A Framework for Spectrally Efficient Noncoherent Communication
Warrier, Dilip Gopinath
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Permalink
https://hdl.handle.net/2142/81326
Description
Title
A Framework for Spectrally Efficient Noncoherent Communication
Author(s)
Warrier, Dilip Gopinath
Issue Date
2000
Doctoral Committee Chair(s)
Upamanyu Madhow
Department of Study
Electrical Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Language
eng
Abstract
"This thesis considers noncoherent communication over a frequency-nonselective channel in which the time-varying channel gain is unknown a priori , but is approximately constant over a coherence interval . Unless the coherence interval is large, coherent communication, which requires explicit channel estimation and tracking prior to detection, incurs training overhead which may be excessive, especially for multiple antenna communication. In contrast, noncoherent detection, which may be viewed as a generalized likelihood ratio test (GLRT) for joint channel and data estimation, does not require separate training. The goal of this thesis is to provide a framework for designing spectrally efficient noncoherent communication systems, analogous to the wealth of signal and code design techniques available for coherent communication. The main results are as follows: (1) A ""signal space"" criterion is developed for signal and code design for noncoherent communication, in terms of the distances of signal points from the decision boundaries. (2) The noncoherent metric thus obtained is used to guide the design of signals for noncoherent communication that are based on amplitude/phase constellations. These are significantly more efficient than conventional differential phase shift keying (PSK), especially at high signal-to-noise ratio (SNR). Also, known results on the high SNR performance of multiple symbol demodulation of differential PSK are easily inferred from the noncoherent metric. (3) The GLRT interpretation is used to obtain a linear complexity (in the block length) implementation of multiple symbol demodulation of differential PSK. The degradation of this scheme from the exact, exponential complexity, implementation can be made as small as desired. (4) A block transformation is demonstrated to produce noncoherent space-time codes with full diversity, starting from an appropriately chosen single antenna noncoherent code. This provides a constructive approach for obtaining high rate noncoherent space-time codes for large coherence intervals. Previous optimization approaches to finding noncoherent space-time codes would be difficult to implement in such a setting, since they involve a search over a space whose dimensions grow exponentially with the block length and the code rate."
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