velopers, suppliers, regulators, investors, consultants, and users of telecommunications technologies and networks since 1984. I want to share my knowledge of telecom- munications with people in the format that best fits their learning styles. Some learn best in a classroom situation, where they can make eye contact with the instructor, view graphics while the instructor is explaining concepts, and ask ques- tions in person. LIDO has been providing seminars for these learners for 23 years. Some people prefer to learn at their own pace, and they like the convenience and ability to track down further information that online learning affords. For these people, LIDO has provided e-learning programs (via software license) since 1999. Today the LIDO Telecommunications Essentials e-learning series includes over 30 hours of rich multimedia content. Yet other people learn best from books-when they can carry their learning tool with them anywhere and read and reread as time and circumstances allow. Therefore, I decided to write this book, to provide a com- prehensive source on telecommunications essentials. Because telecommunications technologies continue to develop at an impressive pace, this second edition provides extensive coverage of the most recent develop- ments in next-generation networks, IP networks and services, optical networking, and broadband access. And because wireless communications has experienced such dramatic growth, this book now includes four chapters devoted entirely to wireless principles, technologies, and applications. With these latest updates, I think you xxiii About LIDO will find that Telecommunications Essentials is truly a complete global reference to communications fundamentals, data networking and the Internet, next-generation networks, and wireless communications. A 1775 quote from Samuel Johnson summarizes LIDO's approach to knowl- edge solutions in telecommunications: "Knowledge is of two kinds: We know a subject or we know where we can find information upon it." LIDO presents this book