Digital transmission is at the core of any communications system, including Power Line Communications (PLC) systems. This chapter distinguishes between modulation and coding for the two classes of PLC systems, namely narrowband and broadband PLC systems. It presents a selection of modulation and coding techniques for each class. The chapter addresses modulation and coding for narrowband PLC systems. It discusses some fundamentals, permutation trellis codes-a combined coding and describes modulation scheme utilizing Frequency Shift Keying (FSK) and convolutional codes. The chapter covers both accepted modulation and coding schemes for broadband systems, as well as some more recent results. For broadband systems, the two important modulation contenders which have previously been considered include spread spectrum and multicarrier techniques. The chapter presents the latest major and arguably most powerful class of codes from information theory, namely Low-Density Parity-Check (LDPC) codes, and shows how these may be adapted for PLC. Controlled Vocabulary Terms: carrier transmission on power lines; frequency shift keying; modulation; parity check codes.
