An Introduction to UIDIGI Copyright © 2000 Marco Savegnago IW3FQG.
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Transcript of An Introduction to UIDIGI Copyright © 2000 Marco Savegnago IW3FQG.
![Page 1: An Introduction to UIDIGI Copyright © 2000 Marco Savegnago IW3FQG.](https://reader037.fdocuments.in/reader037/viewer/2022103004/56649cb75503460f9497d635/html5/thumbnails/1.jpg)
An Introduction to UIDIGI
Copyright © 2000
Marco Savegnago IW3FQG
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What is UIDIGI?
• UIDIGI is custom TNC2 (or TNC2 clone) firmware which provides advanced APRS* digipeater capabilities.
(*) APRS is a registered trademark of Bob Bruninga WB4APR .
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Why UIDIGI ?
• UIDIGI is optimized for APRS digipeating service and provides unique features for operation within a complex APRS network.
• UIDIGI uses readily available TNC2 (or TNC2 clone) hardware.– The TNC2/clone can be found new or used
and offers the least expensive TNC option for an APRS digipeater.
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Who needs UIDIGI ?
• Any APRS digipeater owner/operator who has a TNC2 and wants to optimize performance in the APRS network.
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Who DOES NOT need UIDIGI ?
• Fixed (Home) or Mobile Operators– UIDIGI does not interface with
common APRS user applications (APRSdos, Mac/Win APRS, APRS+SA, UI-VIEW).
– Standard TNC firmware or a Baycom modem should be used for these applications.
• Gateway Operators– UIDIGI does not support HF or Internet
Gateway operations.
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Why UIDIGI was written?
• I had several unused TNC2s at home and didn’t want to buy a new 1200 baud TNC in the year 2000!
• New and used TNC2s (and clones) are easy to get.
• A TNC-only based digipeater is more reliable than a computer based system, which is critical if the digi is located on a remote mountaintop.
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Characteristics of UIDIGI
• Can be installed in any TNC2 or 100% compatible clone
• Digipeats ONLY the AX.25 UI frames
• Routes and makes call substitution of frames addressed to generic addresses (RELAY, WIDE TRACE), flooding addresses (WIDEn-N, TRACEn-N) and directional addresses (based on SSID)
• Supports preemptive digipeating
• Ignores duplicated frames sent in a defined interval
• Provides password protected remote parameter modification
• Replies to the ?APRS? query
• Supports up to 3 unique Beacons (Text /Path/Interval)
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Limitations of UIDIGI
• Cannot be used as an APRS gateway
• Does not support weather stations (not yet!)
• Cannot be used in conjunction with APRS application programs like UI-VIEW or WinAPRS.
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Why an APRS dedicated digipeater? (1/6)
• APRS is based on the AX.25 protocol but uses only characteristics which allow data broadcast via Unnumbered Information (UI) frame types.– AX.25 is primarily a connection oriented
protocol, but supports unconnected operations.
• UI digipeating differs from transport of information between two connected stations.– One packet broadcast to many recipients
– No guarantee that all recipients received packet
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• Initial APRS operations used simple AX.25 frame addressing and routing schemes which provided sufficient performance in the low density operating environment.
– Typical digipeating addresses such as CQ or APRS
– Simple generic digipeating paths of RELAY and WIDE were used
– Mobile (moving) stations could always utilize same digipeating path, without the need to modify TNC parameters
– Digipeater TNCs could be set to respond to their own callsign and the generic aliases of RELAY and WIDE
• The above simple network architecture performed adequately until the number of users started to increase and network coverage areas widened.
– Digipeating paths were increased to span wider coverage areas (e.g. via RELAY,WIDE,WIDE)
– Multiple digipeaters which overlapped a coverage area would create duplicate packets and/or packet annihilation (simultaneous transmission by multiple digis which results in packets that destructively cancel each other)
– Lack of duplication checking in TNCs could result in a digi sending the same packet multiple times
• IW3FQG> APRS v RELAY, WIDE, WIDE• IW3FQG> APRS v DIGI1*, WIDE, WIDE• IW3FQG> APRS v DIGI1, DIGI2*, WIDE• IW3FQG> APRS v DIGI1, DIGI2, DIGI1*
Why an APRS dedicated digipeater? (2/6)
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• Increasing network complexity and resulting network congestion required additional techniques to be devised.
• APRS functionality is based on standard AX.25 frame handling; however , modifications would be required to implement the APRS improvements.
• An APRS digipeater would act as simple AX.25 digipeater plus it would employ new rules to reduce channel congestion by minimizing packet duplication and frame length.
• The first method introduced forced the substitution of the generic callsign with the callsign of the digipeater which repeated the packet.
Why an APRS dedicated digipeater? (3/6)
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• The second method (called flooding) set simple rules for propagation of a frame for n-hops without increasing the frame length.
– A path of WIDEn-N was defined where “n” is the total number of hops and “N” starts at “n” and is decremented each time a digipeater repeats the packet.
Example:A Source Frame of IW3FQG>APRS v RELAY,WIDE2-2
DIGI1 acts upon the RELAY IW3FQG>APRS v DIGI1,WIDE2-2
DIGI2 acts upon the first hop of the WIDE2-2 and decrements the hop count: IW3FQG>APRS v DIGI1,WIDE2-
1*
DIGI3 acts upon the second hop of the WIDE2-2 and decrements the hop count to 0 IW3FQG>APRS v DIGI1,WIDE2*
No further digipeating will occur since the hop counter has reached zero.
