Multi-Activation Fluid Antenna System with a Single RF Chain for Fast Multi-User Access

Fluid Antenna System (FAS) has emerged as a promising technology for ultra-dense sixth-generation (6G) networks. The system employ dynamically reconfigurable radiating positions to mitigate inter-user interference and enhance spectral efficiency without requiring channel-state information (CSI) at the transmitter. Existing studies have shown that fluid-antenna multiple access (FAMA) with a single activated radiating position can effectively support multi-user communication. However, its spatial multiplexing capability is increasingly limited by physical constraints as user density grows. To enhance the spatial multiplexing capability of FAMA in dense multi-user scenarios, a multi-activation strategy is introduced by utilizing a meta-fluid antenna with ultra-fast switching, controlled via a single radiofrequency (RF) chain. This approach enables a greatly expanded set of independent radiating states without introducing additional signal processing. Experiment results demonstrate that multi-activation FAMA achieves reliable multi-user multiplexing and maintains a high signal-to-noise-plus-interference ratio (SINR) under various Rayleigh-fading environments. We further show that the SINR can be optimized within a 15 μs timeframe under a multi-user Rayleigh-fading channel, making the proposed scheme highly suitable for fast-changing wireless environments.