Hi,
As Bruce has said, if you are thinking about digital up & digital down,
it is best that you make it codec-agnostic data-pipe. If you want to
implement FEC, there are several interesting approaches. The satellite
can decode what it receives, correct uplink errors, re-encode and send.
Another approach is to pass everything, without dropping invalid
packets, letting receiving users to correct the bit errors that have
accumulated on the uplink and downlink (this has the advantage that
users may play with their own FEC algorithms). An interesting design
constraint for a data-pipe intended for digital voice is latency.
Finally, since no one else mentioned this yet, it's worth checking out
the LilacSat-1 from Harbin Institute of Technology. This is the only
existing satellite that uses codec2 and it has an analog FM uplink and
the downlink is codec2 interleaved with the telemetry in a 9k6 BPSK
protected with convolutional coding.
If able to choose, I would prefer a data pipe with digital up & down,
since this allows many experiments besides codec2 (and also playing with
codec rates), and perhaps supporting simultaneous users (maybe it's good
to take a look to the remarks I wrote at the end of
https://destevez.net/2016/10/lilacsat-1-codec-2-downlink/)
Regarding what Steve says about 100kHz FM, I don't think that such a
wideband signal is manageable from the spectral allocation point of
view, at least for the 70cm band (but should be OK for 13cm or higher).
Also, I wouldn't get too enthusiastic about trying to push a
high-baudrate signal. Most of the satellites I've seen in 70cm use 19k2
or less.
73,
Dani EA4GPZ.
El 2019-01-16 18:09, cshearer escribió:
Hello,
Starting plans of a cube sat project and have been contemplating
the use of this codec method (instead of other possible options) for
the project and not sure if this has been yet done or what the
thoughts would be on the use of this codec vs other methods as I want
to incorporate both digital voice and analog voice options. Initial
thoughts are to use DV codec2 method for possible greater benefits for
both better RF & audio qualities vs analog FM for a cross banded voice
repeater as a part of the satellites mission. The implementation would
be via on board modem to transmit the digital modulation using an MCU
for the direct modulating of the down-link from the received analog
up-link input.
Possible mode configurations would be:
Mode 1 = Up-link Analog FM / Down-link DV Narrow band (Modulated
directly onboard satellite via MCU hardware modem)
Mode 2 = Up-link DV Narrow-band / Down-link DV Narrow-band (Direct
pass through of digital data signal, no reprocessing of signal)
Mode 3 = Up-link Analog FM / Down-link Analog FM
These configuration modes would allow real time in flight mission
testing / comparison of the DV codec2 vs analog in 2 different
configurations)
Would like to know thoughts and would appreciate any points of
discussions for this application.
Thank you,
NE3KO
_______________________________________________
Freetel-codec2 mailing list
Freetel-codec2@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/freetel-codec2
_______________________________________________
Freetel-codec2 mailing list
Freetel-codec2@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/freetel-codec2
