TABLE OF CONTENTS Fundamental digital transmission concepts and binary baseband transmission techniques are described in this chapter. A thorough knowledge of these techniques is essential for the study of digitally modulated systems. The derivation and physical interpretation of the power spectral density (psd) function of binary signals is followed by the study of bandlimiting effects and the description of the frequently used eye diagram concept. The most important Nyquist transmission theorems for intersymbol interference (ISI)-free transmission with associated filter synthesis and equalization techniques are presented. Finally, the probability of error (P e ) performance in an additive white Gaussian noise environment is studied.
Particular attention is given to binary baseband systems, that is, systems in which only two signaling levels are used. In later chapters we will see that binary systems are more power efficient, but less spectrally efficient than multistate M-ary systems. Spectral efficiency (the alternative term bandwidth efficiency is also frequently used) may be expressed in terms of transmitted bits/second/hertz (b/s/Hz). This normalized quantity is a valuable system parameter. For instance, if a data rate of 10 Mb/s is transmitted in a 6-MHz-wide channel, the spectral efficiency is 10 Mb/s per 6 MHz, or 1.67 b/s/Hz.
The study of coherent digital modulation-demodulation (modem) systems is frequently performed in the equivalent baseband of modulated systems. The block diagram of a binary modem is shown in Fig. 3.1 and its corresponding equivalent baseband model in Fig. 3.2. A brief description of the major functional blocks...
