3.1.3.2 LMS-T Operation
The following sequence defines the changes and sequence required when changing to LMS-T
operation :-
Step Menu Sub Menu Option Setting
1 Advanced Modulation Modulation
Type
LMS-T
2 Advanced Modulation Guard Interval As Required. 1/8
or 1/16. Must
match receiver
3 Advanced,Basic Modulation Modulation As Required 16Q
or QPSK
4 Advanced Modulation FEC Rate 2/3 Only
5 Advanced Modulation Polarity Normal
6 Advanced Modulation Width 10MHz or 20MHz
7 Advanced,Basic Modulation Power As Required
8 Advanced,Basic Modulation Frequency As Required
9 Advanced,Basic Modulation RF Output On
The encoder will set the data rate appropriately to match the modulation scheme settings.
The Table below defines the corresponding bit rates for LMS-T operation for both 10MHz and 20MHz
operation.
Modulation GI
CR
1/8
10MHz 20MHz
1/16
10MHz 20MHz
QPSK 2/3 9.2 18.4 9.7 19.5
16QAM 2/3 18.4 36.8 19.5 39
64QAM 2/3 27.6 45.2 29.2 58.5
Note 64 QAM not available on current software.
These rates can be confirmed by checking the Advanced/Multiplexer/Bit Rate menu.
It should be noted that this corresponds to the total data rate which includes the video, audio and any
user data.
Due to the improvement that LMS-T has over DVB-T these settings give approximately 50%
improvement of bit rates for the same level of ruggedness of the RF link.
For example DVB-T 16QAM, 1/32 GI, 1/2 CR gives 12Mbits whereas LMS-T 16QAM gives 18Mbits
3.1.3.3 ASI Operation
The L1500 can be used as an MPEG2 HD encoder providing an ASI output. The modulator and RF Up
converter are not required in this operating mode.
This provides ASI streams up to 90Mbits.
Step Menu Sub Menu Option Setting
1 Advanced Modulation Modulation Type ASI
2 Advanced Multiplexer ASI Bit Rate As Required
3 Advanced Video Encoder Bit Rate As Required
The encoder bit rate cannot be set above the Mux bit rate, if an attempt is made to exceed the mux
setting the encoder value will clamp to the highest allowed rate.
3.1.3.4 Remux Operation
The L1500 can be used to re-multiplex an additional service into the ASI data stream. This allows
two services can be transmitted on one RF Channel.
Step Menu Sub Menu Option Setting
1 Advanced Remux Enable On
It is important that the remultiplexed service multiplexer rate and the internal generated service
multiplexer data rate are within the available RF modulated data rate.
Images are for illustration only and may differ from components supplied
Link Research Ltd www.linkres.co.uk Support UK/Europe + (44) 1923 474099 USA +(1)9786715700
Page 9 of 31 CL140045 Issue C Link L1500 Series System Manual
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