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Multi-Band Sensing in FR3 with Background Dense Multipath Components

Dexin Wang, Roberto Bomfin, Ahmad Bazzi, Marwa Chafii

Abstract

Multi-band sensing has emerged as a key enabler of integrated sensing and communication (ISAC), one of the six primary usage scenarios defined for IMT-2030 (6G). The introduction of frequency range 3 (FR3, 7-24 GHz), comprising non-contiguous sub-bands across a wide frequency span, further reinforces the importance of multi-band operation. In such scenarios, frequency-dependent propagation effects that are collectively referred to as dense multipath components (DMC), including clutter, diffraction, and diffuse scattering, must be carefully considered. Building on prior literature and our experimental observations, this paper proposes a novel ISAC channel analysis tailored to multi-band sensing, based on a channel model with background DMCs. It also assesses the sensing trade-offs among sub-bands by analyzing Cramér-Rao bound (CRB)-based fundamental limits. Furthermore, a scalable multi-band estimator is proposed that resolves angular ambiguities arising from the grating lobes effect. Simulation results of the multi-band estimator demonstrate substantial gains in estimation accuracy and reductions in false alarm rate over single-band estimators operating on each constituent sub-band within the CRB-achieving regime. In a representative test case, the proposed estimator achieves reductions of 37.41% and 17.04% in the root mean squared error of delay estimation compared to single-band estimators operating at 8.75 GHz and 21.7 GHz, respectively.

Multi-Band Sensing in FR3 with Background Dense Multipath Components

Abstract

Multi-band sensing has emerged as a key enabler of integrated sensing and communication (ISAC), one of the six primary usage scenarios defined for IMT-2030 (6G). The introduction of frequency range 3 (FR3, 7-24 GHz), comprising non-contiguous sub-bands across a wide frequency span, further reinforces the importance of multi-band operation. In such scenarios, frequency-dependent propagation effects that are collectively referred to as dense multipath components (DMC), including clutter, diffraction, and diffuse scattering, must be carefully considered. Building on prior literature and our experimental observations, this paper proposes a novel ISAC channel analysis tailored to multi-band sensing, based on a channel model with background DMCs. It also assesses the sensing trade-offs among sub-bands by analyzing Cramér-Rao bound (CRB)-based fundamental limits. Furthermore, a scalable multi-band estimator is proposed that resolves angular ambiguities arising from the grating lobes effect. Simulation results of the multi-band estimator demonstrate substantial gains in estimation accuracy and reductions in false alarm rate over single-band estimators operating on each constituent sub-band within the CRB-achieving regime. In a representative test case, the proposed estimator achieves reductions of 37.41% and 17.04% in the root mean squared error of delay estimation compared to single-band estimators operating at 8.75 GHz and 21.7 GHz, respectively.
Paper Structure (35 sections, 54 equations, 9 figures, 1 table)

This paper contains 35 sections, 54 equations, 9 figures, 1 table.

Table of Contents

  1. Introduction
  2. Background Concepts and Related Works
  3. This Work
  4. System Model
  5. The Specular Components (SC)
  6. Geometric parameters
  7. Path gains
  8. The Dense Multipath Components (DMC)
  9. Delay domain characteristics
  10. Angle domain characteristics
  11. The Noise
  12. Fundamental Limits and Empirical Metrics
  13. Cramér-Rao Bound (CRB)
  14. The Approximate CRB
  15. Estimation Signal-to-Noise Ratio (ESNR)
  16. ...and 20 more sections

Figures (9)

  • Figure 1: Bi-static ISAC scenario with $K-1$ scatterers under background DMC interference. The geometric sensing parameters associated with each path are shown.
  • Figure 2: Flowchart of the algorithm. Each subsection that discusses the algorithm from \ref{['subsec:sub-band-selection']} to \ref{['subsec:weighted-combination']} corresponds to a box with bolded text.
  • Figure 3: The PDP of the DMC for an 8.75 GHz sub-band with a decay rate of $\tilde{\beta} = 0.5$ and a 21.7 GHz sub-band with a decay rate of $\tilde{\beta} = 1.5$ at $P^{\tt{T}} = -40$ dBm/Hz and $\alpha = -20$ dB.
  • Figure 4: The modified Cassini ovals from the BGG contours for two different sub-bands with different decay rates and VMD parameters at $P^{\tt{T}} = -50$ dBm/Hz and $\alpha = -5$ dB.
  • Figure 5: The delay $\sqrt{\mathop{\mathrm{CRB}}\nolimits}$ vs. $P^{\tt{T}}$ for individual sub-bands and the combined multi-band (both approximate and exact for the latter case). The angular spread of DMC is not modeled here, i.e. $\pmb{R}_m^{\tt{T}} = \pmb{R}_m^{\tt{R}} = \pmb{I}$.
  • ...and 4 more figures