Alan, though we may disagree as to the amount or nature of FHSS in ROS,
the bottom line is that the FCC engineers, as well as the ARRL
engineers, reviewed both the documentation and the signal footprint, and
have concluded it is FHSS. While their opinion might be changed through
dialog, that is unlikely at this point, so the most sure approach is
just to agree it is FHSS and petition for a variance with necessary
limitations. It is highly unlikely that the FCC will reverse their
decision, especially since the author, whom the FCC expected to tell the
truth, wrote a 9-page paper claiming it was FHSS, titles, "INTRODUCTION
TO ROS: THE SPREAD SPECTRUM". To try to re-characterize it as something
else in order to get approval puts the credibility of the author in
serious doubt, especially after the fiasco over the posting of an FCC
announcement that it was legal that the FCC claims they did not make.
Admit it is FHSS, but petition for a variance or modification of the
rules to allow it on the basis that it is not harmful to other modes,
and that will probably be granted. It is too late, and too much dirty
water has passed under the bridge, to even imagine that any other way
can be successful.
I think we have beat this horse to death at this point and should move
on to another topic.
73 - Skip KH6TY
Alan Barrow wrote:
I'll preface this by saying that I'm not trying to defend or crucify
ROS. But when we are dealing with definitions & the FCC, it's very
important we be clear & accurate on our definitions.
KH6TY wrote:
> By definition, it is SS "if" the pattern is independently generated
> from the data.
One test, but not the only test
> The original intent of FHSS was to make third-party decoding
> impossible without knowledge of the code that generated the tones or
> carriers.
True, emphasis on "original intent". There are many, many SS
implementations & usages that are not done to prevent third party
decoding. It's actually a very good way to share spectrum with
dissimilar usages. And nearly all FHSS can be easily decoded independent
of knowing the code now unless the data itself is highly encrypted.
> FCC rules disallow encryption because we are required to police the
> bands ourselves. As long as there is not a pattern to the frequencies
> generated, that is independent of the data, one of the necessary and
> sufficient conditions to qualify as FHSS is missing.
This is overly simplistic. I have first hand experience with FCC
dealings with regard to "code generators" used for randomization of
amateur digital signals. All that is required is to make available upon
demand the code sequence. You don't have to offer a decoder, nor do OO's
have to be able to monitor it, etc. Just make the code sequence
available upon request.
> However, in the case of ROS, the repeated pattern is not there, so,
> until the regulations are changed, ROS is illegal FHSS, even though
> the spreading is limited and capable of third-party monitoring.
Sorry, this is overly simplistic. Many US legal codec/modems do not meet
this test. ROS may or may not be legal, but it's not your repeated test
definition that makes it so.
The most legit issue that technically makes it SS is that a single data
bit is sliced into smaller bits when sent. IE: the code rate is much
greater than the data rate. (which directly correlates with spreading
factor as well).
> That is a result of a historical attempt to prevent encryption, but
> this can probably be changed through the petition process with public
> comment. Until then, hams in the US have no choice but to abide by the
> regulations as written.
First hand experience: It does not take petition with public comment.
Just professional dialog with the FCC, and a willingness to provide
details on the encoding sequence if requested.
> In the author's own words, three necessary and sufficient elements
> make it SS, and a search of the literature says the same:
>
> 1. The signal occupies a bandwidth much in excess of the minimum
> bandwidth necessary to send the information.
> 2. Spreading is accomplished by means of a spreading signal, often
> called a code signal, which is independent of the data.
> 3. At the receiver, despreading (recovering the original data) is
> accomplished by the correlation of the received spread signal with a
> synchronized replica of the spreading signal used to spread the
> information.
This is close to, but not exactly the ITU (and thus US Federal)
definition of SS. But I agree with you, ROS by the author's description
met the legal definition of SS. But the real question is, should it be
treated the same as traditional SS which normally uses a much larger
(100x or more) spreading factor and thus would negatively impact an
entire HF amateur allocation.
> The operative phase here is "independent of the data".
So how bout randomizers used to maximize average power? (used reduce
crest factor). Viterbi encoders?
> It is just unfortunate that the FCC regulations, as currently written,
> do not allow ROS on HF and that they really need to be updated. Note
> that SS is already permittted above 222 MHz, where there is plenty of
> space to use for spreading that does not exist on HF. In fact, the
> encryption aspect is not even mentioned, except in other parts of the
> regulations disallowing encryption. The regulations were obviously
> written to prevent extremely wide SS signals from interfering with
> other users. Since ROS is no wider than a phone signal, there is no
> reason the regulations should not be modified to allow it (perhaps
> with other necessary limitations), but until then, and right now, ROS
> is illegal below 222 Mhz. It is that simple!
>
>
> Compare the repeated pattern of MFSK64 to the random pattern of ROS as
> data is applied.
Invalid test. Do the same with P3 with compression turned on.
I understand what you are trying to do, and agree with some points. But
also see a very simplistic approach to SS "tests" that will ultimately
do us a dis-service.
Have fun,
Alan
km4ba
