Network Functions - Promax MO-180 Manual De Usuario

4.5 NETWORK functions

The selection of this item allows us to access those functions related to the
configuration of the modulator to operate in an MFN or SFN network. Let's review each
option.
Mode
Choose whether the modulator is to be used in a Single Frequency Network
(SFN) or in a Multi-Frequency Network (MFN). In an SFN the modulator synchronises
its internal clock with an external 10 MHz reference or with the input HP transport
stream in case an external 10 MHz reference is missing. Proper SFN synchronisation
requires a Megaframe Initialisation Packet (MIP) in the incoming TS (or in both
transport streams in the case of hierarchical transmissions) and a one-pulse-per-
second (1pps) reference. In an MFN, the modulator is synchronised with either the
chosen input TS (slave mode) or with the internal/external 10 MHz reference (master
mode).
MFN Multi-frequency network with mater or slave synchronisation.
SFN Single frequency network with external synchronisation.
Modulator config.
Some parameters of the modulator (constellation, symbol interleaver,
hierarchical modes with parameter α, HP & LP convolutional rates, guard interval,
number of carriers, time slicing, MPE-FEC, cell ID and channel bandwidth) may be
configured using the values carried on the MIP packet. This applies to both MFN and
SFN operation.
Local Configure the modulator using the values entered by the user.
MIP Configure the modulator using the MIP packet.
Local dly offset
In MFN this is the non-negative local delay offset to add to the intrinsic latency
of the modulator. The valid range goes from a few ms (the exact number depends on
the channel bandwidth, number of carriers, guard interval and symbol interleaver
depth) up to 1 second. In SFN this is the positive or negative local delay offset that we
add to the dynamic delay automatically calculated by the modulator using the MIP
packet, the 1pps signal and the 10 MHz reference clock. The valid range for this offset
in SFN is such that the total delay (calculated as the dynamic delay plus the local delay
offset plus the transmitter delay offset embedded in the MIP) lies between a few ms
and 1 second. The minimum delay depends on the same parameters as in MFN. When
the total delay is below the minimum or above the maximum (although clipped at 1s),
this is flagged by the modulator as an error. The local delay offset can be set with a
resolution of 100 ns.
Page 24
USER'S MANUAL MO-180
04/2008