New DSC Recommendations

VHF Marine Band radios, protocol, radio communication theory, practical advice; AIS; DSC; MMSI; EPIRB.
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New DSC Recommendations

Postby jimh » Fri Oct 14, 2016 10:20 am

The International Telecommunications Union (ITU) has updated their recommendation M.493, "Digital selective-calling system for use in maritime mobile service," to revision 14. The new revision was adopted last fall, September 2015. One of the participants of the ITU committee that worked out the changes is Glenn Dunstan, an Australian gentleman who also runs the website [GMDSS INFO--which has unfortunately gone to a domain name harvester and no long contains useful information]. In a posting about the newly revised recommendations for DSC, Glen characterized the changes in ITU-R M.493-14 as follows:

The new version, 493-14, contains a number of important changes:

- Class D and E GMDSS systems (for recreational vessels) must be fitted with an integrated GPS receiver
- New Class H (handheld) - also must have integrated GPS
- New Class M (MoB) device - fitted with DSC and AIS
- the user interface requirements in Annex 3 have been made mandatory

There was also a general tidy up of paragraphs and tables.
Source: [original on-line source is no longer available; please see an separate article that has information on how to access an archive of the GMDSS.COM.AU website.]

The most interesting element of the revised recommendation is that CLASS-D DSC radios MUST have an integrated GPS or GNSS receiver, and so must CLASS-H handheld DSC radios.

The newer ITU-R M.493-14 document can be obtained at no cost from the ITU website at

https://www.itu.int/rec/R-REC-M.493

The recommendation is a very technical document, and not what one might call light reading.

In the United States, the Federal Communications Commission (FCC) is the regulating authority for marine radios. The FCC is presently requiring that radios sold for use in the USA must comply with the previous version of the recommendation, ITU-R M.493-13. I believe this is codified in the USC at 47 CFR 80.225 - Requirements for selective calling equipment. See https://www.law.cornell.edu/cfr/text/47/80.225 which says, in part:

Beginning March 25, 2009, the Commission will not accept new applications..for certification of non-portable [i.e. fixed-mount] DSC equipment that does not meet the requirements of ITU-R M.493-13 and, in the case of Class D DSC equipment only, IEC 62238.


As seen recently in their action against one major radio manufacturer (ICOM), the FCC has been quite strict in insisting on compliance. In some cases the offending practices in current-production radios were quite minor.

For example, ICOM was cited by the FCC (and fined) because their DSC radios did not comply with the requirements. Apparently one of the discrepancies found by the FCC in the ICOM radio was in regard to a requirement alerting the operator of the radio when the automatic position update information has become stale. The regulations say:

If the automatic position update is not available, a displayed and audible reminder to manually update the position should occur...before the position information is 4 hours old.


The out-of-compliance radio sounded the alarm at 4-hours; the remedy was to change the alarm to sound at 3-hours 59-minute, i.e., "before the position information is 4 hours old." By sounding the alarm one-second sooner, the radio complied with the recommendation. (Your government bureaucrats at work.)

There is no telling when and if the FCC will revise its regulations to adopt the new ITU recommendation. Perhaps it will be possible for the radio manufacturers to make new radios that comply with the new ITU recommendation and still have the radios comply with the old version, too. I don't know if such backwards compliance is possible.

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Re: New DSC Recommendations

Postby jimh » Tue Oct 18, 2016 10:28 am

The FCC made a request for comments on proposed changes to the regulations of the Maritime Radio Service (Part 80 of the FCC regulations). The complete proposal and all public comments are available from the FCC website. Several comments were filed in regard to the recommendation that DSC radios of CLASS-D should be required to have integral GNSS receivers. Here are some excerpts from those public comments:

GARMIN objected to the recommendation of a built-in GNSS receiver in every radio, saying, in part:

Garmin Invites the FCC To Considerer Carefully RTCM’s Proposal of Requiring “Integrated” GPS Receivers in All VHF Radios.

