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PA2AGA > TCPDIG 27.10.96 17:43l 138 Lines 5112 Bytes #-10841 (0) @ EU
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Date: Sun, 27 Oct 96 13:10:08 MET
Message-Id: <tcp_96_227B>
From: pa2aga
To: tcp_broadcast@pa2aga-1
Subject: TCP-Group Digest 96/227B
X-BBS-Msg-Type: B
>it gets all of the parity frames.
>
>The beauty of this scheme is that the same four parity frames can
>reconstruct *any* combination of up to four erased data frames, so
>each ground station can use the same parity frames to fill in whatever
>combination of data frames (up to 4 max) that it is missing, without
>requesting any retransmissions. This is clearly a major benefit when
>there are many ground stations listening, as to a beacon transmission.
>
>As presented, each frame carries a CRC and is either received
>correctly or not at all. A further refinement would add a code to each
>frame capable of correcting some errors within each frame. A
>convolutional code would be a good choice here, as that would buy some
>gain against gaussian noise. Interleaving here would also buy some
>fade resistance.
>
>If the frame CRC were eliminated, then the RS code might be able to
>salvage slightly errored frames that would otherwise be entirely
>erased. In this case we'd probably want to add some more RS parity
>frames using the bits saved from the frame CRC. Again, a careful
>study would indicate the tradeoffs for a particular link.
>
>I have published several FEC encoder/decoder routines on my web page,
>including Viterbi, RS and Fano encoders/decoders. All of them run on
>modern PCs at speeds orders of magnitude faster than needed for
>Microsat data rates. It's time we tried something like this.
>
>Phil
>
And I agree but have not the knowledge to use them.
Karl k5di
Karl F. Larsen ---- k5di@acca.nmsu.edu --- http://acca.nmsu.edu/~k5di/ -->
------------------------------
Date: Thu, 24 Oct 1996 08:18:06 +1000 (EST)
From: csmall@gonzo.vk2xlz.ampr.org (Craig Small)
Subject: wampes on FreeSCO
Alan Cox typed:
> Most of those run Linux and OpenBSD too. The sparc hardware is of great
> interest for packet radio as the chips on the serial ports happen to be
> Z8530's and able to do sync. Thus a baycom modem to a sparc ought to work
> nicely without any bit level funny drivers
Another thing I've learnt from the linux-m68k guys is that some Ataris have
the Z8530, or equivalent/improvement for their serial ports as well. They
were wondering why there were 5 or so different device drivers for them.
BTW: Here's a question about one of our favourite chips; how do you tell
what sort of SCC you have in software (no suggestions of reading the number
printed on the top of the chip ;)
- Craig vk2xlz
------------------------------
Date: Thu, 24 Oct 1996 10:20:07 +0100 (BST)
From: Alan Cox <alan@cymru.net>
Subject: wampes on FreeSCO
> If you have a lot of code for SCO Unix but want to move to a more modern
> OS then either should be able to run your legecy code. FreeSCO is
> apparently SysV R3.2 (quite old) while FreeBSD is 4.4BSD+ and both FreeBSD
> and Linux are moderately POSIX compliant.
Some Linux stuff off CD will pass posix.1 (and if you are curious NIST
have made the .1 test suite available for free now). You need some patches
to the test suite (its got bugs too 8)).
As to wordperfect. It runs the SCO one under iBCS2, and Oracle 7 and a fair
bit of stuff. Wordpefect and Corel draw are available native anyway.
On the real topic - ie networking. SCO is about as standard a sys5 3.2
streams as you can get so its a great base for someone to do the AX.25
as streams stuff
Alan
------------------------------
Date: Fri, 25 Oct 1996 22:54:50 +0100 (BST)
From: Alan Cox <alan@cymru.net>
Subject: wampes on FreeSCO
> Another thing I've learnt from the linux-m68k guys is that some Ataris have
> the Z8530, or equivalent/improvement for their serial ports as well. They
> were wondering why there were 5 or so different device drivers for them.
People keep changing how they address/use the things. On the sparc for
example you have to put uS settle times between I/O operations and the chips
are memory mapped. On the PI2 its DMA driven, some of the PC cards have
other oddities etc. Getting down to below 5 drivers is a big item to do
but one that might get down to 3 or 4, and as we support stuff like AX.25
and X.25 on the sparc console ports we share more code.
Alan
------------------------------
End of TCP-Group Digest V96 #227
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