Joint Uplink and Downlink Resource Allocation and Antenna Activation for Pinching Antenna Systems

Abstract: In this paper, we explore a novel joint uplink and downlink framework utilizing a pinching antenna system (PASS). We consider two waveguides, one dedicated to transmission and one to reception, and both of them are connected to a base station (BS). Each type of waveguide consists of several pinching antennas (PAs) in some preconfigured positions. In this framework, we assume the BS can serve downlink and uplink user equipments (UEs) at the same time using the same spectrum resources through the presented PASS. In this aspect, we formulate a sum rate optimization problem that jointly optimizes the antenna activation factor, the BS transmit power, and the UE's transmit power, subject to power budget constraints for the BS and the UEs, as well as minimum rate requirements for the UEs. The formulated problem is highly non-convex and difficult to solve directly. Hence, we divide the main problem into two sub-problems: the antenna activation sub-problem and the power allocation sub-problem. Then, we solve the antenna activation problem utilizing a distance and spatial correlation-based algorithm. Meanwhile, the resource allocation problem is solved using a successive convex approximation (SCA)-based algorithm. Numerical results show that our proposed framework can achieve around 60-90\% performance gains over its time division duplex (TDD) where the uplink and downlink transmissions are served in different orthogonal time slots.