-filed, still-pending action that already tolled the window, a fresh assertion of this patent against present-day conduct has no recoverable damages period and no ongoing infringement to enjoin.
• Practical takeaway: a demand letter citing claims 1 or 7 of this patent should be answered with the expiration date and § 286, not with an IPR. Filing an IPR against an expired patent is generally a wasteful exercise (the Board has repeatedly declined to institute where no live controversy remains), and it would buy you nothing that expiration doesn't already give you.

If you nevertheless need an administrative validity challenge (e.g., to knock out the patent as a predicate for a collateral estoppel or a related-family dispute), the tools are limited and you should not expect PTAB to be one of them: an expired patent cannot support an IPR that matters. The realistic avenues are district-court invalidity and, for the sibling US 5,539,730, the same expiration analysis (it carries the same 1994-01-11 priority).

If you are a patent owner or licensor: the correct advice is the reverse of the usual — do not invest in "hardening" a PTAB record that doesn't exist. Neither the '168 patent nor its parent '730 is enforceable against post-2014 conduct, and any licensing program premised on them should be re-underwritten to confirm it isn't resting on expired rights.

Verification step I could not complete (flagged so you can close it): run the definitive live checks before relying on the "zero proceedings" finding — (1) USPTO Patent Center, application 08/475,303, "Proceedings" tab; (2) PTAB E2E search for patent number 5,566,168 at https://ptacts.uspto.gov; (3) CourtListener docket search for "5,566,168" to confirm no live litigation tolling the § 286 window. My searches returned no litigation or Federal Circuit activity, but I did not get a confirmatory hit either way, so treat that sub-finding as unverified rather than established.

Summary in one line

No AIA trial has ever touched US 5,566,168 — zero proceedings, zero estoppel, all seven claims untested — but the defensively relevant fact isn't the empty PTAB docket; it's the 2014-01-11 expiration, which makes a present-day assertion of these claims dead on the damages element under § 286.

I'll research the assignment chain for US 5,566,168, starting with the USPTO Assignment Center and cross-referencing sources.

Let me dig into the USPTO assignment records specifically and check for any post-issuance transfers.

Let me look for the actual assignment records in the USPTO legacy assignment database and any Ericsson name-change records.

Assignment & Ownership Analysis — US 5,566,168

Method note / limitation up front. I ran targeted searches against the USPTO Assignment Center and its legacy index (assignments.uspto.gov, legacy-assignments.uspto.gov), Google Patents legal events, FPO, and general web indices. I was unable to retrieve the reel/frame-level assignment records for this patent in this session — the Assignment Center is a JavaScript query interface that does not expose its result tables to web indexing, and no legacy assignment PDF for app. 08/475,303 surfaced. I therefore report only what is independently corroborated below and explicitly mark unavailable fields rather than fabricating reel/frame numbers, execution dates, or correspondent names. Per your rule, I do not treat the absence of retrievable records as proof of absence of records.

Inventors

• Only one inventor. The specification does not name co-inventors, and the AIA-format bibliographic block lists Dent alone.
• Dent was a long-tenured Ericsson/GE engineer, not a transient inventor. He is one of the most prolific named inventors in the Ericsson portfolio (e.g., the LOGPOLAR transmitter work cited in this very specification as U.S. Pat. No. 5,048,059, also his). There is no indication that Dent (or any co-inventor) departed the original assignee within 12 months of filing — the single-inventor, single-employer pattern here is the ordinary "employee invention assigned by operation of the employment agreement" case, not the multi-inventor mass-departure pattern that precedes portfolio fire-sales.
• Prosecution-chain note relevant to inventorship: this patent is a divisional of app. 08/179,954 (filed 1994-01-11, issued as US 5,539,730). Dent is the inventor on both; the parent/divisional split reflects a unity-of-invention restriction (apparatus/method claims vs. the satellite/hub claims), not a change in inventive entity.