Garmin is particularly concerned that RTCM’s proposed revision to Section 80.225(a)(1), which would require each marine VHF radio to be equipped with its own “integrated” GPS receiver, may lead to greater burdens on both consumers and manufacturers than are justified by the corresponding safety improvement. RTCM posits that this change will promote safety by ensuring that each individual device will be able to provide its own location fix. This would purportedly aid both the individual mariner (who will ostensibly be more aware of his/her position) and emergency personnel who would presumably be able to locate distressed mariners more easily.

While Garmin supports the purpose and principle of RTCM’s proposal, it is concerned that, depending on how this change is implemented, it could impose significant burdens on consumers without providing any corresponding safety benefits. As an initial matter, Garmin requests that the commission clarify its interpretation of “integrated.” If the requirement means that every marine VHF radio must have its own GPS receiver embedded within the device itself, that obligation would lead to more expensive devices, but, as explained below, not necessarily guarantee provision of safety-enhancing position data.

The VHF radios that Garmin currently sells do not include embedded GPS receivers in each device. Instead, Garmin markets and sells VHF radios for boaters to use as part of a hard- wired, networked, GPS-enabled onboard system – a Garmin marine system. Such a Garmin marine system may include a variety of devices and systems, including: a GPS receiver, VHF radio, sonar, radar, and other instruments and sensors, as well as a multi-function display that combines these capabilities for maximum boater situational awareness, safety, and convenience.5 The backbone of this system or network is the high-quality GPS receiver that is placed in an area of the vessel above deck and with an unobstructed view of the sky. Careful placement and installation ensures that the GPS receiver can obtain a strong signal from the distant satellites and provide continuous position, velocity, and time (“PVT”) information to the network. In this setup, Garmin’s VHF radios are physically connected to the GPS receiver through the network to ensure that the radio can take advantage of the PVT data provided by the GPS receiver, particularly in situations when the VHF radio may need to be used to place a distress call using the radio’s Digital Selective Calling capability. Garmin customers are motivated to utilize the network capability of its devices through dealer installation programs and overall ease-of- installation and networking. Garmin devices are “plug-and-play” compatible with one another, certified to the latest compatibility standards for use with other manufacturer’s products (NMEA 2000), ship from the factory with appropriate interconnectivity hardware and cables, and include a variety of interdependent features that encourage integration. Further, Garmin VHF radios sound an audible alarm to the user if the radio is not connected to the marine network, further encouraging interconnectivity. Given this arrangement, maintaining a separate GPS receiver embedded in each VHF radio would not improve boater safety.



The Coast Guard of the United States of America (USCG) also commented on mandatory integration of GNSS receivers in radios, specifically pointing out:

ITU-R Recommendation M.493-14 (09/2015) requires that Class D (VHF) and Class E (HF) digital selective calling equipment be provided with an integral electronic position fixing device. Recognizing that approximately 90% of VHF DSC distress calls received in the U.S. do not have position information, the U.S. Coast Guard supports this requirement.

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Re: New DSC Recommendations

Postby jimh » Tue Oct 18, 2016 10:51 am

I don't find Garmin's position to be supportable on the basis of a burden being imposed on consumers. The whole premise of digital selective calling distress alert transmission is to digitally send the transmitting ship's location. The USCG experience shows that this does not occur in 90-percent of the cases, precisely because the boater has failed to integrate an external GNSS receiver with their DSC radio, as Garmin suggests should be the preferred practice.

Compare DSC distress alerting with 911 calls from mobile telephones, which is quite analogous. In the case of mobile telephones, the entire mobile telephone industry had to come up with a method for mobile telephones to indicate their position in a 911 emergency call. This led to the inclusion of GNSS receivers in mobile telephone and the invention of the whole Assisted GPS technology to allow those GNSS receivers to be able to get very rapid position fixes. Mobile telephone providers have to maintain A-GPS features on their networks, and mobile telephone manufacturers have to built the GNSS receiver and the A-GPS capability into every mobile telephone. This is an enormously greater burden on a much larger industry than the FCC is asking for the Maritime Radio Service. Adding a GNSS receiver to a marine radio cannot actually cost more than about $20 in manufacturing, and it will make the radio a self-contained system that can work without interconnection to other devices. In the present market, radios with GNSS receivers are generally only about $60 to $80 more than identical models without the built-in receiver. (Compare prices and models at http://continuouswave.com/forum/viewtopic.php?f=9&t=460.)

