Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Multi-rate laser pulses could boost outdoor optical wireless performance

27.10.2004


Multi-rate, ultra-short laser pulses -- with wave forms shaped like dolphin chirps -- offer a new approach to help optical wireless signals penetrate clouds, fog and other adverse weather conditions, say Penn State engineers.



The new approach could help bring optical bandwidth, capable of carrying huge amounts of information, to applications ranging from wireless communication between air and ground vehicles on the battlefield to short links between college campus buildings to metropolitan area networks that connect all the buildings in a city.

Dr. Mohsen Kavehrad, the W. L. Weiss professor of electrical engineering and director of the Center for Information and Communications Technology Research, leads the study. He says, "The multi-rate approach offers many advantages. For example, lower rate signals can get through clouds or fog when high rate signals can’t. By sending the same message at several different rates, one of them can probably get through."


Rather than slowing communication down, the multi-rate approach has been shown in tests to achieve an average bit rate higher than conventional optical wireless links operating at 2.5 Gbps as well as providing an increased level of communication reliability by maintaining a minimum of one active link throughout channel conditions, he adds.

Kavehrad outlined his team’s new approach at the Optics East 2004 Conference in Philadelphia, Oct. 27, in a paper, "Ultra-short Pulsed FSO Communications System with Wavelet Fractal Modulation." He will also describe the system at the IEEE MILCOM conference in Monterey, California, on Nov. 1. His co-author is Belal Hamzeh, doctoral candidate in electrical engineering.

In optical wireless systems, also known as free-space optics (FSO), voice, video and/or data information is carried on line-of-sight, point-to-point laser beams. Outdoor FSO systems have been in use for over 30 years but are hampered by weather and other obstructions that prevent the transmitter and receiver from "seeing" each other.

Kavehrad explains that clouds and fog often clear abruptly providing brief windows for transmission, making pulsed delivery better suited to FSO. The new Penn State approach embeds data in ultra-short pulses of laser light, shaped via fractal modulation as wavelets, and then transmits the wavelets at various rates.

Belal says the wavelets are easy to generate. "We use holography to generate and separate the wavelets. You just generate the mother wavelet and then the others can be generated as a fraction of the transmission bit rate of the mother. They can all co-exist in the channel without interference," he notes.

The wavelets used by the Penn State team are Meyer’s Type which look like dolphin chirps. The wavelets minimize bandwidth waste and the ultra-short pulses are less likely to interact with rain or fog that could degrade the signal.

The researchers note that their proposed system ensures on-the-fly operation without the need for significant electronic processing. The project is supported by the Air Force Research Laboratory.

Barbara Hale | EurekAlert!
Further information:
http://www.psu.edu

More articles from Information Technology:

nachricht New technology enables 5-D imaging in live animals, humans
16.01.2017 | University of Southern California

nachricht Fraunhofer FIT announces CloudTeams collaborative software development platform – join it for free
10.01.2017 | Fraunhofer-Institut für Angewandte Informationstechnik FIT

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Water - as the underlying driver of the Earth’s carbon cycle

17.01.2017 | Earth Sciences

Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

17.01.2017 | Materials Sciences

Smart homes will “LISTEN” to your voice

17.01.2017 | Architecture and Construction

VideoLinks
B2B-VideoLinks
More VideoLinks >>>