Original assignee

• Entity named on the issued patent: Ericsson GE Mobile Communications Inc. (Google Patents "Original Assignee"; the EP family member EP 0 662 775 lists "ERICSSON GE MOBILE INC" as applicant).
• What it was: a joint venture between L.M. Ericsson and General Electric, formed 1989, running the combined GE/Ericsson mobile-radio business (land-mobile radio, the U.S. AMPS cellular infrastructure and subscriber lines, mobile data, defense systems). Principal U.S. operations in Research Triangle Park, North Carolina. This is a genuine operating company with a large product line, not a holding vehicle.
• Corporation status / current owner: Ericsson acquired GE's interest and the entity's name was changed to Ericsson Inc. (the "Current Assignee" recorded on Google Patents). Ericsson Inc. is a wholly-owned subsidiary of Telefonaktiebolaget LM Ericsson (publ) — an active, publicly traded operating company (Nasdaq: ERIC). Ericsson is not in bankruptcy, was not dissolved, and has not been acquired by any third party.
• Did Ericsson ship a product embodying the claims? Split answer, and it matters for the verdict:
  • The broader TDM-downlink/FDMA-uplink disclosure (the parent '730 subject matter) maps closely onto Ericsson's commercial cellular access technology.
  • But the claims actually at issue here (claims 1–7) are satellite/hubspot-beam architecture claims — a multi-beam satellite with per-beam retransmission and inter-beam time-slot/frequency reuse. Ericsson did not commercialize a satellite system embodying these claims in the relevant era. So on the narrow claims, I cannot point to a shipping Ericsson product.

Assignment timeline

I could not obtain the Assignment Center entries (reel/frame, correspondent, recording dates). What is corroborated by the Google Patents legal-events/bibliographic data and the EP family record is a chain of at most two links, all within the Ericsson corporate family:

• 1994-01-11 (priority) / 1995-06-07 (divisional filing) — Reel/Frame: not retrieved

  • Conveyance: Assignment (inventor → employer; presumably by employment obligation) — type inferred, not read from a reel/frame record
  • Assignor: Paul W. Dent
  • Assignee: Ericsson GE Mobile Communications Inc.
  • Correspondent: not retrieved in this session
  • Context: ordinary employee-invention assignment to the original operating assignee.

• Date not retrieved (recorded between the 1993 Ericsson buy-out of GE's JV stake and the present) — Reel/Frame: not retrieved

  • Conveyance: Change of Name (Ericsson GE Mobile Communications Inc. → Ericsson Inc.)
  • Assignor: Ericsson GE Mobile Communications Inc.
  • Assignee: Ericsson Inc.
  • Correspondent: not retrieved in this session
  • Context: internal corporate reorganization / change of name only — no change in ultimate beneficial ownership (both entities are Ericsson).

• 2014-01-11 — anticipated expiration (no assignment associated; listed for completeness of the chain timeline).

Critically: no post-issuance transfer to any third party — NPE, aggregator, or otherwise — surfaced in any indexed source. Google Patents, FPO, USPTO.report, the EP/Global-Dossier family record, and Unified Patents' patent page for US-5566168-A all continue to show the patent as Ericsson-owned to expiry. There is no recorded assignment to an entity outside the Ericsson family.

If you need the definitive record, query https://assignmentcenter.uspto.gov/ → Patent Assignment Search → enter 5566168 (or app. 08/475,303), and separately 08/179,954 for the parent. The two fields to capture from that result set are the reel/frame and the correspondent of record on each recording.

Timeline diagram

timeline
    title Ownership of US 5566168
    1994 : Priority application filed
         : Inventor Paul W Dent
    1995 : Divisional application filed
    1996 : Patent issued to Ericsson GE
    1990s : Name change to Ericsson Inc
    2014 : Patent term expires

Note: the "1990s" label reflects that the name-change recording date was not retrievable; all events shown are within the Ericsson corporate family.

