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ZL3AI > APRDIG 30.09.03 10:47l 229 Lines 9201 Bytes #999 (0) @ WW
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Subj: TAPR Digest, Sep 27, 2/7
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Another thought on reducing congestion in busy metro areas...
From: WA8LMF2@aol.com
Date: Sat, 27 Sep 2003 05:20:29 EDT
X-Message-Number: 3
I think the time has passed for dumb trackers consisting of TNCs
transmitting raw NMEA strings. There might have been some justification
for these things in APRS' infancy, to avoid taking an entire computer
mobile, when the channel occupancy was low, and before specialized
APRS-aware hardware became available (so you had to improvise with standard
TNCs). But not now.
I consistently see several mobiles around here beaconing 100-byte-plus raw
$GPRMC or $GPGLL strings over WIDE2-2 or WIDE3-3 paths, every minute or two
even at rest, when an APRS-compressed-format or Mic-E could do it in 1/3rd
or 1/4th the air time.
The inexpensive (< $35) TinyTrak implements a far smarter tracker that can
send the same position data (and a comment and full choice of
symbol/overlay) in FAR less time AND will send far fewer beacons when the
car is parked. Not to mention that it uses far less DC power, it's
settings don't get lost every time the power hiccups, and that it frees up
a much more expensive TNC for use elsewhere. And the absolutely free bonus
that the shorter strings are a lot more likely to be received successfully!
Should we start a crusade to stamp out TNC dumb trackers to reduce needless
channel loading?
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
Ham Radio/Mobile SSTV page: http://members.aol.com/wa8lmf/ham
APRS Stuff
http://members.aol.com/wa8lmf/aprs
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Subject: Re: Another thought on reducing congestion in busy metro areas...
From: wes@johnston.net
Date: Sat, 27 Sep 2003 07:12:45 -0400 (EDT)
X-Message-Number: 4
Thing is, you can hook up a tiny trak in parallel to a TNC... so you have a
tracker which runs the same way wether you have a laptop in the car or not.
Wes
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Subject: Re: Another thought on reducing congestion in busy metro areas...
From: "Georgette Sampson" <georgette.sampson@cox.net>
Date: Sat, 27 Sep 2003 07:43:07 -0500
X-Message-Number: 5
>Should we start a crusade to stamp out TNC dumb trackers to reduce needless
>channel loading?
Not a crusade, but a roundup "rope, tie, and brand them."
Bring your spurs...
I think the single-channel and Internet APRS mode has pretty much
drowned-out other areas of development. When I think of APRS, I'm thinking
of it as an enhancement of a voice system. Little data-bursts at the start
or end of a voice transmission, rather than an end to itself. My thinking,
is that every voice radio ought to have a data-burst along with the voice,
or a data-burst at some interval if no voice is used. The whole WIDE issue
is really just a distraction.
I'm really interested in the CMX882/CMX264 chips for a personal project,
for this reason; although, many of that companies chips are interesting (as
far as something more sophisticated than the non-FEC legacy data modes).
I think it's sad that people are still designing trackers using PIC's and
resistor based D/A converters and complaining about digipeaters and channel
loading.
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Subject: APRS Igate traffic graph
From: "Andrew Rich" <vk4tec@hotmail.com>
Date: Sat, 27 Sep 2003 22:44:24 +1000
X-Message-Number: 6
I have been playing with mysql and PHP graphs with APRS data
Makes for some intersting expirement
example
http://www.tech-software.net/callsign_count.php.png
Andrew VK4TEC
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Subject: Re: Part 2/2 -Re: Take Control - oh let's just go backwards
From: Henk de Groot <henk.de.groot@hetnet.nl>
Date: Sat, 27 Sep 2003 14:12:24 +0200
X-Message-Number: 7
At 19:07 26-9-03 -0400, Bob Bruninga wrote:
>What should he do, transmit once and then wait 30 minutes to see if he is
>a participant in the event or not? geeze... APRS network disintegration
>at its finest...
Two problems with this line of thinking.
