Simulation of Adaptive Array Algorithms for OFDM and Adaptive Vector OFDM Systems

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dc.contributor.authorCheung, Bing-Leung Patricken
dc.contributor.committeechairReed, Jeffrey H.en
dc.contributor.committeememberWoerner, Brian D.en
dc.contributor.committeememberBuehrer, R. Michaelen
dc.contributor.departmentElectrical and Computer Engineeringen
dc.date.accessioned2014-03-14T20:44:44Zen
dc.date.adate2002-09-04en
dc.date.available2014-03-14T20:44:44Zen
dc.date.issued2002-09-03en
dc.date.rdate2003-09-04en
dc.date.sdate2002-09-04en
dc.description.abstractThe increasing demand for high data rate services necessitates the adoption of very wideband waveforms. In this case, the channel is frequency-selective, that is, a large number of resolvable multipaths are present in this environment and fading is not highly correlated across the band. Orthogonal frequency division multiplexing (OFDM) is well-known to be effective against multipath distortion. It is a multicarrier communication scheme, in which the bandwidth of the channel is divided into subcarriers and data symbols are modulated and transmitted on each subcarrier simultaneously. By inserting guard time that is longer than the delay spread of the channel, an OFDM system is able to mitigate intersymbol interference (ISI). Deploying an adaptive antenna array at the receiver can help separate the desired signal from interfering signals which originate from different spatial locations. This enhancement of signal integrity increases system capacity. In this research, we apply adaptive array algorithms to OFDM systems and study their performance in a multipath environment with the presence of interference. A novel adaptive beamforming algorithm based on the minimum mean-squared error (MMSE) criterion, which is referred to as frequency-domain beamforming, is proposed that exploits the characteristics of OFDM signals. The computational complexity of frequency-domain beamforming is also studied. Simulation results show employing an adaptive antenna array with an OFDM system significantly improves system performance when interference is present. Simulations also show that the computational complexity of the algorithm can be reduced by half without significant performance degradation. Adaptive array algorithms based on the maximum signal-to-noise ratio (MSNR) and the maximum signal-to-interference-plus-noise ratio (MSINR) criteria are also applied to adaptive vector OFDM systems (AV-OFDM). Simulation results show that the adaptive algorithm based on the MSNR criterion has superior performance in the multipath environment but performs worse than the one based on the MSINR criterion under the flat fading channel.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-09042002-142835en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-09042002-142835/en
dc.identifier.urihttp://hdl.handle.net/10919/34915en
dc.publisherVirginia Techen
dc.relation.haspartOFDM_beamforming.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectAVOFDMen
dc.subjectOFDMen
dc.subjectAdaptive Algorithmsen
dc.subjectAdaptive Antennasen
dc.titleSimulation of Adaptive Array Algorithms for OFDM and Adaptive Vector OFDM Systemsen
dc.typeThesisen
thesis.degree.disciplineElectrical and Computer Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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