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[HLL] Frame-Layout



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Hi,


some thoughts about frame-layout:

* Old frame-format has to be revised - more info later...

* 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 ?

* Is there a public implementation of gsm half-rate compress/expand ?

* 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) ?
  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 ?

Thats enough for today ;-)


Volker

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