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Título: Detection techniques and performance analysis for fading multipath channels with unresolved components
Autores: Danilo, Florence A.
Fecha: 2000
Publicador: McGill University - MCGILL
Fuente:
Tipo: Electronic Thesis or Dissertation
Tema: Engineering, Electronics and Electrical.
Descripción: Personal communication services (PCS) is one of the fastest growing sectors in telecommunications. PCS can be provided by wireless cellular communication systems, that operate in radio environments characterized as multipath fading channels. This thesis addresses the subject of signal detection and performance analysis over multipath Ricean/Rayleigh fading channels, when the multipath delays are known and the path resolvability assumption is not satisfied. The path resolvability condition asserts that the signal autocorrelation function vanishes ("strict") or it is small ("approximate") at inter-path delays. The strict path resolvability assumption is rarely satisfied, and even the approximate path resolvability condition is not always satisfied in practice. For example, the approximate path resolvability is not satisfied for narrow-band systems such as GSM, IS136, or their third generation derivatives and it is neither satisfied for wide-band systems, such as IS95 or W-CDMA, in indoors due to the relatively small multipath delays of these environments.
Existing demodulation schemes for multipath fading channels, such as Rake receivers, provide diversity gains but they are based on the path resolvability assumption. This thesis shows the severe limitations of the classical Rake receiver over unresolved multipath fading channels, and generalizes the Rake concept to improve performance. The optimal receiver that assumes knowledge of the specular component (specular coherent), and the optimal scheme that assumes knowledge of the specular component magnitudes only (non-coherent), are derived for unresolved Ricean multipath fading channels. It is shown that both include an orthogonalization (or decorrelation) stage that vanishes when the multipath is resolved. This thesis presents explicit forms of the Minimum Mean-Square Error estimator of the likelihood ratio estimator-correlator forms, and shows that the decorrelation operation is present in the estimation process. Based on the insight provided by these optimal schemes, suboptimal receivers more suitable for implementation are proposed.
Performance analysis results, for several binary modulation formats, demonstrate the importance of the decorrelation operation in yielding diversity gains and eliminating error floors under multipath unresolvability conditions. It is also shown that the knowledge of the specular component phase does not provide significant gains at high SNR for orthogonal FSK. Finally, it is shown that SNR gains can be obtained by exploiting the knowledge of the specular component magnitude.
Idioma: en