DVB-S.2 system flow

The flow chart of DVB-S2 system is shown in figure 1. Because of its good expansibility, each part contains more options, adaptations and other units, which is far more complicated than DVB-S.

Figure 2

Mode adaptation is the interface of input data stream, which is used to adapt various input stream formats of DVB-S2. For fixed code modulation (CCM) mode, the mode adaptation part includes transparent unpacking of DVB-ASI stream (or DVB parallel transport stream) and 8-bit cyclic redundancy check.

The stream performs two functions adaptively: baseband framing and scrambling. In order to cooperate with the subsequent error correction coding, baseband framing needs to pack the input data with a fixed length (different error correction coding schemes have different "fixed lengths") and fill in useless bytes to make up for the deficiency.

Forward error correction adopts the form of LDPC (inner code) and BCH (outer code) cascade.

The mapping part converts the input serial code stream with forward error correction into a parallel code stream conforming to the specific constellation according to the specific modulation modes (QPSK, 8PSK,16PSK, 32APSK) adopted later.

In the framing part of the physical layer, energy diffusion and empty frame insertion are realized by scrambling.

The modulation part completes baseband shaping and modulation.