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ETSI
ETSI EN 302 755 V1.1.1 (2009
UPL User Packet Length
VCM Variable Coding and Modulation
4 DVB-T2 System architecture
4.1 System overview
The generic T2 system model is represented in figure 1. The system input(s) may be one or more MPEG-2 Transport
Stream(s) [i.1] and/or one or more Generic Stream(s) [i.2]. The Input Pre-Processor, which is not part of the T2 system,
may include a Service splitter or de-multiplexer for Transport Streams (TS) for separating the services into the T2
system inputs, which are one or more logical data streams. These are then carried in individual Physical Layer Pipes
(PLPs).
The system output is typically a single signal to be transmitted on a single RF channel. Optionally, the system can
generate a second set of output signals, to be conveyed to a second set of antennas in what is called MISO transmission
mode.
The present document defines a single profile which incorporates time-slicing but not time-frequency-slicing (TFS).
Features which would allow a possible future implementation of TFS (for receivers with two tuners/front-ends) can be
found in annex E. It is not intended that a receiver with a single tuner should support TFS.
Bit
Interleaved
Coding &
Frame
Builder
OFDM
generation
TS or
GS
inputs
Input
processing
Input
pre-
processor(s)
T2 system
Figure 1: High level T2 block diagram
The input data streams shall be subject to the constraint that, over the duration of one physical-layer frame (T2-frame),
the total input data capacity (in terms of cell throughput, following null-packet deletion, if applicable, and after coding
and modulation), shall not exceed the T2 available capacity (in terms of data cells, constant in time) of the T2-frame for
the current frame parameters. Typically, this will be achieved by arranging that PLPs within a group of PLPs will
always use same modulation and coding (MODCOD), and interleaving depth, and that one or more groups of PLPs with
the same MODCOD and interleaving depth originate from a single, constant bit-rate, statistically-multiplexed source.
Each group of PLPs may contain one common PLP, but a group of PLPs need not contain a common PLP. When the
DVB-T2 signal carries a single PLP there is no common PLP. It is assumed that the receiver will always be able to
receive one data PLP and its associated common PLP, if any.
More generally, the group of statistically multiplexed services can use variable coding and modulation (VCM) for
different services, provided they generate a constant total output capacity (i.e. in terms of cell rate including FEC and
modulation).
When multiple input MPEG-2 TSs are transmitted via a group of PLPs, splitting of input TSs into TSPS streams
(carried via the data PLPs) and a TSPSC stream (carried via the associated common PLP), as described in annex D,
shall be performed immediately before the Input processing block shown in figure 1. This processing shall be
considered an integral part of an extended DVB-T2 system.
The maximum input rate for any TS, including null packets, shall be 72 Mbit/s. The maximum achievable throughput
rate, after deletion of null packets when applicable, is more than 50 Mbit/s (in an 8 MHz channel).