Fluid Antenna Multiple Access at Transmitter Side

Fluid antenna system (FAS) provides a promising way to achieve massive connectivity by enabling each user to exploit spatial moments of deep fades caused by interference. However, most FAS literature assumes that fluid antennas are solely deployed at the receiver side, which may impose excessive burden on the user equipment (UE) and limit the FAS performance. In this paper, we propose a flexible FAS multiple access scheme, namely transmitter-side fluid antenna multiple access (t-FAMA), in which transmit antennas can be switched instantly to one of M positions within a line space to obtain suitable channel conditions. Unlike existing receiver-side FAS, the t-FAMA system can exploit abundant processing resources and choices of antenna locations at the base station (BS). To investigate the performance of t-FAMA, we identify the fairness of t-FAMA systems. We first analytically characterize the maximin fairness of the signal-to-interference ratio (SIR). Then, the t-FAMA resource allocation design is derived in closed-form. Simulation results show that the proposed t-FAMA scheme outperforms existing receiver-side fluid antenna multiple access scheme in terms of fairness.