This incremental cost is actually less than the cost of a basic NMEA-2000 network installation, which would be necessary under Garmin's proposal to permit "plug-and-play" integration of an external GNSS receiver with a radio.

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Re: New DSC Recommendations

Postby conch » Wed Oct 19, 2016 11:35 am

It seems the new rules regarding a mandated integrated GNSS make the SH GX6000 obsolete before it even is offered for sale.

The Garmin argument asking to be allowed an external GPS receiver for their radios seem along the lines of the same reasoning used as best practice/location for the external AIS antenna for the SH GX6000 to "improve performance".

[Now quoting my own earlier comment about AIS--jimh]
"Also, the GX6000, like the GX6500 transponder model, uses a separate antenna input for the AIS receiver. This may seem like an inconvenience for the typical recreational boater, but the GX6000 series is designed for best performance. By requiring a separate AIS receiver antenna it should improve performance in AIS and communication radio reception, as the antenna won't be split between two receivers, which can cause some signal loss for very weak signals"

Chuck

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Re: New DSC Recommendations

Postby jimh » Wed Oct 19, 2016 8:18 pm

CHUCK aka CONCH--you have mixed together two disparate notions. I will explain

There is no regulation on AIS antennas. An AIS receiver or AIS transponder is free to use any sort of antenna; the antenna is not covered by regulations. You can share an antenna between an AIS receiver and a communication transceiver; you can share an antenna between an AIS Class-B transponder and a communications transceiver. You can use a coupler or combiner or sharing device, or you can use separate antennas. You can have two antennas or one antenna. You can mount them where you like. It is your choice.

The recommendation in M.493-14 is in regard to a DSC radio, and not an AIS radio. The part of the recommendation pertaining to GNSS receivers in DSC radios has not actually been quoted in this discussion. Let me introduce its exact language:

12.7 Position updating
DSC equipment should accept valid IEC 61162 position information including the time at which the position was determined, from an external source utilizing the data interface described in § 12.6, for automatic update of own ship’s DSC position.

The DSC Class D and E Equipment should, and the DSC Class A and B equipment may also be provided with an integral electronic position fixing device. In which case, the DSC equipment should automatically switch to the internal source if the external IEC 61162 position information is not valid or not available. Antennas for integral electronic position fixing devices should be mounted externally, such that they are provided with an unobstructed view of the sky.


Now let's parse that to make its meaning clearer:

"The DSC Class D ...Equipment should...be provided with an integral electronic position fixing device."

What is at question is the precise meaning of "integral electronic position fixing device." We can, for the purpose of this discussion, presume that the position fixing device will be a GNSS receiver. So we now must decide what constitutes an "integral GNSS receiver."

But before we do that, let's read more of the recommendation. It goes on to say, in that same section:

"Antennas for integral electronic position fixing devices should be mounted externally, such that they are provided with an unobstructed view of the sky."

The recommendation therefore is a Class-D DSC radio:

--SHOULD have an integral GNSS receiver, and

--SHOULD have an external antenna for that integral receiver.

