I IEEE .COMMUNICATIONS MAGAZINE A Structured Overview of Di 'ita1 Communications-A Tutoria r Review-Part II BERNARD SKLAR I N THE first part of this two-part paper, a structure and hierarchy were developed for tracing the key signal processing steps of a typical digital communications system. With the structure as a guide, formatting, source coding, and modulation transformations were examined. Also treated were potential trade-offs for power-limited and bandwidth-limited systems. In Part 11, the signal processing overview continues with channel coding, multiplexing and multiple access, frequency spreading, encryption, and synchronization. To complete the over- view,fundamental link analysis relationships are re- viewed in the contextof a satellite repeater channel. In Part I of this paper (August 1983, IEEE Communica- tions Magazine), a block diagram was introduced for a typical digital communications system; it is repeated here in Fig. 1. Also in Part I, the basic signal processing functions or transformations were classified into seven basic groups: formatting and source coding, modulation, channel coding, multiplexing and multiple access, frequency spreading, encryption, and synchronization. Figure 2 illustrates these transformations; formatting, source coding, and modulation were treated in Part I. Also treated were trade-offs among probability of bit error (PR), bit energy per noise density (&/No), and bandwidth efficiency (RIW). The remainder of the signal processing steps outlined in Figs. 1 and 2 are treated here in Part 11. Channel Coding Channel encoding (see Figs. 1 and 2) refers to the data transformation, performed after source encoding but prior to 0163-~804/83/1000-0006 $01.00 IC' 1983 IEEE 6