SRT acquires Class B AIS patent, consequences uncertain

SRT_Acquisition_of_Patent_release_clips_aPanbo.jpgFor me, this story began with a March 5th email titled “AIS patent wars – a tax on safety?” It referenced the SRT stock market announcement partially shown above and went on to say:

The whole point of using CSTDMA instead of SoTDMA in the original design of Class B was to avoid any problems with patents to ensure the successful uptake of the system by manufacturers. I see this as a tax on safety and a desperate attempt by SRT to force manufacturers to use their solutions rather than those from competitors and so create a pseudo-monopoly in the Class B world, which cannot be good for competition or the end user. To say I am furious would be putting it mildly…

The author of that email asked to remain anonymous, which is easy because I only know him as a nickname with an inscrutable email address who occasionally writes me with what seems like an insider’s knowledge of AIS technology and the regulatory process that made it happen. But anonymous recollections and opinions don’t have the weight of on-the-record testimony, and worse is “off the record” information which I can’t share at all. I ran into lots of both while researching this patent and that’s one reason why this entry will focus on documents that are publicly available or that I have seen with my own eyes. Readers will have to draw their own conclusions and the ultimate consequences seem murky anyway.

Patent 7512095 began as SIS

US_Patent_7512095_Multiple_Access_Communication_System_for_Moveable_Objects_aPanbo.jpgIt’s easy for anyone to Google the full details of Patent 7512095. The invention is named a Multiple Access Communication System for Moveable Objects and AIS is not specifically referenced, nor are the SOTDMA and CSTDMA transmission techniques discussed in my recent entry about the “new” SOTDMA Class B standard. That may partially explain why several anonymous sources involved with AIS seem surprised that a CSTDMA related patent exists at all, though others are not.

US_Patent_Application_60477125_Simple_Identification_System_aPanbo.jpgIt takes just a little more digging to find the 2003 Provisional Patent application that preceded the one granted in 2009. (Go to the official USPTO search site, fill in the CAPTCHA, and search for Application Number “60477125”.) Though still not called CSTDMA, this SIS patent concept is clearly about the Carrier Sense TDMA technique that replaced SOTDMA as the first Class B standard. In fact, the necessary “shorter packet” explains why a new two-part Class B static data message had to be created, which went on to cause a number of issues (as also discussed last week). Note, too, the first paragraph reference to the “patent issues which impact cost” {of the then current SOTMA AIS method}. While the differences between the 2003 patent application and the 2009 patent are great, be careful about drawing conclusions; I’m told that it’s common for provisional patent language to be broadened considerably in the final draft.

The IEC connection

IEC_TC80_WG15_members_2015_aPanbo.jpgI’ve never met the original patent applicant, Mark Johnson, but know him to be the proprietor of Shine Micro and purportedly the engineer behind some of the best AIS receivers on the planet. He’s also a longtime member of IEC TC 80/WG 15 — the AIS working group of the IEC’s subcommittee on maritime navigation and radiocommunication equipment and systems — as is Andreas Lesch, Johnson’s co-inventor for patent 7512095 (who apparently sold his share to SRT last March). Therein lies something of a mystery given the often heard notion that TC 80/WG 15 developed alternative CSTDMA to avoid patent restrictions.

I have seen some credible documentation of the Class B/CS standards-making process, including what seems to be a long email chain amongst WG 15 members. It seems clear, and it’s acknowledged by many, that Mark Johnson took a lead in developing the CSTDMA standard, writing on June 7, 2003, “I will be proposing a non-SOTDMA lower cost Class B variant that is low in cost, very ‘polite’, and compatible with existing Class A AIS. I am quite confident that it avoids the IPR issues.” That was one day before he filed the SIS provisional intellectual property claim referenced above, but again be careful with conclusions. One anonymous explanation of this apparent inconsistency is that the patent was filed only as a potential defense if some other entity claimed CSTDMA rights.


The IEC has a clearly stated policy that anyone participating in the work should reveal any known patent or pending patent application, either their own or of other organizations, and there’s a form for the purpose. If you go to the IEC’s patent declarations database and search on IEC Class B AIS Standard “62287” you will only find one declaration, partially shown above. It was filed by Anders Håkan Lans in 2007, stating that he would license manufacturers of SOTDMA Class B on a non-discriminatory basis with reasonable terms and conditions, though it seems that the IEC did not complete the B/SO standard until after the Håkan Lans patent claim was cancelled after reexamination. RAND or FRAND licensing terms are acceptable to the IEC, however, though the “free of charge” option #1 above is probably preferable, and patents under option #3 are not supposed to be in IEC standards.

