ABSTRACT Standard OFDM systems are associated with a rectangular grid in the time-frequency plane. However such a setup is in general not optimal for pulse shaping OFDM systems for doubly dispersive channels. We introduce lattice-OFDM systems (LOFDM), which are OFDM systems constructed with respect to general lattices in the time-frequency plane. We show how to design optimal pulse shapes for L...

There is a growing demand for higher data rate systems that can function in a highly mobile environment. This mandates the design of communication systems that can function in doubly selective channels. Pulse-shaped multi-carrier modulation schemes prove to be an attractive option for transmission over doubly-dispersive channels. The pulse shapes are designed to yield an inter-symbol/inter-carr...

Single-carrier cyclic prefix (SCCP) has been proposed as an alternative to orthogonal frequency division multiplexing (OFDM). While the implementation complexity of the two schemes are comparable, SCCP avoids the peak-to-average power ratio problem that plagues OFDM. Both OFDM and SCCP receivers leverage the fast Fourier transform for computationallyefficient frequency-domain equalization. For ...

It is proved that every doubly stochastic quantum channel that is properly averaged with the completely depolarizing channel can be written as a convex combination of unitary channels. As a consequence, we find that the collection of channels expressible as convex combinations of unitary channels has non-zero Borel measure within the space of doubly stochastic channels.

Orthogonal time frequency space (OTFS) modulation is a 2-dimensional (2D) modulation scheme designed in the delay-Doppler domain, unlike traditional modulation schemes which are designed in the time-frequency domain. Through a series of 2D transformations, OTFS converts a doubly-dispersive channel into an almost non-fading channel in the delay-Doppler domain. In this domain, each symbol in a fr...

In this article we consider the approximate description of doubly–dispersive channels by its symbol. We focus on channel operators with compactly supported spreading, which are widely used to represent fast fading multipath communication channels. The concept of approximate eigenstructure is introduced, which measures the accuracy Ep of the approximation of the channel operation as a pure multi...

We adopt the concept of channel diagonalization to time-frequency signal expansions obtained by DFT filter banks. As a generalization of the frequency domain channel representation used by conventional orthogonal frequency-division multiplexing receivers, the time-frequency domain channel diagonalization can be applied to time-variant channels and aperiodic signals. An inherent error in the cas...