A Framework for Spectrally Efficient Noncoherent Communication

"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."

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Warrier, Dilip Gopinath

Contributors dc:contributor

• Upamanyu Madhow

• Engineering, Electronics and Electrical

Language dc:language

eng

Identifier

(MiAaPQ)AAI9955679

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/81326