Editorial [special issue introduction]

In this special issue, ten selected quality papers are presented to address a variety of emerging topics. The multi-input- multi-output (MIMO) radar imaging system is explored in the sensor networks for the surveillance purpose. A new cognitive radio technology that concatenates the available narrow-band white spaces to increase the precision of the range estimation system is addressed. A pseudogradient algorithm is proposed for navigation of autonomous mobile robots operating in unknown environments. The theoretical performance bounds for orthogonal frequency-division multiplexing (OFDM) ranging systems operating in multipath channels are derived subject to Fisher information analysis. An extensive measurement campaign is presented, where data from heterogeneous sensors are collected simultaneously to characterize the diversity of navigation systems in real environments. A new measure for non-line-of-sight identification is demonstrated for wireless localization systems built upon the MIMO-OFDM technology. The approximate maximum likelihood algorithm to estimate the direction-of-arrivals of multiple acoustic sources is studied. A new energy-based acoustic source localization scheme is proposed and the associated Cramer????????? Rao lower bound analysis is presented. A novel acoustic target tracking system is presented using the random set theory. A new system using the nonlinear extended Kalman filter and Hsiao-Chun Wu (S?????????97-M?????????99-SM?????????05) received the Ph.D. degree in electrical and computer engineering from the University of Florida, Gainesville, FL, USA, in 1999. From March 1999 to January 2001, he was with the Motorola Personal Communications Sector Research Labs as a Senior Electrical Engineer. In 2001, he joined the faculty in the Department of Electrical and Computer Engineering, Louisiana State University, Baton Rouge, LA, USA. From August 2008 to December 2008, he was a Visiting Associate Professor at the Department of Electrical Engin- ering, Stanford University, Stanford, CA, USA. He has published more than 170 peer-refereed technical journal and conference articles in electrical and computer engineering. the particle filter (PF) along with interacting multiple model algorithm is proposed for maneuvering mobile station tracking with bearings-only measurements. These ten papers cover a broad scope of experimental measurements, algorithm design, system integration, and theoretical analysis. They may help the scientists to better understand and utilize sensor networks in advanced localization and target-tracking applications for both civil and military purposes.