All of this may help to understand SRT’s stance on the patent and also the recollections of the one TC 80/WG 15 participant willing to go on-the-record so far. That’s Joe Hersey, Jr., who is now retired from a 27-year USCG career deeply involved with telecommunications and standards-making, but who remains secretary of the US National Committee’s Technical Advisory Group to IEC TC80. Here’s his answer to my query about the Johnson/IEC patent situation back in 2003:

Yes, I believe that the IEC and its Working Group 15 (responsible at that time for Class A and B) were very well aware early in the CSTDMA development process that Mark had filed a provisional patent application, although I cannot speak to exactly when they became aware. Mark had made it very clear from the beginning of development of the standard that he had done so, but that its use was being offered free of charge on a non-discriminatory basis. The Working Group was very much aware of the patent difficulties associated with the Class A device and wanted to ensure the Class B avoided such difficulties. Since IEC could not complete a Class B CSTDMA standard until the technique were recognized in ITU-R Rec M.1371, the IALA AIS technical working group, had to prepare a CSDTMA amendment to that Recommendation too. The IALA AIS TWG members were also aware of the pending patent application, and that its use was being offered free of charge on a non-discriminatory basis.

And here’s Hersey’s response to my question about the possible effects of SRT’s licensing plan:

Because this patent has been long known and understood by the AIS standards committee members to be offered free of charge on a non-discriminatory basis, I question how SRT’s plan to suddenly offer licenses on a FRAND basis could be beneficial to the AIS industry and consumers. IEC, ITU-R, ITU-T and ISO have long held a common patent policy that requires participants in standards committees who hold a patent which may affect a standard under development to file a statement indicating which of three conditions licensing would be offered: free of charge and non-discriminatory, non-discriminatory and reasonable terms & conditions, or neither. If neither, the standard could not include provisions depending upon that patent. Hakan Lans filed noting the second option under the Class B SOTDMA standard IEC 62287-2. No filing was ever made regarding the Class B CSTDMA standard, despite Mark Johnson and Andreas Lesch (the later co-owner of the patent) being intimately involved in the standard’s development.

SRT on the record

I first looked into the IEC connection back in March and it happened that CEO Simon Tucker gave me SRT’s official take on it just after WG 15 had used its facility for a meeting where the patent was briefly discussed. You’ll see that Tucker had much more to say about why SRT acquired the patent and why their management of it may be a benefit to the industry and consumers:

This Patent and its founding prior-art IPR was known to the relevant IEC committees for many years, including before and during the development of the CSTDMA based Class B standard. However no formal license statement and or license procedure for this patent had been established by the owners. SRT was the first company to develop a low cost Class B and today offers a full range of AIS products from AIS Aids to Navigation and Class A to Class B and Coast station technology and product solutions, each of which offers best in class functionality and reliability. Our investment in leading edge technologies and robust and reliable derivative products has seen AIS products be substantially reduced in size and cost, simultaneously with their functionality and performance substantially increased. SRT has a long term commitment to AIS and is thus, of all companies, interested in its continued development within the correct standards process as defined by the IEC committee. As a responsible company SRT took the opportunity to acquire rights to the Patent to secure its use for the AIS standard going forward. Last week {March 20}, SRT hosted the IEC standards committee meeting at which this topic was discussed. The IEC AIS standards committee has a clear process for the licensing of IPR / Patents which are required for technical standards created by the IEC, and SRT confirmed that, as a responsible international company, that it would be following this process and therefore offering licenses for the Patent on a FRAND basis. This action by SRT ensures that a critical part of the AIS standard is secure for the benefit of all AIS stakeholders for the future and normalizes its availability. This is great news for the long term stability and continued evolution of AIS technology and products.

Regardless of the patent’s history and its possible safety in SRT’s hands, the underlying concern I first heard — “A tax on safety?” — remains, at least for some. Here is Simon Tucker’s recent response on that subject:

I see no valid reason why the licensing of a long known and established patent which ensures a technology standard works well should affect end user pricing; proof of this is that licenses are already agreed and there has been no price increase. Essential and other IPR licensing into products is a normal procedure in most products and industries these days – the average mobile phone or drug can have up to 20 of these. It’s down to the manufacturer to keep pace through continuous investment in R&D to generate more value in their product than the cost of the third party IPR they wish and or have to use. In our view this is a natural competitive process which in the end ensures that real R&D continues, and that companies seeking to provide the market with products never become lazy. Of course those companies who have chosen not to invest in new core technologies and products for years on end, take their profits and run, will not want or like change. But in my view the evolving requirements of the market are to be respected at all times and it expects manufacturers to continuously invest in order to win their business.

