US 5416780

I have the authoritative full text of this patent in my context. Let me verify current litigation/docket status with searches before summarizing.

Summary of US Patent 5,416,780

Bibliographic data (per the authoritative full text provided, and cross-checked against Google Patents, Unified Patents, and Justia):

Note on a discrepancy: the authoritative Google Patents text lists filing 1992-04-16 and issue 1995-05-16 (priority 1991-06-28). The Unified Patents portal lists slightly different day values (application 1992-04-15, grant 1995-05-15, priority 1991-06-27). I have used the values from the supplied authoritative patent text and flag the one-day variance as a source disagreement rather than resolving it. Examiners of record were Shick Hom and Douglas W. Olms (per Unified Patents).

Abstract (verbatim)

"A location independent personal telecommunications system is presented that utilizes an out-of-band bi-directional burst data communications network to assist in the routing of personal communications via an in-band voice and data communications network. Access to the out-of-band network for communication is regulated by a multiple access communications protocol. Each user is synchronized with the other users of the network to the protocol and will access the network only during certain time periods that are reserved by the protocol for message traffic between network users. A collision avoidance scheme is included in the protocol to resolve instances of simultaneous transmission of message traffic by multiple users during the same time period."

Plain-language overview of the independent claims

The patent has three independent claims — claim 1 (method), claim 7 (network/apparatus), and claim 12 (system) — with dependent claims 2–6, 8–11, and 13–19 respectively.

• Claim 1 — Method of sharing one bi-directional channel. Establishes a repeating time frame containing both "primary" and "secondary" time periods; every user synchronizes to that frame; primary users may transmit only in the primary periods and secondary users only in the secondary periods. The core idea is time-slot-type separation by user class on a single shared channel, with the slots reserved by class but not individually dedicated to any specific user.

• Claim 7 — Communications network. A single-channel, bi-directional data link accessed on a repeating frame with primary and secondary periods. Each primary and secondary user has (a) a clock for tracking the frame and (b) a transceiver that identifies its class's authorized periods and transmits only in them (primary users in primary periods, secondary users in secondary periods). Coupled to the link is a means for broadcasting a synchronization message to align all users' clocks to the frame.

• Claim 12 — Communications system (the personal-telecoms application). Combines (a) a telephonic network delivering in-band service to subscribers, (b) a "command" network of user transceivers delivering out-of-band service (typically one secondary transceiver per subscriber plus at least one primary relay transceiver), and (c) a central control node that responds to out-of-band messages from a subscriber to control how the in-band service is provided to that subscriber. This is the location-independent personal-number call-routing concept.

Key dependent limitations worth noting:

• Claims 2–3 / 9–10: transmit a data message and listen for an acknowledgement in the same authorized period; if no acknowledgement, retransmit in the next same-type period.
• Claims 4–5 / 11: if still unacknowledged, retransmit in a randomly selected future authorized period, repeating up to a selected retry count, then fall back to alternative means (this is the "collision avoidance scheme").
• Claim 6: synchronization via a dedicated sync period and sync message updating each user's clock.
• Claims 8, 13–19: the wireless RF data link; per-user protocol means; the resolving of simultaneous-access conflicts.

Litigation / docket search result

I found no CAFC 2026 docket (or any court docket) involving US 5,416,780. I searched for the patent number combined with "litigation," "CAFC," "2026 docket," and assignee name. Results returned only:

• The Google Patents family page, which carries a generic "Family has litigation" Darts-IP link (family ID 24905150) but no case number or court;
• Third-party citing documents (Unified Patents portal, Justia, patent-art citations in unrelated patents); and
• An unrelated USPTO/PTAB exhibit (IPR2024-00846, Microsoft) that merely lists "5416780" inside a prior-art search string — not a case against this patent.

The absence of 2026 litigation is consistent with the record: the patent is marked "Expired – Fee Related," with anticipated expiration 2012-05-16, so its enforceability window closed long before 2026. I could not retrieve the Darts-IP family-litigation record itself; if any historical suit exists, I do not have authoritative details for it and am flagging that as an uncertainty rather than asserting there was none.

Uncertainty notes: (1) the one-day bibliographic variance between sources noted above; (2) the Darts-IP "family litigation" flag is unverified; (3) examiner names come from a secondary aggregator (Unified Patents), not the authoritative text.

I'll search for litigation involving US patent 5416780 across patent litigation databases.

Let me check the Unified Patents litigation portal and other case-specific sources.

The patent page itself contains a "Family has litigation" flag with a Darts-IP family link. Let me investigate that and search litigation-specific databases.

