US 7027426

US Patent 7027426, titled "Multi-channel mobile ad hoc network," was invented by Thomas Jay Billhartz. The patent was filed on August 5, 2002, and issued on April 11, 2006. Its original assignee was Harris Corp, and the current assignee is Stingray IP Solutions LLC.

Abstract:
The patent describes a mobile ad hoc network comprising multiple wireless mobile nodes and wireless communication links connecting these nodes over a plurality of channels. The method for operating this network includes, at a source node, sending a route request over each of the plurality of channels to discover routing to a destination node, and then selecting a route to the destination node on at least one of these channels. The route request may be sent sequentially over each channel and preferably includes a source node channel identifier.

Independent Claims Overview:

Claim 1 (Method for Operating a Mobile Ad Hoc Network):
This claim outlines a method for establishing communication in a multi-channel mobile ad hoc network. It involves a source node initiating a route discovery process by sending route requests across all available electrically separate wireless channels to find a destination node. Intermediate nodes, upon receiving these requests, evaluate their ability to support the requested route and, if capable, forward the request further to other intermediate nodes or the destination node, again over all electrically separate channels. Once the destination node receives a request, it generates a reply for each discovered route back to the source node. The source node then selects a route from the discovered options, which may utilize one or more of the channels, and proceeds to send a transmission along that chosen route.

Claim 8 (Method for Operating a Mobile Ad Hoc Network - Simplified):
This claim presents a more concise method for operating a multi-channel mobile ad hoc network. It focuses on two core steps at the source node: first, sending a route request over each of the electrically separate wireless channels to discover potential routes to a destination node; and second, selecting one of these discovered routes to the destination node, which can involve at least one of the plurality of electrically separate channels.

Claim 18 (Mobile Ad Hoc Network System):
This claim describes the physical system itself—a mobile ad hoc network. This network consists of multiple mobile nodes connected by wireless communication links that operate over several electrically separate wireless channels. Each mobile node in this network is equipped with a communications device for wireless interaction and a controller for routing. The controller specifically includes a route discovery unit, which is responsible for transmitting route requests across each of the electrically separate channels to find routing paths to a destination node, and a route selection unit, which then chooses a route to the destination node on at least one of these channels.

CAFC 2026 Dockets:
As of April 26, 2026, no specific dockets for US patent 7027426 were found in the CAFC 2026 dockets. The patent is noted as "Expired - Lifetime" with an expiration date of October 11, 2022. While litigation activity is noted for this patent family in district courts between 2019 and 2022, there is no indication of active dockets specifically within the CAFC in 2026.

US patent 7027426 has been involved in multiple litigation cases. The details available from the patent record are as follows:

