[ax25-layer2] 7-byte address proposal

[Robert Bruninga]

>>> pete at ae5pl.net 08/02/06 7:07 AM >>>
> While it is necessary to investigate how to accommodate 7
>character callsigns, it isn't going to go far if we completely 
>discount current equipment and current implementations.

For 7 character addresses:

Clarify if this would work....  and correct me if I am wrong...

If I remember correctly the AX.25 spec limited the TRANSMISSION
of callsigns to be the UPPERCASE ASCII subset, but made no
mention of reception.  Thus, I have seen many TNC's that
will actually receive just fine, abd decode mixed-case AX.25 addresses.

My thoughts for this would be to use mixed case as a means of
transmitting an additional bit per character.    To use this, first
remove the Numeric DIGIT and move it to the SSID field.  So
a 7 byte call such as WB4APRS would be come WBAPRS-4
This is 100% backwards compatible.  Now, then, use the added
6 bits for up to 64 different callsign variants for that station.
(Like SSID Used to do).

This is also 100% backwards compatible with APRS, since APRS
has always defined the callsign field to be mixed case and
different case combinateions have always been treated as 
separate stations.  For example:

wBAPRS-4  could be my home station
WbAPRS-4  could be my bike
WBaPRS-4  could be my boat
WBApRS-4  could be my canoe

Yes, another "kludge" as they say, but just something to
investigate.  I know there are lots of problems with it.
And first woud  be a list of all existing TNC's that dont
care about mixed case on receive...

If the majority placed the same upper-case-only
restriction on reception as they did on transmission,
then this idea is a non-starter.  But if most will handle it OK,
then it is worth investigating?

Bob, WB4APR


The beauty of this is that most TNC's and most software may 
already be case insensitive and so they would display at 
least the first 6 bytes in the original way, but software that
needed an additioaly byte could then also pick out the 7th
byte.