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Proceedings Paper

Likelihood method for BPSK and unbalanced QPSK modulation classification
Author(s): King C. Ho; Liang Hong
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Paper Abstract

Automatic classification of the digital modulation type of a signal is a branch of non-cooperative communication techniques, which has found many applications in electronics warfare, surveillance and threat analysis. We propose in this paper a classifier based on the likelihood method to distinguish BPSK signal and unbalanced QPSK signal embedded in additive white Gaussian noise (AWGN). Unbalanced QPSK signal occurs when the in-phase and quadrature components of a QPSK signal have different power. The proposed classifier first calculates the log-likelihood functions of BPSK and UQPSK signals using AWGN model and IID data sequence. The ratio of the two log-likelihood functions is dependent on the unbalanced factor. When the unbalanced factor is not known to a receiver, it will be replaced by the maximum likelihood estimation, yielding the generalized likelihood ratio test to classify the two modulation types. The proposed classifier performs better than the classifier without taking into account the unbalanced factor when the SNR and the unbalanced factor are high. At low SNR, the performance of the proposed classifier is comparable to the one without considering the unbalanced factor.

Paper Details

Date Published: 28 August 2001
PDF: 8 pages
Proc. SPIE 4395, Digital Wireless Communication III, (28 August 2001); doi: 10.1117/12.438282
Show Author Affiliations
King C. Ho, Univ. of Missouri/Columbia (United States)
Liang Hong, Univ. of Missouri/Columbia (United States)


Published in SPIE Proceedings Vol. 4395:
Digital Wireless Communication III
Raghuveer M. Rao; Soheil A. Dianat; Michael D. Zoltowski, Editor(s)

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