Time-Varying Wavelet Packet Division Multiplexing

Abstract

Wavelet packet division multiplexing (WPDM) is an emerging multiplexing scheme in which the properties of wavelet packet basis functions and their close relationships with perfect reconstruction filter banks are exploited to provide higher capacity, flexibility, and robustness to several adverse channel environments. In contrast to the conventional time division multiplexing (TDM) and frequency division multiplexing (FDM) schemes, the waveforms used to represent the data symbols of each user overlap in time and frequency. However, they are intrinsically orthogonal, that is, they form a wavelet packet, and therefore, the symbols can be recovered using a simple correlator receiver. The fact that the waveforms overlap in time and frequency provides an increase in capacity over TDM and FDM, and substantial robustness to adverse channel environments, while their close relationships with multi-rate filter banks provide particularly simple transmitter and receiver structures. While the wavelet packet hopping (WPH) scheme provided a general hopping framework, it required intricate implementation. This chapter shows that by giving up a little of the generality of the WPH scheme, one can avoid these technical difficulties while retaining the fundamental benefits of WPH.