Litigation Involving US Patent 7027426

1. Jurisdiction: Texas Eastern District Court [cite: The full patent text]
   • Case Number: 2:21-cv-00043 [cite: The full patent text]
   • Filing Date: Implied 2021 (from case number).
   • Plaintiff(s): Not explicitly stated in the provided patent text.
   • Defendant(s): Not explicitly stated in the provided patent text.
   • Outcome or Current Status: Not explicitly stated in the provided patent text.
2. Jurisdiction: Texas Eastern District Court [cite: The full patent text]
   • Case Number: 2:21-cv-00201 [cite: The full patent text]
   • Filing Date: Implied 2021 (from case number).
   • Plaintiff(s): Not explicitly stated in the provided patent text.
   • Defendant(s): Not explicitly stated in the provided patent text.
   • Outcome or Current Status: Not explicitly stated in the provided patent text.
3. Jurisdiction: Texas Eastern District Court [cite: The full patent text]
   • Case Number: 2:21-cv-00195 [cite: The full patent text]
   • Filing Date: Implied 2021 (from case number).
   • Plaintiff(s): Not explicitly stated in the provided patent text.
   • Defendant(s): Not explicitly stated in the provided patent text.
   • Outcome or Current Status: Not explicitly stated in the provided patent text.
4. Jurisdiction: Texas Eastern District Court [cite: The full patent text]
   • Case Number: 2:21-cv-00193 [cite: The full patent text]
   • Filing Date: Implied 2021 (from case number).
   • Plaintiff(s): Not explicitly stated in the provided patent text.
   • Defendant(s): Not explicitly stated in the provided patent text.
   • Outcome or Current Status: Not explicitly stated in the provided patent text.
5. Jurisdiction: Texas Eastern District Court [cite: The full patent text]
   • Case Number: 2:21-cv-00045 [cite: The full patent text]
   • Filing Date: Implied 2021 (from case number).
   • Plaintiff(s): Not explicitly stated in the provided patent text.
   • Defendant(s): Not explicitly stated in the provided patent text.
   • Outcome or Current Status: Not explicitly stated in the provided patent text.
6. Jurisdiction: Texas Eastern District Court [cite: The full patent text]
   • Case Number: 2:21-cv-00025 [cite: The full patent text]
   • Filing Date: Implied 2021 (from case number).
   • Plaintiff(s): Not explicitly stated in the provided patent text.
   • Defendant(s): Not explicitly stated in the provided patent text.
   • Outcome or Current Status: Not explicitly stated in the provided patent text.
7. Jurisdiction: New Jersey District Court [cite: The full patent text]
   • Case Number: 3:21-cv-11989 [cite: The full patent text]
   • Filing Date: Implied 2021 (from case number).
   • Plaintiff(s): Not explicitly stated in the provided patent text.
   • Defendant(s): Not explicitly stated in the provided patent text.
   • Outcome or Current Status: Not explicitly stated in the provided patent text.
8. Jurisdiction: Delaware District Court [cite: The full patent text]
   • Case Number: 1:19-cv-02245 [cite: The full patent text]
   • Filing Date: Implied 2019 (from case number).
   • Plaintiff(s): Not explicitly stated in the provided patent text.
   • Defendant(s): Not explicitly stated in the provided patent text.
   • Outcome or Current Status: Not explicitly stated in the provided patent text.
9. Jurisdiction: California Central District Court [cite: The full patent text]
   • Case Number: 2:22-cv-07541 [cite: The full patent text]
   • Filing Date: Implied 2022 (from case number).
   • Plaintiff(s): Not explicitly stated in the provided patent text.
   • Defendant(s): Not explicitly stated in the provided patent text.
   • Outcome or Current Status: Not explicitly stated in the provided patent text.

Proceedings overview

There are no AIA trial proceedings on file for US patent 7027426. This indicates that the patent has not been challenged through IPR, PGR, or CBM trials at the USPTO. For a defendant, this means the patent's claims remain untested by PTAB proceedings, and an IPR-based defense is still a viable option to explore.

Strategic summary

All claims of US7027426 are currently untested by PTAB proceedings. This patent has not been subjected to IPR, PGR, or CBM trials, meaning no claims have been canceled or sustained by the PTAB. There are no estoppel implications as no proceedings have been filed.

Recommended next steps

If facing assertion of US patent 7027426, consider initiating an AIA trial proceeding, such as an Inter Partes Review (IPR), to challenge the patentability of the claims. The absence of prior PTAB activity means that all prior art grounds remain available for a potential petitioner (subject to statutory bars like the one-year time bar for IPR petitions).

Inventors

• Thomas Jay Billhartz (Harris Corp)

Original assignee

Harris Corp was the original assignee. Harris Corp is a global aerospace and defense technology innovator, providing products, systems, and services for commercial and government customers. It is unclear from the patent text whether they shipped a product directly embodying the claims of US7027426B2. As of today, Harris Corporation merged with L3 Technologies in 2019 to form L3Harris Technologies.

Assignment timeline

• 2002-08-05 (executed) / recorded 2002-08-05 — Reel 013176/0876

  • Conveyance: Assignment
  • Assignor: BILLHARTZ, THOMAS JAY
  • Assignee: HARRIS CORPORATION, FLORIDA
  • Correspondent: Not specified in available data.
  • Context: Original assignment from inventor to employer.

