ailable, the door is open now, the wireless data boom will be even more dynamic for new applications ranging from telemetry to video. because the types of devices and content are much more The 1990s saw a proliferation of wireless voice services; varied. References 1. Coincidently, this period corresponds to 3. http://www.gvf.org. Respect to Commercial Mobile Services: the time this author has been employed 4. http://www.irda.org. Sixth Report, July 17, 2001. as a communication engineer. 5. http://qualweb.bluetooth.org. 8. Motorola, "Motorola Personal Unfortunately, I can take only partial credit for the amazing advances of 6. Dataquest, quoted by Krazit, Tom in Communications Sector (PCS) "Microsoft Joins Home Wi-Fi Refocuses Messaging Division" this era! Announcements," PCWorld.com (press release), December 3, 2001. 2. Many thanks to the University (http://www.pcworld.com/news/ 9. Adapted from the Shosteck Group of Wisconsin in Madison and article/0,aid, 10517,00.asp), September white paper, Lessons from Metricom and Melange Solutions in San Diego, 19,2002. MobileStar: Success Factors for the for whom some of this material was originally 7. FCC, Annual Report and Analysis of Portable Internet Access Market developed. Competitive Market Conditions with (January 2002). Section Two Section Two Section Two Section Two Section Two Section Two RF engineering This page intentionally left blank Chapter 2.1 Basic features of radio communication systems Ed da Silva 2.1.1 Introduction The method we use here is to start with an overview of a communication system. The system is then divided This chapter describes communication systems which to show its sub-systems and the sub-systems are then use radio waves and signals. Radio signals are useful for expanded to show individual circuits and items. two main reasons. They provide a relatively cheap way of communicating over vast distances and they are ex- 2.1.1.2 Objectives tremely useful for mobile communications where the use of cables is impractical. The general objectives 