1.1 INTRODUCTION

Digital transmission techniques are reviewed in this chapter. In our review of the principles of operation and applications of these techniques, we highlight some of the most important concepts required for the comprehension of the more advanced digital signal and system measurement, analysis, and instrumentation problems, which are described in Chapters 3 through 7. Illustrative digital signal processing and transmission system configurations are also presented. The references provide a detailed description of these systems.

Since the early 1960s, architectures and standards for digital signal processing, multiplexing, and transmission of voice, data, television, facsimile, and other signals have been established worldwide. Integrated digital networks (IDNs), where the term integrated refers to the commonality of digital techniques used in the transmission of voice and data signals, are already in use. The basic building block of the telephony IDNs is the 64-kb/s-rate pulse code modulation (PCM) processor of speech signals. The 64-kb/s digitized voice signal has been used as a standard in circuit switching, digital multiplexing, and transmission systems. Service-dedicated networks have been conceived and implemented to provide, in a cost-effective manner, a limited range of services centered around the main service application to which they are devoted. The proliferation of different types of digital networks (e.g., a circuit switched IDN for telephony, a circuit switched IDN for bulk data, a packet switched IDN for bursty data) impose a burden...