NPE / troll-pattern signals

Verdict

Insufficient data.

Justification: the only evidence available shows a simple two-link, intra-family chain — inventor Paul W. Dent → Ericsson GE Mobile Communications Inc. (original assignee) → Ericsson Inc. (current assignee), with the second link being a change of name, not a transfer of beneficial ownership — and no post-issuance assignment to any third party appears in any indexed source, with the patent expiring 2014-01-11 still in Ericsson hands. This is the archetypal "only the original assignment (plus a name change)" fact pattern that the rubric classifies as Insufficient data; it is not an NPE chain — zero of the eight troll signals is affirmatively present, and the one unresolved field (correspondent of record, signal 3) is unavailable to me rather than negative. If a definitive, reel/frame-grounded verdict is required, the single remaining lookup is https://assignmentcenter.uspto.gov/ searched by 5566168 and 08/179,954; on current evidence I expect it to return only an inventor→Ericsson assignment and an Ericsson change-of-name, i.e., continuous operating-company ownership, not an NPE.

Verification links

• USPTO Assignment Center: https://assignmentcenter.uspto.gov/ (search patent 5566168, app. 08/475,303, parent app. 08/179,954)
• Google Patents (assignee + legal events): https://patents.google.com/patent/US5566168/en
• Parent, same title: https://patents.google.com/patent/[US5539730A](/patent/US5539730A)
• EP family member (applicant "ERICSSON GE MOBILE INC"): https://patents.google.com/patent/EP0662775B1/en
• Unified Patents page (assignee listed as Ericsson Inc, no NPE assertion history): https://portal.unifiedpatents.com/patents/patent/US-5566168-A

I'll search for the specific prior-art references cited against US 5,566,168.

Let me pull the "References Cited"/"Patent Citations" section directly from Google Patents and FreePatentsOnline.

Prior-Art Analysis for US 5,566,168 — "TDMA/FDMA/CDMA hybrid radio access methods"

Important scope / confidence statement up front

The task asks me to work through "each patent citation" for US 5,566,168 as listed on the face of the patent (the examiner's References Cited / "Patent Citations" block). I want to be explicit about a limitation rather than fabricate: the authoritative full text you supplied does not contain the "Patent Citations" (prior-art cited) block — it contains only the "Cited By" (forward-citation) block, which is truncated. My searches this session likewise surfaced the specification text, the family data, the abstract, the claims, and forward citations, but not the front-page list of references cited against this patent. See the "Uncertainty disclosure" at the end.

So this section is organized as:

1. What the authoritative text itself identifies as prior art / related art (these are the citable references I can actually ground).
2. Forward citations (for completeness — not §102 art).
3. A §102 assessment per grounded reference.
4. Explicit statement of what I could not verify.

I have not substituted any similar-looking number, and I have kept US 5,566,168 distinct from the unrelated Japanese Patent No. 5566168 (GNSS) and UPC case 1568/2025, per the earlier section.

1. References grounded in the authoritative text of US 5,566,168

These fall into three buckets: (a) U.S. patents incorporated by reference (i.e., cited on the face of the patent as "hereby incorporated by reference"); (b) patent applications/patents of the same assignee cited as related; and (c) non-patent prior art discussed narratively in the Background.

(a) U.S. patents incorporated by reference in the specification

Note on A1–A4: These are incorporated-by-reference technical building blocks, not asserted anticipatory art. Critically, they are commonly owned (same assignee, Ericsson) and at least some are same-inventor (Dent). Even where a §102(e) date critique could be raised, none of them discloses the combination recited in claims 1 or 7 — the satellite multi-beam payload plus hub-side allocation of active slots to coincide with inactive slots in neighboring beams (claim 1), or the paired uplink-frequency/downlink-slot allocation mirroring the reuse plan (claim 7).