Litigation Search — U.S. Patent No. 5,416,780

Bottom line

I was not able to identify any specific, verifiable litigation in which U.S. Patent No. 5,416,780 ("Telecommunications system and protocol for avoiding message collisions on a multiplexed communications link," inventor Rajendra Patel, assignee Network Access Corporation) was asserted as an infringed patent.

I want to be explicit and honest about the limits of this result, because there is a conflicting signal worth flagging.

Patent identity (per the authoritative patent text)

What the record shows

1. No litigation found. Searches across general web, patent-portal pages (including the Unified Patents patent page for US-5416780-A at https://portal.unifiedpatents.com/patents/patent/US-5416780-A), and litigation-adjacent sources did not turn up any district court, ITC, or CAFC case naming 5,416,780.

2. The hits that mentioned "5416780" were not litigation against this patent. They fell into three categories, none of which are infringement suits on this patent:

   • Prior-art citations / searches in unrelated inter partes review exhibits (e.g., Microsoft IPR2024-00846 and Google IPR2024-00[233/234] file histories) where "5416780" appears in a list of searched patent numbers — these are about other patents (e.g., 8,886,954; 9,298,905; 9,032,039).
   • Patent-office family links in WO/EP search reports listing US 5,416,780 alongside US 5,315,636, CA 2069727, JP 5191516, EP 0520194.
   • A different patent entirely: JP 5416780 B2 — a Japanese patent to Kabushiki Kaisha Toshiba (registered 2013-11-22, publication 2014-02-12, "無線システムおよび無線機器" / "Radio system and radio device"). This is a completely separate patent and must not be confused with US 5,416,780, per the literal-identifier rule.

3. ⚠️ One conflicting signal you should be aware of. The Google Patents page for US5416780A (https://patents.google.com/patent/US5416780/en) contains a "Family has litigation — First worldwide family litigation filed" indicator, linked to a Darts-IP family record (family ID 24905150) at https://patents.darts-ip.com/?family=24905150. Google flags this at the family level, meaning the litigation (if any) may attach to a family member — most likely the parent patent US 5,315,636, or one of the foreign members (EP 0520194, CA 2069727, JP 5191516) — rather than to 5,416,780 itself. I was unable to retrieve and verify any specific case behind that flag (the Darts-IP record is behind a subscription, and my searches did not surface matching court documents). I am therefore flagging it rather than asserting it as confirmed.

Case-by-case listing

Recommendations to confirm definitively

Since I could not fully resolve the Darts-IP "family has litigation" flag, I recommend verifying directly:

• Unified Patents litigation portal — https://portal.unifiedpatents.com/litigation/caselist (search by patent number, then cross-check family member US 5,315,636).
• Darts-IP family record — https://patents.darts-ip.com/?family=24905150 (subscription; this is the source of the "family has litigation" flag).
• PACER / CourtListener / Free Law Project — search for "Network Access" and for the patent numbers 5,416,780 and 5,315,636 in complaints.
• RPX Insight (insight.rpxcorp.com) and Docket Alarm — for any legacy cases from the 1990s era when Network Access Corp. (a successor to the "Personal Telecommunications System" / cellular-locating business) may have litigated.

If you can authorize a paid Darts-IP or RPX lookup, that would likely resolve the single remaining open question in one step.

Caveat: This reflects what I could retrieve as of the search date. I did not obtain a case-specific hit tying US 5,416,780 to any suit, and I have not auto-corrected any patent number. The Toshiba JP 5416780 B2 is a distinct patent and is not evidence of litigation on the US patent.

I'll verify the structured ODP result against public sources before writing this up.

Let me check for reexaminations, CBM/PGR activity, and any assertion/litigation history.

Proceedings overview

Total AIA trial proceedings on file against US 5,416,780: zero (0). The structured "PTAB proceedings on file" block — the canonical USPTO Open Data Portal list — returns no IPRs, no PGRs, and no CBM reviews. My independent web searches confirm this: every hit for "5416780" in a PTAB context resolves to a prior-art search string inside some other party's exhibit, not to a proceeding naming this patent. The bottom-line defensive posture for a defendant is therefore neither "hardened" nor "dead" — it is untested: no claim of '780 has ever been challenged at the Board, and no claim has ever been canceled. Whether a demand letter has teeth depends entirely on claim construction and § 102/§ 103 art you develop yourself, not on any existing PTAB record.

No proceedings to report — and here is why that is expected

There is no proceeding to place at the top of the list. Rather than pad the output, I'll explain the negative result and what it actually signifies, because the absence is explainable and not an artifact of a search failure.

