Deviser S7200 User Manual page 56

Part II: Settings and Measurements
The S7200 measures DVB-T2 rotated constellation, as shown below. This constellation is only for PLP content.
If the DVB-T2 signal includes multiple PLPs, tap PLP ID to select one. Changing the PLP will also affect the
constellation display (if each PLP has a different modulation type).
The physical layer signaling in DVB-T2 is transmitted inside preamble symbols, known as P1 and P2 symbols,
at the beginning of each T2 frame. The P1 symbol is the first OFDM symbol transmitted in the T2 frame and is
intended for fast identification of available T2 signals. P2 symbols are transmitted right after the P1 symbol,
and carry Layer 1 (L1) signaling divided into pre- and post-signaling. L1 pre-signaling consists of very basic
information (200 bits) and is always transmitted with the most robust configuration available (BPSK and
code rate 1/5). L1 post-signaling, meanwhile, enables the reception of the actual data and is transmitted
with constellations BPSK, QPSK, 16QAM or 64QAM and code rate 1/2. L1 post-signaling is composed of two
parts: configurable and dynamic. The configurable portion signals the configuration of the PLPs and is
seldom changed during the transmission of T2 signals. The dynamic portion signals the position of the PLPs in
each frame and changes from frame to frame.
Use the L1 Info key to view signaling information (see right).
The term PLP (Physical Layer Pipe) was introduced for DVB-T2.
In Mode A, only one data stream is being fed into the DVB-T2
modulator; in Mode B, there are multiple inputs. This standard
can be used to transmit data with different robustness and
data rates, a function called Variable Coding and
Modulation (VCM).
Use the PLP Info key to view PLP information (see below).
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