Pinching-Antenna Assisted ISAC: A CRLB Perspective

TL;DR

This work evaluates the impact of pinching antennas on ISAC positioning from a CRLB perspective. By deriving the CRLB for pinching-antenna systems and contrasting it with conventional antenna layouts, the authors show that pinching configurations can yield uniformly better positioning accuracy and mitigate large disparities across users. The analysis reveals how antenna placement, height, and spacing influence the CRLB, including a convex dependence on spacing with an explicit optimum for a simple case, and unveils a local-maximum property indicating sensing-placement tradeoffs. Numerical results corroborate the theory, demonstrating significant CRLB gains, multi-user fairness, and the feasibility of flexible, user-centric positioning via reconfiguration. Overall, the paper highlights pinching antennas as a low-cost, adaptable approach to enhance sensing performance in ISAC networks.

Abstract

Recently, pinching antennas have attracted significant research interest due to their capability to reconfigure wireless channels as well as their array configuration flexibility. This letter focuses on how these features can be used to support integrated sensing and communications (ISAC) from the Cramer Rao lower bound (CRLB) perspective. In particular, the CRLB achieved by pinching antennas is first derived and then compared to that of conventional antennas. The presented analytical and simulation results demonstrate that using pinching antennas can significantly reduce CRLB and, hence, enhance positioning accuracy. In addition, this letter also reveals that the low-cost and reconfigurability features of pinching antennas can be utilized to realize flexible user-centric positioning.

Figures (4)

• Figure 1: Averaged CRLBs, $\bar{ {\rm CRB}_m}$, achieved by the considered antenna systems, where $N_{\rm WG}=2$ and $d=3$ m. For the pinching-antenna system, on each waveguide, there are $\frac{N}{N_{\rm WG}}$ antennas, which are equally spaced. Due to the singularity issue experienced by conventional antennas discussed in Section \ref{['subsectioncompare']}, users are assumed to be excluded from a square area with its side being $a$ and its center at the origin.
• Figure 2: CRLBs achieved by the considered antenna systems. $N=20$, $N_{\rm WG}=2$ and $d=3$ m. On each waveguide, there are $\frac{N}{N_{\rm WG}}$ antennas, which are equally spaced. .
• Figure 3: Using pinching antennas to achieve flexible user-centric positioning. $N=20$, $N_{\rm WG}=2$ and $d=3$ m. On each waveguide, there are $\frac{N}{N_{\rm WG}}$ antennas, which are equally spaced in a segment with its length being $\frac{D_{\rm L}}{2}$ and its center at the focal points shown in the figures.
• Figure 4: Impact of the antenna spacing on the CRLB. $N=4$ pinching antennas are activated in a square-shape area with the antenna spacing being $\Delta$ and ${\rm U}_m$ located at the center of the area, where $N_{\rm WG}=2$. The analytical results are based on \ref{['optimal']}.