Attribution of the false positives I did find (important, so nobody mistakes them for the patent's docket):

That last row is a real trap: searching the bare numeral "5416780" without the "US" or "5,416,780" formatting pulls a Toshiba JP grant. Anyone doing a quick manual check should use "5,416,780" or US5416780 to avoid it.

Why zero proceedings is plausible here — three structural reasons:

1. The patent was never a litigation target at scale. '780 issued 1995-05-16 to Network Access Corporation and is marked Expired – Fee Related, anticipated expiration 2012-05-16 (per the authoritative text; Unified Patents shows 2012-05-15 — same one-day source variance flagged in the bibliographic section). AIA trials only exist from 2012-09-16 forward. So the entire IPR-eligible window for this patent is roughly 2012-09-16 to 2012-05-16 — which is negative. On the face of the record, the patent expired four months before the first IPR could be filed. That alone explains the empty docket more than any merits question does. (IPRs on already-expired patents are permissible in principle where live infringement liability remains, but a petitioner pays six-figure fees for a patent with no prospective injunctive value and a § 286 damages window closing — a poor business case.)
2. PGR was never available. PGR is limited to patents with an effective filing date on or after 2013-03-16. '780 claims priority to 1991-06-28 (§ 120 to US 07/723,169, now US 5,315,636), so it is squarely pre-AIA. No PGR could ever be filed against it — zero is the correct and only possible number.
3. CBM was unavailable on two independent grounds. The CBM transitional program required a patent directed to a "financial product or service," and it sunset entirely for petitions filed after 2020-09-16. '780 is a personal-telecommunications/multiple-access-protocol patent, not a financial-services patent, and any CBM petition would have been time-barred regardless. Zero is again structurally correct.

Flags and uncertainties:

• The Darts-IP "Family has litigation" flag on the Google Patents page (family ID 24905150) is unverified. It may reflect a suit involving sibling patent US 5,315,636 or the EP/CA/JP family members (EP 0520194 A3, JP H05191516 A, CA 2069727 A1), or a sub-threshold dispute, rather than an action on '780 itself. I do not have a case number, court, or date for it, and I am deliberately not inventing one. Treat the flag as an open thread, not as evidence of a '780 PTAB or district-court record.
• My searches covered PTAB/ODP-style queries, CAFC-adjacent language, and assignee-name queries. They do not constitute a substitute for a paid docket service (Darts-IP, Lex Machina, Docket Navigator) or a Docket Alarm / PTAB E2E docket pull. If the flag matters to your case, that is the check to run.

Strategic summary

Claim status: 19 claims, all UNTESTED. Nothing at the Board has canceled anything. Claims 1 (method), 7 (network), and 12 (system) are the three independents, with dependents 2–6, 8–11, and 13–19 — exactly as set out in the claim summary. There are no canceled claims, no sustained claims, and no IPR certificate narrowing the patent. Anyone who tells you "claims 1–5 are dead" based on PTAB history is misreading the record; there is no such history.

Estoppel landscape: a blank slate, which cuts both ways. With no IPR ever instituted, § 315(e)(2) estoppel has never attached to anyone. No petitioner, real party in interest, or privy is barred from raising any § 102/§ 103 ground — there is no prior "raised or reasonably could have raised" set to work from. Practically, this means a defendant has the full universe of prior art available, unconstrained by a prior petitioner's choices. The offsetting risk: because no claim has been tested, you also have zero PTAB precedent telling you how a panel reads "primary time period," "secondary user," "not individually dedicated for use by any specific user," or the claim-12 "command communications network" / "in-band" vs. "out-of-band" division. Claim construction is entirely open and your local court's Phillips analysis will control.

On the merits you'd be attacking: a pre-AIA patent with a 1991 priority date in the multiple-access-protocol space is historically vulnerable — the art is crowded (frequency/time-division multiple access, slotted ALOHA with randomized retransmission, polling protocols), and the specification's own § 112 posture has soft spots. Two candidates worth a look from the face of the document: (a) the claims recite very generically what the specification implements with heavy structural detail (relay stations, base stations, personal communicators, service node 106, the DMD 188 dual-modulator circuit), which invites written-description/enablement and § 112(b) indefiniteness arguments on the functional "means for resolving simultaneous communication conflict" language in claims 15 and 19; and (b) claims 1 and 7 hinge on a "primary/secondary user" taxonomy that the specification defines by traffic expectation ("primary users 14 more likely than secondary users 16 to initiate burst communications") rather than by structure — that can be attacked as indefinite or as not imparting patentable weight, and simultaneously limits the claims to networks that actually exhibit the asymmetry.

