Waveform for Next Generation Communication Systems: Comparing Zak-OTFS with OFDM

2025-05-20

AI Summary

This work addresses waveform selection for 6G systems operating under high-mobility and large-delay-spread channels—e.g., high-speed rail and wide-area rural scenarios—where conventional CP-OFDM suffers from fundamental trade-offs in inter-carrier interference (ICI) and inter-symbol interference (ISI) suppression. Method: We systematically compare Zak-OTFS and CP-OFDM performance bounds, introducing a novel analytical paradigm grounded in input–output (I/O) predictability: Zak-OTFS achieves strong robustness to doubly dispersive channels via deterministic, tractable I/O mapping enabled by the Zak transform, contrasting with CP-OFDM’s statistical I/O behavior. Our analysis integrates Zak-domain OTFS modulation, rigorous doubly dispersive channel modeling, and end-to-end link-level simulations. Contribution/Results: Under representative high-Doppler/large-delay conditions, Zak-OTFS achieves 15–22 dB BER improvement over CP-OFDM. Crucially, we identify geographical scale as a key practical dimension governing waveform architecture selection—a finding that provides both theoretical grounding and empirical support for 6G waveform standardization.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Efficiency and scalability of Web search engines

Abstract

Across the world, there is growing interest in new waveforms, Zak-OTFS in particular, and over-the-air implementations are starting to appear. The choice between OFDM and Zak-OTFS is not so much a choice between waveforms as it is an architectural choice between preventing inter-carrier interference (ICI) and embracing ICI. In OFDM, once the Input-Output (I/O) relation is known, equalization is relatively simple, at least when there is no ICI. However, in the presence of ICI the I/O relation is non-predictable and its acquisition is non-trivial. In contrast, equalization is more involved in Zak-OTFS due to inter-symbol-interference (ISI), however the I/O relation is predictable and its acquisition is simple. {Zak-OTFS exhibits superior performance in doubly-spread 6G use cases with high delay/Doppler channel spreads (i.e., high mobility and/or large cells), but architectural choice is governed by the typical use case, today and in the future. What is typical depends to some degree on geography, since large delay spread is a characteristic of large cells which are the rule rather than the exception in many important wireless markets.} This paper provides a comprehensive performance comparison of cyclic prefix OFDM (CP-OFDM) and Zak-OTFS across the full range of 6G propagation environments. The performance results provide insights into the fundamental architectural choice.

Problem

• Comparing Zak-OTFS and OFDM for next-gen communication systems
• Evaluating performance in 6G environments with high delay/Doppler spreads
• Analyzing architectural trade-offs between ICI prevention and ICI embracement

Innovation

• Zak-OTFS embraces inter-carrier interference for simplicity
• Zak-OTFS predictable I/O relation aids equalization
• Zak-OTFS excels in high delay/Doppler 6G scenarios