(b) Same-assignee related applications/patents cited

(c) Non-patent prior art discussed in the Background

2. Forward citations ("Cited By") — context only, not §102 art

The authoritative text lists 105 forward citations. Representative examples (these are later documents citing US 5,566,168 and are not prior art):

• US 5,717,686 — Lockheed Martin, "Cellular spacecraft TDMA communications system with call interrupt coding…" (1998).
• US 5,796,726 — Ericsson, "Systems and methods for random access in TDMA satellite radiotelephone communications" (1998).
• US 6,112,094 — Ericsson, "Orthogonal frequency hopping pattern re-use scheme" (2000).
• US 6,490,261 — Ericsson, "Overlapping slot transmission using phased arrays" (2002) — which expressly lists both US 5,539,730 and US 5,566,168 (Dent) among its referenced U.S. patents.
• US 6,631,124 — "Methods and apparatus for allocating resources in hybrid TDMA communication systems," whose background expressly names U.S. Pat. No. 5,566,168 to Dent (issued Oct. 15, 1996) as an example of a proposed hybrid TDMA/CDMA system — a useful third-party corroboration of the patent's identity, inventor, assignee, and issue date, though it is not anticipatory art.

Source: https://patents.google.com/patent/US5566168/en (Cited By table); https://patents.justia.com/patent/[6490261](/patent/6490261) (referenced-cited list); US 6,631,124 PDF (background section).

3. §102 assessment against the actual claims

To be analytic rather than conclusory:

• Claim 1 requires, inter alia: (i) a satellite with a multiple-beam antenna; (ii) hub multiple multiplexing means packing each beam's traffic into active time slots of a TDM frame that also has inactive slots; (iii) per-beam retransmission; and (iv) the key limitation — "time slot allocating means to allocate said active time slots in each beam so that they coincide with inactive time slots in neighboring beams."
• Claim 7 requires a satellite + control-station architecture and "time slot and frequency allocating means" pairing each outstation's uplink frequency with its downlink receive time slot, such that allocated downlink slots and associated uplink frequencies in one beam correspond to unallocated slots and frequencies in neighboring beams.

None of the references grounded in the authoritative text discloses limitation (iv) of claim 1 or the paired slot/frequency allocation of claim 7. In particular:

• AMPS, GSM, and IS-54 are single-beam/terrestrial access schemes with no inter-beam slot staggering.
• PTARMIGAN SCRA teaches TDM-downlink/FDMA-uplink but expressly needs a duplexer or separate antennas and discloses no beam-level time reuse.
• The four incorporated U.S. patents (A1–A4) are receiver/DSP building blocks.
• The companion/parent applications (B1–B3) are same-inventor family members, not independent art.

Conclusion for §102: On the record available to me, no grounded reference anticipates claims 1 or 7, and none anticipates dependent claims 2–6 (saturated TWTs; class-C max-efficiency amplifiers; powering down during inactive slots; contiguous subframe packing; non-overlapping neighboring subframes). A §103 attack would more plausibly combine PTARMIGAN-SCRA-type TDM/FDMA art with a multi-beam satellite payload reference — but I have not verified which multi-beam-satellite references, if any, appear on the patent's References Cited block.

4. What I could not verify — explicit uncertainty disclosure

• I could not retrieve the patent's front-page "References Cited" (prior-art cited) list. My searches returned the specification body, claims, family status, and the forward-citation ("Cited By") table, but not the examiner/applicant citation block. Therefore I cannot claim to have enumerated "each patent citation for 5566168" as literally listed in the USPTO record, and I have deliberately not fabricated any numbers, titles, or dates for references I did not see.
• Exact bibliographic dates/titles for U.S. Pat. Nos. 5,048,059 / 5,241,702 / 5,295,112 / 5,331,666 were not confirmed this session; the descriptions above are taken from how US 5,566,168 characterizes them.
• For a definitive answer to "each patent citation," the sources to consult are the USPTO PatentCenter/Public PAIR "References Cited" tab for application 08/475,303, the front page of the printed patent (US 5,566,168 B1), and the EPO search report for EP 0 662 775 B1 (the EP counterpart), which typically flags X/Y documents. I was not able to open these in this session.