Pattern signals: none exist. No serial petitioner. No defensive aggregator (Unified Patents appears only as a data aggregator portal, not as a filer against '780). No owner-side PTAB appeal activity, because there was nothing to appeal. The Arthrex/Director-review line of cases and the 2025 discretionary-denial process memorandum are doctrinally interesting but have no application to this patent — there is no institution decision to review.

Recommended next steps

For a defendant today: this is a substantive-validity fight, not a documentary fight. Concretely:

1. Do not rely on any PTAB record — there isn't one. If you need to establish the negative for the court or for an insurer, cite the USPTO Patent Trial and Appeal Board End-to-End (PTAB E2E) system at https://ptacts.uspto.gov/ and the USPTO Open Data Portal proceeding search, both filtered on patent number 5416780. An empty result there is your evidence. Archival fallback: the Google Patents page's "Family has litigation" Darts-IP link — but note it carries no case number, so it is not self-proving.
2. Establish the expiration date in writing and lead with it. Anticipated expiration 2012-05-16 (authoritative text; Unified Patents says 2012-05-15) and status "Expired – Fee Related" mean no prospective relief. Under § 286 damages are limited to the six years before filing, and any pre-2012-05-16 conduct is outside even that window. For most defendants, the entire damages exposure is a historical residue, and an injunction is unavailable as a matter of law. This is a more powerful and cheaper defense than any IPR would have been.
3. If you are nonetheless facing live assertion (rare for a patent expired this long, but possible on a tail-damages theory), build your invalidity case de novo from § 102/§ 103 art, and take a § 112 position on the "means for resolving simultaneous communication conflict" limitations (claims 15, 19) and the traffic-expectation-based "primary/secondary user" definition. There is no estoppel to navigate and no adverse FWD reasoning to distinguish.
4. Chase the Darts-IP flag before you certify a clean history. Because I could not retrieve it, treat any representation that "there is no litigation history at all" as unverified. A Lex Machina / Docket Navigator / Darts-IP pull on family ID 24905150, and a separate pull on sibling patent US 5,315,636, is the correct next step if the litigation flag matters to your posture.
5. Preserve the two-source bibliographic discrepancy already on the record: filing 1992-04-16 vs. 1992-04-15, issue 1995-05-16 vs. 1995-05-15, priority 1991-06-28 vs. 1991-06-27. I've used the authoritative-text dates throughout. This is a one-day variance across aggregators, not a substantive issue, but flag it if precision matters to a court filing.

If, on re-check, the Darts-IP flag resolves to an actual PTAB proceeding that post-dates the ODP ingest, the entire analysis above changes and the structure reverts to a standard per-proceeding walkthrough (type, filed date, panel, grounds, institution reasoning, FWD claim-by-claim, settlement terms, CAFC appeal). I found no such proceeding, and I am not going to manufacture one to fill the template.

I'll research the assignment record for US 5,416,780 using the tools available.

I attempted to retrieve the USPTO Assignment Center / Patent Assignment Search records for US 5,416,780, along with corporate-history and NPE-directory cross-references. Findings and limits below.

Inventors

Notes:

• The authoritative front page shows a single inventor. No joint inventors.
• Network Access Corp's broader portfolio (per GoodIP's assignee page) shows a small, tightly clustered inventor group across 14 applications — Rajendra Patel (13), David W. Thorn (5), Girish Patel (4), Zye-Kong Cheng (3), Yeong-Haw Yang (3), Gerald K. Coley (3), Abdolreza S. Naeini (2), Kenneth A. Lauffenburger (2), Charles C. Miller (2). Only R. Patel appears on this patent.
• Unusual-pattern check: unclear. I found no verifiable data on inventor departure dates, tenure, or post-filing moves. I cannot assert "inventors departed within 12 months of filing." Employer attribution rests solely on the recorded assignment, not on an independent payroll/10-K source.

Original assignee

Network Access Corporation — named as both original and current assignee on Google Patents, and identified as "Parent Company" by Unified Patents.

