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Applications:
- High-Security Surveillance Applications
- Helicopter links
- UAV/UGV Applications
- Mobile and Portable AV Applications
Key System Features:
- Secure – Optional Fixed Key Scrambling System or AES
- 6-8 MHz BW COFDM Modulation
- 49 MHz to 6 GHz (In-Bands) with External Down-Converters
- Low System Latency (~40 mS)
- Optional Diversity Combining
- Built-in MPEG-2 Decoder
- High-Speed Data Transmission Option
The 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 security and link reliability for the most demanding short or long distance Audio/Video (A/V) point to point transmission applications.
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 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 full rack-width housing can be mounted in a 19-inch instrumentation rack, can sit on a desk top or be used for portable applications. Control and status monitoring can be accomplished via a Remote Control Unit (RCU) or via an external IBM PC and Cobham Surveillance (GMS Products) MS 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. 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 MPEG2 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 surveillance, and law enforcement, where personnel are reacting to real-time events.