GARMIN does not make an argument for that. GARMIN argues that their provision of another, separate, non-integral GNSS receiver somewhere on their network should be allowed because it will reduce of the burden on the consumer of the cost of the gear. Again, this is a somewhat specious argument because, at the least, the cost of the network to connect the DSC radio to a stand-alone GNSS receiver on a network will be a greater burden than having to buy a radio with an integral GNSS receiver. Building a network costs at least $100 and more if labor and installation is considered. Buying a radio with a GNSS receiver internal to the radio only costs $60 to $80. GARMIN's argument assumes that the boater will already have bought a Garmin chart plotter or Garmin GNSS receiver and built a Garmin network. That's not a realistic assumption. Further, what Garmin proposes is to remain with the status quo, which, as the USCG comments, has produced a completely unworkable system in which 90-percent of the DSC radios used to make distress alert class do not transmit a position. This is real world experience that contradicts Garmin's stance.

Also, the Standard-Horizon GX6000 can be completely IN CONFORMANCE with the M.493-14 because it provides PRECISELY what is recommended, that is, it has an INTEGRAL GNSS receiver with an EXTERNAL ANTENNA. Note that the SCU-131 GNSS receiver

--is connected directly to the GX6000 to a specialized port, not to a network,

--is powered by the GX5000 not by some other source, and

--is an integral component of the receiver.

It is not a separate component connected to a network of many devices that sends its data to the network; it sends its data directly and only to the GX6000. I cannot see any basis for a claim that the GX6000 is already obsolete in that it won't comply with M.493-14. In any case, since the FCC has not adopted M.493-14 but instead insists radios comply with the earlier M.493-13, Standard-Horizon is complying with the regulations in effect now. If the FCC decides to adopt M.493-14, Standard-Horizon would just bundle the SCU-131 GNSS receiver with the radio and sell them together.

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Re: New DSC Recommendations

Postby conch » Thu Oct 20, 2016 10:37 am

I agree Standad-Horizon would have to include the antenna packaged along with the GX6000 to be compliant with the [M.493-14 recommendation].

The Garmin VHF radio can accept a GPS receiver directly without any additional network using the 19x HVS over NMEA-0183.

The full comment submitted by Garmin was explaining the benefit of an external GPS antenna for improved reception/performance. The Coast Guard agreed with them. I was trying to say and compare that both Standard-Horizon and Garmin present similar benefit and arguments for using external antenna when it suits their product and purpose.

I have the Standard Horizon GX1600, HX870, and GX2200 VHF radios and consider them some of the best values aboard my Whalers, they all work without a fault. The screen interface icons of the HX870 appear to be the same as I see on the first pictures of the GX6000 and are easy to use. I do not use an external GPS antenna with the GX2200 at this time. I have a hardtop mounted Garmin 19x antenna for Garmin MFDs that I could switch to if needed. The GX1600 receives GPS info from a Garmin 740s, on my Sport 15, all have a unique MMSI entered.

Chuck

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Re: New DSC Recommendations

Postby jimh » Thu Oct 20, 2016 4:34 pm

conch wrote:...The Garmin VHF radio can accept a GPS receiver directly without any additional network using the 19x HVS over NMEA-0183....


As far as I can see, ALL present DSC radios can accept data from an external GNSS receiver via NMEA-0183, but the USCG experience shows that this is not a workable solution in that 90-percent of the existing DSC radios that have initiated a distress alert call have not sent their position, according to USCG data.

But external GNSS sensors using an NMEA-0183 interface to connect to a radio would have to be powered by some other source. They would not be integral with the radio like a device like the SCU-131 would be; the SCU-131 plugs into the GX6000 and is powered by it through that plug-in connection. That is much more integral than wiring up an external GNSS for power and then figuring out how to connect it to the radio--that's what boaters have mostly NOT been able to accomplish and what seems to be the driving force behind the recommendation to make the GNSS sensor integral with the radio.

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Re: New DSC Recommendations

Postby conch » Thu Oct 20, 2016 7:32 pm

How are you parsing this sentence from the proposed language "In which case, the DSC equipment should automatically switch to the INTERNAL source if the external IEC 61162 position information is not valid or not available."

