Broadband Directional Wireless Communication Networks
Prof. Christopher C. Davis
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| Dr. Christopher Davis |
Demand for broadband wireless access from everywhere to everywhere is growing worldwide. It would be highly desirable if such wireless connections provided bandwidths up to 100Mb/s. The electromagnetic spectrum is very crowded, and many regions of the spectrum are already reserved for other uses. Consequently, it is impossible to provide broadband wireless access for a large number of users if broadcast techniques are used.
To provide the needed capacity, much greater use of narrow beam, directional wireless communications is needed. In this way space is used efficiently. Transmitters only direct their signals to the receivers that they want to communicate with. Broadcast schemes on the other hand waste energy filling the whole space with signals, which become “interference” for all but the intended recipient of the signal.
Professor Christopher Davis, his colleagues Professor Stuart Milner, Dr. Quirino Balzano, and Dr. Igor Smolyaninov, and their students are building and studying the performance of high data rate directional wireless links and networks. They use a combination of free space optical (FSO) laser communication, RF communication at 24GHz, and millimeter wave communication at 80GHz, and currently have data transfer rates up to 1.25Gb/s. The biggest challenge in this research is to direct the narrow beams of laser and RF transceivers directly at each other in a dynamic, reconfigurable way. This is the pointing, acquisition, and tracking (PAT) problem. Professor Davis and his group are using agile mechanical gimbals and optical beam steering techniques to point hybrid FSO/RF transceivers in this way. They are studying various techniques including optical beacons and GPS for locating nodes in their networks and pointing to them. In addition they have developed novel techniques to mitigate the deleterious properties of the atmosphere on the propagation of laser beams in FSO systems.
Prof. Davis and Prof. Milner were awarded a three-year National Science Foundation grant for related research, titled "Transceiver and Network Technology Developments for Directional Hybrid Wireless Networks."
The team's prior research, as well as the research of others, has shown that mobile ad-hoc networks (MANETs) do not scale. For this research project, Davis and Milner plan to create a higher communication tier using autonomously configuring directional links in a flexible backbone network that connects MANET-like small clusters in an architecture that is "base-station-like."
This research will address important, unsolved research problems in stabilization, pointing, acquisition, tracking (SPAT), bootstrapping, and topology control algorithms needed to make "hybrid" directional free space optical (FSO) and radio frequency (RF) networks a reality.
The researchers also will build and study new optical wireless nodes with novel design features that make them potentially valuable in indoor optical wireless applications where RF is not desirable because of interference problems, such as in the healthcare industry.
Recently, Prof. Davis and Prof. Stuart Milner were awarded a three-year grant worth $1,048,279 from the Air Force Office of Scientific Research (AFOSR). The grant will support their related research, titled "Quantifying and Assuring Information Transfer in Dynamic Heterogeneous Wireless Networks."
Researchers at the University of Maryland, Cornell University and the University of Illinois will conduct a theoretical investigation of next generation, complex, heterogeneous, wireless networks aimed at quantifying, controlling and managing information transfer for theater, tactical and strategic support.
In their previous AFOSR-sponsored research, Davis and Milner focused on scalability, control, and capacity limits of heterogeneous, wireless networks that involve mobile ad hoc networks (MANETs), links with disparate data rates from bits-per-second to above Gb/s, and directional wireless (free-space optical and RF) backbones, with an emphasis on the transfer of packets. In this effort, Davis and Milner will focus on network architectures and protocols that support information transfer. The researchers will address information-centric topology management and control vis-à-vis network topology management and control. The research project is intended to provide new analytical and mathematical tools to understand the factors affecting communications in complex wireless networks and their effect on network performance.
Research Group Members:
Christopher Davis, Stuart Milner, Quirino Balzano, and Igor Smolyaninov
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