• 2020-06-04 (executed) / recorded 2020-06-05 — Reel 052853/0153

  • Conveyance: Patent Security Agreement
  • Assignor: ACACIA RESEARCH GROUP LLC; AMERICAN VEHICULAR SCIENCES LLC; BONUTTI SKELETAL INNOVATIONS LLC; CELLULAR COMMUNICATIONS EQUIPMENT LLC; INNOVATIVE DISPLAY TECHNOLOGIES LLC; LIFEPORT SCIENCES LLC; LIMESTONE MEMORY SYSTEMS LLC; MERTON ACQUISITION HOLDCO LLC; MOBILE ENHANCEMENT SOLUTIONS LLC; MONARCH NETWORKING SOLUTIONS LLC; NEXUS DISPLAY TECHNOLOGIES LLC; PARTHENON UNIFIED MEMORY ARCHITECTURE LLC; R2 SOLUTIONS LLC; SAINT LAWRENCE COMMUNICATIONS LLC; STINGRAY IP SOLUTIONS LLC; SUPER INTERCONNECT TECHNOLOGIES LLC; TELECONFERENCE SYSTEMS LLC; UNIFICATION TECHNOLOGIES LLC
  • Assignee: STARBOARD VALUE INTERMEDIATE FUND LP, AS COLLATERAL AGENT, NEW YORK
  • Correspondent: FRANK P. PRESTIA, RATNERPRESTIA, P.O. BOX 1010, VALLEY FORGE, PA 19482-1010. This correspondent appears multiple times in this chain.
  • Context: Security interest granted by multiple Acacia-related entities to Starboard Value.

• 2020-04-21 (executed) / recorded 2020-06-23 — Reel 053019/0876

  • Conveyance: Assignment
  • Assignor: EAGLE TECHNOLOGIES, INC.; L3HARRIS TECHNOLOGIES, INC.; HARRIS GLOBAL COMMUNICATIONS, INC.
  • Assignee: ACACIA RESEARCH GROUP LLC, TEXAS
  • Correspondent: MICHAEL J. ROSSI, ESQ., 321 SUMMER STREET, BUFFALO, NY 14222.
  • Context: Transfer from L3Harris (successor to original assignee Harris Corp) to Acacia Research Group LLC.

• 2020-05-04 (executed) / recorded 2020-06-23 — Reel 053326/0636

  • Conveyance: Assignment
  • Assignor: ACACIA RESEARCH GROUP LLC
  • Assignee: STINGRAY IP SOLUTIONS LLC, TEXAS
  • Correspondent: JOHN M. DUNCAN, ESQ., 230 PARK AVENUE, SUITE 1000, NEW YORK, NY 10169.
  • Context: Transfer from Acacia Research Group LLC to Stingray IP Solutions LLC, a subsidiary.

• 2020-06-30 (executed) / recorded 2020-07-08 — Reel 053654/0254

  • Conveyance: Release of Security Interest in Patents
  • Assignor: STARBOARD VALUE INTERMEDIATE FUND LP
  • Assignee: LIMESTONE MEMORY SYSTEMS LLC; ACACIA RESEARCH GROUP LLC; AMERICAN VEHICULAR SCIENCES LLC; BONUTTI SKELETAL INNOVATIONS LLC; UNIFICATION TECHNOLOGIES LLC; SAINT LAWRENCE COMMUNICATIONS LLC; TELECONFERENCE SYSTEMS LLC; R2 SOLUTIONS LLC; INNOVATIVE DISPLAY TECHNOLOGIES LLC; STINGRAY IP SOLUTIONS LLC; SUPER INTERCONNECT TECHNOLOGIES LLC; NEXUS DISPLAY TECHNOLOGIES LLC; MOBILE ENHANCEMENT SOLUTIONS LLC; LIFEPORT SCIENCES LLC; MONARCH NETWORKING SOLUTIONS LLC; PARTHENON UNIFIED MEMORY ARCHITECTURE LLC; CELLULAR COMMUNICATIONS EQUIPMENT LLC
  • Correspondent: FRANK P. PRESTIA, RATNERPRESTIA, P.O. BOX 1010, VALLEY FORGE, PA 19482-1010. This correspondent appears multiple times in this chain.
  • Context: Release of security interest by Starboard Value to various Acacia-related entities.

• 2020-06-04 (executed) / recorded 2021-11-11 — Reel 058825/0107

  • Conveyance: Corrective Assignment
  • Assignor: STINGRAY IP SOLUTIONS LLC
  • Assignee: STARBOARD VALUE INTERMEDIATE FUND LP, AS COLLATERAL AGENT, NEW YORK
  • Correspondent: FRANK P. PRESTIA, RATNERPRESTIA, P.O. BOX 1010, VALLEY FORGE, PA 19482-1010. This correspondent appears multiple times in this chain.
  • Context: Corrective assignment related to the patent security agreement.

