Exploiting Near-Field Dynamics with Movable Antennas to Enhance Discrete Transmissive RIS

Abstract: The design of low complexity transceivers is crucial for the deployment of next generation wireless systems. In this work, we combine two emergent concepts of Movable antennas (MA) and transmissive reconfigurable intelligent surfaces (TRIS), which have recently emerged as promising technologies for enhancing wireless communication performance. In this paper, we propose a base station (BS) architecture that integrates a single MA with a TRIS operating in their near-field region. We address the joint optimization of MA location and the quantized TRIS phase configuration. Due to the non-convex coupling between spatial positioning and discrete phase constraints, an alternating optimization (AO) framework is developed, where the MA position is updated via gradient ascent (GA) and the TRIS phases are optimized through quantized phase alignment. Simulation results demonstrate that the proposed architecture significantly outperforms conventional BS equipped with a fixed fully-active antenna array under the same channel model and transmit power constraint. Moreover, MA repositioning effectively mitigates the performance degradation caused by discrete TRIS phase quantization in near-field propagation environments.