ISR News Story
Polarization and Wavelength Diversity for Fade Resistance in Optical Wireless Communication Systems (ISR IP)
ISR intellectual property available to license
U.S. Patent: 7,106,971
A researcher at the University of Maryland has developed a "delayed-diversity" communication scheme that solves the problem of fading. The scheme takes advantage of the subtle changes in the characteristics of the atmospheric path between the transmitter and the receiver. By introducing a short delay during a multiple data stream transmission, the probability of a simultaneous error in the streams is markedly reduced. Although the delayed diversity scheme introduces a short latency into the link, data arrives continuously at the receiver. This short delay is of no consequence for data transfer and would not be noticeable during voice communication. Further, the delayed diversity scheme does not require more transmitter power and may also be implemented with simultaneously transmitted, different wavelengths.
It has been demonstrated that delayed diversity significantly reduces fading on a 1 km test range using a 633 nm laser transmitter working at eye-safe intensity levels. Applications of the scheme include optical wireless communications for short-range, high data links in LAN; bridging gaps in ground-based networks as well as ground-to-satellite communications; and packet-switched networks to achieve higher data transmission.
For more information
ISR-IP-Davis ISR-IP-optical ISR-IP-wireless-networks
June 18, 2007