TECH NEWS /// Screenshot from Sony receiving board during mobile test
Lite content, allowing a wider carrier spacing and thus preventing Doppler effect issues when the receiver is moving at high speed. T2 Lite also features two
extra LDPC code rates. Time slicing is still supported at transport stream level. T2 Lite frames can be broadcast at pre-defined times only, and the receiver can be turned off during T2 Base frames to preserve battery life in portable devices.
RAI R&D AND RAI WAY TRIAL The test network is based on a dedicated headend in the RAI facility in Aosta. A Harmonic re-multiplexer receives the national “Rai HD” programme from its “native” TS (to be aired in DVB-T standard) and multiplexes it with local content (generated in the same facility by RAI Regional Services) and with a 3D content loop-played from a local video server. These three channels are then included into the T2 Base PLP.
The T2 Lite live content comes via SDI from the local production facility master control room. It is ingested through a Dektec DTU 2145 PCI adaptor, down-scaled in resolution to fit the typical mobile receiver screen capabilities, then compressed in AVC through the Dektec DTC-
TX Modulator and ETL DSCF2705
The T2 Lite measurement campaign affirmed the success of two transmitters working as an SFN.
315 DtEncode software package.
The Harmonic device muxes
the three HD content (T2 Base) with the mobile content (T2 Lite) and adds the references for SFN operation, generating the T2-MI stream. Through radio link connections, the T2- MI stream is delivered to the transmitting sites in St. Vincent
(Salirod transmit site) and in Aosta (Gerdaz transmit site). At each of these sites, the
data stream is routed to a Screen Service modulator. This device is still a prototype, and it’s made of two separate units. The Base and Lite PLPs are time sliced, so the Slave modulator takes care of the Base and sends it to the
Master; whereas the Lite PLP is handled and the final RF output is synthetised.
The subsequent Screen Service amplifier boosts the output up to 50 W (Aosta) or 100 W (St. Vincent) RMS, which is aired through dedicated antennas. The modulators of the two transmitting sites get the relevant time and frequency reference signals from the GPS receiver card hosted in the modulator chassis. Building the receiver was a
bit more complicated. Since no commercial T2 Lite capable receiver is available, Sony supplied RAI specialists with a sample board based on the company’s CXD2861 silicon tuner and a prototype receiver that can output T2 Lite content as a parallel data stream, which is then decoded into baseband video.
The receiving system fits
into a light van. It is also equipped with a position tracking device and a data recorder to track the RF parameters and receiving conditions during mobile reception. Tests were conduced under these modulation parameters: T2 Base: 256 QAM Rotated,
FEC 3/4, FFT 32k, GI 1/128, PP7, with 28.2 Mbps payload T2 Lite: QPSK Rotated, FEC 1/2, FFT 8k, GI 1/32, PP4, with of 2.2 Mbps payload.
RESULTS We were really impressed during the T2 Lite mobile test. Even on the typical curving roads you find on the mountains, with frequent 180
////////////////14 TV Technology Asia-Pacific I February-March 2014
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