• 2020-06-30 (executed) / recorded 2021-11-11 — Reel 058266/0599

  • Conveyance: Corrective Assignment
  • Assignor: STARBOARD VALUE INTERMEDIATE FUND LP, AS COLLATERAL AGENT
  • Assignee: STINGRAY IP SOLUTIONS LLC, TEXAS
  • Correspondent: FRANK P. PRESTIA, RATNERPRESTIA, P.O. BOX 1010, VALLEY FORGE, PA 19482-1010. This correspondent appears multiple times in this chain.
  • Context: Corrective assignment related to the release of security interest.

Timeline diagram

timeline
    title Ownership of US 7027426
    2002 : Assigned to Harris Corporation
    2020 : Security Agreement to Starboard Value
         : Assigned to Acacia Research Group LLC
         : Assigned to Stingray IP Solutions LLC
         : Release of Security Interest
    2021 : Corrective Assignment to Starboard
         : Corrective Assignment to Stingray

NPE / troll-pattern signals

1. Shell-entity transfer — present.

   • Stingray IP Solutions LLC is the current assignee. Its name ("IP Solutions") suggests a licensing-only entity. Stingray IP Solutions LLC has been identified in patent litigation.
   • Acacia Research Group LLC, a prior assignee, is a known patent assertion entity.
   • Reel 053326/0636 (2020-05-04 / 2020-06-23) shows the transfer to Stingray IP Solutions LLC.

2. Known asserter in the chain — present.

   • Acacia Research Group LLC is listed as a prior assignee (Reel 053019/0876). Acacia Research Corporation is a well-known NPE.

3. Repeat correspondent across the chain — present.

   • FRANK P. PRESTIA of RATNERPRESTIA appears on Reel 052853/0153 (2020-06-04 / 2020-06-05), Reel 053654/0254 (2020-06-30 / 2020-07-08), Reel 058825/0107 (2020-06-04 / 2021-11-11), and Reel 058266/0599 (2020-06-30 / 2021-11-11). This recurrence across security agreements and corrective assignments for Acacia-related entities is a strong signal.

4. Cascading transfers — present.

   • Within approximately one month in 2020, the patent was assigned from L3Harris to Acacia Research Group LLC (Reel 053019/0876) and then from Acacia Research Group LLC to Stingray IP Solutions LLC (Reel 053326/0636). This rapid transfer between related entities is a cascading transfer.

5. Pre-litigation transfer — present.

   • The patent was assigned to Acacia Research Group LLC in June 2020 (Reel 053019/0876) and then to Stingray IP Solutions LLC also in June 2020 (Reel 053326/0636). Litigation records show multiple cases filed in Texas Eastern District Court in 2021 (e.g., 2:21-cv-00043, 2:21-cv-00201, 2:21-cv-00195, 2:21-cv-00193, 2:21-cv-00045, 2:21-cv-00025) and other districts in 2019, 2021, and 2022. The transfers in 2020 immediately precede these widespread assertions.

6. Bankruptcy fire-sale — not present.

7. Privateering — unclear. While Harris Corp is an operating company, the transfer to Acacia Research Group LLC (a known NPE) could indicate privateering. However, without specific SEC filings or other external documentation, it cannot be confirmed with high confidence.

8. Defensive aggregator (anti-NPE) — not present.

Verdict

NPE — high confidence. This verdict is supported by the presence of a known patent asserter (Acacia Research Group LLC) in the chain (Reel 053019/0876), the subsequent transfer to a shell entity (Stingray IP Solutions LLC) (Reel 053326/0636), the clear pattern of cascading transfers in 2020, and the pre-litigation timing of these transfers preceding multiple lawsuits in 2021. Furthermore, the consistent use of FRANK P. PRESTIA as correspondent for various Acacia-related transactions strengthens this conclusion.

