Background to Wireless

Abstract

This chapter introduces certain fundamental concepts or background needed to understand wireless systems. Concepts such as what are radio waves, how radio waves travel—on earth, towards the sky and towards space are introduced. Use of different frequency bands in the electromagnetic spectrum and their characteristics are described. The concept of digital modulation is introduced, showing why and how it became popular, and its advantages over analog modulation (AM and FM) in all wireless systems. It shows why AM and FM are technologies of a by-gone era, that is no longer in use. The concept of digital modulation is extended further with OFDM (Orthogonal Frequency Division Multiplex), elaborating on its principles and some of its unique features. As a corollary to this modulation is the rise of DSP (digital signal processing), which is described to show why DSP is such an important feature of modern technologies? How rise of DSP resulted in important changes to wireless communication network is described. How it helps in making the device smaller, smarter, helping an entire generation of people globally recognize the cell phone as their primary device for communication, is the major emphasis of this chapter.