• Primary line of business: Telecommunications equipment and services. Its earliest patents (US 4,782,519; 4,853,955; 4,903,263; 5,086,461) cover retrofitting existing 1ESS/1AESS telephone switching equipment — including SS7 protocol capability and ISDN capability. The 1991–1992 filings (US 5,233,643; 5,315,636; this patent) shift to a "personal telecommunications system" with out-of-band burst signaling. GoodIP classifies its focus markets as telecommunications and lists GTE Mobilnet and Aeris Net as "main competitors," which is consistent with a small telecom-equipment/service venture.
• Did it ship a product embodying the claims? Unclear / not established. I found no product literature, datasheet, or service-mark evidence, and no SEC filings (the entity does not appear to be a reporting company). The claimed system is an infrastructure architecture (service node + relay/base stations + personal communicators); absence of evidence is not evidence of absence.
• Current status: Google Patents lists the current assignee as Network Access Corp, i.e., no recorded post-issuance transfer is reflected. I found no evidence of acquisition, merger, dissolution, or bankruptcy. Status is best described as unverified but presumptively the original owner of record, with the patent itself expired – fee related, anticipated expiration 2012-05-16 (Unified Patents: 2012-05-15; $0 lifetime renewal fees).

Assignment timeline

⚠️ Data-retrieval limitation — state plainly: I could not retrieve the underlying USPTO Patent Assignment Search record for this patent. Searches returned only patent-content portals (Google Patents, Justia, Unified Patents, uspto.report), none of which expose the assignment reel/frame, conveyance code, or correspondent of record. I am therefore reporting no reel/frame numbers, no correspondent names, and no security agreements — because I did not obtain them, not because I verified their absence. I will not fabricate reel/frame identifiers.

What is documented in the authoritative source (Google Patents legal events for US 5,416,780):

• 1992-04-16 (executed) / 1992-04-16 (recorded) — Reel/frame: not retrieved
  • Conveyance: Assignment of assignors' interest (original inventor-to-company assignment; recorded contemporaneously with filing)
  • Assignor: Rajendra Patel
  • Assignee: Network Access Corporation
  • Correspondent: not retrieved — no attorney/firm data available. Cannot assess recurrence.
  • Context: Formation/original assignment — the inventor assigned rights to the company on the filing date. This is the standard founding assignment, not a transfer of an already-issued patent.

No other assignment, security agreement, merger, change-of-name, license, or release appears in any source I could reach. Per the rules, I state this as a retrieval gap crossed with a negative finding: the only ownership event visible anywhere is the 1992 original assignment, and no evidence of any post-issuance transfer surfaced. On the available evidence the patent was never separated from Network Access Corporation.

Timeline diagram

timeline
    title Ownership of US 5416780
    1991 : Priority date from parent application
    1992 : Application filed
         : Assigned to Network Access Corp
    1995 : Patent issued
    2012 : Patent expired

NPE / troll-pattern signals

Cross-checks performed and what they returned:

• Google Patents legal events: only the 1992-04-16 "Assigned to NETWORK ACCESS CORPORATION / ASSIGNMENT OF ASSIGNORS INTEREST / Assignors: PATEL, RAJENDRA" entry; no later events; status "Expired – Fee Related."
• Darts-IP "Family has litigation" flag (family ID 24905150) on the Google Patents page: carries no case number, court, or party. Consistent with the prior-section finding — unverified, and I still cannot confirm any historical suit.
• IPR2024-00846 (Microsoft) exhibit and the Google Patents 8,886,954 file-history exhibit: "5416780" appears only inside examiner search-string tables. Not a case against this patent.
• "Other versions: US4818615A" in the authoritative text: this is a metadata error in the scrape (Google Patents shows it as an "other version," which is impossible for a 1994-issue US patent). Flagging as a data artifact, not an assignment or a real family member.

⚠️ Contradiction to flag against prior sections: the previously generated summary cited Unified Patents dates as 1992-04-15 / 1995-05-15 / priority 1991-06-27, one day earlier than the authoritative Google Patents text (1992-04-16 / 1995-05-16 / 1991-06-28). This persists and remains unresolved; it does not affect the assignment analysis.

Verdict

Insufficient data (no records beyond the original assignment).

Justification: the only ownership event documented anywhere — the 1992-04-16 inventor-to-company assignment of Rajendra Patel's interest to Network Access Corporation — is the standard founding assignment, and nothing in the authoritative text, Google Patents legal events, or any asserter directory shows the patent ever leaving the original assignee. None of the eight NPE signals is present; two (repeat correspondent, pre-litigation transfer) are unclear strictly because I could not retrieve Assignment Center reel/frame or correspondent data, and a retrieval gap is not a finding. Combined with the patent's 2012 expiry and $0 lifetime renewal fees, the record is most consistent with a dormant small telecom vendor's patent that was never monetized through an NPE chain.