Verification: https://assignmentcenter.uspto.gov/

To identify the most relevant prior art for US patent 7027426, a review of its patent citations, as provided in the patent text, has been conducted. The patent 7027426 itself describes a "Multi-channel mobile ad hoc network" with a core inventive feature being the use of a plurality of electrically separate wireless channels for route discovery and selection. The analysis below for each cited patent focuses on whether its title and general description suggest this multi-channel aspect.

Here are the patent citations and their potential for anticipation under 35 U.S.C. § 102:

Most Relevant Prior Art for US7027426

1. US5412654A

• Full Citation: US5412654A, "Highly dynamic destination-sequenced destination vector routing for mobile computers", International Business Machines Corporation.
• Publication/Filing Date: Priority Date: 1994-01-10; Publication Date: 1995-05-02.
• Brief Description: This patent describes a highly dynamic destination-sequenced destination vector (DSDV) routing for mobile computers.
• Potential Anticipation (35 U.S.C. § 102): This reference pertains to general ad-hoc routing protocols, specifically DSDV. While it establishes prior art for fundamental concepts of routing in mobile ad-hoc networks, its title and known description do not indicate the use of "multiple electrically separate wireless channels" for route discovery and selection, which is a central feature of US7027426's claims. Therefore, it would potentially anticipate the broader aspects of mobile ad-hoc network operation (e.g., presence of nodes, communication links, routing), but not the specific multi-channel features detailed in claims 1, 8, and 18, which specify operations over "a plurality of electrically separate wireless channels".

2. US5987011A

• Full Citation: US5987011A, "Routing method for Ad-Hoc mobile networks", Chai-Keong Toh.
• Publication/Filing Date: Priority Date: 1996-08-30; Publication Date: 1999-11-16.
• Brief Description: This patent details a routing method designed for ad-hoc mobile networks.
• Potential Anticipation (35 U.S.C. § 102): Similar to US5412654A, this patent broadly covers routing methods in ad-hoc mobile networks. Its title does not suggest the multi-channel routing paradigm (i.e., operations across a "plurality of electrically separate wireless channels") as defined in the claims of US7027426. It could potentially anticipate general elements of ad-hoc network structure and basic routing procedures, but likely not the specific multi-channel route discovery and selection processes that differentiate US7027426.

3. US6308843B1

• Full Citation: US6308843B1, "Foldable clothes-lines", Barry R. De Boer.
• Publication/Filing Date: Priority Date: 1998-04-30; Publication Date: 2001-10-30.
• Brief Description: This patent describes foldable clothes-lines.
• Potential Anticipation (35 U.S.C. § 102): The title of this patent, "Foldable clothes-lines," indicates that it is completely unrelated to communication networks or mobile ad hoc networks. Therefore, it is highly unlikely to anticipate any claims of US7027426. This appears to be a clerical error in the patent's citation list.

4. US6304556B1

• Full Citation: US6304556B1, "Routing and mobility management protocols for ad-hoc networks", Cornell Research Foundation, Inc.
• Publication/Filing Date: Priority Date: 1998-08-24; Publication Date: 2001-10-16.
• Brief Description: This patent discloses routing and mobility management protocols specifically for ad-hoc networks, including the Zone Routing Protocol (ZRP).
• Potential Anticipation (35 U.S.C. § 102): This patent covers ad-hoc routing, specifically mentioning ZRP, which US7027426 notes as a protocol to which its invention can be applied. However, the title and general description do not clearly indicate the use of "multiple electrically separate wireless channels" for routing purposes as a defining characteristic. It may anticipate general ad-hoc network routing mechanisms, but not the specific multi-channel features described in US7027426's claims.

5. US6385174B1

• Full Citation: US6385174B1, "Method and apparatus for transmission of node link status messages throughout a network with reduced communication protocol overhead traffic", Itt Manufacturing Enterprises, Inc.
• Publication/Filing Date: Priority Date: 1999-11-12; Publication Date: 2002-05-07.
• Brief Description: This patent focuses on methods and apparatus for transmitting node link status messages with reduced communication protocol overhead in a network.
• Potential Anticipation (35 U.S.C. § 102): While this patent addresses network communication and efficiency, its title does not suggest the distinctive multi-channel routing described in US7027426. It likely relates to managing network information efficiently, but not specifically to route discovery or selection across multiple distinct electrical channels. Therefore, it is unlikely to anticipate the multi-channel aspects of US7027426's claims.