As for actual license details, a​n anonymous and displeased manufacturer showed me an email that appeared to originate from SRT and proposed “a quick and amicable agreement without publicity or any disruption to your business”​ with the following terms: “….there are well set precedents/norms for essential IPR such as this which is 5% of the net of tax retail price. We estimate that the average Class B retail price is in the region of $700, thus indicating a per unit royalty of $35 per unit. Our legal right to the per unit royalty extends to all sales over the last 6 years prior to our first expression of rights, and then going forward in the future. Thus, there would be a lump sum in regard to the arrears and then quarterly payments on sales until March 2019 when the patent expires.”

On the other hand, another anonymous AIS manufacturer responded to the initial SRT patent news with: “I don’t think it is a major issue for us. I do think they are trying to protect themselves from an onslaught of $200 Class Bs from China. In that sense it should help us as well.” There are at least six independent Class B AIS manufacturers: Garmin, Furuno, Icom, AMEC, Weatherdock, and Vesper Marine.

Vesper Marine challenges the patent

USPTO_application_to_rexxam_patent_7512095_aPanbo.jpgFinally, there’s the question of Patent 7512095’s validity. In late April, a Seattle law firm representing Vesper Marine asked the U.S. Patent Office to reexamine all 14 of its claims against what’s known as prior art. The 124 page petition and many related documents can be viewed or downloaded at the USPTO search site (search for Application Number “90/013498”) and may in themselves be an indicator of the industry costs in such circumstances.

Here are Joe Hersey’s thoughts on the patent’s validity:

I am uncertain whether the patent is a valid claim to an original invention for a number of reasons. I believe some question to this effect existed at the time, but because it was understood that the patent was being offered free of charge, it was not considered to be a concern. For example, Mark did not invent the CSTDMA technique alone but did so in cooperation with the USCG R&D Center, David Pietraszewski in particular. The Coast Guard has, in my opinion, an equally legitimate claim to the invention of the CSTDMA technique. Secondly, the “listen before transmit” technique central to CSTDMA slot access is not uncommon in telecommunications technology.

In early June, the Patent Office announced its determination that “A substantial new question of patentability affecting claims 1-14 of the ‘095 Patent is raised by the Third Party’s request…” and that the reexamination will proceed (as shown below).


So that’s the situation as well as I can report it at this time. Of course, I welcome corrections and commentary. The reexamination process as I understand it has several steps to go: SRT has an opportunity to respond to the reexamination request, the Vesper Marine representatives may respond to their response, and then the USPTO will make a judgement on the patent’s validity. That’s why I wrote that the consequences are murky. The patent may affect AIS developers and users in some ways until 2019 or not. But what’s happened so far has happened, confusing and complex though it may be, and there may be consequences for the companies and individuals involved. The floor is open.

Ben Ellison

Ben Ellison

Panbo editor, publisher & chief bottlewasher from 4/2005 until 8/2018, and now pleased to have Ben Stein as a very able publisher, webmaster, and editing colleague. Please don't regard him as an "expert"; he's getting quite old and thinks that "fadiddling fumble-putz" is a more accurate description.

23 Responses

  1. Ross Norsworthy says:

    It seems to me that you can’t tell everyone the patent is for their protection and does not incur remuneration, and then some day we wake up and find out we owe a boatload of back payments and payments going forward. That is entrapment in anybody’s ethos.

  2. gobsmacked says:

    “SRT and Mr. Johnson have entered into an agreement to exploit the commercial potential of the Patent.”
    ​”​I see no valid reason why the licensing of a long known and established patent which ensures a technology standard works well should affect end user pricing​”
    “We estimate that the average Class B retail price is in the region of $700, thus indicating a per unit royalty of $35 per unit. Our legal right to the per unit royalty extends to all sales over the last 6 years prior to our first expression of rights, and then going forward in the future. Thus, there would be a lump sum in regard to the arrears and then quarterly payments on sales until March 2019 when the patent expires.​”​

  3. Ben Ellison Ben Ellison says:

    Let me add that if you have some professional connection to the AIS industry or related regulatory bodies, please at least state your affiliation. That and other Panbo commenting policies here:
    And no offense meant to Ross Norsworthy — he did use his real name and I’m not even sure he has a stake in AIS anymore — but he certainly had a stellar career in the field:

  4. JoeH says:

    Ben, Ross has been an engineering consultant to the Coast Guard for many years and he’s still in that capacity today. He’s a member of IEC TC80 and their WG15 on AIS as well as the IALA eNav committee’s working group on AIS. He’s still active in AIS and in particular development of its high speed terrestrial/satellite expansion VDES (VHF Data Exchange System).
    He’s also chairman of RTCM’s SC 131 committee developing a standard for a multi-system shipborne navigation receiver, and is on the RTCM board.

