New book on delay-Doppler communication

By: , Posted on: September 14, 2022

We interviewed Emanuele Viterbo about his new book Delay-Doppler Communications: Principles and Applications, co-authored with Yi Hong and Tharaj Thaj,

  • What are the effects of high mobility communication environments on wireless channels?

In high mobility communication environments, wireless channels exhibit time-varying fading due to multipath propagation delays and Doppler shifts caused by moving terminals and scatterers. These scenarios will soon appear in fully interconnected autonomous vehicles, drones, flying taxis, high-speed trains, airplanes, and LEO satellite networks. Here, the performance of traditional communication systems would suffer severe degradation.

  • What is OTFS and what role does delay-Doppler communications play in OTFS?

Orthogonal time frequency space (OTFS), proposed by Hadani et al., is a physical layer waveform that can combat not only multipath delay but also severe Doppler shifts found in high mobility communication environments.

OTFS is an embodiment of delay-Doppler (DD) communications. The principle of DD communications is to multiplex information symbols in the delay-Doppler domain, in order to effectively exploit the sparse nature present in the geometry of wireless channels and to enhance channel diversity. In particular, information symbols are multiplexed on 2D orthogonal basis functions in the DD domain. This operation is equivalent to spreading the information symbols across the entire time-frequency resources to exploit the channel diversity. As a result, OTFS converts the time-varying into a time-independent 2D channel in DD domain.

  • What advantages does OTFS have over OFDM?

Orthogonal Frequency division multiplexing (OFDM) can only achieve a near-capacity performance over a time-varying fading channel with very small Doppler shifts but suffers severe performance degradation with large Doppler shifts, typically found in high-mobility environments.

On the other hand, OTFS is resilient to multipath delays and multiple large Doppler shifts and demonstrated significant performance gain over traditional OFDM in high mobility communication environments. It is worth mentioning that OTFS can outperform OFDM even in the absence of Doppler shifts.

  • What approach does your book take to presenting delay-Doppler communications?

The book starts by introducing some fundamental concepts of wireless communication channels. The mathematical and physical relations between the different domains used to represent channels and waveforms are introduced. We explain the limitations of the OFDM multicarrier techniques in high-mobility channels. We introduce a unified notation to describe OTFS modulation and demodulation operations using the Zak transform approach. Then we present the specific features and advantages of OTFS with regard to detection, channel estimation, and applications to multiuser and multiple antenna cases with practical software-defined radio (SDR) demonstrations.

  • Who will find the book beneficial?

Wireless communications systems designers and R&D engineers, graduate students, and researchers in physical layer communications would benefit from reading this book.

The book provides sufficient background to be self-contained for the readers with a basic knowledge of digital communications. Readers familiar with OFDM will be able to transition from their time-frequency domain mindset to the delay-Doppler domain.

MATLAB code functions are provided to illustrate the various system blocks and enable the readers to run their own simulations and help them understand the key idea of the delay-Doppler domain waveforms that can overcome severe Doppler shifts in high-mobility communications.

  • How do you see OTFS progressing in the next few years?

OTFS and delay-Doppler communications have many potential applications that can fit into high-mobility communication scenarios. Those potential applications can range from satellite communications, underwater acoustic communications, radar signal processing, future high mobility mobile and wireless communications, and possibly many more.

             

Ready to read this book?

Delay-Doppler Communications: Principles and Applications is available on the Elsevier store.

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