6. US20010033556A1

• Full Citation: US20010033556A1, "Scalable unidirectional routing with zone routing protocol extensions for mobile AD-HOC networks", Srikanth Krishnamurthy.
• Publication/Filing Date: Priority Date: 2000-02-12; Publication Date: 2001-10-25.
• Brief Description: This patent application describes scalable unidirectional routing, particularly with extensions to the Zone Routing Protocol (ZRP), for mobile ad-hoc networks.
• Potential Anticipation (35 U.S.C. § 102): Similar to US6304556B1, this reference builds upon ZRP for ad-hoc networks, focusing on scalability and unidirectional routing. Its title does not indicate the explicit use of "multiple electrically separate wireless channels" for routing. While it contributes to the general field of ad-hoc network routing, it does not appear to anticipate the specific multi-channel features claimed in US7027426.

Summary of Potential Anticipation:

Based on the titles and general descriptions of the cited patents, none of them overtly disclose the core inventive concept of US7027426: performing route discovery and selection over a plurality of electrically separate wireless channels. The cited patents primarily focus on various aspects of routing within a single-channel ad-hoc network context or general network management. Therefore, while these patents may establish prior art for general components of a mobile ad hoc network (e.g., nodes, links, routing protocols), they do not appear to anticipate the distinguishing multi-channel features explicitly recited in most of US7027426's claims (e.g., claims 1, 8, and 18, and their dependent claims, which rely on the multi-channel aspect). A definitive determination of anticipation would require a detailed, claim-by-claim comparison against the full disclosure of each cited reference.

Obviousness Analysis under 35 U.S.C. § 103 for US Patent 7027426

This analysis assesses the obviousness of US Patent 7027426, "Multi-channel mobile ad hoc network," by identifying combinations of prior art references that would render the claimed invention obvious to a person having ordinary skill in the art (PHOSITA) at the time of the invention (priority date: August 5, 2002).

Person Having Ordinary Skill in the Art (PHOSITA)

A PHOSITA in this field would possess knowledge in wireless communication networks, particularly mobile ad hoc networks (MANETs), including routing protocols (e.g., AODV, DSR), Medium Access Control (MAC) layer protocols, network performance optimization, and Quality of Service (QoS) considerations.

Motivation to Combine Prior Art

The background of US7027426 explicitly identifies a problem with conventional mobile ad-hoc networks: they "assume that all nodes are on the same channel permanently," leading to "limited bandwidth" and "single channel operation" as a significant factor in bandwidth availability. [Description, BACKGROUND OF THE INVENTION] The patent states its object is to "provide a multichannel mobile ad hoc network to efficiently make use of a plurality of channels." [Description, SUMMARY OF THE INVENTION]

A PHOSITA, facing the known limitations of single-channel operation in MANETs, would be motivated to combine existing routing protocols with multi-channel communication techniques to improve network throughput, reduce contention, and enhance overall network efficiency. This motivation is explicitly addressed by the problems described in the '426 patent and the solutions proposed in the prior art.

Obviousness Combinations and Rationale

The independent claims (Claims 1, 8, and 18) of US7027426 focus on a mobile ad hoc network utilizing a plurality of electrically separate wireless channels for route discovery and selection, allowing routes to span multiple channels. This combination can be found obvious when considering the following prior art references:

Primary References for Combination:

1. Tseng et al., "A Multi-Channel MAC Protocol with Power Control for Multi-Hop Mobile Ad Hoc Networks," IEEE, pp. 419-424, 2001. (hereinafter "Tseng")
2. Johnson et al., "The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks (DSR)," Internet Engineering Task Force (IETF) MANET Working Group, Internet Draft, Nov. 21, 2001. (hereinafter "Johnson")
3. Perkins et al., "Ad hoc On-Demand Distance Vector (AODV) Routing," Internet Engineering Task Force (IETF) MANET Working Group, Internet Draft, Nov. 9, 2001. (hereinafter "Perkins AODV")

