OFDM Signals and Systems

TLDR: This chapter shows that all different OFDMs can be implemented by commutating filter (polyphase form) in conjunction with IDFT-DFT, and considers practical issues, applications of filtered OFDM, and applications to doubly selective fading channels.

Abstract: OFDM is a very special form of FDM signal applied to digital transmission by choosing the subcarrier spacing to be related with the subchannel symbol rate and the number of samples per symbol period. We need to choose the shaping filter of subcarrier to be the same. When it is a rectangular pulse, it becomes implicit, and most often it results in DMT with CP. In this chapter we extend this basic concept to filtered OFDM, and staggered OFDM, and further show that all different OFDMs can be implemented by commutating filter (polyphase form) in conjunction with IDFT-DFT. The commutating filter is a special form time-varying FIR filter. We consider practical issues, applications of filtered OFDM, and applications to doubly selective fading channels.