Corroborating sources used: https://patents.google.com/patent/US5566168/en • https://uspto.report/patent/grant/5566168 • https://www.freepatentsonline.com/5566168.html • https://patentimages.storage.googleapis.com/ca/b4/e4/1abab34bac25a6/EP0662775B1.pdf (EP counterpart specification) • https://patents.justia.com/patent/6490261 • US 6,631,124 B1 (background naming US 5,566,168 to Dent).

Consistency check with prior section: This section is consistent with the earlier-generated summary (same bibliographic data, same claim-1/claim-7 framing, same "expired 2014" status) and does not contradict it. The one flagged discrepancy — the two different companion application numbers printed in the specification (08/179,953 vs. 08/179,053) — is newly noted here and left uncorrected per the operating rules.

I'll try to close the one gap flagged in the Prior Art section — the front-page "References Cited" list — since a §103 analysis is only as good as the art actually cited on the face of the patent.

The front-page citation list still isn't surfacing directly. Let me try the FPO front page and the EP counterpart's search report, which typically carry the same cited art.

Obviousness Analysis — US 5,566,168 under 35 U.S.C. § 103

Patent: US 5,566,168 A · TDMA/FDMA/CDMA hybrid radio access methods · Dent · Ericsson GE Mobile Communications Inc. · priority 1994‑01‑11 · issued 1996‑10‑15 · expired 2014‑01‑11
Governing law: Pre‑AIA § 103 (priority 1994; AIA first‑to‑file effective 2013‑03‑16), applied through KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), and Graham v. John Deere Co., 383 U.S. 1 (1966).

Two flags before the analysis:

1. Date contradiction. The task header states "Current Date: April 26, 2026," but the prior sections in this analysis (litigation/§ 286 discussion) used 2026‑09‑28, which is also the system date I was given. I flag this rather than silently reconcile it; it does not change the outcome (the patent is expired either way), but any § 286 lookback date computed from "April 26, 2026" should be recomputed.
2. The front-page References Cited block for US 5,566,168 remains unretrieved. I searched again this session (FPO front page, Google Patents "Patent Citations," EP counterpart search report) and could not surface the examiner's cited‑art list. Consistent with the Prior Art section, I therefore build this § 103 analysis on (a) the art grounded in the patent's own text and (b) well‑known field knowledge that I label as such. I am not inventing reference numbers or dates. The one concrete new lead surfaced — British Technology Group's US 5,400,328 appearing alongside US 5,566,168 in a third patent's citation table — is not verified as art cited against the '168 patent, so I do not rely on it.

1. Level of ordinary skill (the Graham threshold question)

A PHOSITA here is an engineer with ~3–5 years in satellite and cellular multiple‑access system design as of January 1994, familiar with: FDMA/TDMA air interfaces (AMPS, GSM, IS‑54); TDM feeder‑link and repeater architectures; multi‑spot‑beam satellite payloads with reuse patterns; and time‑slot/frequency‑assignment scheduling. This matters because the more the claims are characterized as scheduling and payload‑architecture choices, the easier the § 103 case becomes under KSR's "predictable variations" and "design incentive" rationales.

I note also that every independent limitation is drafted in means‑plus‑function form ("multiple multiplexing means," "time slot allocating means," "time slot and frequency allocating means"). Under § 112(f) these are limited to the corresponding structures disclosed in FIGS. 8, 10, and 11 and their equivalents — i.e., a DSP bank/switch‑based multiplexer and a programmed slot/frequency allocator. That narrows the claims for § 103 purposes to ordinary hardware/software schedulers, which is a point against the patent, not for it.

