2026-09-19T11:51:33Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/335932022-01-13T07:54:39Zcom_1721.1_7582com_1721.1_7581col_1721.1_131023col_1721.1_131024
Milica Stojanovic.
Wang, Daniel Y
Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Department of Ocean Engineering
2006-07-31T15:15:26Z
2006-07-31T15:15:26Z
2005
2005
http://hdl.handle.net/1721.1/33593
63788806
Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.
Includes bibliographical references (p. 67).
High-rate underwater acoustic communication can be achieved using transmitter/receiver arrays. Underwater acoustic channels can be characterized as rapidly time-varying systems that suffer severe Inter Symbol Interferences (ISI) caused by multi-path propagation. Multi-channel combining and equalization, as well as time-reversal techniques, have been used over these channels to reduce the effect of ISI. As an alternative, a spatiotemporal focusing technique had been proposed. This technique is similar to time-reversal but it explicitly takes into account elimination of ISI. To do so, the system relies on the knowledge of channel responses. In practice, however, only channel estimates are available. To assess the system performance for imperfectly estimated time-varying channels, a simulation analysis was conducted. Underwater acoustic channels were modeled using geometrical representations of a 3-path propagation model. Multi-path fading was incorporated using auto regressive models. Simulations were conducted with various estimator delay scenarios for both the spatiotemporal focusing and simple time-reversal. Results demonstrate performance dependence on the non-dimensional product of estimation delay and Doppler spread.
(cont.) In particular, it has been shown that when this product is low, the performance of spatiotemporal focusing remains superior to simple time- reversal.
by Daniel Y. Wang.
S.M.
Nav.E.
67 p.
2390242 bytes
2392963 bytes
application/pdf
application/pdf
eng
Massachusetts Institute of Technology
M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.
http://dspace.mit.edu/handle/1721.1/7582
Ocean Engineering.
Electrical Engineering and Computer Science.
Spatiotemporal processing and time-reversal for underwater acoustic communications
Thesis
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<Abstract>High-rate underwater acoustic communication can be achieved using transmitter/receiver arrays. Underwater acoustic channels can be characterized as rapidly time-varying systems that suffer severe Inter Symbol Interferences (ISI) caused by multi-path propagation. Multi-channel combining and equalization, as well as time-reversal techniques, have been used over these channels to reduce the effect of ISI. As an alternative, a spatiotemporal focusing technique had been proposed. This technique is similar to time-reversal but it explicitly takes into account elimination of ISI. To do so, the system relies on the knowledge of channel responses. In practice, however, only channel estimates are available. To assess the system performance for imperfectly estimated time-varying channels, a simulation analysis was conducted. Underwater acoustic channels were modeled using geometrical representations of a 3-path propagation model. Multi-path fading was incorporated using auto regressive models. Simulations were conducted with various estimator delay scenarios for both the spatiotemporal focusing and simple time-reversal. Results demonstrate performance dependence on the non-dimensional product of estimation delay and Doppler spread.</Abstract>
<Abstract>(cont.) In particular, it has been shown that when this product is low, the performance of spatiotemporal focusing remains superior to simple time- reversal.</Abstract>
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