I wonder if what was really intended was for a class D VHF to have a backup/no operator involved GPS source for a DSC distress call. Possibly a typo/error in the first use of the word integral in 12.7, maybe it should have been the word internal. That seems to make more sense and adds the backup GPS source, and gives the radio something to automatically switch to.
Like this

The DSC Class D and E Equipment should, and the DSC Class A and B equipment may also be provided with an INTERNAL electronic position fixing device. In which case, the DSC equipment should automatically switch to the internal source if the external IEC 61162 position information is not valid or not available. Antennas for integral electronic position fixing devices should be mounted externally, such that they are provided with an unobstructed view of the sky.

Is the SH SCU-131 just a GPS antenna or a GPS antenna with receiver? Nothing on their site yet.
Are there any regs on the number receiver channels for the GPS? Does it make a noticeable difference? SH claims 66 and Garmin 32. Maybe better as a separate thread.

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Re: New DSC Recommendations

Postby jimh » Thu Oct 20, 2016 10:32 pm

conch wrote:How are you parsing this sentence from the proposed language "In which case, the DSC equipment should automatically switch to the INTERNAL source if the external IEC 61162 position information is not valid or not available."[?]

I read that fragment of a sentence exactly as it is written.

conch wrote:Are there any regs on the number [of] receiver channels for the GPS?

None that I know of.


conch wrote:[Does] the number [of] receiver channels for the GPS...make a noticeable difference?

Yes.

conch wrote:[Standard-Horizon specified] 66 and Garmin 32. Maybe better as a separate thread.

As for what significance the number of "channels" a GNSS receiver has, I started a new thread. See

Use of the Term "channels" in GNSS Receivers
viewtopic.php?f=9&t=1573&p=9433#p9432

Number of channels in the receiver has no bearing on the proposed regulations for DSC radios since I don't know of any requirement in them about the position fixing device for a DSC radio.

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Re: New DSC Recommendations

Postby jimh » Fri Oct 21, 2016 9:12 am

conch wrote: I was trying to say and compare that both Standard-Horizon and Garmin present similar benefit and arguments for using external antenna when it suits their product and purpose.


Standard-Horizon has not filed any comments about the proposed DSC recommendations, so they have made no comment regarding the inclusion of GNSS receivers in the radio. Since Standard-Horizon is already manufacturing radios with GNSS receivers built-in, I don't see that Standard-Horizon would have an argument to make against the new regulations.

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Re: New DSC Recommendations

Postby jimh » Fri Oct 21, 2016 10:47 am

I'd like to get the discussion back on track to review the recommendations made in ITU-R M.493-14. Again, let's use Glenn Dunstan's summary of the salient features. Glen said:

The new version, 493-14, contains a number of important changes:

--Class D and E GMDSS systems (for recreational vessels) must be fitted with an integrated GPS receiver
--New Class H (handheld) - also must have integrated GPS
--New Class M (MoB) device - fitted with DSC and AIS
--the user interface requirements in Annex 3 have been made mandatory

There was also a general tidy up of paragraphs and tables.


The first three bullet points refer to GNSS receivers in DSC radios of Class D, E, H, and M. This has already been discussed, but I want to present more of the actual text to better understand what the proposal recommends:

12.6 Data interface

DSC equipment should be provided with facilities for exchange of data from shipborne navigational equipment or systems, or other shipborne equipment as necessary in accordance with IEC 61162 series for purposes including automatic position updating.

12.7 Position updating

DSC equipment should accept valid IEC 61162 position information including the time at which the position was determined, from an external source utilizing the data interface described in § 12.6, for automatic update of own ship’s DSC position.

The DSC Class D and E Equipment should, and the DSC Class A and B equipment may also be provided with an integral electronic position fixing device. In which case, the DSC equipment should automatically switch to the internal source if the external IEC 61162 position information is not valid or not available. Antennas for integral electronic position fixing devices should be mounted externally, such that they are provided with an unobstructed view of the sky.

