The Basics of COFDM Digital Video

OFDM (Orthogonal Frequency Division Multiplexing) transmission technology provides a superior means of transmitting wireless information in high multi-path environments. Analog systems use a single carrier. When this carrier encounters fades due to multipath, the signal is lost or distorted. OFDM systems use 2000 carriers within the main signal. Each carrier may be modulated in one of several ways, trading off data rate for signal robustness. The loss of one or more carriers may 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. Signal blockage, however, impacts both analog and digital systems negatively. COFDM systems have become the standard for transmission in Europe. COFDM 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 COFDM. The RF transmission section is manufacturer dependent. COFDM receivers act in the reverse, relying on an RF receiver, COFDM demodulator, and an MPEG 2 decoder. Systems have typically been built to comply with a European standard called DVB-T, which helps with interoperability of various manufacturers’ products.

DTC’s Role in COFDM

DTC has provide the law enforcement and military community with the latest digital video technology. DTC has the knowledge to effectively apply COFDM systems for use in law enforcement and military applications.

Today, DTC has offer a variety of transmitters for airborne law enforcement downlinks, stationary links, and tactical links. The company is collaborating on new products to provide man-portable and body worn transmitter solutions, as well as briefcase tactical receiver kits, including monitor and recorders.

DTC repackages devices for manportable applications. This will include paying close attention to size, weight and power of these devices, as well as the ability to withstand environmental extremes. It will also include the integration of recording devices and monitors into "grab and go" briefcase style receive kits. DTC’s experience in antenna design will ensure optimal performance of COFDM systems.