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Zhou Z.,University of Connecticut | Pengt Z.,University of Connecticut | Cui J.-H.,University of Connecticut | Jiang Z.,Usnaval Research Laboratory
Proceedings - IEEE INFOCOM | Year: 2010

In this paper, we investigate the multi-channel MAC problem in underwater acoustic sensor networks. To reduce hardware cost, only one acoustic transceiver is often preferred on every node. In a single-transceiver multi-channel long-delay underwater network, new hidden terminal problems, namely multi-channel hidden terminal and long-delay hidden terminal (together with the traditional multi-hop hidden terminal problem, we refer to them as "triple hidden terminal problems"), are identified and studied in this paper. Based on our findings, we propose a new MAC protocol, called CUMAC, for long delay multi-channel underwater sensor networks. CUMAC utilizes the cooperation of neighboring nodes for collision detection, and a simple tone device is designed for distributed collision notification, providing better system efficiency while keeping overall cost low. Analytical and simulation results show that CUMAC can greatly improve the system throughput and energy efficiency via effectively solving the complicated triple hidden terminal problems. ©2010 IEEE.


Ellingson S.W.,Virginia Polytechnic Institute and State University | Taylor G.B.,University of New Mexico | Craig J.,University of New Mexico | Hartman J.,Jet Propulsion Laboratory | And 9 more authors.
IEEE Transactions on Antennas and Propagation | Year: 2013

LWA1 is a new radio telescope operating in the frequency range 10-88 MHz, located in central New Mexico. The telescope consists of 258 pairs of dipole-type antennas whose outputs are individually digitized and formed into beams. Simultaneously, signals from all dipoles can be recorded using one of the instrument's 'all dipoles' modes, facilitating all-sky imaging. Notable features of the instrument include high intrinsic sensitivity (6 kJy zenith system equivalent flux density), large instantaneous bandwidth (up to 78 MHz), and four independently steerable beams utilizing digital 'true time delay' beamforming. This paper summarizes the design of LWA1 and its performance as determined in commissioning experiments. We describe the method currently in use for array calibration, and report on measurements of sensitivity and beamwidth. © 1963-2012 IEEE.

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