Differential Spatial Modulation with Transmit Diversity for Pinching-Antenna Systems

TL;DR

This paper introduces a differential spatial modulation scheme for pinching-antenna systems that enables noncoherent transmission with transmit diversity, reducing the need for channel state information and increasing spectral efficiency.

Contribution

The paper proposes a novel DSM scheme with Alamouti coding for PA systems, allowing noncoherent transmission and full transmit diversity without requiring instantaneous CSI.

Findings

The proposed scheme achieves full transmit diversity.

The BER analysis closely matches simulation results.

The pinching position-based index modulation enhances spectral efficiency.

Abstract

Pinching antenna (PA) systems provide a new spatial degree of freedom by flexible activation of pinching positions. However, the resulting effective channel strongly depends on the activated pinching positions, rendering conventional coherent transmission generally relies on accurate acquisition of instantaneous channel state information (CSI) and incurring substantial pilot overhead. To address this challenge, we propose a differential spatial modulation (DSM) scheme for PA systems, termed as DSM-PA. Specifically, a differential transmission scheme with an embedded Alamouti coding structure is designed, where information bits are conveyed via phase variations between adjacent symbol blocks. This design enables noncoherent transmission without requiring instantaneous CSI while simultaneously achieving transmit diversity. Moreover, to fully exploit the spatial degrees of freedom of PA systems, a pinching position-based index modulation (IM) rule is developed to enhance spectral efficiency. An asymptotically tight upper bound on the average bit error rate (BER) over quasi-static Rician fading channels is derived using the moment-generating function (MGF) method. The diversity analysis also reveals that the proposed DSM-PA scheme achieves full transmit diversity. Finally, simulation results verify the accuracy of the BER analysis and demonstrate the effectiveness of the proposed DSM-PA scheme.