User`s manual

100-M0145X2 8 of 36
www.cobham.com/gms
3. General System Information
The MVRD (Messenger VETA Receiver Decoder) receives and demodulates DVB-T 2k carriers’ signals
with bandwidths of 6, 7 or 8 MHz; additionally, optional 1.25 or 2.5 MHz RF bandwidths with 400
carriers allow both increased reception range and larger quantity of simultaneous A/V links to operate
in the same frequency band. The wider bandwidths provide greater throughput that allow the system
to transfer the highest quality video.
The MVRD has dual Diversity inputs and internal RF Block-Down Converters (BDCs) with a user selected
(at time of purchase) frequency band. The MVRD’s Maximal Ratio Diversity Combiner provides
optimum reception in difficult fading and multipath environments. Additionally, the Diversity
combining can provide up to 2.5 dB in link performance, increasing the receiver’s sensitivity to -97.5
dBm at 8 MHz bandwidth.
One of the biggest problems encountered in the transition from analog to digital A/V systems has been
the inherent digital coding/decoding delays that in some digital systems are 400ms or more. The VETA
Transmitters & Receivers employ internal MPEG-2 or MPEG-4
(4)
(User Selectable) Encoders and
Decoders with specially designed ‘low-delay’ coding technology, which provides an end to end latency
down to 44ms without the introduction of any further MPEG encoding artifacts. This ensures that the
picture you see is what is happening now - crucial for applications such as surveillance, and law
enforcement, where personnel are reacting to real-time events.
The MVRD also includes internal low-latency Audio/Video Decoder (MPEG-2 or MPEG-4
(*)
) and output
circuits that provide video, two audio and data channels. Security of transmission is ensured by the use
of Standard ABS encryption or, for greater security, the optional AES 128 or 256 bit scrambling
algorithms.
Control and status monitoring can be accomplished via the VR Front Panel or via an external IBM PC
and GMS’ M.S. Windows application control software. Critical performance parameters like Signal to
Noise Ratio (SNR), Pre and Post FEC Bit Error Rate (BER) and Packet Errors are provided both on the on
the On-Screen Display and M.S. Windows control program.
The MVRD includes an optimal internal low-latency Audio/Video (SD Only) MPEG-2/4 Part 4 Decoder
and output circuits that provide composite video and two audio channels. Ancillary Data extraction is
available in all Modes. Security of transmission is ensured by the use of Standard ABS encryption or, for
greater security, the optional AES 128 or 256 bit scrambling algorithms.
(*)
Option Dependant
3.1 Product Control & Status Monitoring Approach
GMS Transmitters and Receivers provide programmable presets or configurations that can be set up
through special programming software by Administrators. Configurations are selected by the user
though M.S. Windows Application programs. Administrators define the configurations for specific
applications. Each configuration completely defines all of the Unit parameters including center
frequency, output RF power level (for TX only), modulation parameters, Video, Audio, User data and
encryption. Field personnel will select specific configuration via pre-determined guidance from the
Administrators. Matching the Transmitter operation to the Receiver operation is as simple as selecting