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Applications:
- High-Security Surveillance Applications
- Helicopter links
- UAV/UGV Applications
- Mobile and Portable AV Applications
Key System Features:
- Robust Link Performance
- Secure – Optional Fixed Key Scrambling System or AES
- Low System Latency (~40 mS)
- 6-8 MHz BW COFDM Modulation
- 49 MHz to 6 GHz (In-Bands) with External Down-Converters
- Built-in MPEG-2 Decoder
- LAN Video Streaming Option
- Compact Enclosure with optional 19-inch Rack-Mount Option
Cobham Surveillance (GMS Products) second generation, Messenger Digital Link (MDL) includes the Messenger Digital Transmitter (MDT), Messenger Digital Receiver (MDR) and one or two external Down-Converters. The MDL provides a unique combination of link reliability and security for the most demanding short or long distance Audio/Video (A/V) point-to-point transmission applications. Additional Messenger features include Mic and Line-level Audio, S-Video, Component Video, local frequency set-up on MDT, Audio/Video (A/V) level control, 16 set-up storage registers, USB-1 control, and optional LAN & USB-2 interfaces on MDR for remote control (Future Option) and A/V distribution over a LAN or the Internet.
The MDL uses a robust digital modulation system known as Coded Orthogonal Frequency Division Multiplexed (COFDM) that provides frequency diversity and powerful Forward Error Correction (FEC) algorithms. The Messenger Digital Receiver (MDR) includes an option for Spatial Post-Detect Diversity Combining to combat short delay spread multipath reflections found in indoor environments. The MDL provides a robust wireless link that is effective against the multipath interference experienced by analog systems, and provides crisp, clear pictures in the most difficult of terrains.
The MDRs versatile housing can be mounted in a suitcase, can sit on a desktop, 19-inch instrumentation rack (with Optional Rack-Mount Kit) or be used for portable applications. Control and status monitoring can be accomplished via the MDR Front Panel, a Remote Control Unit (RCU) or via an external IBM PC and Cobham Surveillance (GMS Products) M.S. Windows application control software. Critical performance parameters like Signal To Noise Ratio (SNR), Modulation Error Ratio (MER) and Pre and Post FEC Bit Error Rate (BER) are provided both on the front-panel and on the On-Screen Display.
For frequencies > 861 MHz, external down-converters (Sold Separately) are used. These down-converters can be remotely mounted at the antenna to optimize system performance. DC Power, control, and the IF signal all exist on a single coax cable.
The MDR receives and demodulates the DVB-T signal and decodes the MPEG-2 Transport Stream to recover video, optional audio (single or dual), and low-rate RS-232 data. This stream can be encrypted with either a simple fixed key scrambling system or AES to provide protection in sensitive applications. The recovered A/V data is decompressed and converted back to analog signals.
One of the biggest problems encountered in the transition from an analog to a digital A/V platform has been the inherent digital coding delays that in some digital systems are 400ms or more. The MDT/MDR combination employs a specially designed ‘low delay’ coding technology, which provides an end-to-end latency of approximately 40ms 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 sports coverage, surveillance, and law enforcement, where personnel are reacting to real-time events.
MDR Special Features
Monochrome Video Mode
Surveillance applications often do not require chrominance data in the video. The MDR has been provided with a luminance (monochrome) only mode. When in this mode bit rate is saved giving sharper monochrome pictures.
Video Only Mode
In applications where audio or data are not required, then the audio and data channels can automatically be switched off. Bit rate is automatically switched over to the video channel in this situation.
High-Speed Data Transmission Option
Using special firmware, the MDL system can be used for high-speed serial synchronous data transmission. In this mode all audio and video processing is turned-off and TTL data is transmitted using a simple data/clock interface.