STM SatLink VSAT - Appendix O. Accessing the Forward Link Signaling

SatLink VSAT User Guide
Publication no. 101557
Rev 14.1.1-2
Copyright 2006-2012 – STM Group, Inc.
Page 181 (182)
Appendix O. Accessing the Forward Link Signaling
When the receiver of the VSAT is switched on (using dvb rx start), the VSAT carries out a Forward
Link acquisition procedure to obtain the DVB-RCS system information necessary to log on to the
network. The DVB RCS system information is transmitted in specific DVB RCS SI tables that are
standardized in EN 301 790. The identifiers that the VSAT uses to find the DVB RCS SI tables are
embedded within standard DVB-S/DVB-S2 Forward Link signaling table sets that are standardized in EN
300 468 and ISO/IEC 13818-1. Table 23: lists the DVB-S/DVB-S2 tables and the DVB RCS SI tables
that are relevant for accessing the DVB RCS network.
DVB-S SI tables
DVB RCS SI tables
Table name
Abbrev
PID
Table name
Abbrev
PID
Network Information Table
NIT
0x0010
RCS Map Table
RMT
Assigned
Program Association Table
PAT
0x0000
PCR Insertion TS Packet
PCR
Assigned
Program Map Table
PMT
Assigned
Satellite Position Table
SPT
Assigned
Superframe Composition Table
SCT
Assigned
Frame Composition Table
FCT
Assigned
Timeslot Composition Table
TCT
Assigned
Terminal Information Message
TIM
Assigned
Terminal Burst Time Plan
TBTP
Assigned
Correction Message Table
CMT
Assigned
Table 23: List of DVB-S/DVB-S2 and DVB-RCS specific tables that are used when accessing the
network
A rough outline of the procedure is as follows:
The VSAT tunes to the transport stream of the Forward Link that it has pre-configured as the ―start-up‖
Forward Link. There it reads the NIT. The NIT PID value is hard-coded in the SatLink VSAT. In the
NIT, the VSAT finds tuning parameters for accessing the satellite and Forward Link transport stream
containing the RMT. If the RMT is on a satellite or transponder other than the ―start-up‖ Forward Link,
the VSAT will re-tune to the Forward Link carrying the RMT. The RCST then reads the PAT and PMT
on the same Forward Link as the RMT. In the PAT, the VSAT finds the PID that identifies the PMT,
which in turn contains the PID value of the RMT. In the RMT, the VSAT uses its preconfigured
population ID to find and thereafter extract tuning parameters for accessing the correct Forward Link
Signaling service (i.e., parameters defining forward and Return Link satellite(s), NCC, and
Superframe_ID for initial log-on). If the Forward Link for DVB-RCS services defined in the RMT is
different from its current Forward Link, the VSAT must retune to the new Forward Link. There, the
VSAT will access the PAT of the new Forward Link and extract the PID that identifies the PMT that is
relevant for its forward signaling. In the PMT, the VSAT will find the PID values of the PCR Insertion
TS Packet, in addition to the other DVB RCS SI tables.