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Re: [HLL] Frame-Layout
At 21:10 04.01.1998 +0100, you wrote:
>-----BEGIN PGP SIGNED MESSAGE-----
>some thoughts about frame-layout:
>* Old format supported 8 logical channels,
> I would like to reduce that to 4:
> * 1 Channel for control (additional control-bandwidth in frame data-zone)
> * 1 Channel for audio (gsm voice-data)
> * 1 Channel for sio-data (transparent user-channel via serial port)
> * 1 Channel <reserved> (might be multiplexed to support a higher
> number of logical channels than standard=4)
> This looks ok, or what do you think ?
Yes. But think about an implentation where only Voicedata is exchanged.
This is more easy to implement and gives more throughput. Any Form of
Controllchannels will drop Bandwith 5-10%.
>* Do we operate the modem in "raw" mode (without error correction,
> but in "real time" operation) ? Sure about that ???
> Does this mean that we can be *absolutely sure* to be able to
> transmit data at 1800 Byte/Sec (14400 Baud Modem) all the time ?
> So also no "retraining sequence" (600mSec++ no data) ?
> Should we add little redundancy to the frames (loosing some bandwidth) ?
Too much CPU wasted. Let us retransmit the Packets or drop them.
> Decryption trashes several sequencial bytes for one bad input-bit !
>* Old frame-layout supported loosing only parts of a frame.
> This meant that a one-bit-error could only trash one logical channel,
> not causing you to loose a whole frame.
> Is this a feature worth to be kept ?
No. Due to the Nature of V.3x more than one Bit is transmitted in a coding
/decoding scheme (4-8Bits at a single Time) so if there is going something wrong
the other 3-7Bits are invalid most of the Time. If we have a V.34 Channel its
better to transmit all Data twice.
That is to much tought about the modempart. If we are going to transmit
things over TCP/IP we will loose whole Packets and not only bits.
We could design diffrend Comunication Layers but make this Sense?
>Thats enough for today ;-)
Hartmut Schroeder Email:email@example.com
http://www.mms.de/~hacko 32U0564185 5937869 (WGS84)
Theory: "Computers are based on Smoke." Argument: "If the Smoke escapes from
the Chips,(attempt to false inserting your CPU) they don't function any more."