Every year, the United States National Committee (USNC) of the International Union of Radio Science (URSI) organizes the Ernest K. Smith Student Paper Competition. Graduate students who are enrolled in a U.S. university are eligible to submit a full paper, of up to 25 pages in length, on any topic of interest to one of the 10 URSI Commissions. The paper must be the unaided work of only one graduate student. The usual guidance provided to a graduate student by a research advisor and/or supervising professor is allowed. After a strict review process, the top three finalists are invited to present their papers during the Plenary Session at the National Radio Science Meeting, which takes place in the month of January in Boulder, Colorado, USA. The three finalists receive a certificate and a monetary award.
 One purpose of the Student Paper Competition is to motivate some of the best young researchers to present their work to a large audience, so that they may receive early recognition for their contributions.
 This is the second year that the top-ranked students are invited to submit their manuscripts for a Special Section of Radio Science dedicated to the USNC-URSI Ernest K. Smith Student Paper Competition. This Special Section contains two contributions: a paper originally submitted to Commission B, “Ewald method for 3-D periodic dyadic Green's functions and complex modes in composite materials made of spherical particles under the dual dipole approximation” by Salvatore Campione and Filippo Capolino, and a paper submitted to Commission C, “Time-reversal techniques for MISO and MIMO wireless communication systems” by Ahmed E. Fouda, Fernando L. Teixeira, and Mehmet E. Yavuz.
 We hope that you find these articles interesting.
Danilo Erricolo, PhD
Department of Electrical and Computer Engineering University of Illinois at Chicago
Chicago, Illinois, USA
Chair, Ernest K. Smith Student Paper Competition