The only value a packet with exactly the same content has is "im still
present" and "nothing changed". If it is important to keep track of the
status of a specific station I think you should not rely on the time of
reception but instead you want to know when the report was transmitted. In
these cases the data should be timestamped, thats where the timestamp is
for. If a timestamp is included then your packet will have a different CRC
each time and will not be bothered by any extensive dupe checking.
Secondly a DIGI_NED digi will not do any dupe checking on directly received
packets, so in the coverage area of the digi the only effect of 30 a minute
dupe check timeout is reduction of the number of packets from outside.
I can't see any harmfull effect, only improvement of the APRS network and
certainly no desintergration. I have yet to see a scenario where this 30
minute check for indirect packets backfired.
Kind regards,
Henk.
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Subject: Re: APRS Grass growing...
From: Henk de Groot <henk.de.groot@hetnet.nl>
Date: Sat, 27 Sep 2003 14:25:38 +0200
X-Message-Number: 8
At 18:30 26-9-03 -0400, Bob Bruninga wrote:
>>By using a 30 minute dupe period, a fixed station will not get digi'd
>>more than once every 30 minutes. A moving station, whose packet changes
>>every time, will not be seen as a dupe and will get digi'd.
>
>Violates the KISS principle and gains nothing. Already a home station is
>only transmitting once every 30 minutes. Why get the digi involved in it?
If every station which is transmitting static data already uses a 30 minute
repeat interval then the measure in the DIGI to have a dupe timeout of 29
minutes has no effect. With this I mean exactly what it says, *no effect*.
There also no negative effect! It saves you however when not everybody uses
30 minutes, like a parked tracker with 1 minute repeat time or a ham that
wants to boost its ego (or doesn't have a clue what he is doing)... I.e.
nothing lost and nothing gained if everybody behaves, a saver if somebody
misbehaves. I don't understand the opposition, or is the concept to
advanced to grasp?
If you don't have a load problem then just use what you use today and don't
fix what isn't broke. If you do have a load problem then I think this is
one of the best measures to take without any negative sideeffect to the
original intent of APRS.
Kind regards,
Henk.
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Subject: Re: Clueless Users? How's that <g>...
From: Henk de Groot <henk.de.groot@hetnet.nl>
Date: Sat, 27 Sep 2003 14:40:02 +0200
X-Message-Number: 9
Hello Dick,
At 01:07 27-9-03 +0000, Dick Stanich wrote:
>Several problems with this. If that mobile is being heard by more than one
>digi, each packet is different, so you would have several checksums with
>the same exact payload, however, the headers would contain different
>information, enough to change effective dupe checking.
Dupe checking should only look at the payload and source address, the
header information changes every time the packet is digipeated so that
should never be taken into account.
>Bob said, Why get the digis involved? Easy answer... because it may be
>easier to control the local network at that level.
Most measures at the DIGI have NULL effect if everybody behaves so they
don't get in the way at all during normal use of the APRS network - you
don't notice the measures at all. They only have effect if users use
excessive paths or use an unacceptable transmit repeat time, thats when the
measures in the DIGI kick in and make the difference between a usable
network and a network crippled by massive QRM.
Note also that using a 29 minute dupe check time is just a suggestion, I
don't tell anybody to do it. If there are other more effective ways to
reduce load then use it. I just think that is one of the most elegant
options to reduce load by demoting redundant packets with a low information
content to give way to the packets with more interesting data.
Alternatively you can also keep the QRM and have the law of physics throw
away packets at random...
Kind regards,
Henk.
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Subject: Re: I guess we're going to agree to disagree Bob. Part 3 of hopefully
3From: Henk de Groot <henk.de.groot@hetnet.nl>
Date: Sat, 27 Sep 2003 14:46:24 +0200
X-Message-Number: 10
At 09:25 27-9-03 -0400, Vince wrote:
> KISS - Keep It Simple Stupid
Agree, as simple and stupid as possible, but not simpler or more stupid
than that...
The simplest solution would be if the clients didn't allow any abusive
settings or even made the settings automatically without any user
intervention in the first place...
Kind regards,
Henk.
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