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Rick I think you have raised some very good
questions and work does need to be done in these areas.
73,
Mike, K1EG
----- Original Message -----
Sent: Saturday, June 18, 2005 10:09
PM
Subject: [digitalradio] HF Digital
network modes
The time available to do free coding with no chance of
renumeration is quite
limited for everyone since it is such a precious
resource and can only be
done by a few people. Ideally, a group would get
together based upon some
kind of target they are trying to
reach.
What should that target be? As we have seen, there are many
different views
on the subject. But are groups such as ARRL or TAPR even
concerned about
some kind of new amateur radio network?
My view is
that we need an easy to use system that can tie together
various
subnetworks, be open sourced if at all possible, be decentralized
and not
dependent upon single point failure systems such as the Winlink
2000
unfortunately is designed.
It would be highly adaptable to the
channel capacity and conditions and
scale adaptably using RF circuits for
the most part, but also use the
internet when you must in order to
reach e-mail addresses. If the internet
fails in part or in whole, the
system needs to continue to operate as well
as possible.
The modes
used need to be very robust which means they have the ability to
accurately
get through under difficult conditions and scale up as
conditions
permit.
Stations can opt to be relays, or gateways but it
has to be an error free
mode in order to permit compression for good
throughput and ability to
deliver solid data. The biggest problem with
TCP/IP seems to be the
overhead. That is certainly an issue for
discussion.
It could use either a sound card mode or
possibly external modems or higher
quality sound
cards.
You will note that many of these parameters are the opposite
of the Winlink
2000 system and actually would be similar to the older RF
Winlink system
with the Netlink capability. It may be that the designers
felt that there
were insurmountable problems with that system in terms of
internet access
but it seems that JNOS2 may have solved some of that. But I
am very unclear
about JNOS stuff.
If we can do MFSK16 in such narrow
bands, why can't we do higher speeds
within a 3 KHz
BW?
73,
Rick,
KV9U
-----Original
Message-----
From: digitalradio@yahoogroups.com
[mailto:[EMAIL PROTECTED]
Behalf Of DuBose Walt Civ AETC
CONS/LGCA
Sent: Thursday, June 16, 2005 11:28
To:
'digitalradio@yahoogroups.com'
Subject: RE: [digitalradio] Re: Question
about HF-email
Just a few comments on what Joel brought
up...
There's no rush to create another HF modem in open source...and I
think that
most of those hams who are working in open source are also
working many
hours at their regular jobs so time to do coding is
limited.
But second, and this is my personal opinion, the folks doing open
source
don't want to just create another modem/mode/messaging system
without
someone publishing a performance specification...be it the League,
TAPR or
other group.
What is really needed? What throughput goal
are we looking for? How robust
should the mode be? Do you want
is primarily a stand-alone system but use
the Internet if available or do
you a system that is primarily dependent on
the Internet but can operate
without it?
Do you want several to many gateway stations between HF and
V/UHF or HF
clients or have every station be able to be a client or
gateway?
What king of routing do you want...static or dynamic?
Do you
want to base the system/mode on TCP/IP or TCP/IP of V/UHF and HF on
some
streaming mode with heavy FEC or what?
Do you want this new mode/modem to
use a computer's internal sound card or
use one or more sound cards or
external sound cards?
So we can see lots of "mistakes" in WinLink and I
don't think anyone wants
to make the same mistakes or duplicate the WinLink
system just to say that
look what we did in open source.
If a new
mode/modem/system is developed, we need to have specific goals for
the
mode/modem/system.
Another "burning question" is what bandwidth on HF will
we wind up with? If
its 3 KHz, I think most open source programmers
aren't going to fool with
looking at another mode using a sound card.
Right now the best type of
modem suited for a sound card seems to be a
multiple tone modem similar to
an OFDM mode. If a high-speed and a
high level of robustness is desired,
then using current or similar current
modes, the bandwidth needed isn't
going to fit into 3 KHz...so if we are
stuck with 3 KHz on HF, why would a
programmer want to waste their time
creating a new mode?
With reference to complex modes, its quite possible to
fit 2 to 4 OFDM type
signals in the same bandwidth if the tones are just
slightly
different...just think of a mode than has channels a, b, c, and
d. So you
get on a certain frequency with 8 other hams and each two
hams select a
different mode or frequency offset for their tones...then you
can have 8
individuals, 4 two person QSOs all occupying the same 6-10 KHz
channel.
Talk about bandwidth utilization...
I do believe that
eventually we will see external "rack" boxes where we plug
in various sound
cards and connect them back to the "mother computer" via
USB or some such
buss. That isn't a very expensive piece of gear to build
or
purchase.
Joel goes on to say...."I don't think the Internet is all
that fragile?
TCP/IP certainly
isn't, although it's true that in many
cases there are no alternative paths
that it requires for redundancy
(robustness), so something has been given up
there."
Joel, I sit hear at
my desk wondering if this E-Mail is going to go out when
I click on the
"Send" button...the reason is that the Internet is backed up
right now and
the gateway between my network backbone and some of other
backbones are
having traffic problems this morning and they don't think the
problems will
be cleared up until later this afternoon. Part of the problem
has to
do with DNS updating and another problem is some ISPs are blocking
lots of
traffic because they think its SPAM or virus laden and in fact
its
not...they are relying on a firm to give them a "blacklist" and
the
blacklist is defective.
I've been 4 days trying to get E-Mail from
one of my customers passed to
another party but their system is rejecting
it and the company swears that
there is nothing wrong with their E-Mail
system.
--
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