C-OFDM Digital Video

C-OFDM - Coded Orthogonal Frequency Division Multiplexed transmission technology provides a superior means of transmitting wireless information in high multipath environments. C-OFDM systems use 2000 coded carriers within the main signal, each carrier is coded modulated  for signal robustness. The loss of one or many coded carriers have no impact on the video received. Adjustable guard intervals minimize multipath interference. The system also uses Forward Error Correction coding, further increasing signal reliability. Multipathed signals are summed at the receiver, actually aiding in signal quality. C-OFDM systems have become the standard for transmission in Europe. C-OFDM transmitters involves three major components: A signal encoder, a modulator, and an RF transmitter. MPEG 2 is the industry standard for encoding an NTSC or PAL signal, the modulation scheme is C-OFDM.

• 99.99% Perfect Video Picture with Zero Color Shift

• Freedom of Movement Inside Buildings With Out Losing Video & Audio

• Upgrade Option Available to Transmit in HDTV

• License Free with Long Reaching Ranges

Applications
- High-Security Surveillance Applications
- Helicopter Links
- UAV/UGV Applications
- Electronic News Gathering (ENG)
- Studio Wireless Links
- Sports
- Point of View
- Mobile and Portable AV Applications

Key System Features
- Robust Link Performance with C-OFDM
- Low Power Consumption (~8.5 Watts)
- Rugged and Compact Design
- Local & Remote Control Interface
- Secure - Optional AES Scrambling
- Output Frequency: 0.36 to 6GHz (In-Bands)
- Built-in 4:2:0 MPEG-2 Encoder

GMS Standard Definition Messenger Transmitter (SDMT) is one of the smallest and lowest power consumption DVB-T compliant C-OFDM transmitters available. GMS offers several companion receivers and ancillary equipment required to cover a wide variety of applications and budgets. Additionally, this transmitter is compatible with most commercial DVB-T receivers and Set-Top Boxes. The SDMT accepts Composite, SVideo or Component video as well as up to two audio channels (Mic or Line Level). Both the video and the audio are compressed according to MPEG specifications (Video MPEG2 and audio MPEG1 Layer II). However, unlike other MPEG systems, the high-frequency video signal components are preserved. The audio, video program element streams are multiplexed with basic service data to indicate the service name. The stream can be scrambled with the AES scrambling system to provide protection in sensitive applications.

A Standard Definition Messenger Link (SDML) is formed when the SDMT is combined with one of GMS Messenger Digital Receivers, one or two external Down-Converters, antennas, and a SD MPEG2 decoder. GMS SDMLs provide a unique combination of security and link reliability for the most demanding short or long distance Audio/Video (A/V) point to point and point to multipoint transmission applications.

SDML uses a robust digital modulation system known as Coded Orthogonal Frequency Division Multiplexed (C-OFDM) that provides frequency diversity and powerful Forward Error Correction (FEC) algorithms. The Messenger Digital Receivers include an option for Spatial Maximal Ratio Pre-Detect Diversity Combining to combat short delay spread multipath reflections found in indoor environments. The SDML 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.

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 SDMT/DDR combination in SP@ML mode can provide an end-to-end latency down to approx. 132ms 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.