Verification link: search patent number 5416780 at the USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (indexed at https://assignment.uspto.gov/patent/index.html). If that search returns a recorded chain, the reel/frame and correspondent fields I could not obtain should be read directly from it; my analysis should be re-run against those entries.

I'll research the prior art cited against/in US 5,416,780, starting with the USPTO record and the references named in the patent itself.

Let me pull the front-page "References Cited" (56) data and the specification-cited patents.

Let me try to pull the front-page references (56) and the EP search report for the family member.

I'll research the prior-art landscape for this patent before performing the § 103 analysis.

Let me look for the specific prior-art references of record and analogous art in the multiple-access protocol field.

Let me retrieve the actual list of references cited on the face of this patent.

Obviousness Analysis — U.S. Patent No. 5,416,780 under 35 U.S.C. § 103

Analyst note / scope. This is a technical validity opinion, not a legal conclusion. I was able to retrieve the patent's authoritative text (supplied), the references the patent itself cites in its specification, the Google Patents "Cited By" set, and a set of independently surfaced multiple-access-protocol references. I was not able to retrieve the examiner's verbatim "References Cited" (the "Patent Art (15)" list) from the Google Patents or Unified Patents pages before hitting my search-step limit; I flag that gap explicitly below rather than reconstructing the list. All patent numbers are quoted literally as retrieved; I have not auto-corrected any identifier.

1. Threshold issues that control which art is available

POSITA definition used below: a communications engineer with a B.S.E.E. and 3–5 years' experience designing mobile/packet-radio multiple-access protocols and stored-program-controlled switching systems as of mid‑1991. This is a highly mature art by 1991 (ALOHA was 21 years old; SS7 was in nationwide deployment).

2. Reference set relied on

2.1 Art identified on the face of / inside this patent (highest confidence)

Caveat on US 5,233,643: its filing date (1991‑10‑08) is after the 1991‑06‑28 priority date but before the CIP filing (1992‑04‑16), and it names the same assignee and one common inventor (Patel). It is therefore not § 102/§ 103 art against claims entitled to the 1991 date, and its same-inventor/same-assignee character raises the common-ownership and "another" issues under pre‑AIA § 102(e)/§ 103(c). Treat it as evidence of what the assignee and the field were doing, not as a clean § 103 reference. Flagged.

2.2 Multiple-access-protocol art independently surfaced (the art that matters most)

2.3 "Cited By" art (later documents — not available as § 103 art, but probative of the field's trajectory)

The Cited-By set (e.g., Benveniste, US 2002/0154653 A1, "Random medium access methods with backoff adaptation to traffic"; AT&T's US 7,095,754, US 7,136,361, US 7,180,905 — TCMA/CPMA tiered/priority contention-free partitioning; US 6,888,819, "Media access control utilizing synchronization signaling"; US 5,533,021; US 5,708,430 — "sequentially broadcasting data according to pre-assigned time slots with and without the reception of a synchronization packet") shows that by the mid-1990s the industry treated synchronization-signal-driven, class/priority-partitioned, backoff-resolved slotted access as routine incremental engineering. These documents postdate the critical date and cannot be used in a rejection; I cite them only to show that no non-obvious technical hurdle remained after 1991.

3. Claim 1 — element-by-element mapping

Claim 1 is a method claim whose heart is: one bidirectional channel ÷ repeating frame ÷ two classes of reserved slots ÷ class-restricted transmission. It does not require retransmission, a sync message, an RF link, a ratio of slots, or that "primary" mean infrastructure.

Claim 7 is the apparatus mirror image (clock means + transceiver means + "means … for transmitting a synchronization message"). Every element is met by the same mapping; the only added element — a sync-message broadcaster — is the oldest element in the field (Framed Aloha's "Aloha Now"; US 4,866,709's instruction message; paging synchronization codewords).

4. Proposed grounds of rejection

Ground 1 — Claims 1 and 7 over US 4,612,637 in view of EP 0 177 094 A2 (and optionally US 4,866,709)

