Flexible-Antenna Systems: A Pinching-Antenna Perspective

TL;DR

This work introduces pinching antennas, a flexible-antenna concept realized by dielectric particles on waveguides, to reconfigure wireless channels and improve LoS links while reducing large-scale path loss. The authors derive analytic expressions for the ergodic sum rate in the simple single-pinching-antenna case, then extend to multiple pins on a single waveguide with TDMA and NOMA, and finally address multi-waveguide MISO interference-channel scenarios. They show that a pinching-antenna network can achieve an interference-channel upper bound by suitably reconfiguring pin locations and beamformers, and provide feasibility analyses plus a search-based algorithm to approach the bound. Across simulations, pinching antennas outperform conventional fixed antennas, with NOMA providing substantial sum-rate gains and the upper bound becoming achievable under practical micro-meter scale adjustments. The results suggest pinching antennas as a low-cost, scalable complement to existing flexible-antenna technologies, with broad relevance for high-frequency and dense deployments.

Abstract

Flexible-antenna systems have recently received significant research interest due to their capability to reconfigure wireless channels intelligently. This paper focuses on a new type of flexible-antenna technology, termed pinching antennas, which can be realized by applying small dielectric particles on a waveguide. Analytical results are first developed for the simple case with a single pinching antenna and a single waveguide, where the unique feature of the pinching-antenna system to create strong line-of-sight links and mitigate large-scale path loss is demonstrated. An advantageous feature of pinching-antenna systems is that multiple pinching antennas can be activated on a single waveguide at no extra cost; however, they must be fed with the same signal. This feature motivates the application of non-orthogonal multiple access (NOMA), and analytical results are provided to demonstrate the superior performance of NOMA-assisted pinching-antenna systems. Finally, the case with multiple pinching antennas and multiple waveguides is studied, which resembles a classical multiple-input single-input (MISO) interference channel. By exploiting the capability of pinching antennas to reconfigure the wireless channel, it is revealed that a performance upper bound on the interference channel becomes achievable, where the achievability conditions are also identified. Computer simulation results are presented to verify the developed analytical results and demonstrate the superior performance of pinching-antenna systems.

Figures (10)

• Figure 2: Illustration of a network with a single waveguide and a single pinching antenna. In the time slot that serves ${\rm U}_m$, the pinching antenna at $\boldsymbol{\psi}^{\rm Pin}_m$ is activated.
• Figure 3: Illustration of a NOMA-assisted pinching-antenna system, with a single waveguide and two pinching antennas. The weak user is uniformly deployed in the square denoted by $A_1$ with its center at $(D_1,D_1,0)$, and the strong user is uniformly deployed in the square denoted by $A_2$ with its center at $(-D_2,0,0)$. The side lengths of the two squares are identical and denoted by $D$.
• Figure 4: Illustration of a network with multiple waveguides and multiple pinching antennas.
• Figure 5: Ergodic sum rates achieved by the considered schemes, with a single pinching antenna and a single waveguide. The coordinates of the points on the waveguide are $(\tilde{x}^{\rm pin}, 0, d)$. In Case I, the users are uniformly distributed within a square, with side length $D$ and its center at $(0,0,0)$. The analytical results are based on \ref{['sum rate pinx3']}, and the approximation results are based on \ref{['approxm pinching an43']}. The upper bound of the conventional antenna is based on \ref{['conv approximation']}. In Case II, the users are uniformly distributed within a rectangle, with its two side lengths being $D$ and $D_{\rm L}$, where $D=10$ m.
• Figure 6: Ergodic sum rates achieved by the considered schemes, with $N$ pinching antennas and a single waveguide. The users are uniformly distributed within a square, with side length $D$ and its center at $(0,0,0)$, and the coordinates of the points on the waveguide are $(\tilde{x}^{\rm pin}, 0, d)$. The upper bound curves are based on the result in \ref{['mulpa1wg']}. The locations of the $N$ pinching antennas are obtained by the search algorithm proposed in Section \ref{['subsection NP']}.

Theorems & Definitions (1)

• proof