Thanks Manu, that looks very useful.
TTFN
Richard.
Manu Abraham wrote:
Richard Mayo wrote:
Manu Abraham wrote:
Richard Mayo wrote:
I am trying to find out about a feature of DVBS-2, the 90 symbols of
un-scrambled data, Physical Layer Signalling (PLS) code, which occurs a
regular intervals. Is the content constant or predictable?
PLSCODE aka Pilot tones are used to identify the Physical Layer params.
This is part of the DVB-S2 specification at the Physical Layer, nothing
abnormal. Some demods allow you to extract the Header, while some do
not. So it depends a lot on which demodulator you are using. Some handle
it in firmware while some do it in the driver.
The PLPARMS cannot be scrambled, since it contains very basic
information. According to the specification, the MODCOD can change at
any given instance of time. This information is present in the Physical
Layer. So therefore a lot will depend on how constant your MODCOD is "at
the least".
Manu
Thanks Manu,
I'm not demodulating the signal, I just wish to identify it with a
receiver with very poor S/N. So what information does it contain?
The PLHEADER is used for receiver synchronization and PL signalling.
According 302 307,
The PLHEADER (one slot of 90 symbols) constitutes of:
SOF (26 symbols), identifying the Start of Frame.
PLS code (64 symbol): PLS (Physical Layer Signalling) code shall be a
non-systematic binary code of length
64 and dimension 7 with minimum distance dmin = 32. It is equivalent to
the first order Reed-Muller under
permutation. It transmits 7 bits for physical layer signalling purpose.
These 7 bits consists of two fields:
MODCOD and TYPE defined as follows:
MODCOD (5 symbols), identifying the XFECFRAME modulation and FEC rate;
TYPE (2 symbols), identifying the FECFRAME length (64 800 bits or 16 200
bits) and the
presence/absence of pilots.
The PLHEADER, represented by the binary sequence (y1, y2,...y90) shall
be modulated into 90 π/2 BPSK symbols
Manu
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