Secondary References for Known Elements:
4. Chakrabarti et al., "QoS Issues in Ad Hoc Wireless Networks," IEEE Communications Magazine, Feb. 2001, pp. 142-148. (hereinafter "Chakrabarti")
5. Perkins et al., "Quality of Service in Ad Hoc On-Demand Distance Vector Routing," Internet Engineering Task Force (IETF) MANET Working Group, Internet Draft, Jul. 2000. (hereinafter "Perkins QoS")

Combination: Tseng + Johnson/Perkins AODV + Chakrabarti/Perkins QoS

Rationale for Combination:
Tseng explicitly describes a "multi-channel MAC protocol with power control for multi-hop mobile ad hoc networks using multiple non-overlapping channels." It notes that "each mobile host is equipped with multiple half-duplex transceivers and can transmit/receive simultaneously on multiple channels," allowing "different nodes in a neighborhood to concurrently communicate on different channels, reducing both contention and the hidden terminal problem." This directly addresses the "plurality of electrically separate wireless channels" in a mobile ad hoc network, and the motivation to improve throughput, a problem identified by the '426 patent. [Description, BACKGROUND OF THE INVENTION]

Johnson and Perkins AODV represent well-known on-demand (reactive) routing protocols for mobile ad hoc networks, defining standard mechanisms for route discovery (Route Request, RREQ) and route reply (Route Reply, RREP). The '426 patent itself explicitly mentions DSR and AODV as types of on-demand routing protocols to which its method can be applied. [Description, DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS]

A PHOSITA, seeking to leverage the multi-channel capabilities described by Tseng at the MAC layer within an ad hoc network, would find it obvious to adapt an existing on-demand routing protocol like DSR (Johnson) or AODV (Perkins AODV) to utilize these channels for routing decisions. This adaptation would naturally involve extending the route discovery and selection processes to account for the multiple available channels.

Detailed Obviousness Analysis for Representative Claim 1:

Claim 1: "A method for operating a mobile ad hoc network comprising a plurality of wireless mobile nodes and a plurality of wireless communication links connecting the plurality of nodes together over a plurality of electrically separate wireless channels, the method comprising: at a source node, sending a route request over each of the plurality of electrically separate channels to discover routing to a destination node; at each intermediate node, determining whether the intermediate node can support the route requested and, if so, forwarding the route request to other intermediate nodes and the destination node over each of the plurality of electrically separate channels; at the destination node, upon receiving the route request, generating a reply to the source node for each discovered route; at the source node, selecting a route to the destination node on at least one of the plurality of electrically separate channels; and at the source node, sending a transmission to the destination node along the selected route."

1. "a mobile ad hoc network comprising a plurality of wireless mobile nodes and a plurality of wireless communication links connecting the plurality of nodes together over a plurality of electrically separate wireless channels": Tseng teaches a "multi-channel MAC protocol... for multi-hop mobile ad hoc networks using multiple non-overlapping channels." Non-overlapping channels are "electrically separate." This directly discloses a mobile ad hoc network operating over multiple channels.

2. "at a source node, sending a route request over each of the plurality of electrically separate channels to discover routing to a destination node": Johnson (DSR) and Perkins AODV describe source-initiated route discovery via flooding RREQs. Given Tseng's disclosure of multiple available channels and nodes with multiple transceivers, a PHOSITA would find it obvious to extend the conventional RREQ flooding mechanism to "each of the plurality of electrically separate channels" to discover all possible paths, including those spanning different channels. This is a logical adaptation to fully exploit the multi-channel capability. The '426 patent itself describes this as the source node sending "the route request RREQ over all the existing channels that the network is currently operating on to reach all nodes... within one-hop." [Description, DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS]

3. "at each intermediate node, determining whether the intermediate node can support the route requested and, if so, forwarding the route request to other intermediate nodes and the destination node over each of the plurality of electrically separate channels": The concept of an intermediate node determining "support" for a route request relates to QoS considerations, which were well-known in MANETs prior to the '426 patent. Chakrabarti discusses "QoS Issues in Ad Hoc Wireless Networks," and Perkins QoS describes "Quality of Service for Ad hoc On-Demand Distance Vector Routing." Forwarding the RREQ to other intermediate nodes and the destination node is a standard feature of DSR (Johnson) and AODV (Perkins AODV) route discovery. In a multi-channel environment enabled by Tseng, a PHOSITA would find it obvious to forward these requests over "each of the plurality of electrically separate channels" to continue path discovery across all available channels.

