Candidate: Hong Li
Advisor: Dr. Yeheskel Bar-Ness
Date: April 11, 2006 (Tuesday)
Time: 10:00 am
Location: 106 KUPF, NJIT

Abstract:

Blind modulation classification (MC) is an intermediate step between signal detection and demodulation, which is used in a wide variety of applications in both military and civilian communication. In military communication systems, MC techniques are applied for real-time signal interception and processing, which are crucial for electronic warfare operations and other tactical actions. As for the civilian systems, MC became an active research and development topic in software defined radio (SDR). Recently, many state-of-the-arts communication technologies, such as orthogonal frequency division  multiplexing (OFDM) modulations, have been emerging. The need for distinguishing OFDM signal from single carrier has become obvious. Besides, some vital parameters of OFDM signals should be extracted for further processing. In comparison to the research on MC for single carrier single antenna transmission, much less attention has been paid to the MC with these emerging modulation methods. A comprehensive classification system is proposed for recognizing the OFDM signal and extracting its parameters. An automatic OFDM modulation classifier is proposed, which is based on the statistical goodness-of-fit test. Since OFDM behaves as Gaussian signal, Cramer-von Mises technique, operating on the empirical distribution function, has been applied to test the presence of the normality. Numerical results show that such approach can successfully identify OFDM signals from single carrier modulations over a wide SNR range. Moreover, the proposed scheme can provide an acceptable performance when frequency-selective fading is present.

Cyclostationarity and correlation tests are then applied to estimate OFDM symbol and cyclic prefix durations. A two-phase searching scheme, which is based on Fast Fourier Transform (FFT) as well as Gaussianity test, is devised to detect the number of subcarriers. In the first phase, a coarse search is carried out iteratively. The exact number of subcarriers is determined by the fine search in the second phase. For performance evaluation, finite-step Markov chain is used to calculate the probability of false alarm and the probability of miss for the proposed algorithm. The efficiency of the proposed scheme is corroborated by Monte Carlo simulations.

Committee Members:

Dr. Yeheskel Bar-Ness, Advisor, Distinguished Professor, Department of ECE, NJIT

Dr. Ali Abdi, Assistant Professor, Department of ECE, NJIT

Dr. Alexander M. Haimovich, Professor, Department of ECE, NJIT

Dr. Wei Su, US Army Communication-Electronics RD&E Center

Dr. Ananthram Swami, US Army Research Lab