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. -----Mensaje original----- De: cshearer [mailto:[email protected]] Enviado el: miércoles, 16 de enero de 2019 18:09 Para: [email protected] Asunto: [Freetel-codec2] Satellite Use of Codec2 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 [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2 _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
