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Title: Time-domain equalization for underwater acoustic OFDM systems with insufficient cyclic prefix
Keywords: Equalizer, Underwater Acoustic, OFDM, Communication, cyclic prefix.
Issue Date: 3-Aug-2011
Citation: YEO SOON KEAT KELVIN (2011-08-03). Time-domain equalization for underwater acoustic OFDM systems with insufficient cyclic prefix. ScholarBank@NUS Repository.
Abstract: Orthogonal frequency division-multplexing (OFDM) is an e ective method to tackle inter-symbol interference (ISI) in underwater acoustic communication and achieve high bit-rates. OFDM requires the length of the cyclic pre x (CP) to be as long as the channel length. However, in short-range shallow water or medium-range deep water acoustic links, the channels are as long as a few hundred taps. This reduces the bandwidth e ciency of the system. This thesis explores methods of reducing the length of CP in OFDM systems, and hence increasing the bandwidth e ciency of these systems. The role of a time domain CSE is to shorten the e ective channel so that a shorter CP can be used. These methods include two time domain channel shortening equalizers (CSE): minimum mean square error (MMSE) and maximum shortening signal-to-noise ratio (MSSNR). Two of the more common MMSE CSEs are unit tap constraint (UTC) and unit energy constraint (UEC). The MSSNR approach and its frequency weighted model minimum ISI (Min ISI) are designed to minimize the shortening signal-to-noise ratio (SSNR). Another method to increase the bandwidth e ciency is by implementing the frequency domain decision feedback equalizer (FD-DFE). The performance of the di erent methods is evaluated on simulated and real acoustic data.
Appears in Collections:Master's Theses (Open)

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