• US 4,612,637 renders the frame structure, the synchronizing broadcast, the shared (not user-dedicated) slots, and the acknowledgement/retry discipline.
• EP 0 177 094 A2 supplies the missing class partition: its hybrid mode literally "form[s] subsets of the population of the sub-stations," each operating in its own prescribed access mode, and its polling mode reserves transmission opportunities to a defined class.
• Motivation (KSR‑sufficient):
  1. Known problem, known remedy. Both references are directed to the same problem — contention when "many users attempt to gain access … at the same time" (US 4,612,637, Background). Splitting the contending population into subsets with disjoint slot sets is a known contention-reduction technique (EP 0 177 094), so using it in the Framed-Aloha frame is "the predictable use of prior art elements according to their established functions."
  2. Traffic asymmetry is the design driver. US 4,612,637's trunking background expressly addresses differing traffic loads (busy vs. quiet periods) and disciplines access accordingly. Giving the heavier-traffic class its own (and in the embodiment, larger) allotment is ordinary capacity engineering; the claim does not even recite a ratio, so the 2:1 primary:secondary split discussed in the specification is not a limitation at all.
  3. A POSITA had reason to expect success — class-partitioned slot assignment strictly reduces the collision set in each slot type, so throughput can only improve relative to the undifferentiated frame.

Ground 2 — Claims 2–3, 9–10 (transmit + listen for ack in the same period; retransmit in the next same‑type period)

• Abramson (1970) teaches transmit-then-wait-for-ack; on failure, retry. US 4,612,637 and US 4,866,709 teach the slot structure and the congestion/acknowledgement observations.
• EP 0 177 094 A2 teaches expressly that a station "can send requests for access at randomly selected times (which may be slotted) in a frame and in the event of contention or propagation errors can retransmit requests one or more times in the same frame" — i.e., multiple transmit/listen cycles inside a single frame, which is the substance of claims 2–3 structured as a Tx/Ack sub-slot pair (Fig. 2C) followed by a retry in the next period.
• Reservation-ALOHA (Roberts, 1973) and its descendants put an acknowledgement/mini-slot inside the reservation slot — the "listen for acknowledgement during the accessed authorized time period" limitation of claims 2/9.
• Motivation: deterministic immediate retry in the next slot is a natural first-order response to a lost ack, and it is cheaper than randomized backoff (lower latency, no backoff timer to run) — a design trade-off squarely within POSITA's skill.

Ground 3 — Claims 4–5, 11, 15, 19 (random future retry; retry counter; alternative route)

• This is the core ALOHA teaching: "if no acknowledgement is heard users wait a random time before re-trying" (Abramson 1970, as recited in US 4,612,637); Framed Aloha confines those retries to the frame; US 4,398,289 / US 4,866,709 teach predetermined and/or random slot selection specifically to reduce the chance of two sub-stations transmitting simultaneously.
• Retry counters and fallback to an alternate route are ubiquitous in the same documents' discussion of stability under heavy traffic and in trunking practice (escalating to a different channel/route after repeated failure).
• Claim 19 is drafted so broadly ("means for resolving instances of simultaneous transmission … during the same time period") that it reads on any ALOHA-type backoff, including the 1970 Abramson protocol alone. This claim is the most vulnerable in the patent.
• Motivation / predictability: Deterministic-then-random escalation is a well-known two-stage backoff (fixed slots cluster retries predictably; randomization breaks the cluster when the fixed slot is persistently contended). Nothing unexpected results from the combination — the specification itself describes it as "one or more fixed and random time periods in the future," i.e., as an implementation choice.

Ground 4 — Claim 6 (sync time period + sync message + clock update)

Directly met by Framed Aloha's "Aloha Now" message (GB 2,063,011A, recited in US 4,612,637) and by US 4,866,709's instruction message with periodic re-transmission "even if no change … has occurred" to accommodate newly powered sub-stations. Motivation: frame synchronisation is a prerequisite to any slotted protocol; no separate inventive act is required.

Ground 5 — Claim 8 (wireless RF link + RF transceiver)

Trunking (US 4,612,637), cordless TDD (CT2/DECT), and the assignee's own US 5,233,643 ("single radio frequency communications channel") each render an RF link + RF transceiver obvious, indeed inevitable.

Ground 6 — Claims 12–19 (the location-independent personal telecommunications system)

Claim 12 is a combination claim: (a) telephonic network providing in-band service; (b) a transceiver network providing out-of-band service, one secondary transceiver per subscriber plus at least one primary relay transceiver; (c) a central control means responsive to out-of-band messages to control the in-band service.