2. Claim 1 — element‑by‑element mapping

The specification's own problem statement is the strongest § 103 evidence in the record. The patent concedes both halves: the reuse problem is old ("A problem can arise in applying frequency re‑use plans to a TDM downlink"), and the answer is a binary selection — split the spectrum three ways, or reuse in time. KSR's "finite number of identified, predictable solutions" rationale applies almost verbatim: where the art discloses two known ways to achieve the same C/I objective, choosing the other one is obvious as a matter of law absent unexpected results.

Likely non‑obviousness counterarguments and their strength:

• The art taught away from time reuse. Weak‑to‑moderate. SCRA's need for a duplexer or dual antennas is a cost teaching, but it teaches nothing against beam‑level time‑slot staggering; the satellite downlink has no duplexer problem (the satellite is not a handheld).
• Full mutual exclusivity is a design sacrifice. Genuine but modest. Requiring neighboring beams' active slots to never coincide means the payload cannot serve overlap regions in the same slot, arguably reducing capacity relative to a frequency‑split plan. A patent owner could argue a PHOSITA would not adopt an approach that gratuitously forfeits capacity. But claims 5–6 show the patentee's own realization that the penalty is bounded (contiguous subframes, non‑overlap), and capacity loss was routinely traded for reuse gain in cellular/satellite planning.
• Unexpected result. None disclosed. The asserted benefits (full bandwidth per beam; lower peak power; simpler amplifier duty) follow directly from the claimed structure — no In re Soni-type showing is possible on this record.

3. Claim 7 — the paired uplink‑frequency / downlink‑slot limitation

Claim 7 layers on the architecture a "time slot and frequency allocating means" that pairs each outstation's FDMA uplink frequency with its downlink receive slot, such that allocated slots and frequencies in one beam correspond to unallocated slots and frequencies in neighbors.

Motivation to combine (claim 7). Three independent KSR‑sanctioned rationales converge:

1. Design incentive / problem known in the field. A front‑end‑less TDD‑like handset forced by the TDM downlink requires that the mobile's transmit opportunity be tied to its receive slot; once the downlink slot is assigned, the uplink frequency must be assigned to the same user. The pairing is not an invention — it is a consequence of the already‑claimed downlink format.
2. Predictable variation of a known reuse plan. The patent admits 3‑cell frequency reuse as conventional. Its own logic is that a time‑reuse plan on the downlink "automatically gives rise to" a matching frequency‑reuse plan on the uplink. A PHOSITA who had adopted time reuse on one link would, for the ordinary duplex reason that a link pair must survive the same interference geometry, mirror the pattern on the other link. Producing the frequency plan as the dual of the time plan is a mechanical mapping, not an inventive step.
3. Market/spectrum economics. Using the full allocated band in each beam rather than thirds is exactly the admitted motivation that drove the patentee; the same motivation drives the claim‑7 pairing. KSR expressly credits "market forces" and "design incentives" as motivation.

Weakness in the § 103 case for claim 7: the complementarity requirement — that the allocated slots and associated uplink frequencies in one beam correspond to unallocated slots and frequencies in neighbors — requires the uplink frequency groups to be disjoint across neighboring beams, i.e., a hard frequency partition on the uplink even while the downlink uses all bandwidth by time. This is more specific than mere reuse planning, and the closest admitted art (SCRA) pairs frequencies with mobiles but is single‑beam. Claim 7 is therefore the harder claim to invalidate and the one to test against the (still‑unretrieved) front‑page art. Practically, the attack would run: SCRA (TDM downlink + per‑mobile FDMA uplink) + terrestrial/satellite reuse‑plan art + the duplex‑pairing inference, with the specification's own 3‑cell admission supplying the "why."

4. Dependent claims 2–6

There is no separate inventive concept in claims 2–6 that rescues them if claim 1 falls. They are conventional payload‑implementation details plus one scheduling rule that follows from claim 1.

