A-STAR Gateway Spec                                       14 Dec 2010
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                                                               WB4APR

This note attempts to broadly define the functionality of an A-STAR
gateway.  An A-Star gateway is identical to a D-star gateway on the 
D-star side. (at least for the initial understanding).  On the APRS 
side, it does the following:

RECEIPT OF A D-STAR QSO REQUEST:

When it sees a connect request to its own CALLSIGN, it accepts the 
connection, brings up the analog repeater PTT and passes D-star 
audio to the repeater.  If there is voice on the repeater input, 
it passes this back to D-star.  The callsign of the A-star gateway
is included in the stream.  If the analog audio has been identified
by an APRS PTT packet, then that callsign is streamed to D-star.

If the A-star gateway node sees a connect request to an APRS callsign 
that it has heard on its own TNC, within the last 10 minutes, it 
accepts the connection, as above.  It also sends out an APRS packet 
message on the APRS-IS to alert the APRS user that he has a call:

FROM: A-STAR gateway APRS-callsign 
TO:   the called callsign 
MSG:  QSY FFF.FFFMHz de [D-Star callee].

RECEIPT OF AN APRS USER-to-D-STAR QSO REQUEST:

This request will be heard as an APRS message on the A-Star 
repeater's input using a simple TNC: 

FROM: the CALLING APRS user. 
TO:   CALLEE callsign of the called party 
MSG:  A*

The A-star gateway will then make this connection via the D-star 
network using the MYCALL of the APRS Caller, with the URCALL of 
the CALLED station, with the R1 callsign of the local A-star 
repeater, and the R2 callsign of the local A-star Gateway. 

Presumably the A-star repeater will have to use one of the special 
D-STAR dongles to have the proper A/D and D/A conversions.

APRS-DETAILS:

Notice, that during any A-star operation, the APRS mobile has his
radio's TNC operating on the same band as his voice.  The mode will
be in PTT mode so that his ID packet goes out whenever he drops his
PTT.  But at any other time, the APRS user can be tuned to any other
frequency as long as his APRS band is on the national APRS signalling
channel.  THis way, he can receive the incoming QSY message.

FOr the D700 and D710 radios different program memories can be used
for these modes.  PM1 might contain the operators normal APRS and
Voice operating mode.  But PM2 switches the TNC over to the A-star
frequency and places the TNC in PTT mode and puts voice PTT on the
same band.  The APRS user interface will be as follows:

RECEIPT OF CALL (while not on the A-star repeater):  He receives an 
audio message alert and a POP-UP message on the front panel of the 
radio telling him who has called and what A-star repeater to tune to.  
In the newer radios, he simply presses the TUNE or QSY button to 
instantly change his B side (voice) band to the A-Star repeater 
channel to receive the call.  In other words, ONE BUTTON response.

RECEIPT OF CALL (while on the A-star channel).  Since the APRS 
operator is already on the A-star channel, the A-star gateway will
know that he is alreay there and ready for a call. The APRS operator
will simply see a front panel pop-up showing who has called and
from where and who is being called.  His voice will be heard as soon
as he speaks.  

INITIATE A CALL:  He simply tunes his voice band and TNC to the 
A-star repeater.  Then he presses the MSG button, selects a previous 
A-STAR message, and edits the callee callsign to who he wants to 
call and presses OK.  If the connection is successful he can begin 
to QSO the called party.  The D710 radio keeps the last 100 messages
so it is easy to call up a previous connection from preveious calls
without having to key-pad it in.

Have I missed anything?

Bob, WB4APR