ABSTRACT
This chapter reviews the principles and the major results of the adaptive linear precoded- orthogonal frequency division multiplexing (LP-OFDM) communication system. Improvements encountered in adaptive multicarrier systems can in fact also be obtained in adaptive LP-OFDM systems. Therefore, the bitrate maximisation problem is described and analysed in the PLC context. A simple representation of an OFDM system is where the precoding and deprecoding blocks have first to be ignored. In this model, basically, the binary information data stream enters a modulation and coding block which produces a series of n digitally modulated symbols, such as quadrature amplitude modulations (QAMs) mapped symbols. The LP-OFDM system is simply obtained by activating the precoding and deprecoding functions in the generic system model. Consequently, note that the resource allocation algorithm has to take into consideration the waveform structure modification. The first constraint is the power spectrum mask that limits the transmitted power for each subcarrier of the OFDM signal. Consequently, PLC transmissions have to fulfil peak power rather than sum-power conditions.
