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 _______________________________________________ linux-dvb mailing list linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