If the automatic position update is not available, a displayed and audible reminder to manually update the position should occur when a) no position information is provided during start up and b) before the position information is 4 hours old. The displayed reminder should remain until position updating has been carried out. Any position information not updated for more than 23½ hours should automatically be erased.
Own ship’s DSC position information and the source of that information (external, internal, or manually entered) should be displayed on the DSC equipment.


To aid in understanding, the references to IEC 61162 are to a standard that recommends use of NMEA-0183 or NMEA-2000 data interconnections between devices. Thus we can restate section 12.6 Data Interface as saying the DSC equipment:

--SHOULD have NMEA-0183 or NMEA-2000 to permit exchange of data with other navigation equipment or systems for purposes including automatic position updating.

That is quite easy to understand. Now we turn to Section 12.7. This section talks about a "electronic position fixing device," which to simplify we can just call a GNSS receiver. Section 12.7 then makes four more points. Let's limit this analysis only to CLASS-D devices for simplicity. This section says the DSC CLASS-D radio equipment:

--SHOULD accept valid NMEA-0183 or NMEA-2000 position and time information from an "other" GNSS receiver (12.7, first paragraph);

--SHOULD have an "integral" GNSS receiver (12.7, paragraph two);

--SHOULD have an "externally mounted" antenna for that "integral" GNSS receiver to get a clear sky view (12.7 paragraph two); and

--SHOULD switch to an "internal" GNSS receiver if the external data source does not provide valid position or is not available (12.7; paragraph two).


There is a bit of confusion here. The words "integral" and "internal" are both used. This is unfortunate. The goal of the rewrite was to clarify the recommendation. This language seems to muddy up the language. For language, I like to use M-W.COM as a source. Here is what they say:

INTEGRAL--(1c) formed as a unit with another part; (2)composed of constituent parts;
Cf.: http://www.merriam-webster.com/dictionary/integral

INTERNAL--(1)existing or situated within the limits or surface of something
Cf.: http://www.merriam-webster.com/dictionary/internal

The conflict in the recommendation in section 12.7 stems from a reference to a radio having an integral GNSS receiver and later to having an internal GNSS receiver. Is the "other" GNSS receiver of 12.6 what is meant by the "integral" receiver of 12.7? Or is an "other" receiver an external receiver. And when that source is not available or invalid, where did we get the "internal", i.e., inside the radio, source of position information?

To make things even a bit more confusing, Glenn's comments use a third term, "integrated." Let's see what M-W.COM says about that:

INTEGRATED--having different parts working together as a unit
Cf.: http://www.merriam-webster.com/dictionary/integrated

I am afraid the re-write of the standard to -14 revision seems to leave this less than completely clear. I can see why manufacturers of radios might have a bit of trouble making a radio that complies--they are aiming at a fuzzy target. It is clear they need to make a DSC radio that can connect to an "other" GNSS receiver via NMEA-0183 or NMEA-2000. But should they make a DSC radio with an integral, internal, or integrated GNSS receiver? Those three words all mean three different things.

Glenn's term "integrated" and the ITU's term "integral" are almost the same. But then the ITU says "internal" which is certainly not the equivalent of the other two terms. Maybe this can be clarified in some way when the recommendation is formally adopted. For example, the FCC could--and should--make it clear what is required for a DSC CLASS-D radio in terms of how it might have an internal or integral or integrated GNSS receiver.

Also note Glenn's use of the term "must" and the ITU's use of "should" in regard to what features the radio will have. I suppose that if the recommendations are adopted by a regulating authority as their formal rules, then "should" becomes "must." Better ask a lawyer about that.

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Re: New DSC Recommendations

Postby conch » Sun Oct 23, 2016 10:07 am

[Changed topic to discuss the languages used in international regulations; this sidebar has not been archived in this thread because none of us are reading the proposed recommendations in ITU-R. M.493-14 in any language other than English.--jimh]

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Re: New DSC Recommendations

Postby jimh » Sat Dec 22, 2018 11:46 am

A follow-up discussion about the behavior of the Standard-Horizon HX890 CLASS-H DSC radio is now in a separate thread.