tailieunhanh - Networking - Wireless Communications

Four laws, two each from the natural sciences and the social sciences, have formed the basis for the development of digital wireless communication networks. This essay describes their interaction, as well as their logical support for spread - spectrum multiple - access techniques. | WIRELESS tiMwanm Signal X Processing X Perspectives H. VINCENT POOR GREGORY W. WORNELL Editors Prentice Hall Signal Processing Series Alan V. Oppenheim Series Editor EPILOGUE Four Lows of Nature and Society The Governing Principles of Digital Wireless Communication Networks Andrew J. Viterbi Four laws two each from the natural sciences and the social sciences have formed the basis for the development of digital wireless communication networks. This essay describes their interaction as well as their logical support for spread-spectrum multiple-access techniques. Overview In this techno-philosophical essay we attempt to demonstrate that the implementation and success of digital wireless communication networks depends primarily on four basic laws and their underlying theories which are attributed respectively to Maxwell and Hertz Shannon Moore Metcalfe 380 Sec. Wireless Propagation and Its Anomalies 381 The first two laws are laws of nature while the last two though often mistakenly thought as such are in reality laws of behavior. The order is in the sequence of their discovery and their importance additionally as the field of wireless communications has matured the emphasis and immediate relevance has shifted gradually downward in the list. Without an appreciation for Maxwell s and Hertz s theories there would be no controlled wireless propagation of electromagnetic waves. Without an understanding of Shannon s theories efficient use of the spectrum through sophisticated signal processing could not be achieved. Without the consequences of Moore s law these signal processing techniques could not be implemented in a useful and economic fashion. And finally Metcalfe s law which we shall explore last helps to predict the success or failure of large new network deployments and consequently the wisdom of business strategies involving proportionally large capital investments. Wireless Propagation and Its Anomalies In a remarkable sequence of achievements in .