the successes of companies that are penetrating the commer- cial marketplace with spread-spectrum products. This revised edition contains new material on the emerging commercial applications of spread-spectrum techniques as well as minor modifications to the book's original fourteen chapters. We believe that since it is based on sound engineering principles and is not bound to a particular implementa- tion technology, it will retain its usefulness for the foreseeable future. Marvin K. Simon Jim K. Omura Robert A. Scholtz Barry K. Levitt PREFACE TO FIRST EDITION Not more than a decade ago, the discipline of spread-spectrum (SS) com- munications was primarily cloaked in secrecy. Indeed, most of the informa- tion available on the subject at that time could be found only in documents of a classified nature. Today the picture is noticeably changed. The open literature abounds with publications on SS communications, special issues of the IEEE Transactions on Communications have been devoted to the subject, and the formation of an annual conference on military communications, MILCOM, now offers a public forum for presentation of unclassified (as well as classified) papers dealing with SS applications in military systems. On a less formal note, many tutorial and survey papers have recently appeared in the open literature, and presentations on a similar level have taken place at major communications conferences. Finally, as further evidence we cite the publication of several books dealing either with SS communications directly or as part of the more general electronic countermeasures (ECM) and electronic counter-counter measures (ECCM) problem. References to all these forms of public docu- mentation are given in Section 1.7 of Chapter 1, Part 1. The reasons for this proliferation can be traced to many sources. While it is undoubtedly true that the primary application of SS communications still lies in the development of enemy jam-resistant communication systems for the military, largely within the confines of classified p