Rapid carrier acquisition and ML channel estimation of fading for coherent communication systems /
Two different problems dealing with coherent communications
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1997.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=736553611&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Two different problems dealing with coherent communications are examined in this research. For coherent communications over an additive Gaussian noise channel, an estimator suitable for the rapid acquisition of quadrature amplitude modulated signals is developed. A linear estimator, assuming known modulation, is derived from the likelihood function using baud-rate samples from the matched filter output. The estimates are computed recursively with phase unwrapping so that iterative searches as in Newton-Raphson are not required. The linear estimator is applied to blind frequency acquisition and combined with testing to eliminate unlikely hypotheses. With proper modeling of the likelihood resulted from the blind search, simulations show that the algorithm quickly rejects all but the correct frequency hypothesis. For coherent communications over a fading environment, a channel estimator applicable to coherent detection of phase shift keying signals is developed. A new approach of utilizing the fading information embedded in both the pilot symbols and the data symbols is used to estimate the channel impulse response. In addition, a significant complexity reduction is achieved using a UMP test. The resulting algorithm has overcome the complexity problem in the optimal realization and yet its performance is not constrained by the minimum pilot symbol insertion rate as required in the interpolation algorithms. Finally, for an imperfect knowledge of the channel, testing is also used to detect mismodeling. With appropriate fading model adjustments, the performance loss is negligible compared to that of known channel models. |
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| Item Description: | Vita. "Major Subject: Electrical Engineering". |
| Physical Description: | xii, 94 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 76-79. |