4. "at the destination node, upon receiving the route request, generating a reply to the source node for each discovered route": This is standard behavior for on-demand routing protocols like DSR (Johnson) and AODV (Perkins AODV), where the destination node responds to route requests with route replies. The need to generate a reply "for each discovered route" would be obvious if multiple distinct routes, potentially involving different channels, reached the destination.

5. "at the source node, selecting a route to the destination node on at least one of the plurality of electrically separate channels": DSR (Johnson) and AODV (Perkins AODV) involve route selection after receiving route replies. Given the multi-channel discovery, the source node would receive replies detailing various paths, some potentially utilizing multiple channels. The selection of a route "on at least one of the plurality of electrically separate channels" is an obvious outcome of choosing from these discovered multi-channel paths. The '426 patent explicitly mentions that the selected route "may include more than one of the plurality of channels" and "may be wholly, or in part, on a different channel than the source node." [Description, DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS]

6. "at the source node, sending a transmission to the destination node along the selected route": Once a route is selected, sending data traffic along that route is the ultimate purpose of any routing protocol (Johnson, Perkins AODV). The multi-channel nature of the selected route would be handled by the underlying multi-channel MAC protocol (Tseng).

Obviousness of Dependent Claims and Other Features:

Many features described in the dependent claims of US7027426 are likewise obvious extensions or existing elements in the prior art:

• Sequential sending of route requests (Claims 2, 13, 23): While the '426 patent states "the route request may be sent over each of the plurality of channels sequentially," [Abstract] this is an implementation detail for flooding on multiple channels, an obvious design choice for managing transceiver activity or avoiding self-interference, if applicable.
• Route request including a source node channel identifier (Claims 3, 14, 24): In a multi-channel network, including channel information in routing messages is an obvious modification to allow nodes to understand the channel context of a received message and to reconstruct multi-channel paths.
• Sending reply back in reverse (Claims 4, 11, 21): This is a well-known characteristic of many on-demand routing protocols, including DSR and AODV, where the path traversed by the RREQ is reversed to form the RREP path.
• Prioritizing discovered routes and using metrics (Claims 5, 6, 15, 16, 25, 26): Chakrabarti and Perkins QoS both teach the importance of QoS in ad hoc networks and discuss various metrics for route selection, such as "available bandwidth, error rate, end-to-end delay, end-to-end delay variation, hop count, expected path durability, and priority." These are precisely the metrics listed in the '426 patent. [Description, DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS] A PHOSITA would readily apply these known metrics to prioritize routes in a multi-channel environment.
• Selected route includes more than one channel (Claims 7, 17, 27): This is the direct result of enabling multi-channel route discovery as described by the combination of Tseng with DSR/AODV, where paths are no longer constrained to a single channel.

Obviousness of Claim 8 (Simplified Method) and Claim 18 (System):

Claim 8, which is a simplified method claim, omits intermediate node processing and reply generation steps but retains the core of multi-channel route request and selection at the source node. The arguments for these steps remain the same as for Claim 1.

Claim 18 describes a system with hardware units (communications device, controller, route discovery unit, route selection unit) to implement the method. The implementation of a method into hardware components is well within the skill of a PHOSITA. A "route discovery unit" configured to transmit RREQs over "each of the plurality of electrically separate channels" and a "route selection unit" to select a route on "at least one of the plurality of electrically separate channels" are straightforward functional descriptions of the method steps, which a PHOSITA would know how to implement given the underlying multi-channel MAC (Tseng) and the adapted routing protocol (Johnson/Perkins AODV).

Conclusion

Based on the combination of Tseng et al. with established on-demand routing protocols like DSR (Johnson et al.) or AODV (Perkins et al.), and considering the known applications of QoS routing (Chakrabarti et al., Perkins et al. QoS), a PHOSITA would have been motivated to combine these references to create a multi-channel mobile ad hoc network with routing capabilities across multiple channels. The resulting claimed invention in US7027426 represents an obvious adaptation of existing technologies to solve a known problem (limited bandwidth and contention in single-channel MANETs) using well-understood principles of network design and protocol extension.