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Over-the-Air Transmission of Zak-OTFS with Spread Pilots on Sub-THz Communications Testbed

Claire Parisi, Venkatesh Khammammetti, Robert Calderbank, Lauren Huie

TL;DR

This work demonstrates over-the-air transmission of Zak-OTFS at sub-THz frequencies (140 GHz and 240 GHz) on a practical hardware testbed, comparing traditional point pilots with spread pilots designed to overlay sensing and communications (ISAC). It shows data transmission and channel prediction via cross-ambiguity, achieving measurable error-rate performance and a PAPR reduction when using spread pilots. By formulating Zak-OTFS with explicit transmitter/receiver architectures and two pilot schemes, the paper validates the viability of Zak-OTFS for harsh sub-THz channels and highlights the potential ISAC benefits of spread pilots. The findings suggest that spread pilots can improve spectral efficiency and power efficiency in next-generation sub-THz systems, contributing to practical pathways for 6G/ISAC deployments.

Abstract

Looking towards 6G wireless systems, frequency bands like the sub-terahertz (sub-THz) band (100 GHz - 300 GHz) are gaining traction for their promises of large available swaths of bandwidth to support the ever-growing data demands. However, challenges with harsh channel conditions and hardware nonlinearities in the sub-THz band require robust communication techniques with favorable properties, such as good spectral efficiency and low peak-to-average power ratio (PAPR). Recently, OTFS and its variants have garnered significant attention for their performance in severe conditions (like high delay and Doppler), making it a promising candidate for future communications. In this work, we implement Zak-OTFS for the over-the-air experiments with traditional point pilots and the new spread pilots. Notably, we design our spread-pilot waveforms with communications and sensing coexisting in the same radio resources. We define the system model and the signal design for integration onto our state-of-the-art sub-THz wireless testbed. We show successful data transmission over-the-air at 140 GHz and 240 GHz in a variety of signal-to-noise ratio (SNR) conditions. In addition, we demonstrate integrated sensing and communications (ISAC) capabilities and show PAPR improvement of over 5 dB with spread pilots compared to point pilots.

Over-the-Air Transmission of Zak-OTFS with Spread Pilots on Sub-THz Communications Testbed

TL;DR

This work demonstrates over-the-air transmission of Zak-OTFS at sub-THz frequencies (140 GHz and 240 GHz) on a practical hardware testbed, comparing traditional point pilots with spread pilots designed to overlay sensing and communications (ISAC). It shows data transmission and channel prediction via cross-ambiguity, achieving measurable error-rate performance and a PAPR reduction when using spread pilots. By formulating Zak-OTFS with explicit transmitter/receiver architectures and two pilot schemes, the paper validates the viability of Zak-OTFS for harsh sub-THz channels and highlights the potential ISAC benefits of spread pilots. The findings suggest that spread pilots can improve spectral efficiency and power efficiency in next-generation sub-THz systems, contributing to practical pathways for 6G/ISAC deployments.

Abstract

Looking towards 6G wireless systems, frequency bands like the sub-terahertz (sub-THz) band (100 GHz - 300 GHz) are gaining traction for their promises of large available swaths of bandwidth to support the ever-growing data demands. However, challenges with harsh channel conditions and hardware nonlinearities in the sub-THz band require robust communication techniques with favorable properties, such as good spectral efficiency and low peak-to-average power ratio (PAPR). Recently, OTFS and its variants have garnered significant attention for their performance in severe conditions (like high delay and Doppler), making it a promising candidate for future communications. In this work, we implement Zak-OTFS for the over-the-air experiments with traditional point pilots and the new spread pilots. Notably, we design our spread-pilot waveforms with communications and sensing coexisting in the same radio resources. We define the system model and the signal design for integration onto our state-of-the-art sub-THz wireless testbed. We show successful data transmission over-the-air at 140 GHz and 240 GHz in a variety of signal-to-noise ratio (SNR) conditions. In addition, we demonstrate integrated sensing and communications (ISAC) capabilities and show PAPR improvement of over 5 dB with spread pilots compared to point pilots.

Paper Structure

This paper contains 16 sections, 13 equations, 7 figures, 1 table.

Table of Contents

  1. Introduction
  2. System Design
  3. Zak- Transmitter
  4. Zak- Receiver
  5. Pilot signal
  6. Point Pilot
  7. Spread Pilot
  8. Sub-THz Testbed Overview
  9. Implementation
  10. Baseband Signal Design & Processing
  11. Over-the-air Communication
  12. Zak- Experiments
  13. Results
  14. Zak- results with point pilot
  15. Zak- results with the spread pilot
  16. ...and 1 more sections

Figures (7)

  • Figure 1: Zak-OTFS baseband Modulation
  • Figure 2: Zak-OTFS baseband Demodulation
  • Figure 3: Sub-THz testbed system diagram
  • Figure 4: on laboratory set-up
  • Figure 5: Zak- constellations at 140 GHz
  • ...and 2 more figures