The obviousness case here is built from four independent, all pre‑1991 teachings:

1. Person-locator / "follow-me" service. The idea of a single personal directory number whose calls are delivered to the subscriber's current location was known art from the early 1980s. The archetype is the Bell-system person-locator patent literature of that era (commonly identified as US 4,313,035, "Method of providing person locator service," 1982) — I did not verify this number in this session; treat the specific citation as a lead, not a confirmed reference. Confidence on the genre: High; on the specific number: Low — flagged.
2. Paging/alert-then-complete. Using a radio alert to a portable device to locate a subscriber and then bridging the incoming call to a nearby telephone was established practice in paging-assisted call delivery/voice-messaging art.
3. Common-channel (out-of-band) signaling controlling in-band voice paths. This is the entire architecture of SS7 / CCIS: a separate packet-signaling network that sets up, routes, and tears down voice circuits on the in-band network. A POSITA reading claim 12 would see the "out-of-band data network controlling the in-band voice network" element as the definition of common-channel signaling. Confidence: High (SS7 was in national deployment by 1991 and the assignee itself owned SS7-related art — see the Network Access Corp. portfolio listing for a 1990‑01‑23 filing on upgrading 1ESS/1AESS offices to SS7).
4. The protocol of claims 1–11 applied to the RF link between personal communicators (secondary) and base/relay stations (primary).

Motivation to combine: the only thing the CIP added over its own parent (US 5,315,636) is the burst protocol; the personal-number system of claim 12 is the parent's subject matter. Combining the parent's location-tracking/call-routing architecture with a known slotted-ALOHA control channel (Grounds 1–4) and with a known out-of-band signaling architecture (SS7) yields claim 12 without any new technical result: the out-of-band channel does what out-of-band channels always did (carry short control messages), and the in-band network does what in-band networks always did (carry voice).

Two additional structural validity risks worth flagging (not § 103, but they bear on the same claims):

• Obviousness-type double patenting / § 102(e) overlap with the parent US 5,315,636, if claim 12 is not entitled to the 1991‑06‑28 date. Whether the parent counts as "another's" work under pre‑AIA § 102(e) depends on the inventive entity of US 5,315,636 versus the sole listed inventor (Rajendra Patel) of this patent, and on the common-ownership provisions — I could not resolve the parent's inventive entity in this session. Flagged uncertainty.
• The "user selected" limitations in claim 5 ("a user selected number of times," "user selected alternative means") are functional and open-ended, which makes them easy to read onto any retry-limit/fallback implementation — again cutting toward obviousness.

5. Why the strongest counter-arguments probably fail

Where the case is genuinely weakest (candor requirement): the strongest non-obviousness story the patentee has is the System-level claim 12 — the specific interlock of out-of-band burst signaling feeding a location look-up table that governs in-band routing, with the personal communicator as both locator beacon and command device. If a fact-finder credited the specific coupling of subscriber-location tracking (via base-station poll signal strength) to the call-routing decision as a non-routine architectural insight, claim 12 could survive a § 103 challenge — but only if it is not entitled to the 1991 date, because the parent US 5,315,636 appears to disclose that very system.

6. Bottom line

• Claims 1 and 7 are, in my assessment, highly likely obvious over Framed-Aloha/dynamic-framelength Aloha art (US 4,612,637; US 4,866,709; GB 2,063,011A; GB 2,069,799; US 4,398,289; Abramson 1970) in view of EP 0 177 094 A2 for the class-partitioned slot allocation.
• Claims 2–6, 8–11, 15, 19 add only ack-in-slot, fixed-then-random retry, retry counters, a sync message, and an RF link — each individually disclosed or the subject of a well-recognized design incentive.
• Claims 12–14, 16–18 are the only claims with a realistic validity story, and that story depends entirely on the priority-date question flagged in § 1, plus resolution of the parent/applicant-own-art issues.
• Claim 19 is the most exposed claim in the patent; it reads on generic ALOHA backoff.

7. Explicit uncertainty flags

1. I did not obtain the examiner's "References Cited" list of record (the Google Patents/Unified Patents "Patent Art (15)"). My primary references are those the patent itself cites plus references independently surfaced in this session. There may be additional examiner-cited art that would strengthen (or weaken) these grounds.
2. US 5,166,929 appeared only in an ambiguous snippet; I could not determine the citation direction. Do not rely on it.
3. The 1991 vs. 1992 critical date for claims 1–11 is an inference from the CIP relationship; I have not compared the parent's specification line-by-line.
4. US 4,313,035 and the precise filing dates of US 5,327,432 and the CT2/DECT standards are given as leads, not verified citations. Treat them as research directions.
5. The one-day bibliographic variance between sources (1992‑04‑16 / 1995‑05‑16 per the authoritative text vs. 1992‑04‑15 / 1995‑05‑15 / priority 1991‑06‑27 per Unified Patents) noted in the earlier summary is carried forward unresolved. It does not change this analysis.
6. The Darts‑IP "family has litigation" flag remains unverified; if litigation exists, the § 103 grounds above are the natural invalidity defenses to expect.