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A Unified Pilot Design for Integrated Sensing and Communications

Pu Yuan

TL;DR

The 2D pilot design demonstrates good scalability and can adapt to different delay and Doppler resolution requirements without violating the OFDM data detection and can overcome the fractional Doppler with limited sensing resources.

Abstract

This paper investigates a unified pilot signal design in an orthogonal frequency division modulation (OFDM)-based integrated sensing and communications (ISAC) system. The novel designed two-dimensional (2D) pilot signal is generated on the delay-Doppler (DD) plane for sensing, while its time-frequency (TF) plane transformation acts as the demodulation reference signal (DMRS) for the OFDM data. The well-designed pilot signal preserves orthogonality with the data in terms of resource occupancy in the TF plane and quasi-orthogonality in terms of codeword in the DD plane. Leveraging these nice properties, we are allowed to implement sensing detection in the DD plane using a simple 2D correlation, taking advantage of the favorable auto-correlation properties of the 2D pilot. In the communication part, the transformed pilot in the TF plane serves as a known DMRS for channel estimation and equalization. The 2D pilot design demonstrates good scalability and can adapt to different delay and Doppler resolution requirements without violating the OFDM data detection and can overcome the fractional Doppler with limited sensing resources. Experimental results show the effective sensing performance of the proposed pilot, with only a small fraction of power shared from the OFDM data,while maintaining satisfactory symbol detection performance in communication.

A Unified Pilot Design for Integrated Sensing and Communications

TL;DR

The 2D pilot design demonstrates good scalability and can adapt to different delay and Doppler resolution requirements without violating the OFDM data detection and can overcome the fractional Doppler with limited sensing resources.

Abstract

This paper investigates a unified pilot signal design in an orthogonal frequency division modulation (OFDM)-based integrated sensing and communications (ISAC) system. The novel designed two-dimensional (2D) pilot signal is generated on the delay-Doppler (DD) plane for sensing, while its time-frequency (TF) plane transformation acts as the demodulation reference signal (DMRS) for the OFDM data. The well-designed pilot signal preserves orthogonality with the data in terms of resource occupancy in the TF plane and quasi-orthogonality in terms of codeword in the DD plane. Leveraging these nice properties, we are allowed to implement sensing detection in the DD plane using a simple 2D correlation, taking advantage of the favorable auto-correlation properties of the 2D pilot. In the communication part, the transformed pilot in the TF plane serves as a known DMRS for channel estimation and equalization. The 2D pilot design demonstrates good scalability and can adapt to different delay and Doppler resolution requirements without violating the OFDM data detection and can overcome the fractional Doppler with limited sensing resources. Experimental results show the effective sensing performance of the proposed pilot, with only a small fraction of power shared from the OFDM data,while maintaining satisfactory symbol detection performance in communication.
Paper Structure (13 sections, 1 theorem, 21 equations, 7 figures, 1 table, 3 algorithms)

This paper contains 13 sections, 1 theorem, 21 equations, 7 figures, 1 table, 3 algorithms.

Table of Contents

  1. Introduction
  2. ISAC Signal Transmitter Design
  3. Sensing Pilot Design and Property
  4. ISAC Signal Generation
  5. Sensing and Communication Receiver Processing
  6. Sensing Pilot Detection
  7. Communication Receiver
  8. Sensing Performance Analysis
  9. Sensing SINR
  10. Fractional Doppler Refinement
  11. Magnitude Based Fractional Doppler Detection
  12. Numerical Results
  13. Conclusion

Key Result

Proposition 1

The inner product of $\mathbf{P}_{[q,p]}$ and $\mathbf{P}_{[j,i]}$ yields the following values,

Figures (7)

  • Figure 1: DD domain repetition results in TF domain zero interpolation.
  • Figure 2: The underlaid sensing pilot with OFDM data.
  • Figure 3: Illustration of 2D pilot property.
  • Figure 4: Impact of fractional Doppler.
  • Figure 5: Communication performance: bit error probability.
  • ...and 2 more figures

Theorems & Definitions (2)

  • Proposition 1
  • Proof 1