  5. maestro says:

    As an ex-employee of SRT, I can’t help feeling that Mr Tucker is desperately trying to find some additional income to counter this years poor financial results, especially given the predictions of major profits this time last year.
    Otherwise, I have to echo Ross’s comments. It’s one thing to embark on a development plan for a piece of kit knowing that there will be some IPR payment involved, so it can be factored into the costing, it’s quite another to be un-expectantly hit with it 6 years down the line.

  6. Butch Davis says:

    This reads as though someone has misplaced their ethics or perhaps I’m just too old to understand modern business methods.

  7. Ben Ellison Ben Ellison says:

    I just got this email from David Pietraszewski, who is credited with a major part in CSTDMA Class B AIS development by Joe Hersey above (and who I queried earlier this week):
    “I have been a government retiree for several years; but I continue to work part-time on AIS related work at the USCG R&D Center as a Sonalysts, Inc. employee.
    I did read your article, “SRT acquires Class B AIS patent…”, and found it interesting. You did your research. I agree with Joe’s comments and have little to add. I have no comment on the status or ownership of the CSTDMA patent. But, I know a lot of work went into getting the CSTDMA radio signal correctly defined and tested.
    In the time period (2002-2003’ish) prior to the patent, both IALA and IEC were investigating the possibility that AIS could be expanded to serve more than the IMO SOLAS class vessels, in particular, the recreational boating community. The notion of using an “energy threshold” to detect unused AIS time slots for the recreational equipment’s broadcasts was developed during that period. The CSTDMA concept evolved and matured during those discussions and became a new form of AIS (the ITU AIS standard was amended). As I recall, some of the high-level “Class B” objectives were to:
    – Avoid potential SOTDMA patient issues. At the time, SOTDMA was “free” for IMO defined “SOLAS” vessels only.
    – Seamlessly mesh broadcast content and VDL use with the operation and display systems of the existing Class A units
    – Use the VDL politely with essentially no impact on Class A performance. For example, Class B Carrier Sense units do not cause Class A units to avoid additional “reserved slots.”
    – Provide minimal notice of a vessel’s presence; position, not tracking, being the objective. The update rate was sacrificed to reduce VDL loading, power needs, and component cost. If tracking is essential, a Class A unit should be used.
    As Joe mentioned, I was quite involved in developing the Class B CSTDMA standard; but credit for designing and building working equipment has to go to the industry folks on that IEC working group.”

  8. Ben Cosier says:

    Regardless of the patent outcome, AIS is a crucial safety tool, worldwide. Underpinning it is an “open standard,” even if developed commercially. This “open standard” needs to meet the needs of its users and be commercially achievable (ie financially as well as otherwise) for the many AIS manufacturers. This is crucial to the viability, deployement, stability, upgrades, and overall operation of a key worldwide safety technology, that is AIS.
    I just hope SRT keeps the standard “open” for the benefit and safety of the international marine community. Imagine if VHF marine radio went digital and different manufacturers used different digital standards, or added their own extra features that would only partly talk to other radios (or not at all).

  9. Derek Love says:

    From my recollections, Davids contribution to Class B-CS was instrumental – I well remember his overriding mantra at the IEC meetings – “Do not harm the VDL”

  10. Karl says:

    Ben’s article and the user comments leave me totally confused. If use of the patent was to be “free of charge and non-discriminatory”, why patent it in the first place?
    Why not make it open-source and thus prior art to prevent someone else from profiting from it?
    2003??? The industry moves at glacial speed…look at how long NMEA 2000 (ostensibly named for its year of adoption) took to gain public acceptance, along with a patchwork of proprietary connectors by manufacturer.
    And, rather than going the patent route, NMEA chose the copyright method of closely guarding its secrets. In my opinion, NMEA has done a disservice in not making their bus totally open-source with complete software development kits available to all, not just royalty payers. After all, it is primarily a “fork” of prior art used in CANBUS systems in wide use in other industries, including CAD/CAM manufacturing, for example, probably why it was not patentable.
    I’m obviously missing the entire point of all this.

