[aprssig] Automatic Voice Relay System (AVRS)

[Robert Bruninga]

AVRS is the perfect marriage of APRS with any of the 
Voice over IP ham radio Programs (IRLP, ECHOlink, etc)

AVRS allows any APRS mobile to voice link to any other
APRS mobile anywhere on the planet by simply knowing his
callsign.  This is accomplished via the global APRS, IRLP 
and ECHOlink systems with only the addition of a single 
AVRS engine on the Internet.  

Something similar to the WU2Z Email engine in NJ.  As seen 
on the web page, the AVRS engine just interacts with the 
APRS-Internet system and monitors the status of all IRLP
and ECHOlink nodes and handles the call-set-up messaging
needed end-to-end:

http://www.ew.usna.edu/~bruninga/avrs.html

MOBILE PLACING A CALL:  To place a call, a mobile simply 
sends a message to AVRS with the message: C XXXXXX 
where XXXXXX is the callsign of the CALLEE.  He needs no 
other knowldege.  AVRS will ack his message via the nearest 
IGate and will respond with an object showing him his nearest 
ECHOlink or IRLP node, its frequency and PL.  And then it will
also send him a message on the status of the call.

RECEIVING A CALL:  If the CALLEE is on the air (has been 
heard  recently on APRS), he will receive the message from 
AVRS saying "XXXXXX is calling you on node #nnnnnn 
on frequency FFFFFF using PL ppp from node #nnnnn.  

The local node #, frequency and PL were determined by the 
AVRS engine looking up the position of the called station and 
the nearest not-busy IRLP or ECHOlink node.

If the CALLEE has not been heard recently AVRS still sends 
him a message saying  "You were called by XXXXX from 
ECHOlink node #nnnnn This is so that if he doesnt get this 
message until a while later the callee can initiate an 
ECHOlink or IRLP call back to node #nnnnn.

All messaging for the AVRS system can be initiated and 
received by any APRS system, but most importantly, they can 
be accomplished from the keypad and display of the D7 and 
D700 APRS radios.  Thus giving true global voice capability 
to dynamic in-the-field users:

FUNCTIONS OF THE AVRS ENGINE:  The AVRS engine 
can be anywhere and is simply software running on a reliable 
internet system.  It monitors not only all traffic on the APRS-IS, 
but also the active node status of both the IRLP and 
ECHOlink systems.  As such, it is all knowing and all seeing.  
The following is a description of this process.  

For simplicity the term "AVRS node" will be used interchangeably 
to refer to "IRLP or ECHOlink or other VOIP nodes".  Here are 
the functions of the AVRS engine.

* Monitors the APRS-IS and accepts APRS CALLER messages from mobiles
* Compares location of CALLER to nearest IRLP or ECHOlink node
* Generates OBJECT to CALLER's Igate showing nearest AVRS 
   node, its Freq and Status using decaying algorithm
* If nearest is BUSY, then also sends back additional next-closest 
   available AVRS node using decaying algorithm
* Compares location of CALLEE to nearest IRLP or ECHOlink site
* Generates OBJECT to CALLEE IGate showing his nearest
   AVRS node and frequency
* If nearest is BUSY, then also sends additional next-closest available

   AVRS node object
* Checks availability of CALLEE  stations. 
* Chooses best SSID (Mobile, else portable, else home.

IF CALLEE IS NOT ACTIVE, THEN:
* Sends message to CALLER saying "CALLEE heard XX hours 
   ago near AVRS node #xxxxx"
* Sends message to CALLEE saying "CALLER called from 
   AVRS node #xxxx at time TTTT.

IF CALLEE IS ACTIVE, THEN:
* Sends message to CALLEE saying "QSO CALLER on 
  FREQUENCY ffffff, PL ppp calling from #nnnnnn"
* Sends message to CALLER saying "Call CALLEE on 
  AVRS node #xxxxx PL ppp"

"Nearest node" is determined by a combination of node 
distance (D) and PHG range (R).  The node with the highest 
ratio of R/D will be chosen.  Also, the AVRS engine has to 
decide on IRLP or ECHOlink or other system based on what 
is available at both ends (including distances at both ends).

IMPLEMENTING AVRS:

AVRS can be implemented by a single software engineer 
willing to invest the time in the project.   Small changes to the 
IRLP and ECHOlink systems might facilitate operations, but 
most everything needed for this global AVRS ham radio QSO 
system is in place.  

For more, see the web page.
I think this is were we are going over the next 5 years.
HT to HT voice calls via AVRS..

I have been pusing this since my presentation at DCC in 
2000.  Progress is being made.  Now all we need is an
author with time on his hands to write the AVRS engine
and more ECHOlink nodes to add their APRS object
packets.

de WB4APR, Bob