Fading Modeling, MIMO Channel Generation, and Spectrum Detection for Wireless Communications

Wei-Ho Chung
Advisor: Kung Yao

Monday, March 9, 2009 at 3:00pm-5:00pm
Engr IV Room 57-124

Abstract:
We investigate the fading channel modelling, MIMO channel generation, and spectrum detection for wireless communications. We propose the modified hidden semi-Markov model (MHSMM) for modeling the flat fading envelope process. The MHSMM incorporate the time-variant statistics of the envelope process in a single model, which facilitates computations of the envelope probability density function and the autocorrelation function. We propose and demonstrate the parameter estimation scheme by simulated and experimental data. Diversity techniques for various communication and MIMO systems exploit the spatial and temporal diversity attributes to mitigate the ill effects of the fading channels. We propose a unified approach capable of generating correlated flat-fading envelope processes with the desired auto-correlation functions, cross-correlation functions, and probability density functions (pdfs). The proposed approach utilizes the Gaussian vector autoregressive process and the inverse transform sampling techniques. Comparing to the past research focusing on generating fading channels of the same family, the novelty of the proposed approach is its capability to generate fading processes of heterogeneous pdfs.

Sensor networks have been shown to be useful in diverse applications. One of the important applications is the collaborative detection based on multiple sensors to increase the detection performance. To exploit the spectrum holes in the cognitive radios, we consider the collaborative spectrum sensing by sensor networks in the likelihood ratio test (LRT) frameworks. We provide explicit algorithms to solve the LRT fusion rules, the probability of false alarm, and the probability of detection for the fusion center. We will discuss the single-sensor detection and collaborative detections of multiple sensors under various fading channels.

Biography:
Wei-Ho Chung was born in Kaohsiung, Taiwan, in 1978. He received the B.Sc. and M.Sc. degrees in Electrical Engineering from National Taiwan University, Taipei City, Taiwan, in 2000 and 2002 respectively. Since 2005, he has been with the Electrical Engineering Department at University of California, Los Angeles, where he is currently a Ph.D. candidate. From 2002 to 2005, he was a system engineer at ChungHwa Telecommunications Company, where he worked on data networks. In 2008, he was an intern working on CDMA systems in Qualcomm, Inc. Since 2007, he has been a Teaching Assistant at UCLA. His research interests include communications, signal processing, and networks.