  11. Ben Ellison Ben Ellison says:

    I agree that you’re missing a lot, Karl, like this sentence:
    “One anonymous explanation of this apparent inconsistency is that the patent was filed only as a potential defense if some other entity claimed CSTDMA rights.”
    That idea is fairly consistent with Joe Hersey’s memory that the patent would be free of charge and non-discriminatory. The patent’s intention may have been only to establish prior art if it didn’t already exist (which is now being reviewed).
    But all this took place 12 years ago, so memories may vary a lot. I sure don’t feel like I know exactly why the patent was filed, though due to Joe Hersey’s and other input I doubt that Mark Johnson filed it with royalty expectations. Hopefully more people who were involved will speak out and the whole story will become clear eventually.
    I’m not going to let these comments sidetrack to NMEA 2000, but note that no manufacturers pay royalties to use N2K. Nor is it a fork of CANbus; it’s an implementation layer built on top of CANbus:

  12. Ben Ellison Ben Ellison says:

    Slightly related news: Garmin is claiming victory regarding Navico’s patent suit over DownVü sonar:
    Marine electronics companies don’t talk about this area much, but there may also be patent issues around side viewing sonar, auto routing, and other technologies.

  13. Martin says:

    Ben,maybe you should also tell the story from the beginning starting with the job of trying to get the whole world adapt a new way of seeing airplanes/ships. That is not cheap, fast or simple.
    This patent discussion feels strange since the whole thing with CSTDMA was avoiding Håkan Lans patent claims on SOTDMA. And now?

  14. Ben Ellison Ben Ellison says:

    More Garmin patent news:
    I’m impressed that Garmin announced this somewhat negative news themselves, but the Johnson Outdoors (Humminbird) PDF further suggests that Garmin may have to stop SideVue sales, at least for a while:

  15. Ben Ellison Ben Ellison says:

    The SRT AIS patent reexamination is not final, but the examiner has tentatively rejected all 14 claims. The 15 page document includes prior art detail for each rejection. To download the doc go to
    fill out the captcha
    search for Application Number “90/013498”
    look for 9/11 “Reexam – Non-Final Action” doc under Image File Wrapper tab
    I believe that SRT now has 2 months to argue its case for patent validity.

  16. Ben Ellison Ben Ellison says:

    Garmin may regret their “Victorious over Navico…” press release now that the ITC seems to have reversed course:
    The issue of side scan patents with Humminbird has not gone well either:
    As for the AIS patent dispute, SRT has filed arguments in support of their claims, as well as new claims, and now the examiner has a while to make a final decision.

  17. Ben Ellison Ben Ellison says:

    Garmin plans to appeal ITC ruling and says it “will have no impact on Garmin products already purchased by our customers and dealers, or any products purchased going forward.”
    Which is quite a difference of opinion from Navico’s take on the situation.

  18. Ben Ellison Ben Ellison says:

    Garmin put out a dealer service bulletin that’s even more emphatic about Navico’s press release being “inaccurate and misleading”…

  19. Ben Ellison Ben Ellison says:

    $37,000,000 serious is where the Garmin/Navico downscan patent dispute has gotten:
    Garmin claims that ClearVu products are not affected by the dispute, but Navico claims otherwise, and made a video to illustrate:
    Meanwhile, Garmin sued Navico, and Raymarine/FLIR, over their marine auto guidance (auto routing) in the U.S.:

  20. Ben Ellison Ben Ellison says:

    Reversal! Garmin is claiming quite a victory:
    But maybe Navico will weigh in?
    This subject is also being discussed on the Forum, which is probably a better spot for it:

  21. Ben Ellison Ben Ellison says:

    I think the Class B AIS patent is dead. The paperwork has piled up and just maybe another appeal is possible, but on 8/24/17 three judges on the U.S. Patent Trial and Appeals Board affirmed the Examiner’s prior rejection of claims.
    Meanwhile there’s another turn in the Garmin/Navico battle, this time affirming the huge fine against Garmin apparently despite their patent victory:

  22. Ben Ellison Ben Ellison says:

    Nice! Apparently Navico and Garmin made peace regarding sonar patents. Both companies sent the exact same press release this morning:

  23. Ben Ellison Ben Ellison says:

    The Class B/CS AIS patent is still alive, as you can see by searching…

    …for application “90/013498” and dive into the Image Files. But — as I understand the documents — the patent claims have so far been rejected by an examiner and then by an appeals board, and are only being reexamined because the board rejections were based on different reasons than the examiner.

    Also, almost all the original claims have been canceled by SRT and Mark Johnson, and many new claims were added. While that’s allowed, I’m told that if the patent survives this process, it will likely not apply to Class B transponders already built.

    Meanwhile, Class B/SO is coming on strong and getting rapidly less expensive, and this patent has nothing to do with it. If you check the FCC for AIS, you’ll see numerous new ones already approved:

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