Constant Envelope OFDM Phase Modulation - Dr. James R. Zeidler

Chapter 1IntroductionHumans have always found ways to communicate, over space and over time. Fromthe messenger pigeon to the Pony Express, from the message in a bottle to cave drawings,smoke signals and beacons, people have used inventive techniques, techniques derivedfrom their natural environment, to share information. A particularly good natural resourcefor communication is electricity for its speed and ability to be controlled withdevices like capacitors, microprocessors, electronic memory storage and batteries. Communicationwas profoundly enhanced with Morse’s telegraph (1837), Bell’s telephone(1876), Edison’s phonograph (1887), and Marconi’s radio (1896). From these early inventions,communications technology has advanced with global telephone networks, satellitecommunications, and magnetic storage systems; and with the rise of the internet anddigital computers, digital communications—the transfer of bits (1’s and 0’s) from onepoint to another—has become important.In particular, wireless digital communications is currently under intensive research,development and deployment to provide high data rate access plus mobility. One challengein designing a wireless system is to overcome the effects of the wireless channel,which is characterized as having multiple transmission paths and as being time varying[421, 427]. Figure 1.1 illustrates a link with four reflecting paths between points Aand B. These reflections are caused by physical objects in the environment. Due to therelative mobility between the points and the possibility that the reflecting objects aremobile, the channel changes with time.1