[Discuss-gnuradio] NOAAPORT DVB-S2 VCM Question

[Patrik Tast]

Hi All,

 

As you all know, VCM is short for Variable Coded Modulation.

 

As I have read on your forum, the new DVBS-2 NOAAPORT transmission is variable.

So far I have noted that users use 8PSK demodulation and FEC?.

FEC?, due to users use AUTO most likely (search all HW supported FEC and lock when found, I guess it is 9/10?).

http://www.novra.com/Website/Novra_Products-Receivers-S200.html

 

Question 1:

Assume that we receive at the same time, a QPSK FEC 3/4 and 8PSK FEC FEC 9/10 signal to be demodulated.

To which does it lock to? Does it lock to one or both at the same time and demodulate it and send it to the client SW?

If locks to both, the demodulator IC must be multi threaded, can do (many) different modulation (VCM) and FEC at the same time and deliver it to the client.

 

Example: 

Receiver locks to both QPSK 3/4 and 8PSK 9/10 at the same time and transmitts demodulated data at the same time to the client.

How does the client (software) know, *that is a QPSK FEC 3/4, that product is that, 8PSK FEC 9/10 that must be that product* ?

 

By pointng our antenna directly at GEOS-11 (West) or GOES-13 (EAST) we can see 3 different modulated signals, FSK, BPSK and QPSK (FEC 3/4).

 

Question 2:

How *variable modulated, different FEC*  is the data when pointing at SES-1 satellite?

 

NOAAPORT from AMC/SES satellite use to be QPSK ~10M data rate, future (DVB-S2) will be ~30M.

8PSK (+ unknown FEC) makes sence to me, alot of datarate advantage. User will need to tune his antenna *better*

 

My conclusion is *DVB-S2 NOAAPORT stream IS NOT VCM*? Is it only 8PSK?

 

Patrik