5. Recommended primary combinations (ranked)

1. PTARMIGAN‑SCRA / TDM‑downlink‑FDMA‑uplink art + multi‑beam satellite payload art + admitted 3‑cell reuse plan → claim 1. Motivation: full‑bandwidth-per‑beam spectral efficiency; the specification's own statement of the problem; predictable substitution of a known reuse dimension (time for frequency).
2. SS/TDMA satellite‑switched beam art + TDM/FDMA hybrid art → claim 1 (and claim 7 with the uplink frequency plan). SS/TDMA's inter‑beam burst‑avoidance constraints are the closest functional analogue of "active slots coincide with inactive slots in neighboring beams."
3. Combination 1 or 2 + standard satellite payload practice (saturated TWTA/class C) + TDM gating → claims 2, 3, 4; + contiguous subframe scheduling → claim 5; + non‑overlap as a consequence → claim 6.
4. Combination 2 + duplex‑pairing inference + the specification's 3‑cell admission → claim 7.

Expectation of success: high for claims 1–6 (all elements are conventional, and the combination's behavior — C/I parity with a frequency‑plan, full‑bandwidth bursts — is predictable from the art). Moderate for claim 7 (the joint, disjoint uplink‑frequency plan must be shown, not merely inferred).

Antecedent‑based § 102 note worth checking: if any single piece of the (unretrieved) front‑page art discloses per‑beam TDM subframes staggered across beams, claim 1 could fall under § 102 rather than § 103. That is precisely why the missing References Cited block matters, and I flag it as the one lookup that could convert this from a strong § 103 case into a § 102 case.

6. Secondary considerations

• No commercial success nexus. As the Assignment section found, Ericsson does not appear to have shipped a satellite system embodying these particular claims (the commercial mapping is to the parent US 5,539,730's terrestrial TDM/FDMA subject matter). Any "industry recognition" argument would therefore lack a nexus to claims 1 and 7.
• Heavy forward citation (105 documents) is not a secondary consideration; it evidences that the patent is a widely indexed prior‑art document, and the later Ericsson patents that cite it (US 6,490,261; US 6,631,124) are same‑assignee follow‑ons, not praise from competitors. If anything, the follow‑on filings suggest the field regarded the technique as a platform to build on, which is consistent with obviousness of the platform.
• Expiration (2014‑01‑11) means no live validity controversy exists; the § 103 analysis above is thus chiefly of historical/defensive value — a demand letter resting on claims 1 or 7 is answerable on the § 286 damages element before validity is even reached (per the litigation/PTAB sections).

7. Where this analysis is uncertain (stated plainly)

• The examiner's cited art is unknown to me. Every conclusion above rests on references grounded in the patent's own text plus field knowledge (SS/TDMA, INTELSAT‑era TDMA, multi‑beam payloads) that I have not verified as being on the '168 front page. Do not represent to any tribunal that a specific front‑page reference exists based on this section.
• I could not verify the front‑page References Cited list, the EP counterpart search report's X/Y designations, or the US prosecution history (whether § 103 rejections were made and overcome, and on what rationale). Those three documents are decisive for converting this analysis into an invalidity contention.
• Discrepancy carried forward: the specification prints both 08/179,953 and 08/179,053 for the same companion application. Per the operating rules I have not corrected it; if the front‑page art list depends on that family, resolve the number before relying on it.

Bottom line: Claims 1–6 of US 5,566,168 are, on the available record, strongly vulnerable under § 103 — the asserted novelty is a design‑choice substitution (time reuse for frequency reuse) that the specification itself frames as the answer to an acknowledged problem, implemented with conventional payload hardware. Claim 7 is moderately vulnerable, turning on whether the joint beam‑disjoint uplink‑frequency/downlink‑slot allocation can be shown to flow from the duplex pairing plus the admitted reuse plan. Confirming the front‑page art and, if possible, a single per‑beam time‑staggered TDM reference could move claim 1 from obviousness to anticipation.