Implementation of a variable rate vocoder and its performance analysis

dc.contributor.authorManjunath, Sharathen
dc.contributor.departmentElectrical Engineeringen
dc.date.accessioned2014-03-14T20:39:46Zen
dc.date.adate2009-06-10en
dc.date.available2014-03-14T20:39:46Zen
dc.date.issued1994-05-01en
dc.date.rdate2013-04-11en
dc.date.sdate2009-06-10en
dc.description.abstractThe use of Code Division Multiple Access (CDMA) technology for cellular radio and personal communications has ushered in a new era wherein the benefits of CDMA can be directly applied to voice transmission. In particular, the resistance to multipath and graceful degradation of performance (voice quality) in the presence of multiple access interference are the significant benefits of CDMA. Spectral efficiency is a key issue in mobile communications. The use of vocoders reduces the average bit transmission rate for each user, thereby reducing the bandwidth necessary to transmit the speech of each user. Qualcomm-Code Excited Linear Prediction (QCELP) algorithm provides a way to implement a variable rate vocoder which could reduce the average bit rate by a factor of two. This thesis describes a software implementation of the QCELP algorithm and the integration of the vocoder with the CDMA transmission and reception segments. A subjective performance analysis of the vocoder, using a Mean Opinion Score (MOS) test on the speech quality under various channel conditions including 1-Ray and 2-Ray Rayleigh fading environments is performed. Objective quality measures such as Signal-to-Noise Ratio (SNR), Segmental SNR (SSNR) and the Coherence Function (CF) are also investigated for comparison with the subjective analysis results.en
dc.description.degreeMaster of Scienceen
dc.format.extentx, 93 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-06102009-063255en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-06102009-063255/en
dc.identifier.urihttp://hdl.handle.net/10919/33511en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V855_1994.M3429.pdfen
dc.relation.isformatofOCLC# 31059066en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V855 1994.M3429en
dc.subject.lcshCode division multiple access -- Computer simulationen
dc.subject.lcshVocoderen
dc.titleImplementation of a variable rate vocoder and its performance analysisen
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineElectrical Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen
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