This chapter discusses the single carrier modulation techniques which have been proposed and used in first generation narrowband PLC systems. It emphasizes the recent insight and research focusing first on frequency/phase shift keying combined with permutation coding. The chapter covers multicarrier modulation which is at the heart of latest narrowband and broadband PLC systems. Several known and more recent schemes are here described including OFDM, FMT, Pulse-shaped OFDM, Wavelet OFDM, OQAM-OFDM, and Cyclic block FMT. The voltage and current modulation is discussed as a simple and effective means to transmit data at low speed and over long distances. If multiple wires are available, multiple input multiple output (MIMO) transmission schemes can be used to exploit spatial diversity. The chapter also discusses the noise mitigation and error control techniques currently found in various PLC protocols and standards, as well as other promising techniques that are still only found in the literature.
