tailieunhanh - Báo cáo hóa học: " Research Article A Hub Matrix Theory and Applications to Wireless Communications"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article A Hub Matrix Theory and Applications to Wireless Communications | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2007 Article ID 13659 8 pages doi 2007 13659 Research Article A Hub Matrix Theory and Applications to Wireless Communications H. T. Kung1 and B. W. Suter1 2 1 Harvard School of Engineering and Applied Sciences Harvard University Cambridge MA 02138 USA 2 US Air Force Research Laboratory Rome NY 13440 USA Received 24 July 2006 Accepted 22 January 2007 Recommended by Sharon Gannot This paper considers communications and network systems whose properties are characterized by the gaps of the leading eigenvalues of AHA for a matrix A. It is shown that a sufficient and necessary condition for a large eigen-gap is that A is a hub matrix in the sense that it has dominant columns. Some applications of this hub theory in multiple-input and multiple-output MIMO wireless systems are presented. Copyright 2007 H. T. Kung and B. W. Suter. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. 1. INTRODUCTION There are many communications and network systems whose properties are characterized by the eigenstructure of a matrix of the form AHA also known as the Gram matrix of A where A is a matrix with real or complex entries. For example for a communications system A could be a channel matrix usually denoted H. The capacity of such system is related to the eigenvalues of HhH 1 . In the area of web page ranking with entries of A representing hyperlinks Kleinberg 2 shows that eigenvectors corresponding to the largest eigenvalues of ATA give the rankings of the most useful authority or popular hub web pages. Using a reputation system that parallels Kleinberg s work Kung and Wu 3 developed an eigenvector-based peer-to-peer P2P network user reputation ranking in order to provide services to P2P users based on past contributions reputation to