Why an APRS dedicated digipeater? (4/6)
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• The third method (called flooding and tracing) is derived from the above second method, and allows a station to know the path that a frame has taken to reach its final destination.
– A path of TRACEn-N was defined where “n” is the total number of hops and “N” starts at “n” and is decremented each time a digipeater repeats the packet. When a digipeater repeats a frame it inserts its callsign into the path.
Example:A Source Frame of IW3FQG>APRS v RELAY,TRACE2-2
DIGI1 acts upon the RELAY IW3FQG>APRS v DIGI1,TRACE2-2
DIGI2 acts upon the first hop of the TRACE2-2 and decrements the hop count: IW3FQG>APRS v
DIGI1,DIGI2*,TRACE2-1
DIGI3 acts upon the second hop of the TRACE2-2 and decrements the hop count to 0 IW3FQG>APRS v
DIGI1,DIGI2,DIGI3*,TRACE2
No further digipeating will occur since the hop counter has reached zero.
Why an APRS dedicated digipeater? (5/6)
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• The last method allows a station to set the preferred geographic propagation route based on the SSID of the destination address. This is an experimental method that can be enhanced or changed.
• UIDIGI 1.8 also provides a new method called preemptive digipeating that allows a digipeater to preemptively repeat a frame when it sees its callsign later in the destination path .
Why an APRS dedicated digipeater? (6/6)
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TNC-based alternatives to UIDIGI
• KANTRONICS KPC-3/KPC-3+– De facto standard for APRS digipeaters– Callsign substitution supported
• Digi callsign inserted in place of generic RELAY or WIDE
– Flooding (WIDEn-N & TRACEn-N) supported– Incomplete packet duplication checking algorithm can result in
multiple transmissions of the same packet– Doesn’t support directional (SSID-based) routing
• PACCOM TINY2 (Standard TNC2 Firmware)– Supports only generic routing (RELAY,WIDE,TRACE)– Callsign substitution supported
• KENWOOD TM D-700– Recently released radio/TNC supports most UIDIGI routing
methods• No preemptive digipeating
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PC-based alternatives to UIDIGI
• APRSDIGI– Handles up to 2 ports with KISS TNC
– Routing techniques partially implemented
• DIGI_NED– Handles up to 15 ports of several of types
• TNC, modem, etc.
– Runs under DOS or Linux– Most routing protocols supported
• WinAPRS or UI-VIEW– Can be configured for digipeater, but
primarily designed as APRS user applications
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The brief history of UIDIGI (1/4)
• At the 1995 Dayton Hamvention I purchased my first GPS handheld receiver and was first introduced to the concept of APRS.
• By 1997 most of the local packet activity was focused on high-speed networking. I was considering donating my (no-longer useful) TNC2s to friends or young hams. I then realized that these could be used to stimulate APRS activity in Italy. Initial demonstrations didn’t generate much interest.
• In 1998 I bought a surplus Z80 development system.
• In 1999 interest in APRS started to grow in my region of Italy (I3). I wrote my first version of UIDIGI and installed it in an APRS digipeater in MonteCorno (site of most of our packet radio network nodes and relay).
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The brief history of UIDIGI (2/4)
• Much of 1999 was spent evolving the design of UIDIGI.– Testing was performed on my home digipeater
– Several versions of UIDIGI were generated
– In later versions, I introduced the advanced routing and duplicate suppression algorithms
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The brief history of UIDIGI (3/4)
• In March 2000 I made the worldwide introduction of UIDIGI and made the first public release (version 1.6).
• In June 2000 I released version 1.7, which included a complete code rewrite and included several enhancements.
• Exposure of UIDIGI to the APRS community leads to utilization of the firmware in digipeaters worldwide.
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The brief history of UIDIGI (4/4)
• At 2000 year-end version 1.8 is in the final beta stage and includes further enhancements.
• In 2000, a dedicated UIDIGI mailing list was created– Central location for UIDIGI software and documentation
– Forum for communications between UIDIGI users
– Information on upcoming versions
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The future of UIDIGI?
• The UIDIGI firmware has nearly matured to the point of meeting my personal goals.
• I hope that it can be used worldwide in various APRS networks.
• I have many other projects and enhancements dealing in digital communications (outside APRS) which I plan on pursuing.
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Addresses
• UIDIGI Home page http://space.tin.it/computer/msavegna/uidigi.htm
• UIDIGI mailing list: http://www.egroups.com/group/uidigi
• Addresses for IW3FQG– Packet Radio:IW3FQG @ I3KUH.IVEN.ITA.EU
– Internet: [email protected]
– Geographic Coordinates: • Latitude: 45 ° 33' 24" N
• Longitude: 11° 32' 34" E
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Reference
• Manual and introduction of UIDIGI by IW3FQG
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Special Thanks
Thanks to:– Greg Noneman WB6ZSU for checking and correcting
my original version of this presentation, for the support in debugging, testing and for the original UIDIGI command spreadsheet
– Allan Sadowski AH6LS for checking and correcting my original version of the UIDIGI English Manual