Spread spectrum techniques for video transmission

A number of analog video transmission systems have become available for short-range, non-licensed applications in the 900-MHz and 2.4-GHz ISM bands. Because these systems use conventional analog transmission techniques and operate without license, their maximum transmitter output power is limited by FCC regulations to a field strength of 50 mV/m at 3 meters (equivalent to 0.7 mW on a dipole antenna), providing ranges less than 1000 feet. The severe range limitation as well as the susceptibility to interference on those systems can be overcome by the use of spread spectrum techniques. FCC regulations allow unlicensed spread spectrum systems to transmit at considerably higher power than conventional narrow-band systems, up to 4 W effective radiated power (ERP). With appropriate video compression techniques, a spread spectrum system can transmit near-live video at ranges up to 100 miles, without the requirement of an FCC license. This presentation describes a system designed to provide high-reliability video transmission through the use of advanced video compression coupled with spread spectrum interference suppression and avoidance techniques, for surveillance applications in the security, vehicle traffic management and other markets.