From: Robin Gilks (cmvz@basware.fi)
Date: Mon Apr 02 2001 - 23:29:43 EEST
Greetings all
I've got a few questions about the implementation of DAMA and 6PACK in Linux
(and any other environment if anyone is familiar with them).
1. Is it possible to use the poll approach in a split frequency environment
where the master TX can be TXing to several users whilst a single user
replies on the input channel.
eg. the master (M1) is talking to 3 users (U1, U2 and U3). M1 TXes on 439MHz
and RXes on 432MHz. U1-3 operate simplex radios, M1 is fullduplex. U2 is
polled by M1 so keys up on 432MHz and starts ending data. Meanwile, M1 TXes
on 439MHz to U1 and U3.
CSMA access is still possible for new users if M1 sends flags whilst the
user channel is busy but M1 itself has no data to transmit - this is the
usual method of split frequency working and avoids the dreaded 'hidden
transmitter' problem.
Is this feasable (I've seen nothing in the specs that says it can't be done)
and more specifically, can the Linux implementation support this fullduplex
style of activity.
2. Does the 6PACK protocol implicitly deny fullduplex operation or is it
up to the host implementation to ignore DCD priority messages and send TX
data whenever it likes. Presumably PTT messages could be output to generate
a 'busy' signal as a result of seeing DCD messages from the TNC to implement
the split frequency scenario above.
3. Does the Linux implementation of 6PACK (and others) insert a delay
between sending the PTT message and starting the data message. ie. does the
TNC have to buffer a substantial amount of data based on the TX delay time
thats in the first byte of the data message or will that time have expired
by the time the TNC receives it (I'm looking at putting 6PACK into an
intellegent modem but it has very limited memory)
4. Are any/all 6PACK implementations in TNCs full or half duplex (got code
to write in a 4 port TNC as well!) or is that irrelevant based on the host
end controlling all activity.
Looking forward to a lively discussion on why on earth I would want to do
these things :-))
-- RobinInternet: obty@mailit.tunk.net http://www.gb7ipd.freeserve.co.uk/ Anorak mode = Shack: (+44) 1628 533311 Fax: (+44) 1628 850165 Club pages (g4xyw modem etc) at http://www.tvipug.org - To unsubscribe from this list: send the line "unsubscribe linux-hams" in the body of a message to mvkbzhh@camp-ing.biz
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